Archive for the 'Vitamin Profiles' Category

At certain times of life, or as a result of lifestyle factors, you may need extra vitamins and minerals, either from your diet or by taking supplements.

Infancy to adolescence

Extra calcium is vital during these years to help build strong bones and protect against the bone disorder osteoporosis in later life.

Adult needs

When girls and women have menstrual periods, they lose iron in the blood. They may then need to eat iron-rich foods or take a supplement, especially if their periods are heavy, to reduce the risk of iron-deficiency anemia.

During pregnancy, women have increased needs for vitamins riboflavin (B2), B12, C, and folate (which is also important for women planning to conceive). Some of these needs can be met through diet, but your doctor should prescribe a prenatal supplement, to help you meet your increased needs for iron, magnesium, selenium, iodine, and zinc during pregnancy.

Mothers who are breast-feeding need extra vitamins A, thiamine (B1), riboflavin, E, and folate to produce enough breast milk. Extra vitamins niacin (B3), C, and D are needed to replenish vitamins passed into breast milk. Extra zinc, iodine, and selenium are also needed.

Men may have extra vitamin and mineral needs depending on their activity level. For example, those involved in sports who tend to sweat a lot may need to replace sodium, potassium, and magnesium.

In addition, for the many people who are following low-carbohydrate diets to lose weight, taking a multivitamin or a B-complex supplement is essential, since foods with carbohydrates contain important B vitamins.

The Over-Fifties

After the age of 50, you may need to focus on foods rich in vitamins B6, B12, and folate because their absorption is reduced I older age. Extra calcium is vital to keep the bones strong, especially after menopause.

Other times

Strict vegetarians will not get enough vitamins B12 and D, iron, and calcium if they do not eat fortified foods or take supplements. Cigarette smokers may need extra vitamin C, which neutralizes damaging free radicals, that are created by inhaled smoke. If you are taking medication, it may interact with absorption of vitamins or minerals. Ask your doctor possible interactions.

Vitamin K
You cannot form a blood clot without vitamin K. This fact was discovered by a Danish doctor experimenting with the diet of chickens who bled spontaneously. He named this vitamin after the Danish word koagulation. The term vitamin K refers to a series of compounds with similar chemical structures. The most important and useful vitamin K compound found in plants is called phytonadione or phylloquinone (vitamin K,). Phylloquinone is the chemical name but the “generic” drug name is phytonadione. The latter name will be used on vitamin labels.

Bacteria found in our intestinal tract make a group of compounds known as menaquinones (vitamin K2). Menaquinones provide some of our daily vitamin K requirement. Vitamin K3, called menadione, can be chemically produced in the laboratory. All of the forms of vitamin K dissolve in body fat, and some people who have trouble absorbing dietary fat into their bodies must take a vitamin K supplement. Injectable and water-soluble forms of vitamin K have been developed to help these people.

Function

Blood clotting is a complex process involving at least eleven factors; all eleven factors are necessary for a clot to form. Vitamin K is needed to make the active form of the factors II, VII, IX, and X, and this is the vitamin’s main function. Some research suggests that vitamin K also plays a role in the formation of bones and other proteins whose function is not well understood. Its major function is in making blood-clotting factors.

Daily Requirements

The Food and Nutrition Board of the National Academy of Sciences have estimated infants’ need for this vitamin at about 5 mcg per day for babies up to six months and 10 mcg per day from age six months to one year. Children’s requirements vary with age, from 15 to 30 mcg per day. The RDA value for adult males is 80 mcg per day and for females it is 65 mcg per day. Bacteria normally found in our intestines provide about half of our daily requirement of vitamin K, and the rest is provided via dietary means.

The average diet provides at least ten times the amount of vitamin K thought to be necessary for efficient blood clotting. The only exception to this rule is the newborn infant. Infants are born without vitamin K-making bacteria in their intestines. New-borns in most countries are routinely given 500 to 1,000 mcg of vitamin K by intramuscular injection immediately after birth to prevent a gradual decline in clotting factors over the days following birth and to prevent possible bleeding. A second dose may have to be given if the mother had been taking anticoagulant or anticonvulsant medicines or if the infant develops bleeding tendency. Clotting factors begin to rise to normal level after about a week, when the appropriate bacteria take up residence in the intestine, but the amount of vitamin K produced in the gut varies depending on whether the infant is formula-fed (higher) or breast-fed (lower).

DIETARY SOURCES

Vitamin K is found in a variety of plants and other food source: Brussels sprouts, spinach, cabbage, cauliflower, soybeans, cheddar, and Camembert cheeses are particularly rich sources. Additional good sources are listed in the accompanying table.

Vitamin K is relatively stable under normal storage and cooking processes.

VITAMIN K CONTENT OF SELECTED FOODS
(Estimated safe and adequate intake for adults e 70-150 mcg per day)

FOOD / APPROXIMATE CONTENT (MCG PER 3 OZ)

Alfalfa 470
Asparagus 50
Bran 62
Broccoli 180
Brussels sprouts 1,350
Cabbage 225
Camembert cheese 14,500
Cauliflower 250
Cheddar cheese 20,000
Coffee beans 35
Green tea 640
Lettuce 116
Liver(beef) 81
Oats 449
Peas 40
Potatoes 72
Soybeans 270
Spinach 300
Turnip greens 585
Watercress 54

Deficiencies

Infants who were not given vitamin K at birth are may have a bleeding tendency during their first five months of life. Diarrhea or antibiotics that kill bacteria in the intestine can make matters worse for infants with an already inadequate intake of vitamin K. Breast-fed infants are more likely to develop a bleeding tendency than bottle-fed babies because breast milk contains only a little vitamin K. Also, the intestinal bacteria of infants who are exclusively breast-fed apparently lack the ability to make as much vitamin K as the formula-fed infants” bacteria do. Formulas with cow’s milk do contain sufficient amounts of vitamin K. For these reasons, most recommend an injection of vitamin K at birth.

