Vitamin B6 ( pyridoxine )

Pyridoxine (Vitamin B6) is an essential coenzyme for many, if not all, of the biochemical reactions involving amino acids, the individual substances that make up protein. These amino acids must be broken down, digested, absorbed, interconverted, and then taken up by the cells. Pyridoxine is required for all of these things to happen. One example is the requirement for pyridoxine in the conversion of the amino acid tryptophan to niacin. Pyridoxine also plays an important role in the body's metabolism of fats and carbohydrates. The synthesis of unsaturated fatty acids requires pyridoxine. Energy cannot be produced for the cells without the vitamin.

One of the first systems to suffer the effects of a deficiency is the nervous system. These effects are more pronounced and lingering in developing children and animals. The convulsions suffered by the infants fed pyridoxine-free formula would eventually have progressed to permanent mental retardation, or even death, had they persisted. The brain needs protein for development and function, and in a pyridoxine deficiency, the protein supply to the brain is severely curtailed.

A long-time pyridoxine deficiency can cause harm to dendrites, animal research has shown. Dendrites are the parts of nerve cells that carry impulses from one brain cell to another. When rats were fed diets severely deficient in pyridoxine, their dendrites shriveled up and became useless. The researchers admitted that the deficiencies were dramatically severe, but added that less severe deficiencies could have the same effect if continued for a long enough period.

A deficiency of pyridoxine interferes with the development of the entire organism, not only the brain. When pregnant animals are maintained on diets containing various levels of pyridoxine, the offspring of the deficient groups are small, sickly, and have impaired motor development. Interestingly, the animals whose mothers are fed diets containing four times the "required" or "adequate" amount of pyridoxine are substantially healthier and better developed than those fed the standard amount.

Pyridoxine deficiency impairs the immune response. During pregnancy, this deficiency reduces the size of the thymus gland - which is involved in the immune response -in both mother and fetus. A deficiency of pyridoxine before pregnancy can also impair the newborn's capacity to fight off disease.

Pyridoxine deficiency also impairs the function of the liver, and prolonged deficiency can cause permanent damage. Whether because of its role in liver function or its role in fat metabolism-probably both - a pyridoxine deficiency raises blood levels of cholesterol. In fact, animals maintained on such a deficiency, with one percent of their diet in cholesterol, will have higher-than normal levels of cholesterol in their blood. Animals maintained on pyridoxine-deficient diets also develop arteriosclerosis.

The standardly recognized symptoms of pyridoxine deficiency include greasy, scaling dermatitis around the eyes, ears, nose, and mouth, and in areas that frequently rub together, such as the inner thighs. Inflammation of the oral area, identical to that which occurs in other B vitamin deficiencies, is also possible. The neuromuscular effects-convulsions, nerve tissue degeneration-can occur in adults and children. Some people are born with a greatly increased need, or dependency, for pyridoxine. A fortunate few may be identified early enough to be treated and saved from mental retardation. Obviously, however, not all mental retardation is a result of pyridoxine deficiency.

Pyridoxine-deficient animals develop arteriosclerosis that is identical to the human disease. This is another one of those places where caution is well-advised before concluding the vitamin is either useless or omnipotent. No responsible physician or nutritionist would claim that pyridoxine deficiency is the cause of heart disease. There is simply too much evidence that our high fat and sugar diet and sedentary but competitive lifestyle are critically involved. Yet there is evidence that pyridoxine is also involved, and that supplying "adequate" amounts of the vitamin may be of help in preventing and treating the disease. But don't assume that someone can avoid heart disease simply by taking vitamin supplements. Such an assumption would be foolhardy.

Pyridoxine has a role in the formation of collagen. This role may apply to heart disease, because many doctors believe that the initial defect in heart disease is in the structure of the arteries, that the integrity of the vessels is damaged and that this lays the groundwork for later deposition of fat and minerals in the vessel. Some researchers believe that pyridoxine deficiency during pregnancy may cause this initial lesion, and that the generally poor nutritional quality of the average American diet perpetuates the deficiency and contributes to heart disease. There is enough evidence of the effects of maternal pyridoxine deficiency-and the prevalence of such deficiency is thought to be great enough-to require us to take this theory quite seriously.

