Vitamin A (Retinol) (HYG-5551-05)

This fact sheet is one in a series containing information to help you select foods that provide adequate daily amounts of vitamins, minerals, and dietary fiber. The Dietary Guidelines Advisory Committee just released the Dietary Guidelines for Americans 2005 that convey the following nine major messages concerning these topics:

Adequate nutrients within calorie needs

Weight management

Physical activity

Food groups to encourage: fruits and vegetables, whole grains, and nonfat or low-fat milk and milk products

Fat

Carbohydrates

Sodium and potassium

Alcoholic beverages

Food safety

What is the importance of vitamin A?

Vitamin A, a fat-soluble vitamin, plays essential roles in vision, growth, and development; the development and maintenance of healthy skin, hair, and mucous membranes; immune functions; and reproduction.

How much do you need?

Vitamin A is also called retinol. Measurement of the amount of vitamin A is taken in retinol activity equivalents (RAE). Carotene, an orange pigment found in food, is split by the body to become two active units of vitamin A. This is also important when calculating the amount of vitamin A in the body.

The U.S. Recommended Daily Allowance (RDA) for vitamin A is 700 RAE per day for women and 900 RAE per day for men. The U.S. RDA given is for adults and changes for women who are pregnant or lactating; therefore, please consult your healthcare provider for differences.

A good source of vitamin A contains substantial amounts of vitamin A and/or carotene in relation to its calorie content and contributes at least 10% of the U.S. RDA for vitamin A in a serving.

Do Americans get enough vitamin A?

According to recent surveys by the U.S. Department of Agriculture (USDA), the average intake of vitamin A (and carotene) by an American adult is adequate.

How to get enough vitamin A.

Eating a variety of foods that contain vitamin A (and carotene) is the best way to get an adequate amount. Healthy individuals who eat a balanced diet rarely need supplements. In fact, too much vitamin A can be toxic. Select foods that contain excellent to good sources of vitamin A each day.

Good Sources of Vitamin A

Food

Serving Size

RAE

%RDA men

% RDA women

Sweet Potato

1/2 C

1400

155

200

Carrot

1 medium

1015

112

145

Kale, boiled

1/2 C

240

26.6

34.2

Mango

1/2 medium

200

22.2

28.5

Turnip Greens

1/2 C

200

22.2

28.5

Spinach, raw

1 C

185

20.5

26.4

Papaya

1/2 medium

150

16.6

21.4

Red Bell Pepper

1/2 medium

140

15.5

20

Apricot

3

135

15

19.2

Cantaloupe

1/2 C

130

14.4

18.5

Milk, Fat Free

1 C

150

16.6

21.4

Romaine

1 C

70

7.7

10

Egg, large

1

95

10.5

13.5

Milk, whole

1 C

75

8.3

10.7

Tomato, raw

1 medium

35

3.8

5

Broccoli

1/2 C

35

3.8

5

Green Bell Pepper

1/2 C

15

1.6

2.1

Orange

1 medium

15

1.6

2.1

How to prepare foods to retain vitamin A.

Vitamin A can be lost from foods during preparation, cooking, or storage. To prevent loss of vitamin A:

Use raw fruits and vegetables whenever possible.

Keep vegetables (except sweet potatoes and winter squash) and fruits covered and refrigerated during storage.

Steam vegetables and braise, bake, or broil meats instead of frying. Some of the vitamin A is lost in the fat during frying.

What about fortified foods?

Low-fat and skim milk are often fortified with vitamin A because it is lost during processing. Margarine is fortified to make its vitamin A content the same as butter.

Most ready-to-eat and instant prepared cereals are fortified with vitamin A. Fortified ready-to-eat cereals usually contain at least 25% of the U.S. RDA for vitamin A. Cereals vary, so check the label on the package for the vitamin A content for that cereal.

What is a serving?

The amount of vitamin A in a serving depends on the weight of the serving. For example, ½ cup of a cooked vegetable contains more vitamin A than ½ cup of the same vegetable raw, because the cooked vegetable weighs more. Therefore, the cooked vegetable provides vitamin A, just not enough in a ½-cup serving to be considered a good source.

Food companies label their products according to regulations set by the Food and Drug Administration (FDA). Terms to define a serving of food that has 20% or more of the RDA include: “high,” “rich in,” or “excellent source of” vitamin A. Terms to define a serving of food that contains 10% or more of the RDA include: “good,” “contains or provides” vitamin A. Terms to define a serving of food that contains less then 10% of the RDA include: “enriched,” “fortified,” or “added” vitamin A.

by Jackie Mosure, Dietetic Intern, College of Human Ecology

Vitamin D - Dietary Supplement Fact Sheet

What are some current issues and controversies about vitamin D ?

Vitamin D and osteoporosis:It is estimated that over 25 million adults in the United States have, or are at risk of developing, osteoporosis. Osteoporosis is a disease characterized by fragile bones, and it significantly increases the risk of bone fractures. Osteoporosis is most often associated with inadequate calcium intake. 

However, a deficiency of vitamin D also contributes to osteoporosis by reducing calcium absorption. While rickets and osteomalacia are extreme examples of vitamin D deficiency, osteopororsis is an example of a long-term effect of vitamin D insufficiency. Adequate storage levels of vitamin D help keep bones strong and may help prevent osteoporosis in older adults, in non-ambulatory individuals (those who have difficulty walking and exercising), in post-menopausal women, and in individuals on chronic steroid therapy. 

Researchers know that normal bone is constantly being remodeled, a process that describes the breakdown and rebuilding of bone. During menopause, the balance between these two systems changes, resulting in more bone being broken down or resorbed than rebuilt. Hormone therapy (HT) with sex hormones such as estrogen and progesterone may delay the onset of osteoporosis. 

However, some medical groups and professional societies such as the American College of Obstetricians and Gynecologists, The North American Menopause Society, and The American Society for Bone and Mineral Research recommend that postmenopausal women consider using other agents to slow or stop bone-resorption because of the potential adverse health effects of HT.

Vitamin D deficiency, which is often seen in post-menopausal women and older Americans, has been associated with greater incidence of hip fractures. In a review of women with osteoporosis hospitalized for hip fractures, 50 percent were found to have signs of vitamin D deficiency. Daily supplementation with 20 μg (800 IU) of vitamin D may reduce the risk of osteoporotic fractures in elderly populations with low blood levels of vitamin D. 

The Decalyos II study examined the effect of combined calcium and vitamin D supplementation in a group of elderly women who were able to walk indoors with a cane or walker. The women were studied for two years, and results suggested that such supplementation could reduce the risk of hip fractures in this population. All women are encouraged to consult with a physician about their need for vitamin D supplementation as part of an overall plan to prevent and/or treat osteoporosis.