Vitamin K deficiency is rare in adults and usually occurs only in people who do not have enough bile to absorb this fat-soluble vitamin; this group must receive supplemental K by injection. Long-term antibiotic therapy, which may destroy vitamin K-producing bacteria in the gut, may lead to a deficiency when coupled with a poor diet.

Deficiency Symptoms

People with a vitamin K deficiency may experience nosebleeds, blood in the urine, stomach bleeding, and many small black-and-blue marks on the skin. It is not uncommon for a person with vitamin K deficiency to vomit blood.

TOXICITY

Large quantities of vitamin K are not stored in the body, despite the fact that it is fat-soluble. Phytonadione is now the only form of vitamin K available in tablet or injection form; it is relatively free of adverse effects when given by mouth or by intramuscular or subcutaneous injection. Serious allergic reactions have been documented with intravenous administration of phytonadione, however, and this route is not recommended.

INTERACTIONS

Vitamin K can interact with oral anticoagulant drugs to decrease their effect. Therefore, if you are taking anticoagulant drugs, you should avoid foods high in vitamin K.

THERAPEUTIC USES

Because of its interaction with anticoagulant drugs, vitamin K is sometimes given as an antidote to these drugs. It is also used therapeutically in cases of prolonged intravenous feeding and in situations where antibiotics are administered to kill all microorganisms in the intestines.

UNSUBSTANTIATED CLAIMS

We cannot recommend that you take this vitamin to treat alcoholism, cancer, cirrhosis, cystic fibrosis, gallstones, hepatitis, jaundice, or ulcers. It also will not delay aging.

Availability

Most vitamin K products are available on a prescription-only basis because it is unusual to be deficient in this vitamin. You should not try to self-medicate clotting disorders.

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Vitamin E is perhaps the most important of the protective anti-oxidant and free-radical-scavenging compounds in the body. It has a clear role in protecting the body against the damaging effects f oxygen. Higher intakes lower the risk for heart disease cancer. Below are listed some other uses for vitamin E based on the ability of this vitamin to act as a fat-soluble free-radical scavenger and antioxidant.

• Reduce environmental hazards such as ozone, nitrogen dioxide, and cigarette smoke. Increasing levels of pollutants in our atmosphere can lead to adverse health effects because these components are reactive and cause free-radical oxidative damage. Some suggest that people who live in areas with air pollution problems should increase their intake of antioxidant vitamins, especially vitamin E. We agree.

• Reduce cardiac toxicity of the anticancer drugs daunorubicin and doxorubicin. These drugs are toxic to the heart muscle because they promote the formation of free-radical intermediates. Vitamin E supplements have been shown to reduce this damage.

• Treat hemolytic anemia associated with hereditary deficiencies of the enzymes known as G6PD and glutathione peroxidase. Both of these conditions can lead to excess oxidation and consequent damage to body tissues. Vitamin E supplements have been shown to reduce breakdown red blood cells in people with these disorders.

• Relieve PMS symptoms. There are several small studies indicating that a supplement of 400 IU per day of vitamin E may reduce some symptoms of premenstrual syndrome. Vitamin E can modulate prostaglandin synthesis through its antioxidant action, and this may be a possible mechanism of action here.

• Relieve intermittent severe leg muscle pains (intermittent claudication). Intermittent claudication is characterized by attacks of lameness and pain brought on by walking. The pain comes from arteriosclerosis in the blood vessels of the legs; the reduced blood flow means that the calf and buttock muscles receive insufficient oxygen. Several studies have evaluated the usefulness of vitamin E in this condition by measuring the exercise tolerance of patients receiving the vitamin compared with patients who received traditional treatment and others receiving no treatment at all. By all criteria, vitamin E in doses over 400 IU per day was shown to be of some benefit after six months of continuous use.

• Relieve nighttime leg cramps. There is limited evidence that vitamin E might offer some benefit to those who suffer from this annoying affliction, but controlled studies on the effectiveness of vitamin E for this problem are lacking. One study showed that a dose of 400 IU, taken before bed, was effective in reducing the frequency and severity of attacks.

• Speed healing of wounds and clearing of scars. Although this use of vitamin E has not been thoroughly tested, many people claim to have experienced great benefit from applying vitamin E creams or the oil from vitamin E capsules directly to wounds and scars. Vitamin E cream is a cosmetically elegant, more expensive way of applying the vitamin to your skin than simply using the oil from a vitamin E capsule, which can be removed by puncturing the capsule with a pin and squeezing the oil out. Either form of the vitamin should be applied to the wound or scar two or three times a day. Presumably vitamin E is working as an antioxidant and free-radical scavenger in preventing further damage to the tender new tissue being formed during the heating process, although this has not been proven. If so, the vitamin would presumably work best when applied to a wound that has closed and is starting to heal. There are few adverse effects to this remedy, as long as you don’t rub the cream or oil directly into an open wound. If you have a stubborn wound that is not healing as fast as you would like, this controversial treatment may be worth a try. But you should remember that a sore that doesn’t heal may be a warning sign of cancer or another serious medical problem, so get medical attention if you have any doubts.

• Decrease platelet aggregation. Aggregation of blood platelets is part of the process of blood clot formation, but an increased tendency to platelet aggregation is dangerous because of the risk for the formation of unwanted clots, leading to strokes and heart attacks. Vitamin E can decrease the aggregation of platelets in doses of greater than 200 IU per day. While this is generally beneficial, you should not take vitamin E if you have blood-clotting problems or are taking “blood thinners” such as warfarin.