There is a lot of evidence that suggests that pyridoxine is involved in cancer. In women with advanced cancer of the breast and other sites, there is biochemical evidence of a deficiency or increased requirement for the vitamin. Dietary pyridoxine levels in these women are large enough to maintain adequate concentrations in the body, yet there is still a shortage. The implication is that pyridoxine is somehow "used up" in the body's defense against cancer, or that the disease merely interferes with pyridoxine metabolism. In persons with Hodgkin's disease, biochemical signs of pyridoxine deficiency normalize when the disease goes into remission. The tantalizing question, and one that really has only begun to be tested, is whether supplementation with pyridoxine could have any effect on the course of the disease.

In at least one study, relatively low-dosage supplementation (twenty-five mg.) with pyridoxine slightly diminished recurrence of bladder tumors. When the people who didn't have recurrences during the first ten months of the study were eliminated from the calculations, the pyridoxine was found to have had a significantly stronger preventive effect than the conventional anticancer medication. Doctors theorized that the pyridoxine may have taken longer to take effect. This would be reasonable if the pyridoxine were actually strengthening the body's immune system.

Obviously, women taking oral contraceptives (and pregnant women) need to be extra careful they are getting enough pyridoxine, and that may not be possible without supplements. Pregnant women have been advised by many doctors to take vitamin-mineral supplements. A pyridoxine deficiency in pregnancy can have obvious symptoms to warn the woman, but it can also sneak up on her and go unnoticed until it is too late. One study measured the concentration of pyridoxine in the bodies of "healthy" pregnant women and found their vitamin status went lower and lower as the pregnancy progressed. The most rapid drop occurred during the period when the fetus was undergoing its most intense growth. This study also found that the higher the mother's pyridoxine levels before and during pregnancy, the higher the birth weight of their babies.

Mega doses of pyridoxine are not required for pregnant women to maintain adequate body concentrations of pyridoxine. In one study, ten mg. kept levels high throughout pregnancy. A supplement of this amount also resulted in high levels of the vitamin in the cord blood of the newborn babies.

All women should probably take extra care with this vitamin, since they tend to have lower concentrations in their bodies than men. This is most likely an indication of increased utilization and need.

Where is it found ?

The richest natural sources of pyridoxine include liver and other organ meats, whole-grain cereals, wheat germ, soybeans, yeast, peanuts, corn, and blackstrap molasses. Some fruits and vegetables are also good sources, including cabbage, bananas, potatoes, avocadoes, peas, and green peppers. Since pyridoxine is water-soluble and sensitive to light, many canning and processing procedures destroy substantial amounts of it. Vegetable sources of the vitamin should be eaten raw for maximum benefit.

There is some evidence that wheat bran may "soak up" some pyridoxine and cause it to be excreted. If you eat a lot of wheat bran, you should make sure you're getting enough pyridoxine, preferably at other meals than those at which you eat bran.

Although some of the best sources of pyridoxine are meats, a study of pyridoxine levels in vegans (people who eat no animal products at all) and meat-eaters found no significant differences between the two groups. Pyridoxine is available in supplements in a wide range of doses, from five mg. to more than 500 mg.

Who is likely to be deficient ?

Vitamin B6 deficiencies, although very rare, cause impaired immunity, skin lesions, and mental confusion. A marginal deficiency sometimes occurs in alcoholics- patients with kidney failure, and women using oral contraceptives. Many nutritionally oriented doctors believe that most diets do not provide optimal amounts of this vitamin.

How much to take

The most common supplemental intake is 10 to 25 mg per day; however, higher amounts (200 to 500 mg per day) may be recommended for certain conditions.

Side effects

Although side effects from vitamin B6 supplements are rare, at very high levels (200 mg or more per day) this vitamin can eventually damage sensory nerves, leading to numbness in the hands and feet as well as difficulty walking. Vitamin B6 supplementation should be stopped if any of these symptoms begin to develop.

Pregnant and lactating women should not take more than 100 mg of vitamin B6. For other adults, vitamin B6 is usually safe in amounts of 200 to 300 mg per day, although occasional problems have been reported in this range. Any adult taking more than 100 to 200 mg of vitamin B6 for more than a few months should consult a nutritionally oriented doctor. Side effects from vitamin B6 are dependent on the level of intake. No one should ever take more than 500 mg per day, even with clinical supervision.

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