Vitamin D and cancer :

Laboratory, animal, and epidemiologic evidence suggests that vitamin D may be protective against some cancers. Epidemiologic studies suggest that a higher dietary intake of calcium and vitamin D, and/or sunlight-induced vitamin D synthesis, correlates with lower incidence of cancer 

In fact, for over 60 years researchers have observed an inverse association between sun exposure and cancer mortality. The inverse relationship between higher vitamin D levels in blood and lower cancer risk in humans is best documented for colon and colorectal cancers. Vitamin D emerged as a protective factor in a study of over 3,000 adults (96% of whom were men) who underwent a colonoscopy between 1994 and 1997 to look for polyps or lesions in the colon. 

About 10% of the group was found to have at least one advanced neoplastic (cancerous) lesion in the colon. There was a significantly lower risk of advanced cancerous lesions among those with the highest vitamin D intake. Additional well-designed clinical trials need to be conducted to determine whether vitamin D deficiency increases cancer risk, or if an increased intake of vitamin D is protective against some cancers. Until such trials are conducted, it is premature to advise anyone to take vitamin D supplements for cancer prevention.

Vitamin D and steroids :

Corticosteroid medications such as prednisone are often prescribed to reduce inflammation from a variety of medical problems. These medicines may be essential for medical treatment, but they have potential side effects, including decreased calcium absorption. 

There is some evidence that steroids may also impair vitamin D metabolism, further contributing to the loss of bone and development of osteoporosis associated with long term use of steroid medications. One study demonstrated that patients who received 0.25 μg of active vitamin D and 1000 mg calcium per day in addition to corticosteroid therapy after a kidney transplant avoided rapid bone loss commonly associated with post-transplant therapy. For these reasons, individuals on chronic steroid therapy should consult with a qualified health care professional about the need to increase vitamin D intake through diet and/or dietary supplements.

Vitamin D and Alzheimer's disease :

Alzheimer's disease is associated with an increased risk of hip fractures. This may be because many Alzheimer's patients are homebound, frequently sunlight deprived, and older. With aging, less vitamin D is converted to its active form. 

One study of women with Alzheimer's disease found that decreased bone mineral density was associated with a low intake of vitamin D and inadequate sunlight exposure. Physicians should evaluate the need for vitamin D supplementation as part of an overall treatment plan for adults with Alzheimer's disease.Vitamin D and caffeine:High caffeine intake may accelerate bone loss. 

Caffeine may inhibit vitamin D receptors, thus limiting absorption of vitamin D and decreasing bone mineral density. A study found that elderly postmenopausal women who consumed more than 300 milligrams per day of caffeine (which is equivalent to approximately 18 oz of caffeinated coffee) lost more bone in the spine than women who consumed less than 300 milligrams per day. However, there is also evidence that increasing calcium intake (by, for example, adding milk to coffee) can counteract any potential negative effect that caffeine may have on bone loss. More evidence is needed before health professionals can confidently advise adults to decrease caffeine intake as a means of preventing osteoporosis.

Calcium

Calcium is a major mineral essential for healthy bones and teeth. There are several minerals known to be essential to the human body and which must be obtained from food. The major minerals (calcium, magnesium, phosphorus, sodium, chloride and potassium) are needed in the greatest quantities or are present in large amounts in the body. The three main functions of minerals are as constituents of the skeleton, as soluble salts which help control the composition of the body fluids, and as essential adjuncts to the action of many enzymes and other proteins.

Calcium Requirements

The UK Department of Health recommended Reference Nutrient Intake (RNI) for calcium is as follows. The RNI is a daily amount that is enough or more than enough for 97% of people. The RNI is similar to the Recommended Daily Amount used previously in the UK.

Age/Sex                                                            Calcium requirement (mg/day)

Infants & children, depending on age                               350-550

Teenage girls                                                                          800

Teenage boys                                                                       1000

Adult men & women                                                              700

Breast-feeding women

extra 550The 1989 US recommendations are generally slightly higher. In 1994 the US recommendations for children aged 1-10 was increased from 800mg to 1,200mg daily and for young adults aged 11-24 years it was increased from 1,200 to 1,500mg. During pregnancy and breast feeding women in the USA are now advised to have 1,400mg calcium daily and American men and women over the age of 50 years are advised to increased their calcium intake towards 1,500mg because the intestinal absorption of calcium declines with age.

Vegan Sources of Calcium

Good plant sources of calcium include tofu (if prepared using calcium sulphate contains more than four times the calcium of whole cow's milk), green leafy vegetables, seeds and nuts. The calcium in green vegetables which are not high in oxalate e.g. kale, is absorbed as well or better than the calcium from cow's milk. Some soya milks e.g. Provamel, Plamil, Granovita are fortified with calcium. Drinking hard water can provide 200mg of calcium daily but soft water contains almost none. Other calcium rich foods include black molasses, edible seaweeds, watercress, parsley and dried figs.

Examples of amounts of foods providing 100mg calcium

Type of Food

Black molasses             20g

Dried figs                      40g

Almonds                       42g

Soya flour                     44g

Parsley                         50g

Kale                             67g

Brazils Nuts                  59g

Wholemeal bread        185g

Protein & Calcium

A high protein diet, especially derived from animal foods, causes calcium loss in the body. The higher sulphur-to-calcium ratio of meat increases calcium excretion, and a diet rich in meat can cause bone demineralisation. A report published in 1988 comparing the amounts of calcium excreted in the urine of 15 subjects showed that the animal-protein diet caused greater loss of bone calcium in the urine (150mg/day) than the all-vegetable protein diet (103mg/day). These findings suggest that diets providing vegetable rather than animal protein may actually protect against bone loss and hence osteoporosis. In one study adults on a low-protein diet were in calcium balance regardless of whether calcium intake was 500mg, 800mg or 1400mg a day. Interestingly The American Dietetic Association, in its 1993 policy statement on vegetable diets, pointed out that the calcium intakes recommended in the USA were increased specifically to offset calcium losses caused by the typically high protein consumption in that country.

Calcium Absorption

Only 20-30% of calcium in the average diet is absorbed. Calcium absorption can be reduced because it binds to fibre, phytate or oxalate in the intestine. Vegan diets contain more than average of these substances. Fibre is no longer thought to limit the availability of calcium from food. Phytate or phytic acid is found in grains, nuts and seeds and can bind with calcium making it less absorbable. However, the body does adapt to lower levels of available calcium and the American Dietetic Association and the UK's Ministry of Agriculture, Fisheries & Foods as well as the Department of Health believe that fibre, phytate and oxalate do not have a significant effect on calcium intake overall.

Although the calcium intake of adult vegans tends to be lower than the recommended optimum, it is close to the Estimated Average Requirement. There have been no reports of calcium deficiency in adult vegans.

The Estimated Average Requirement (UK) of a nutrient in the diet is an estimate of the average needs of a group of people. About half may need more, and half may need less.

Osteoporosis

Osteoporosis is the major cause of bone fractures in the elderly. One in four British women are affected by this disease. It is better prevented than treated and prevention includes an adequate intake of calcium throughout life, but especially in childhood and young adulthood; and minimising major risk factors e.g. smoking, heavy alcohol use and lack of physical exercise. Diets high in protein and in salt (sodium chloride) also increase calcium loss from the body and may have an effect on osteoporosis. Post-menopausal women are more prone to osteoporosis because they produce less oestrogen, which protects the skeleton in younger women.