• Alleviate deficiencies in cystic fibrosis patients. Individuals with cystic fibrosis do not absorb fats, and they show deficiencies of the fat-soluble vitamins, especially vitamin E. Doses of 200 IU per day or more are needed.

• Reduce risk of cataracts. Studies have shown that people who take vitamin E supplements have a lower risk of cataract formation. Lipid peroxidation may be part of ill process of the formation of cataracts. More studies are needed to define the optimal doses and the extent of their benefit, but vitamin E supplements may be beneficial for this and many other degenerative conditions in the elderly.

• Benefit people who engage in heavy exercise. Vitamin has long been used by athletes in the hope of improved performance. Strenuous exercise has been shown to result in increased lipid peroxidation and free-radical damage in muscle tissue. Most studies on vitamin E and exercise have been done in animals; careful studies on student athletes in England and on members of a college swimming team in Louisiana have shown that vitamin E did not help, but studies with high-altitude mountain climbers indicated that vitamin E supplements have some benefits compared to placebo. More work is needed in this area.

• Reduce tardive dyskinesia. Tardive dyskinesia is a side effect of antipsychotic drugs. It is characterized by involuntary head movements and may be a consequence of free-radical damage to nerves. Small studies have shown that vitamin E in very high doses (1,600 IU per day) helps reduce these movements.

• Protect premature infants. Premature infants have a low capacity for protection against oxidative damage. Vitamin E is sometimes supplemented to prevent damage to their lungs and eyes. Earlier use of a vitamin E injection product resulted in some deaths associated with the product, and most supplementation now is given orally.

• Prevent cancers, heart disease, atherosclerosis, and decreased immune function.

• Slow the progression of Alzheimer’s disease. A well-designed study showed that high-dose vitamin E (2,000 IU per day for three years) slowed the progression of Alzheimer’s as well as did a drug called selegiline, a standard treatment. While this study does not represent a major breakthrough, this benign vitamin may help people with Alzheimer’s and their families. Further study may reveal other uses in mental degeneration.

SUBSTANTIATED CLAIMS

Treatment of cystic breast disease

Noncancerous breast lumps affect millions of American women. Early studies indicating benefit with vitamin E have not been substantiated.

Treatment of angina

While vitamin E has a role in the prevention of heart disease and prevention of further heart attacks after the first, it does not seem to be of help in treating angina.

Improvement of sexual function

Sorry - despite its reputation, vitamin E will not do anything for your sexual prowess. A Canadian evaluation could not demonstrate any effect of vitamin E on the sexual activities of couples when compared with a group receiving a placebo.

Vitamin E has also been promoted for other uses for which its value has not been proven. We cannot recommend that you take this vitamin to treat acne, allergies, anemia, arthritis, athlete’s foot, backache, baldness, bedsores, boils, bronchitis, bursitis, colitis, the common cold, constipation, cystitis, dandruff, diabetes, emphysema, eyestrain, fatigue, fluid retention, gallstones, gout, hay fever, headache, hemorrhoids, impetigo, impotence, infertility, kidney stones, loss of vision, measles, Meniere’s disease, menstrual cramps, mental illness, multiple sclerosis, muscular dystrophy, nephritis, night blindness, obesity, osteoporosis, Parkinson’s disease, phlebitis, prostatitis, sciatica, sinusitis, sunburn, thyroid disease, ulcers, vaginitis, or warts.

Availability

Another controversial point about vitamin E is the merit of using the natural form, d-alpha tocopherol, versus either of the synthetic forms, dl-alpha tocopherol or dl-alpha tocopheryl acetate. Most common vitamin products contain synthetic vitamin E. However, the natural d-alpha tocopherol seems to bind better with one of the proteins that help move vitamin E into and within the cell. The implications of this observation are that wit equal amounts of synthetic or natural vitamin E, the natural would be better-utilized. Since generic natural vitamin E is readily available and not much more expensive than the synthetic kind, we recommend purchase of the natural product. But be careful: Some brands have Nature or Natural as pan of the brand name, thus giving the consumer the impression that the vitamin E in the bottle is the natural kind. But unless the product label says it is d-alpha tocopherol, the vitamin E is synthetic. The “semisynthetic” d-alpha tocopheryl acetate is recommends also. The acetate group confers stability to the molecule and is readily removed by enzymes in the intestine, thereby releasing the d-alpha tocopherol.

Recently some vitamin E products have appeared on the shelves labeled as all natural vitamin E, but close examination of the label reveals that the capsules contain a mixture of natural d-alpha tocopherol and synthetic dl-alpha tocopherol. The products are basically mislabeled and should be avoided. If you want to take the all natural vitamin E, demand a product that 100 percent d-alpha tocopherol. Some natural vitamin E products contain “mixed tocopherols.” These products contain mixture of tocopherols obtained from the plant source (usual soybeans). As far as we know, 400 IU of mixed natural tocopherols is as beneficial as 400 IU of d-alpha tocopherol. The knowledgeable consumer can make a good choice in purchasing dietary supplements, but it will require careful scrutiny of the label. When in doubt, ask your pharmacist for assistance.

Another product is micronized or emulsified vitamin E. These products are water-soluble because the vitamin has been dispersed into fine droplets in water. For those with fat absorption problems, it may be worthwhile to use these water-soluble products because they do not need to be absorbed like fats. But if you have no problem with fat absorption, the cheaper vitamin E oil capsules will work well.

Capsules and tablets of vitamin E are available without a prescription in strengths ranging from 200 to 1.000 IU. The concentration in multivitamin products is usually 30 IU. Vitamin E ointments, lotions, and creams are also available without a prescription. The usual concentration of vitamin E in these products is 30 IU per gram.

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Vitamin E

No other vitamin has attracted as much attention from both basic scientists and clinical scientists over the past decade as vitamin E. Interest grew as researchers learned that oxidative damage to vital tissues plays an important role in the development of many chronic diseases and in the aging process. The presence of vitamin E in cell membranes helps protect the cell because it serves as a fat-soluble free-radical scavenger and antioxidant. It works hand in hand with the other antioxidant vitamins and compounds in the body.

FUNCTION

Vitamin E sits in cell membranes, and its primary function is as a biological antioxidant and cell membrane protector. Oxygen is life-giving, but it can also be harmful. One of the most potentially damaging reactions involving oxygen is with unsaturated fatty acids. Free radicals generated during normal metabolic reactions in which oxygen is involved can react with unsaturated fatty acids in cell membranes to form substances called organic peroxides. Organic peroxides are toxic to cells because they can take part in a chain reaction with other neighboring fatty acids, eventually destroying the cell. Without vitamin E and other anti-oxidant vitamins, oxygen can, in effect, convert fluidiike unsaturated fatty acids to inactive solids, rendering them unable to function. The body has several other antioxidants and free-radical-scavenging compounds that back up and complement the action of vitamin E. For example, vitamin C is needed to regenerate vitamin E after it has been inactivated by picking up a free radical.

There is ample research on this role for vitamin E. For instance, people who eat more polyunsaturated fat in their diet need more vitamin E to prevent cellular damage. Relatively little vitamin E in the diet may lead to the deposition of oxidized fats in tissues. That is not to say that vitamin E can stop the aging process; it cannot. But it is possible that vitamin E deficiency may speed the aging of essential tissues. Unless free radicals are quenched, they can react with blood fats, setting up an inflammatory process associated with atherosclerosis that leads to the formation of blood clots, and possibly heart attack. A free-radical attack on the cell nucleus can result in mutations that could lead to cancer. Low vitamin E intake has been associated with a higher risk of heart disease and cancer. Thus vitamin E’s main function is unlike most other vitamins in that it does not participate in biochemical reactions. Rather, vitamin E simply acts as a sponge to soak up damaging free radicals.

DAILY REQUIREMENTS

The strength of vitamin E was originally based on measures of biological activity and expressed in international units (IU), and different forms of the vitamin have slightly different IU equivalents.

In human nutrition, the most important form of vitamin E is alpha tocopherol, and the natural form of this substance is d-a!pha tocopherol. It has a strength of 1.5 IU per mg. Synthetic alpha tocopherol, dl-alpha tocopherol, comes in two types: dl-alpha tocopheryl acetate (with an acetate group to stabilize die vitamin E) has a strength of 1 IU per mg, and dl-alpha tocopherol (without the acetate) has a strength of 1.1 IU per mg. In 1980 the RDA for vitamin E was changed from lUs to d-alpha tocopherol equivalents (TE). One TE is equivalent to 1 mg of d-alpha tocopherol and also to 1.5 IU. Vitamin products still! use IU to express the amount of contained vitamin E. Nutrition tables have switched to TE values, however.

Based on early studies, an RDA of 30 IU of vitamin E per day was set in 1968. In 1974 the National Research Council reduced the RDA to 10 TE (15 IU) for adult males and 8 TE (12 IU) for adult females on the basis of dietary surveys that revealed that most diets contained between 10 and 15 IU per day. The RDA value has not been altered since 1974. Since there were no obvious signs of vitamin E deficiency in the United States, ii was assumed that the previous recommendation was too high. This decision was extremely controversial. On one hand, there was no evidence that 15 IU per day would not satisfy human needs for the vitamin. On the other hand, emerging knowledge of the important role vitamin E plays in removing damaging free-radical compounds in the cells suggests to many (including us) that more, not less, vitamin E is needed for optimal health. Since vitamin E is nontoxic, it is not unreasonable to push for higher intakes. This controversy is still not settled. While it would be difficult to get more than 30 IU from food, it seems prudent to increase our consumption of whole grains and unprocessed foods to increase vitamin E intake.

DIETARY SOURCES

The tocopherols are made by plants, probably as protection against oxidation of their vital fatty acids. Animals pick up their tocopherols from plant sources and use them as protection from the adverse effects of oxygen. There are more than six tocopherols found in plants, but alpha-toeopherol is the most potent. Unlike vitamins A and D, which are stored only in body fat and the liver, vitamin E is found in all body tissues in the cell membranes, so it is present in meats, but in rather low amounts. Over 60 percent of the dietary vitamin E consumed in the United States comes from plants, especially from corn or cottonseed oil (in margarine), green vegetables, and wheat germ. Other good sources are listed in the accompanying table.

VITAMIN E CONTENT OF SELECTED FOODS
(Average adult ROA is 10 TE, or 15 IU)

FOOD / APPROXIMATE CONTENT (IU PER 3 OZ.)

Almonds 13.5
Almond oil 5.8
Apricot oil 19.0
Brazil nuts 5.9
Cabbage 6.4
Cashew nuts 4.6
Corn oil 19.0
Cottonseed oil 40.0
Hazelnuts 19.0
Margarine 16.2
Peanuts 6.3
Peanut oil 14.4
Safflower nuts 31.5
Sunflower seeds 28.0
Walnuts 20.0
Wheat germ 144.0
Whole wheat flour 27.0

Vitamin E is destroyed in the presence of oxygen and heat. Thus the vitamin E content of foods varies widely depending on how they were handled during processing and storage. Prolonged freezing of vitamin E-containing foods will destroy vitamin E content unless care is taken to prevent exposure to air. Eating uncooked fresh fruits and vegetables will help increase vitamin E intake.