There has been much publicity about the role of dietary calcium in preventing osteoporosis but the fact remains that it is more common in Westernised countries where calcium intakes and consumption of dairy products are high compared to the rest of the world.Osteoporosis is comparatively rare in rural subsistence cultures, even though calcium intakes are much lower. Lifestyle factors, such as physical activity, lower protein intakes, little alcohol consumption and the rarity of smoking, may offer protection to people in these populations.

Cow's Milk & Health

The advertising blurb surrounding cow's milk would make anyone think it is an absolutely essential and natural product for humans. Most people when thinking of increasing their calcium intake would immediately reach for a carton of milk or slab of cheese. However, there are several reasons for not using these products as a nutrient source. Whole cow's milk is suited to the nutritional needs of calves who double their weight in 47 days and grow to 300 pounds within a year. In fact, human beings are the only species to drink the milk of another species, and the only species to drink milk beyond infancy. In addition about 90% of the world's adult population (in Britain the figure is probably 25%) is deficient in the enzyme needed to digest milk properly. The enzyme lactase is present in infants for digesting their mother's milk, but levels decline after the age of five years. Adults who lack the enzyme suffer from bloating, cramping, wind and diarrhoea if they drink milk.

The most significant connection between milk and ill-health is probably through its contribution to heart disease. Too much saturated fat in the diet can lead to atherosclerosis, where the arteries 'fur up' with cholesterol deposits and cannot deliver enough blood to the vital organs. The heart is particuarly susceptible. Milk and other dairy products account for about half of all saturated fats eaten in this country. Meat accounts for the rest. The UK has the highest level of heart disease in the world.

Child-care expert Dr Benjamin Spock, once an advocate of drinking cow's milk, has joined several doctors questioning its nutritional value and warning of a possible link to juvenile onset diabetes and allergies. "Breast-feeding is the best milk feeding for babies," says Dr Spock. Dr Spock is backed up by Dr Frank Oski, director of pediatrics at John Hopkins University and Dr Neal Barnard, president of the 2000-member Physicians' Committee for Responsible Medicine. Dr Oski states that cow's milk is overrated as a source of calcium, is often contaminated with traces of antibiotics, can cause allergies and digestive problems and has been linked to juvenile diabetes. 

Conclusions

The calcium intake of vegans tends to be slightly below the recommended optimal amounts but the body does adapt to lower intakes and there have been no reports of calcium deficiency in vegans. The fact that vegans have a slightly lower protein intake and exclude meat from their diet encourages their bodies to retain calcium so their dietary need may be lower than the typical omnivore. Studies of the bones of vegans suggest that the likelihood of osteoporosis is no greater than for omnivores.

Vitamin K

Vitamin K is a fat-soluble vitamin. The "K" is derived from the German word "koagulation". Coagulation refers to blood clotting, because vitamin K is essential for the functioning of several proteins involved in blood clotting (1). There are two naturally occurring forms of vitamin K. Plants synthesize phylloquinone, also known as vitamin K1. Bacteria synthesize a range of vitamin K forms, using repeating 5-carbon units in the side chain of the molecule. These forms of vitamin K are designated menaquinone-n (MK-n), where n stands for the number of 5-carbon units. MK-n are collectively referred to as vitamin K2 (2). MK-4 is not produced in significant amounts by bacteria, but appears to be synthesized by animals (including humans) from phylloquinone. MK-4 is found in a number of organs other than the liver at higher concentrations than phylloquinone. This fact, along with the existence of a unique pathway for its synthesis, suggests there is some unique function of MK-4 that is yet to be discovered (3).

Function

The only known biological role of vitamin K is that of the required coenzyme for a vitamin K-dependent carboxylase that catalyzes the carboxylation of the amino acid, glutamic acid, resulting in its conversion to gamma-carboxyglutamic acid (Gla) (4). Although vitamin K-dependent gamma-carboxylation occurs only on specific glutamic acid residues in a small number of proteins, it is critical to the calcium-binding function of those proteins (5, 6).

Coagulation (clotting)

The ability to bind calcium ions (Ca2+) is required for the activation of the 7 vitamin K-dependent clotting factors in the coagulation cascade. The term, coagulation cascade, refers to a series of events, each dependent on the other that stops bleeding through clot formation. Vitamin K-dependent gamma-carboxylation of specific glutamic acid residues in those proteins makes it possible for them to bind calcium. Factors II (prothrombin), VII, IX, and X make up the core of the coagulation cascade. Protein Z appears to enhance the action of thrombin (the activated form of prothrombin) by promoting its association with phospholipids in cell membranes. Protein C and protein S are anticoagulant proteins that provide control and balance in the coagulation cascade. Because uncontrolled clotting may be as life threatening as uncontrolled bleeding, control mechanisms are built in to the coagulation cascade. Vitamin K-dependent coagulation factors are synthesized in the liver. Consequently, severe liver disease results in lower blood levels of vitamin K-dependent clotting factors and an increased risk of uncontrolled bleeding (hemorrhage) (7).

Some people are at risk of forming clots, which could block the flow of blood in arteries of the heart, brain, or lungs, resulting in heart attack, stroke, or pulmonary embolism, respectively. Some oral anticoagulants, such as warfarin, inhibit coagulation through antagonism of the action of vitamin K. Although vitamin K is a fat-soluble vitamin, the body stores very little of it, and its stores are rapidly depleted without regular dietary intake. Perhaps, because of its limited ability to store vitamin K, the body recycles it through a process called the vitamin K cycle. The vitamin K cycle allows a small amount of vitamin K to function in the gamma-carboxylation of proteins many times, decreasing the dietary requirement. Warfarin prevents the recycling of vitamin K by inhibiting two important reactions and creating a functional vitamin K deficiency (see diagram). Inadequate gamma-carboxylation of vitamin K-dependent coagulation proteins interferes with the coagulation cascade, and inhibits blood clot formation. Large quantities of dietary or supplemental vitamin K can overcome the anticoagulant effect of vitamin K antagonists, so patients taking these drugs are cautioned against consuming very large or highly variable quantities of vitamin K in their diets (see Drug interactions). Experts now advise a reasonably constant dietary intake of vitamin K that meets current dietary recommendations (60-80 mcg/day) for patients on vitamin K antagonists, like warfarin (8).

Bone mineralization

Three vitamin-K dependent proteins have been isolated in bone. Osteocalcin is a protein synthesized by osteoblasts (bone forming cells). The synthesis of osteocalcin by osteoblasts is regulated by the active form of vitamin D, 1,25(OH)2D3 or calcitriol. The mineral-binding capacity of osteocalcin requires vitamin K-dependent gamma-carboxylation of three glutamic acid residues. The function of osteocalcin is unclear, but is thought to be related to bone mineralization. Matrix Gla protein (MGP) has been found in bone, cartilage, and soft tissue, including blood vessels. The results of animal studies suggest MGP prevents the calcification of soft tissue and cartilage, while facilitating normal bone growth and development. The vitamin K-dependent anticoagulant protein S is also synthesized by osteoblasts, but its role in bone metabolism is unclear. Children with inherited protein S deficiency suffer complications related to increased blood clotting as well as to decreased bone density (6, 7, 9).