Deficiencies

Most vitamin E deficiency signs and symptoms are related to oxidative damage to cell components. One perplexing point is that while a vitamin E-deficient diet is life-threatening to animals, humans are not affected as severely. Vitamin E-deficient animals develop sterility, liver damage, muscular dystrophy, heart degeneration, and anemia, but no such vitamin E deficiency symptoms exist for humans. Part of the reason for the difference may be that vitamin E is widespread in our diets and that we have some reserves stored in our body fat.

A true human vitamin E deficiency state was not discovered until the 1960s. When a group of premature infants was accidentally given formula with no vitamin E. The infants became anemic and developed edema (swelling) that responded to vitamin E treatments. In Illinois, a group of volunteers was given a diet with low levels of vitamin E. These studies showed that red blood cells from normal individuals survived longer than cells from those who were vitamin E-deficient. There were no other obvious deficiency signs in the volunteers. The findings of this study, which originally set out to determine how much vitamin E would be needed to return the volunteers’ red blood cells to normal, led to the 1968 recommendation by the Food and Nutrition Board to set the RDA at 30IU of vitamin E.

Patients who have a problem absorbing and digesting dietary fats may with time develop a vitamin E deficiency. People with bile problems (bile is involved in fat absorption) have difficulty absorbing fats, as do premature infants and cystic fibrosis patients. After several years (less time for infants), signs of net damage begin to appear, leading to loss of reflexes, loss of sensation, muscle weakness, problems with eye movement, a difficulty with balance and coordination. If the vitamin E deficiency is not corrected, the damage may be irreversible.

Because of the high susceptibility of the red blood cell membranes to oxygen damage, hemolysis (bursting of red cells) may occur in people deficient in vitamin E. Patients with inherited conditions that predispose them to oxidative stress, such glucose-6-phosphate dehydrogenase (G6PD) deficiency, are prone to vitamin E deficiency. Iron is a pro-oxidant that can place an increased demand on vitamin E stores. Patients take an iron-containing product or those who have trouble eliminating iron from their body should take vitamin E supplements.

Toxicity

There are no major side effects associated with vitamin E; it is remarkably nontoxic.

One of the best evaluations of vitamin E toxicity was conducted at the National Institutes of Health. Twenty-eight institute employees voluntarily took doses ranging between 100 and 800 IU a day for an average of three years. A battery of tests designed to uncover possible toxic effects was performed on each volunteer, and none was found. There are a few reports in the medical literature describing possible stomach upset, diarrhea, dizziness, and increased blood-clotting time with high doses of vitamin, but most agree that vitamin E is nontoxic in doses below 800IU per day.

Interactions

Vitamin E facilitates the absorption, tissue storage, and utilization of vitamin A. People who must take vitamin A to correct a deficiency should also take vitamin E. However, in huge doses (greater than 2,000 IU), vitamin E can actually slow the absorption of vitamins A and K from the gastrointestinal tract.

Vitamin E can also inhibit formation of the active forms of vitamin K, thereby inhibiting the ability of blood to clot. It can also inhibit the ability of blood platelets to aggregate. This may be beneficial, for less-sticky platelets theoretically confer a reduction in the risk of stroke, blood clots in the lungs, and heart attacks.

Vitamin E supplements should probably not be used in doses larger than 50 IU per day by people taking anticoagulant drugs, aspirin or similar drugs with an effect on platelets, or those with blood-clotting disorders.

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You can satisfy your vitamin D requirement simply by being out in the sun. That’s why vitamin D is commonly called the “sun shine vitamin.” Until the discovery of vitamin D in 1924, many urban children suffered from rickets, a crippling bone disease resulting from insufficient calcium. Some thought that rickets was caused by a lack of sunshine and fresh air, while others felt dietary factor was responsible for this problem. By 1920 it was shown that both notions were true, and that either cod liver oil which contains large amounts of both vitamins A and D, or exposure to sunlight would prevent or cure the disease.

The term vitamin D describes two dietary substances with the ability to increase the absorption of calcium into the blood stream from the intestine. The first substance, now called vitamin D3 or cholecalciferol, is made in the body from cholesterol that has been exposed to the ultraviolet rays of direct sunlight. Electric lights do not give off the kind of light needed to convert cholesterol to vitamin D3; you must be exposed directly to the sun. Sitting behind a window on a sunny day also doesn’t work because the glass absorbs ultraviolet rays. The second form called vitamin D2, or ergocalciferol, is made in the laboratory by exposing ergosterol, a fatty substance found in plants, to ultraviolet light. Vitamin D2 is the form often used for food fortification. Both D2 and D3 are equally potent; your body can us either form.

Function

Vitamin D is best described as a regulator of calcium levels in the body. In fact, vitamin D is so important to calcium function that many researchers consider it a hormone, not a vitamin. The two most important ways that vitamin D functions to maintain normal calcium levels are the absorption of calcium through the intestines into the bloodstream and the mobilization of calcium from bone, where 95 percent of body calcium is stored. For vitamin D to affect calcium absorption, it must be converted in the liver to 25-hydroxycholecalciferol and then by the kidney to 1,25-dihydroxycholecalciferol. The latter form is called calcitriol and it is this activated form of the vitamin that induces the formation of a specific calcium-binding protein in the in intestinal cells. By an independent mechanism, calcitriol also stimulates absorption of phosphate from the intestine. In addition, vitamin D exerts a direct effect on the kidneys to prevent the release of calcium and phosphates from the body via the urine.

Vitamin D. as calcitriol, is a key to maintaining calcium blood levels. Because of the critical importance of blood and issue calcium for nerve function, muscle contraction, blood clotting, and other functions, the calcium level is under tight control, and vitamin D is involved in that control. If blood calcium levels drop and little dietary calcium is available, vitamin D (along with parathyroid hormone) is involved in stimulating the release of calcium from bone to bring the blood calcium jack to normal. This makes your bones more brittle and easier to break. You can see the importance of taking in enough calcium in the diet so that bone loss does not occur.

Both the vitamin D that you convert in the skin after exposure to sunlight and that which you get from your diet must be converted lo calcitriol, and both the liver and kidneys are involved in this process. Liver disease does not impede the conversion, but kidney failure is serious because less-than-optimal amounts of calcitriol are then produced, leading to calcium deficiency symptoms. The kidney damage seen in some diabetics may result in bone loss by this mechanism, and calcitriol is often given to stabilize calcium levels.

There is interest in the role vitamin D plays in the development of cancer. The vitamin has been shown to have inhibitory effects in animal models of several human cancers, but it remains to be seen whether some therapeutic advantage for vitamin D can be found in human cancer treatment and prevention.

DAILY REQUIREMENTS

Vitamin D is measured either in units based on biological activity (IU) or as micrograms (mcg) of cholecalciferol. Ten mcg of cholecalciferol is equal to 400 IU of vitamin D activity. As with vitamin A, most nutritional tables express requirements as mcg of cholecalciferol, but the vitamin products still use the IU value. One hundred IU of vitamin D per day is probably all that is needed to prevent deficiency symptoms, but 400 IU is the value recommended as the RDA for most people. Few people need to take more than that, and people who live in the Sunbelt and expose themselves to the sun probably don’t need to take any vitamin D in their diets. On the average, we make 6 IU of vitamin D every hour for every square inch of skin exposed to the sun. This varies because people whose skin color is darker make less vitamin D. People with a very dark skin color make about 4 IU per square inch per hour because less light penetrates the skin to the layer where the conversion is carried out. In the winter, it has been estimated that 2-3 hours of exposure of the face to the sun would be needed to achieve synthesis of the RDA value. So for most people, dietary intake of supplements of preformed vitamin are important.

DIETARY SOURCES

While sunshine provides enough vitamin D for people who live in warm and sunny climates, those who live in northern areas with fewer days of sunshine and extended periods of cloud cover and darkness have to depend on dietary sources of vitamin D. Unfortunately, vitamin D is present in limited concentrations in most of the foods we eat. In order to prevent rickets many countries, including the United States and Canada, have fortified common food items with vitamin D. Milk is one of our major dietary sources of vitamin D because it is fortified with irradiated ergosterol to provide vitamin D activity equivalent to 400 IU (10 mcg) per quart. Fortified margarine is also very high in vitamin D. Vitamin D is chemically stable and survives the usual modes of food processing. Additional food sources are listed in the accompanying table.

VITAMIN D CONTENT OF SELECTED FOODS
(Average adult RDA is 400 IU, or 10 mcg)

FOOD / APPROXIMATE CONTENT (IU PER 3 OZ)

Butter 36
Cheese 27
Cod liver oil 10,000
Eggs 45
Liver 45
Margarine (fortified) 270
Milk (fortified) 36
Milk (human) 6
Mushrooms 135
Salmon 360
Sardines 450
Shrimp 135
Sunflower seeds 83
Tuna 225

Deficiencies

When a growing child is deficient in vitamin D, he or she develops rickets, a disease in which newly formed bone lacks calcium. Vitamin D-deficient adults may develop osteomalacia, or adult rickets. Osteomalacia is most likely to occur during times if increased calcium need, such as pregnancy. It also occurs in some elderly people and people with kidney failure. Until recently, people with kidney failure had to take enormous amounts of vitamin D2 to maintain normal calcium levels, and frequently even this was not enough. Now the active form of vitamin D, calcitriol, which does not have to be converted in the body, is available on a prescription-only basis.

Deficiency Symptoms

In rickets, soft, defective bone is especially likely to form at siles of active growth. This results in benL bowed legs, late tooth development, weak muscles, and lisllessness. In osieomalacia. there is a generalized loss of calcium from bones throughout the body, leaving large areas of porous, bridle bone without calcium to strengthen the matrix. Osteomalacia must be distinguished from osteoporosis. in which calcium is also lost from bones, hui the losses are not general in nature. They are isolated in specific locations in (he skeleton, for example the hip, and are associated with the drop in estrogen after menopause.

TOXICITY

Vitamin D can be toxic if you take too much. It should never be taken in daily doses larger than 400 IU per day, except if prescribed by your doctor to treat a specific condition. In adults single doses of 150,000 IU or more are toxic, and daily dose: of 2.000 IU or more taken on a regular basis can lead to abnormally high blood calcium levels. Infants taking more than 400 IU every day may experience toxicity symptoms: weakness tiredness, headache, nausea and vomiting, loss of appetite, constipation or diarrhea, excessive thirst and urination, protein ii the urine, high blood pressure, high blood cholesterol, premature atherosclerosis, mental retardation, and slower-than-normal growth. In addition, calcium may be deposited in vital tissues leading to serious consequences such as liver damage and kidney failure.

INTERACTIONS

Phenytoin and barbiturates (taken to control seizures) can stimulate the metabolism of vitamin D to inactive forms and lead to vitamin D deficiencies.