Cell growth

Gas6 is a vitamin K-dependent protein that was identified in 1993. It has been found throughout the nervous system, as well in the heart, lungs, stomach, kidneys, and cartilage. Although the exact mechanism of its action has not been determined, Gas6 appears to be a cellular growth regulation factor with cell signaling activities. It may also play important roles in the developing and aging nervous system (10, 11).

Deficiency

Overt vitamin K deficiency results in impaired blood clotting, usually demonstrated by laboratory tests that measure clotting time. Symptoms include easy bruising and bleeding that may be manifested as nosebleeds, bleeding gums, blood in the urine, blood in the stool, tarry black stools, or extremely heavy menstrual bleeding. In infants, vitamin K deficiency may result in life-threatening bleeding within the skull (intracranial hemorrhage) (7).

Adults

Vitamin K deficiency is uncommon in healthy adults for a number of reasons: 1) vitamin K is widespread in foods (see Food sources), 2) the vitamin K cycle conserves vitamin K, and 3) bacteria that normally inhabit the large intestine synthesize menaquinones (vitamin K2), though it is unclear whether a significant amount is absorbed and utilized. Adults at risk of vitamin K deficiency include those taking vitamin K antagonist anticoagulant drugs and individuals with significant liver damage or disease (7).

Infants

Newborn babies that are exclusively breast-fed are at increased risk of vitamin K deficiency for the following reasons: 1) human milk is relatively low in vitamin K compared to formula, 2) the newborn's intestines are not yet colonized with bacteria that synthesize menaquinones, and 3) the vitamin K cycle may not be fully functional in newborns, especially premature infants. Infants whose mothers are on anticonvulsant medication to prevent seizures are also at risk of vitamin K deficiency. Vitamin K deficiency in newborns may result in a bleeding disorder called vitamin K deficiency bleeding (VKDB) of the newborn. Because VKDB is life threatening and easily prevented, the American Academy of Pediatrics and a number of similar international organizations recommend that an injection of phylloquinone (vitamin K1) be administered to all newborns (12).

Controversies around vitamin K administration and the newborn

Vitamin K and childhood leukemia: Controversy arose regarding the routine use of vitamin K injections for newborns in the early 1990s when two retrospective studies were published that suggested the possibility of an association between vitamin K injections in newborns and the development of childhood leukemia and other forms of childhood cancer. However, two large retrospective studies in the U.S. and Sweden that reviewed the medical records of 54,000 and 1.3 million children, respectively, found no evidence of a relationship between childhood cancers and vitamin K injections at birth (13,14). Moreover, a pooled analysis of 6 case-control studies including 2,431 children diagnosed with childhood cancer and 6,338 cancer-free children found no evidence that vitamin K injections for newborns increased the risk of childhood leukemia (15). In a policy statement, the American Academy of Pediatrics recommended that routine vitamin K prophylaxis for newborns be continued because VKDB is life threatening and the risks of cancer are unproven and unlikely (16). Full text of the AAP policy statement on vitamin K and the newborn.

Lower doses of vitamin K1 for premature infants: The results of two studies of vitamin K levels in premature infants suggest that the standard initial dose of vitamin K1 for full term infants (1.0 mg) may be too high for premature infants (17,18). These findings have led some experts to suggest the use of an initial vitamin K1 dose of 0.3 mg/kg for infants with birth weights less than 1,000 g (2 lbs, 3 oz) (19), and an initial dose of 0.5 mg for other premature infants (17).

The Adequate Intake (AI)

In January 2001, the Food and Nutrition Board (FNB) of the Institute of Medicine established the adequate intake (AI) level for vitamin K in the U.S. based on consumption levels of healthy individuals (20).

Adequate Intake (AI) for Vitamin K

Life Stage                              Age                            Males (mcg/day)         Females (mcg/day)

Infants                               0-6 months                               2.0                              2.0

Infants                              7-12 months                              2.5                              2.5

Children                            1-3 years                                  30                               30

Children                            4-8 years                                  55                               55

Children                          9-13 years                                  60                               60

Adolescents                  14-18 years                                  75                               75

Adults                           19 years and older                       120                              90

Pregnancy                     18 years and younger                     -                                75

Pregnancy                     19 years and older                         -                                90

Breastfeeding                18 years and younger                     -                                75

Breastfeeding                19 years and older                         -                                90

Disease Prevention 

Osteoporosis

The discovery of vitamin K-dependent proteins in bone has led to research on the role of vitamin K in maintaining bone health.

Dietary vitamin K and osteoporotic fracture

Epidemiological studies have demonstrated a relationship between vitamin K and age-related bone loss (osteoporosis). The Nurses Health Study followed more than 72,000 women for 10 years. Investigators found that women whose vitamin K intake was in the lowest quintile (1/5) had a 30% higher risk of hip fracture than women with vitamin K intakes in the highest four quintiles (21). A study of over 800 elderly men and women followed in the Framingham Heart Study for 7 years found that men and women with dietary vitamin K intakes in the highest quartile (1/4) had only 35% of the risk of hip fracture experienced by those with dietary vitamin K intakes in the lowest quartile (approximately 250 mcg/day vs. 50 mcg/day of vitamin K). However, the investigators found no association between dietary vitamin K intake and bone mineral density (BMD) in the Framingham subjects (22). Because the primary dietary source of vitamin K is generally green leafy vegetables, high vitamin K intake could just be a marker for a healthy diet that is high in fruits and vegetables (23).

Vitamin K-dependent carboxylation of osteocalcin and osteoporotic fracture

Osteocalcin, a bone-related protein that circulates in the blood, has been shown to be a sensitive marker of bone formation. Vitamin K is required for the gamma-carboxylation of osteocalcin. Undercarboxylation of osteocalcin adversely affects its capacity to bind to bone mineral, and the degree of osteocalcin gamma-carboxylation has been found to be a sensitive indicator of vitamin K nutritional status (3). Circulating levels of undercarboxylated osteocalcin (ucOC) were found to be higher in postmenopausal women than premenopausal women and markedly higher in women over the age of 70. In a study of 195 institutionalized elderly women, the relative risk of hip fracture was six times higher in those who had elevated ucOC levels at the beginning of the study (24). In a much larger sample of 7500 elderly women living independently, circulating ucOC was also predictive of fracture risk (25). Although vitamin K deficiency would seem the most likely cause of elevated blood ucOC, investigators have also documented an inverse relationship between measures of vitamin D nutritional status and ucOC levels, as well as a significant lowering of ucOC by vitamin D supplementation (6). It is also possible that an increased ucOC level is a marker for poor vitamin D or protein nutritional status.