THERAPEUTIC USES

Vitamin D supplements may be given to counteract the symptoms of vitamin D deficiency reviewed earlier in this profile. However, such symptoms will not be alleviated by vitamin D unless they are, in fact, caused by vitamin deficiency.

In addition to the prevention and treatment of the deficiency diseases rickets and osteomalacia, vitamin D may be prescribed for people whose parathyroid gland is not properly functioning. The parathyroid is involved in the regulation of calcium use by the body. When the blood calcium is low, the parathyroid releases a hormone that stimulates the kidneys to convert vitamin D to its active form, calcitriol, which in turn stimulates the absorption of more calcium through the intestines and the removal of some calcium from bones. The process continues until the imbalance is corrected. An improperly functioning parathyroid will not stimulate the conversion of vitamin D to calcitriol. Plain vitamin O may be used to treat this condition, but people often do not respond even to larger doses of the vitamin. Other vitamin D derivatives, dihydrotacbysterol (DHT) or calcilriol (Rocaltrol), are more effective and are used as the treatment for people who do not respond to plain vitamin D.

Conditions associated with low blood levels of phosphate, such as Fanconi’s syndrome, are treated with vitamin D as well. Vitamin D can help to restore normal phosphate levels by increasing absorption from the intestine.

There is some interest in the use of derivatives of vitamin D to treat psoriasis. A topical synthetic compound with a chemical structure similar to calcitriol called calcipotriene is available as a prescription ointment (Devonex) and is helpful for some.

Vitamin D, along with calcium, is frequently recommended to help stop the bone loss of osteoporosis. A supplement with 400 IU of vitamin D and 1 to 2 g of calcium is appropriate and has been shown to help slow down the loss of bone mass and decrease fractures due to weak bones in elderly women. Giving the active form of the vitamin, calcitriol, may work better if bone loss is severe. The best advice is to try to build and maintain bone mass with exercise and good dietary calcium and vitamin intakes prior to menopause. At menopause, calcium supplements with vitamin D are a good idea.

UNSUBSTANTIATED CLAIMS

We cannot recommend that you take this vitamin for acne, aging symptoms, alcoholism, allergies, arthritis, backache, bedsores. broken bones, bronchitis, burns, cancer, canker sores, carbuncles, cataracts, the common cold, constipation, cystic fibrosis, cystitis, diabetes, eczema, emphysema, epilepsy, eyestrain, fatigue, fever, gallstones, glaucoma, herpes simplex, herpes zoster, high cholesterol, jaundice, leg cramps, liver cirrhosis, meningitis, osteoporosis. pyorrhea, rheumatic fever, sciatica, sleeplessness, stress, tuberculosis, virginities, or worms.

AVAILABILITY

Vitamin D, at a dose of 400 IU, is an ingredient of virtually every multivitamin formula. Pure vitamin D products are available in strengths of 400 IU to 1,000 IU per tablet, Ergocalciferol drops, capsules, tablets, and injection dosage forms are also available

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DEFICIENCIES

About 15 percent of Americans, mostly infants and children, get less than the RDA value for vitamin A. Fortunately, the average person has about a two-year supply of vitamin A in their liver, so you have to eat a vitamin A-deficient diet for many months before symptoms will develop.

Deficiency Symptoms

Mild vitamin A deficiency may be easily overlooked. Dry, rough skin is common. Sometimes the skin can crack and may even become infected. The infection develops because cracks and rough areas in the skin leave openings for microorganisms to enterr and because vitamin A is needed for a strong immune response.

The most recognizable sign of vitamin A deficiency is night blindness (difficulty seeing at night or in low light). This is followed by further damage to the cornea in the form of a condition called xerophthalmia. If left untreated, severe vitamin A deficiency can lead to permanent blindness. Vitamin A deficiency is leading worldwide cause of blindness in childhood and is an enormous problem in many developing countries.

People who are deficient in vitamin A have an increased susceptibility to respiratory infections because of changes in the cells that line the respiratory tract. Because of their depressed immune response, deficient children develop more severe forms of common childhood diseases. And as mentioned earlier, measles can be lethal in a vitamin A-deficient child.

Other possible effects of vitamin A deficiency include slow growth, thickening of bone, kidney stones that originate with changes in some of the cells that line the kidney tubules, diarrhea, and reduced production of steroid hormones in the body. Steroids are produced by the adrenal gland and are a part of your natural response to stress and your immune function. Failure to make these important hormones will leave your immune system in a less-than-ideal slate. Damage to hearing, taste, and smell, nerve damage, and reduced sweat gland function may also occur.

It is possible to measure vitamin A in your blood, but the results of this test are difficult to interpret because of the large amounts that are stored in the liver. Repeatedly low blood value are a direct indication of a severe vitamin deficiency that demands immediate attention.

Toxicity

Adults may develop symptoms of vitamin A toxicity after taking more man 50,000 IU a day for long periods of time or after taking a single dose of 300,000 IU or more. Infants given 7,500 to 15,000 RE (25,000-50,000 IU) of vitamin A for thirty days have developed toxicity symptoms. In children, vitamin A toxic has usually been caused by an overzealous parent giving excessive quantities of supplemental vitamin A. Infants and children who are given 6,000 RE (20,000 IU) of vitamin A a day and who are not deficient are likely to develop overdose symptoms after several months.

Vitamin A overdose is characterized by vomiting, fatigue, swelling due to fluid accumulation, hydrocephalus (water on brain), and headache (caused by excess fluid in the skull, resulting in increased pressure on the brain). Vitamin A overdose has, in some cases, been misdiagnosed as a brain tumor. Other symptoms of overdose are liver and lymph gland enlargement, difficulty sleeping, joint pains, constipation, and rough skin. The effects of an overdose of vitamin A will usually reverse themselves after you stop taking the vitamin.

Since the body will convert as much carotenoid to retinol as it needs, it is possible to have excess unconverted carotene in the blood. A very high concentration of unconverted carotenoids in the blood is known as hypercarolenosis and can cause a yellow discoloration of the skin. This condition has been confused with jaundice, but the two are not related. Hypercarotenosis is unsightly but usually not dangerous.

Toxicity and Pregnant Women

Pregnant women taking excess vitamin A risk bearing a child with birth defects because of the action of the vitamin on the developing fetus. Some of the possible defects are urinary tract malformations, hydrocephalus, and bone deformities. If you are pregnant, do not exceed your doctor’s recommendation for any vitamin or drug, including vitamin A. Current recommendations are to take no more than 10,000 IU per day during pregnancy, and prenatal vitamins contain no more than this amount. But vitamin supplements containing up to 50,000 IU per capsule are readily available, so be careful when selecting a product.

Interactions

Vitamin A can interact with corticosteroid-type drugs, oral contraceptives, calcium, zinc, and mineral oil. It can also interfere with certain blood tests.

Therapeutic Uses

Vitamin A supplements may be given to counteract any of the standard symptoms of vitamin A deficiency reviewed earlier in the profile. However, such symptoms will not be alleviated by viamin A unless they are, in fact, caused by vitamin deficiency.

Antioxidant Uses

Plant carotenoids are excellent free-radical scavengers and quenchers of singlet oxygen. As such, they play a role in protecting our cells against oxidative damage and presumably help protect us from a number of chronic diseases linked to free-radical damage.

Measles

As discussed earlier, measles can be life-threatening if the child deficient in vitamin A. It has been recommended that the vitamin A status of all seriously ill patients with measles be checked and a high-dose supplement given if needed. A program of pro¬viding vitamin A supplements to children in some developing countries has lowered the infant death rate due to infections.

Cancer Prevention

Animals deficient in vitamin A get cancer more often and their tumors spread more quickly than animals without this deficiency. There is evidence that the same thing holds true for people: Those who are deficient in vitamin A may be at an increased risk of developing cancer, and individuals who do get the disease may find that their cancer spreads more quickly. Low vitamin A intake from vegetables is directly related to an increase in cancer of the lung, bladder, and larynx. However, it is not know; whether the protective effect of vitamin A can be attributed to beta carotene, other plant carotenoids, retinol, or some other component of green and yellow vegetables. Our best advice is to eat plenty of vegetables, as high vegetable intake is consistently associated with lower risk of cancer.

Retinoic acid is me form of vitamin A required for norm cell differentiation and thus cancer prevention. Unfortunately, it is metabolized too quickly and is too toxic in high doses to be practical for therapeutic use in cancer treatment. Other synthetic derivatives of retinoic acid (called, as a group, retinoids) show some promise and are under investigation.

Treatment of Acne

One of the symptoms of vitamin A deficiency is acne like condition. This observation led to the use of vitamin A capsules as an acne treatment in the 195s and 1960s and consequently to the discovery that high doses of vitamin A are toxic. After several decades of using vitamin A capsules to treat acne, the consensus is that the treatment is only marginally effective and carries a significant risk of toxicity.

In the 1970s retinoic acid applied to the skin became popular as an acne treatment, and it is still used today. Topical retinoic acid appears to reduce the plugging of sebaceous (oil-producing) glands. Plugged sebaceous glands can become infected and turn into pimples. Retinoic acid also mildly irritates the skin and causes peeling, which also helps to free plugged sebaceous glands.

Retinoic acid cream or lotion is not the ideal treatment. It can take months for the treatment to begin working, and it is irritating to the skin. In the search for more potent and less toxic retinoic acid derivatives, researchers have discovered several that can be taken by mouth without the usual adverse effects. isotretinoin, or 13-cis-retinoic acid, has been of some benefit to people who suffer from the most severe form of acne and who have not responded to other forms of treatment. These retinoic acid derivatives are strong teratogens (they cause birth defects), and patients on the drug must take steps to make sure they do not get pregnant.

Treatment of Psoriasis

Several retinoic acid derivatives are used with some success to eat psoriasis. These drugs are available only by prescription and carry a significant risk for causing birth defects if taken during pregnancy.

NSUBSTANTIATED CLAIMS

We cannot recommend that you take this vitamin to treat alcoholism, allergies, angina pectoris, arteriosclerosis, arthritis, asthma, ad breath, broken bones, bronchitis, canker sores, cataracts, colitis, the common cold, constipation, cystitis, diabetes, diarrhea, double vision, ear infections, emphysema, epilepsy, eye-strain, fever, flu, gout, hair problems, hay fever, headache, heart attack, heart failure, hemorrhoids, hemophilia, hepatitis, infertility, jaundice, kidney stones, learning disabilities, liver cirrhosis, meningitis, mononucleosis, muscular dystrophy, nail problems, osteomalacia, prostate trouble, psychosis, sinusitis, stroke, swollen glands, thyroid disease, tuberculosis, vaginitis, varicose veins, or worms.

Availability

Despite its toxicity, vitamin A can be obtained in any strength without a prescription. Attempts by the FDA to attempt to limit the doses that can be purchased without a prescription have been met with fierce opposition by nutritionally oriented consumer groups.

We do not recommend taking more than 10,000 IU a day unless you are under the guidance of a licensed health care professional who is expert in therapy with vitamin A. This is especially true if you are or might become pregnant. Do not lake vitamin A doses over 10,000 IU per day if you are pregnant or if there is any chance you may become pregnant.

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