Vitamin K antagonists and osteoporotic fracture

Certain oral anticoagulants, like warfarin, are known to be antagonists of vitamin K. Two recent studies examined the chronic use of warfarin and the risk of fracture in older women. One study reported no association between long-term warfarin treatment and fracture risk (26), while the other found a significantly higher risk of rib and vertebral fractures in warfarin users compared to nonusers (27). A meta-analysis of the results of 11 published studies found that oral anticoagulation therapy was associated with a very modest reduction in bone density at the wrist, and no change in bone density at the hip or spine (28).

Vitamin K supplementation studies and osteoporosis

Vitamin K supplementation of 1,000 mcg/day of phylloquinone (Vitamin K1) for 2 weeks (more than 10 times the AI for vitamin K) resulted in a decrease of ucOC levels in postmenopausal women, as well as increases in several biochemical markers of bone formation. In Japan, intervention trials in hemodialysis patients and osteoporotic women using very high pharmacologic doses (45 mg/day) of menatetrenone (MK-4) have reported significant reductions in the rate of bone loss (29, 30). MK-4 is not found in significant amounts in the diet, but can be synthesized in small amounts by humans from phylloquinone. The dose used in the Japanese studies is about 50 times higher than the AI for vitamin K. Experts are not sure whether the effects of such high doses of MK-4 represent a true vitamin K effect.

In the absence of long-term intervention studies using nutritionally optimal doses of vitamin K, evidence of a relationship between vitamin K nutritional status and bone health in adults is considered weak. Further investigation is required to determine the physiological function of vitamin K-dependent proteins in bone and the mechanisms by which vitamin K affects bone health and osteoporotic fracture risk (6).

Vascular calcification and cardiovascular disease

One of the hallmarks of cardiovascular disease is the formation of atherosclerotic plaques in arterial walls. Calcification of atherosclerotic plaques occurs as the condition progresses, resulting in decreased elasticity of the affected vessels and increased risk of clot formation, the usual cause of a heart attack or stroke. One study of postmenopausal women found low dietary vitamin K intake to be associated with increased risk of aortic calcification, as visualized by chest x-ray (31). Additionally, laboratory tests examining the vitamin K-dependent gamma-carboxylation of osteocalcin indicated that elevated blood levels of undercarboxylated osteocalcin (ucOC) were also associated with increased aortic calcification. The mechanism by which vitamin K may promote mineralization of bone, while inhibiting mineralization (calcification) of vessels is not entirely clear. One hypothesis is based on the function of two different bone proteins, osteocalcin and matrix Gla protein (MGP). MGP has been found to inhibit the calcification of cartilage and bone during early embryonic development. Osteocalcin appears later during bone development and appears to promote bone mineralization. Some investigators have hypothesized that high levels of MGP found in calcified vessels may represent a defense against vessel calcification, but that inadequate vitamin K nutritional status results in inadequate carboxylation, and presumably inactive MGP. Thus, insufficient dietary vitamin K may increase the risk of vascular calcification (32). However, it should be noted that this line of reasoning is based on animal research and only one epidemiological study in humans. Further investigations are necessary to establish the nature of the role of bone proteins in human atherosclerotic plaque calcification.

Sources

Food sources

Phylloquinone (vitamin K1) is the major dietary form of vitamin K. Green leafy vegetables and some vegetable oils (soybean, cottonseed, canola, and olive) are major contributors of dietary vitamin K. Hydrogenation of vegetable oils may decrease the absorption and biological effect of dietary vitamin K. If you wish to check foods you eat frequently for their nutrient content, including vitamin K, search the USDA food composition database or view a list of foods containing a specific nutrient. A number of good sources of vitamin K are listed in the table below along with their vitamin K content in micrograms (mcg).

Food                                         Serving                                          Vitamin K (mcg)

Olive oil                               1 Tablespoon                                                6.6

Soybean oil                          1 Tablespoon                                              26.1

Canola oil                            1 Tablespoon                                                9.7

Mayonnaise                         1 Tablespoon                                              11.9

Broccoli, cooked                 1 cup (chopped)                                          420

Kale, raw                            1 cup (chopped)                                          547

Spinach, raw                       1 cup (chopped)                                          120

Leaf lettuce, raw                  1 cup (shredded)                                         118

Swiss chard, raw                 1 cup (chopped)                                          299

Watercress, raw                  1 cup (chopped)                                            85

Parsley, raw                        1 cup (chopped)                                           324

Intestinal bacteria

Bacteria that normally colonize the large intestine synthesize menaquinones (vitamin K2), which are an active form of vitamin K. Until recently it was thought that up to 50% of the human vitamin K requirement might be met by bacterial synthesis. Recent research indicates that the contribution of bacterial synthesis is much less than previously thought, although the exact contribution remains unclear (34).

Supplements

In the U.S. vitamin K1 is without a prescription in multivitamin and other supplements in doses that generally range from 10-120 mcg per dose (35). A form of vitamin K2, menatetrenone (MK-4) has been used to treat osteoporosis in Japan and is currently under study in the U.S (36).

Safety

Toxicity

Although allergic reaction is possible, there is no known toxicity associated with high doses of phylloquinone (vitamin K1), or menaquinone (vitamin K2) forms of vitamin K (20). The same is not true for menadione (vitamin K3) and its derivatives. Menadione can interfere with the function of glutathione, one of the body's natural antioxidants, resulting in oxidative damage to cell membranes. Menadione given by injection has induced liver toxicity, jaundice, and hemolytic anemia (due to the rupture of red blood cells) in infants, and is no longer used for treatment of vitamin K deficiency (5, 7). No tolerable upper level (UL) of intake has been established for vitamin K (20).

Drug interactions

The anticoagulant effect of vitamin K antagonists (e.g., warfarin) may be inhibited by very high dietary or supplemental vitamin K intake. It is generally recommended that individuals using warfarin try to consume the AI for vitamin K (90-120 mcg), while avoiding large fluctuations in vitamin K intake that might interfere with the adjustment of their anticoagulant dose (8). Large doses of vitamin A and vitamin E have been found to antagonize vitamin K. Excess vitamin A appears to interfere with vitamin K absorption, while a form of vitamin E (tocopherol quinone) may inhibit vitamin K-dependent carboxylase enzymes. Bleeding was reported in a man taking 5 mg of warfarin and 1,200 IU of vitamin E daily (7). When given to pregnant women, warfarin, anticonvulsants, rifampin, and isoniazid can interfere with fetal vitamin K synthesis and place the newborn at increased risk of vitamin K deficiency (12). Prolonged use of broad spectrum antibiotics may decrease vitamin K synthesis by intestinal bacteria. Cephalosporins and salicylates may decrease vitamin K recycling by inhibiting vitamin K epoxide reductase (diagram). Cholestyramine, cholestipol, orlistat, mineral oil, and the fat substitute olestra may decrease vitamin K absorption (35).

Linus Pauling Institute Recommendation

Although the AI for vitamin K was recently increased, it is not clear if it will be enough to opitmize the gamma-carboxylation of vitamin K-dependent proteins in bone (see Osteoporosis). Multivitamins generally contain 10 to 25 mcg of vitamin K while vitamin K or "bone" supplements may contain 100 to 120 mcg of vitamin K. To consume the amount of vitamin K associated with a decreased risk of hip fracture in the Framingham Heart Study (about 250 mcg/day), an individual would need to eat a little more than 1/2 cup of chopped broccoli or a large salad of mixed greens every day. Though the dietary intake of vitamin K required for optimal function of all vitamin K dependent proteins is not yet known, the Linus Pauling Institute recommends taking a multivitamin/mineral supplement and eating at least 1 cup of dark green leafy vegetables daily. Replacing dietary saturated fats like butter and cheese with monounsaturated fats found in olive oil and canola oil will also increase dietary vitamin K intake, and may also decrease the risk of cardiovascular diseases.

Older adults (65 years and older)

Because older adults are at increased risk of osteoporosis and hip fracture, the above recommendation for a multivitamin/mineral supplement and at least 1 cup of dark green leafy vegetables/day is especially relevant.

Osteoporosis: Vitamin C and Keeping Healthy

Vitamin C Vitamin C is widely known as a powerful antioxidant as well as an effective cell protector and immunity booster. But supplements of Vitamin C have recently been recognized as having an important role in the prevention and treatment of osteoporosis because of its ability to increase bone density.

A typical dosage of Vitamin C is about 500mg to1000mg per day. Higher doses are controversial and should be discussed with your doctor.

Natural sources of vitamin C are found in citrus fruits, but are also in many vegetables. Other good sources of vitamin C include:

· Red chili peppers · Guavas · Red cabbage

In order to get the most Vitamin C from your foods, eat them promptly after preparation. Exposure to light and oxygen can rapidly decrease the amount of Vitamin C in fresh fruits and vegetables.

When shopping for vitamin C, avoid specialized products such as esterified C, time-released C, or vitamin C with rose hips. There is no evidence that these products are any better than basic Vitamin C (ascorbic acid).

Keeping Healthy As you can see, increasing your intake of calcium is not the only thing you need to do for the prevention and treatment of osteoporosis. A range of other minerals and vitamins, when working together, also play important roles in bone health. Maintaining adequate amounts of calcium, magnesium, vitamins D, K, and C as well as other minerals is essential in maintaining healthy bones. Remember to talk to your doctor before starting any new diet or using any nutritional supplements. Osteoporosis affects more than 28 million people in the United States. It is characterized by a loss of bone mass resulting in fragile bones and an increased risk of fractures of weight-bearing bones. If it progresses, osteoporosis can lead to loss of height, stooped posture, humpback, and severe pain. Osteoporosis affects both men and women, however women are at higher risk for this condition, especially after menopause.

Not everyone will get osteoporosis. However, everyone can benefit from healthy bones. A lack of certain minerals and vitamins play a role in the onset of osteoporosis. By adopting a healthy lifestyle and maintaining sufficient levels of calcium, magnesium and other minerals, men and women can keep their bones healthy and strong.

Here are some general tips for maintaining healthy bones:

• Reduce the amount of protein, such as meat, in your diet. This will help prevent too much calcium from being excreted by the body.
• Avoid carbonated beverages. This will reduce sugar and phosphorus in your diet, which also helps prevent too much calcium from being excreted by the body.
• Increase calcium in your diet. Dairy products, green leafy vegetables and legumes are great sources of calcium. Use low fat products if you need to also control your weight. Look for other products, such as orange juice, that have added calcium.
• Get more Vitamin D by getting at least 15 minutes of direct exposure from the sun each day. If you live in a climate where this is not always possible, take a multivitamin that has the recommended daily amounts of Vitamin D.
• Exercise. Make exercise a part of your daily routine. Weight-bearing exercises, such as low-impact aerobics, jogging, and walking are helpful in minimizing bone loss.

SupplementsDespite all our best intentions, sometimes it is just not possible to eat right and get all the appropriate amounts of vitamins and minerals in our diet - especially if we are at risk for osteoporosis. That's when taking nutritional supplements can be helpful. However, be sure to talk to your doctor before starting any diet or taking and nutritional supplements.

If you have osteoporosis, are at risk for osteoporosis, or are interested in maintaining healthy bones, increasing your intake of the following minerals and vitamins will help.

Calcium Calcium is the most abundant mineral found in the body and most of it is found in our bones. It is one of the most important minerals involved in the treatment and prevention of osteoporosis. Adequate amounts of calcium in your diet can help reduce bone loss by 30 - 50 percent!

There are many forms of calcium supplements available. However, in order to be effective, calcium must be properly absorbed by the body. Look for chelated forms of calcium (calcium citrate, calcium lactate, or calcium gluconate) because it is the easiest form for most people to absorb. The recommended amount of calcium is 1000mg to 1500 mg per day. However, since your body can't absorb more than about 500 mg of calcium at a time, you should divide your doses and take them at different times of the day. Also, for maximum absorption, take your calcium supplements with food.

You can also increase your intake of calcium by eating calcium-rich foods. Food sources that are high in calcium include:

• Kelp
• Turnips
• Collard greens
• Dairy products

Magnesium Magnesium is a mineral that plays an important role in maintaining healthy bones. It contributes to increased bone density and helps prevent the onset of osteoporosis. Most people do not get enough magnesium in their diets, especially if they eat large amounts of processed foods in which much of the magnesium is removed.

Since magnesium works closely with calcium, it is important to have an appropriate ratio of both minerals in order for them to be effective. A good rule of thumb is a 2:1 calcium-to-magnesium ratio. For example, if you take 1000mg of calcium, you should also take 500mg of magnesium.

The recommended amount of magnesium is 300mg to 500mg daily. As with calcium, chelated forms of magnesium are absorbed best by the body. Magnesium oxide is also available and is often less expensive, but it is poorly absorbed by the body. Since high doses of magnesium can cause diarrhea, you should divide your doses and take them with meals throughout the day.

You can also increase your intake of magnesium by eating magnesium-rich foods. Food sources that are high in magnesium include:

• Brown rice· Buckwheat· Corn· Dandelion greens· Dark green vegetables· Legumes· Nuts (almonds, cashew, brazil)· Rye· Seeds (sunflower, sesame, pumpkin) · Wheat germ/bran · Whole grain cereals
• Vitamin D Vitamin D helps enhance calcium absorption in the body and helps with bone formation. When taken along with calcium, Vitamin D plays a critical role in maintaining bone density.
• The best source of Vitamin D is the sun. However, for many people daily sun exposure is not possible or not enough. As a nutritional supplement for osteoporosis, the recommended amount of Vitamin D is 200 IU to 400 IU per day. Be careful not to take too much Vitamin D. Excessive amounts can be toxic and cause hypercalcemia (too much calcium in the blood), seizures, nausea, vomiting, and death.
• You can also increase your intake of Vitamin D by eating Vitamin D-rich foods. Food sources that are high in Vitamin D include:
• Butter and margarine · Cheese · Egg yolk · Fish liver oils · Fortified cereals and bread · Fortified milk · Herring · Mackerel · Oysters · Salmon
• Vitamin K Vitamin K helps promote strong bones by binding calcium and other minerals to the bone. The recommended dosage of Vitamin K is 150mcg a day. Avoid taking too much Vitamin K as high doses can cause flushing and sweating. In addition, if you are taking the blood thinner warfarin (Coumadin), talk to your doctor before taking a Vitamin K supplement as it may lessen the effects of the drug.
• You can also increase your intake of Vitamin K by eating Vitamin K-rich foods. Food sources that are high in Vitamin K include:
• Broccoli · Brussels sprouts · Cauliflower · Chick peas · Dairy products · Eggs · Kale · Seeds · Vegetable oils (olive, canola)

Trace Elements As the name suggests, only trace amounts of some minerals are needed for the body to function properly. Taken as supplements, certain trace elements can promote bone formation and help to prevent osteoporosis. Most people get enough trace elements in their diets. However, for the prevention and treatment of osteoporosis, supplements can be helpful.

Boron Recent studies suggest that boron is important for calcium metabolism. In addition, it has proven to be an effective mineral for the treatment and prevention of osteoporosis because of its ability to activate important vitamins and minerals in the body.

Additional research needs to be conducted in order to determine a recommended daily amount of boron. In the meantime, experts suggest 3mg to 5mg a day for the treatment and prevention of osteoporosis. Higher doses of boron can cause nausea, vomiting, diarrhea, and fatigue. 

Food sources that contain boron include:

• Apples · Beet greens · Broccoli · Cabbage · Cherries · Grapes · Legumes · Nuts · Peaches · Pears
• Silicon Scientists have determined that silicon helps with the growth and maintenance of skin, hair, ligaments, tendons, and bones as well as in the development of normal skeletal growth.
• Silicon is found in whole, unprocessed foods. Since most people eat a lot of processed foods, supplementing silicon may be helpful in maintaining a healthy diet. Like boron, additional research needs to be conducted in order to determine a recommended daily amount of silicon. In the meantime, experts suggest 25mg to 50mg a day for the treatment and prevention of osteoporosis.
• Food sources that contain silicon include:
• Asparagus · Cabbage · Cucumbers · Dandelion greens · Lettuce · Mustard greens · Olives · Parsnips · Radishes · White onions · Whole grains (rice and oats)
• Trace Elements As the name suggests, only trace amounts of some minerals are needed for the body to function properly. Taken as supplements, certain trace elements can promote bone formation and help to prevent osteoporosis. Most people get enough trace elements in their diets. However, for the prevention and treatment of osteoporosis, supplements can be helpful.
• Zinc/CopperA zinc deficiency is associated with decreases in bone density. Likewise, copper is an important mineral in the normal growth and development of the skeletal system. That is why it is important to maintain adequate levels of zinc and copper in your diet to prevent and/or treat osteoporosis.
• Supplements of zinc and copper need to be balanced. As a rule of thumb, every 30mg of zinc needs to be balanced by 2mg of copper. Recommended doses for the treatment and prevention of osteoporosis are 15mg to 30mg zinc and 1.5mg to 3mg copper a day.
• Food sources that contain zinc include:
• Brazil nuts · Oats · Oysters · Peanuts · Pecans · Pumpkin seeds · Rye · Split peas
• Food sources that contain copper include:
• Buckwheat · Crab · Liver · Mushrooms · Peanut butter · Seeds and nuts · Split peas · Vegetable oils (sunflower, olive)

Children's Calcium Requirements

Childhood Nutrition BasicsWhen considering their children's nutrition, parents often think more about fat grams, carbs, and calories, and forget about calcium, a mineral that is important to help build strong and healthy bones.

Calcium Requirements
How much calcium do your kids need?
It depends on how old they are, but the American Academy of Pediatrics recommends that children who are:
1-3 years old get 500mg per day (about 2 servings of milk)
4-8 years old get 800mg per day (about 3 servings of milk)
9-18 years old get 1300mg per day (about 4 servings of milk)
Unfortunately, most children, especially teens, get much less than their recommended daily requirements for calcium. This makes it important to think about calcium as you plan your children's diet.

Foods With Calcium
Milk is the food that is most often associated as being high in calcium.
It is important to note that there are plenty of other foods that are good sources of calcium though, including other dairy products, many vegetables, calcium fortified orange juice, and other calcium fortified foods.

Foods that are good sources of calcium can include:

low fat plain yogurt: 300-450mg per serving (1 cup)
american cheese: 350mg per serving (2 oz)
cow's milk (either whole milk or low fat milk): 300mg per serving (1 cup)
calcium fortified soy milk, rice milk, or goat's milk: 300mg per serving (1 cup)
calcium fortified orange juice: 300mg per serving (1 cup)
cheddar cheese: 300mg per serving (1.5 oz)
cooked dried white beans: 161mg per serving (1 oz)
dried figs: 169mg per serving (10 figs)
spinach: 120mg per serving (1 cup raw or 1/2 cup cooked)
soft serve ice cream: 118mg per serving (1/2 cup)
oranges: 50mg per serving (1 medium orange)
instant oatmeal: 100mg (1 packet)
sweet potatoes: 44mg per serving (1/2 cup mashed)
broccoli: 35mg per serving (1 1/2 cup raw or 1/2 cup cooked)

Dark green, leafy vegetables, tofu, lentils, sardines, and salmon, are also good sources of calcium, which in addition to soy milk and orange juice, are good sources of calcium for kids with a milk allergy.
Foods or meals that are prepared with the above foods, such as pizza, a grilled cheese sandwich, lasagna, or a burrito with beans and cheese, are also good ways to get enough calcium.
Keep in mind that the amount of calcium in many prepared foods can vary depending on which brand you buy. For example, one type of cheese might have only 5% of your child's daily allowance of calcium (about 50mg), while another might have 30% or 300mg. Reading food labels and being on the lookout for foods that have at least 20-30% calcium can help to make sure that your kids are getting enough calcium.
And remember that kids over age 9 years need 1300mg of calcium, which is above the 1000mg or 100% daily value that is listed on food labels. So while you can still add up the % Daily Value of calcium for each food your kids eat to see if they are getting enough, make sure it adds up to 130% for older kids.

Calcium Fortified FoodsMany other foods, including bread and cereal, may also be fortified with calcium, and can help boost your child's daily intake of calcium. Check the nutrition facts label to find those brands that are fortified with calcium.
Claims on the package itself, for example that the food is 'high in calcium,' 'rich in calcium,' or an 'excellent source of calcium,' can also help you find foods that are high in calcium, with 20% of more of the calcium DV. On the other hand, a food that is just a 'good source of calcium' is going to have just 10% to 19% of the calcium DV.

Calcium Supplements
It can be hard to get kids enough calcium if they don't like milk, yogurt, and orange juice. Making things even more difficult is the fact that these types of picky eaters are also unlikely to want to eat other foods that are good sources of calcium, such as spinach and broccoli.
You may think that you can make up for your kids not getting enough calcium in their diet by giving them a vitamin, but the average vitamin has very little calcium in it. For example, a Flintstones Complete multivitamin only has 100mg of calcium in it. Even the Flintstones Plus Calcium vitamin only has 200mg of calcium in it, which is less than even a single glass of milk.
You may have to ask your Pediatrician if your older child can take Tums or a calcium chew vitamin, like Viactiv, if your kids aren't getting much calcium from other sources. At 500mg each, these supplements make it easy to make sure your kids are getting enough calcium. If your kids do drink some milk, consider adding a packet of Nestle Carnation Instant Breakfast mix to boost the calcium content of a glass of milk by another 250mg. If your kids drink it with a grilled cheese sandwich made with bread and cheese that are 'high in calcium,' then they may get up to 900mg of calcium in one meal!

From Vincent Iannelli, M.D.,

Benefits of Vitamins & Antioxidants

There has been recent excitement and interest surrounding the benefits of vitamins and antioxidants. They have been acclaimed as the new ‘Fountain of Youth’ and studies have shown they can reduce the risk of many life-threatening diseases.

Antioxidants are vitamins and minerals (including Vitamin A, B1, B2, B6, B12, C, D, E, K, Pantothenic acid, Biotin and Folacin) that occur naturally in the body and are found in fresh wholefoods, especially fruit and vegetables. They are nature’s defence against oxidation, which occurs in our bodies every second of every day. Oxidation is simply the natural deterioration of our bodies, like when fruit goes brown if left without its skin. Each time we take a breath, the oxygen we take in becomes part of the oxidation process, a by-product of which is free radicals.

Free radicals are molecules of oxygen with unpaired electrons that float freely throughout our bodies seeking to re-balance themselves by stealing electrons from normal healthy cells. This disrupts the structure of the other healthy molecules and results in cellular damage. Free radicals are produced not only through normal bodily processes, but also from outside sources such as air pollution and tobacco smoke. All of the cells in our body are continually exposed to these damaging molecules, which many scientists now believe may contribute to the development of a host of chronic diseases, including cancer, premature aging, cataracts, heart disease, senility and arthritis.

Free radicals are attacking our bodies constantly, which means we must be proactive about preventing them. Along with reducing fat and salt intake, not smoking, and regular exercise, eating foods rich in antioxidants (fruits, vegetables, nuts, and leafy greens) or taking antioxidant supplements should help reduce the damage caused by these free radicals. Antioxidants capture free radicals before they have a chance to damage delicate tissues.

Research has proven that taking them will make a significant difference to your health. For example, in the Journal of the National Cancer Institute, almost 30,000 residents of north central China were given either a placebo or a dietary supplement containing one of seven vitamin-mineral combinations.

Those who received a daily dose of beta-carotene, vitamin E and selenium had a reduced cancer rate of 13 percent.

In another recent study reported at the American Heart Association (AHA) Scientific Session in November, women who consumed high amounts of antioxidant-rich foods such as carrots and spinach had a 33 percent lower risk of heart attack and a 71 percent lower risk of stroke, than women who ate few antioxidant-containing foods.

Antioxidants protect key cell components from damage by neutralizing the free radicals, they have been shown to reduce stress and help prevent cancer, heart disease and sun damage they also aid in the prevention of skin wrinkling and premature ageing. Healthier skin promotes beautiful hair and stronger nails thus health and beauty are combined.

Vitamins and minerals are incredibly fragile it is hard for us to get the right amount of antioxidants purely from our food because often cooking them will destroy their goodness. Exposure to the air or light for even short periods damages most vitamins and minerals. So often we cannot possibly eat enough of the foods which contain these because much of the antioxidants are lost in the process of food preparation. It is a good idea to take supplements in powder or pill form as this way you are guaranteed to get enough antioxidants to ensure that you get the most out of your health.

Medical Encyclopedia: Vitamin C

Alternative names Ascorbic acid

Definition
Vitamin C is a water-soluble vitamin that is necessary for normal growth and development.

Function
Vitamin C is required for the growth and repair of tissues in all parts of your body. It is necessary to form collagen, an important protein used to make skin, scar tissue, tendons, ligaments, and blood vessels. Vitamin C is essential for the healing of wounds, and for the repair and maintenance of cartilage, bones, and teeth.
Vitamin C is one of many antioxidants. Vitamin E and beta-carotene are two other well-known antioxidants. Antioxidants are nutrients that block some of the damage caused by free radicals, which are by-products that result when our bodies transform food into energy.
The build up of these by-products over time is largely responsible for the aging process and can contribute to the development of various health conditions such as cancer, heart disease, and a host of inflammatory conditions like arthritis. Antioxidants also help reduce the damage to the body caused by toxic chemicals and pollutants such as cigarette smoke.
Vitamin C deficiency can lead to dry and splitting hair; gingivitis (inflammation of the gums) and bleeding gums; rough, dry, scaly skin; decreased wound-healing rate, easy bruising; nosebleeds; weakened enamel of the teeth; swollen and painful joints; anemia; decreased ability to ward off infection; and, possibly, weight gain because of slowed metabolic rate and energy expenditure. A severe form of vitamin C deficiency is known as scurvy, which mainly affects older, malnourished adults.
The body does not manufacture vitamin C on its own, nor does it store it. It is therefore important to include plenty of vitamin C-containing foods in your daily diet.

Food Sources
All fruits and vegetables contain some amount of vitamin C. Foods that tend to be the highest sources of vitamin C include green peppers, citrus fruits and juices, strawberries, tomatoes, broccoli, turnip greens and other leafy greens, sweet and white potatoes, and cantaloupe.
Other excellent sources include papaya, mango, watermelon, brussels sprouts, cauliflower, cabbage, winter squash, red peppers, raspberries, blueberries, cranberries, and pineapples.

Side Effects
Vitamin C is water soluble and is regularly excreted by the body. Therefore, toxicity is very rare. Amounts greater than 2,000 mg/day, however, are not recommended because such high doses can lead to stomach upset and diarrhea.

Recommendations
The best way to get the daily requirement of essential vitamins, including vitamin C, is to eat a balanced diet that contains a variety of foods from the food guide pyramid.
Vitamin C should be consumed every day because it is not fat-soluble and, therefore, cannot be stored for later use.
The recommened daily intakes of dietary vitamin C (according to the U.S. RDA) are listed below.

Pediatric
Neonates 1 to 6 months: 30 mg
Infants 6 to 12 months: 35 mg
Children 1 to 3 years: 40 mg
Children 4 to 6 years: 45 mg
Children 7 to 10 years: 45 mg
Children 11 to 14 years: 50 mg
Adolescent girls 15 to18 years: 65 mg
Adolescent boys 15 to18 years: 75 mg

Adult
Men over 18 years: 90 mg
Women over 18 years: 75 mg
Breastfeeding women: first 6 months: 95 mg
Breastfeeding women: second 6 months: 90 mg

Because smoking depletes vitamin C, people who smoke generally need an additional 35 mg/day.