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Monday, May 19, 2008

VITAMIN DEFICIENCIES 2

Vitamin B6 deficiency is seen occasionally in individuals who eat very few plant foods. Seizures occur in babies fed formulas deficient in B6. This has especially been a problem when a relatively high kidney excretion develops during pregnancy, while a mother was given high dose supplements. A number of drugs interfere with vitamin B6 utilization, such as isoniazid, used in the treatment of tuberculosis. Eating a natural varied diet, it is not difficult to get plenty of pyridoxine. It is the vegetable source of vitamin B6. Scurvy is another vitamin deficiency with worldwide prevalence as well as a colorful history. This condition is caused by a deficiency of ascorbic acid, also called vitamin C. It was a common cause of mortality in sailors during the fifteenth and sixteenth centuries. James Lind, a British naval surgeon, developed a simple cure in 1747 by giving the sailors two oranges and one lemon every day. Their swollen gums, weakness, and bleeding tendencies responded dramatically, giving rise to the nickname, “Limeys.” In more recent times scurvy appears more commonly in alcoholics, food faddists, and the impoverished elderly living on a grossly unbalanced diet.
The principal manifestations of scurvy are hemorrhages in the skin, swollen and bleeding gums, aching muscles, fatigue, and emotional changes. These symptoms appear after two months of depletion. Appearing occasionally in children, scurvy produces tenderness and swelling in the legs. Extreme pain may be present. Finally, after the teeth erupt, swollen gums and bleeding develops. Skeletal changes show signs of growth retardation. In some cases of a vitamin-D deficiency syndrome, rickets, may co-exist.
A carefully taken feeding history is helpful for the diagnosis of infantile scurvy. After 46 months of age any infant fed solely with the bottle, using only boiled cow’s milk or a milk substitute, may develop this disease. Fresh orange juice or another dietary source of vitamin C is rapidly curative. Extremely high supplements of ascorbic acid are seldom necessary. They may produce an abnormal dependency, based on the development of increased excretion originating in the kidneys to compensate for this superabundance.
Large doses of vitamin C can also inactivate vitamin B12. That, at times, unfavorably affects reproduction. Vitamin A is primarily manufactured by the conversion of dietary betacarotene into the active form, retinol. One of the first symptoms of vitamin A deficiency is inability to see in reduced light (night blindness). A later change in the eye is the presence of dryness, xerophthalmia. The conjunctiva becomes opaque, the secretion of tears decreases, then a sticky secretion appears over the cornea, called the Bitot spot. This mark has the appearance of a flake of meringue. Further destruction of the cornea may occur, leading eventually to blindness.
In treating the acute disease, a supplement of vitamin A is recommended. The prevention of deficiency using a balanced diet containing green and yellow vegetables, fresh fruit, and vitamin-supplemented milk is entirely adequate. Green and yellow foods such as carrots, cantaloupe, squash, and dark green leafy vegetables are considered excellent sources for this vitamin.
A high intake of carotene appears in adults using carrot juice or a similar food concentrate excessively. Carotenemia may color the skin, but should not be confused with jaundice. It is considered harmless and will subside when the carotene intake is reduced. Hypervitaminosis A, on the other hand, can produce an acute toxicity. In infants, it presents as drowsiness, vomiting,
and other signs of increased intracranial pressure. Adults commonly develop a headache within hours after any injection of a toxic dose. Blurred vision, nausea, vomiting, or drowsiness may also develop. The skin peels and hair loss occurs. With chronic ingestion of high doses, liver changes resembling cirrhosis are seen. Psychiatric side effects manifest themselves, but prognosis is good when vitamin A ingestion ceases.
Vitamin E is the common name of a group of related fat-soluble vitamin, called tocopherols. They vary in their potency, with the alpha form being thought most active. A number of animals develop a Vitamin E deficiency syndrome, with deterioration in the muscle fibers, impaired reproduction, or anemia. Clinically, these insufficiencies are rare in adults. When the diet contains enough polyunsaturated fatty acids, plenty of dietary vitamin B is usually available. Unfortunately, optimistic expectations of many researchers have been disappointed in spite of the literature proclaiming the miracleworking powers of this vitamin. We do not know for certain whether vitamin B supplementation can favorably affect physical endurance, cardiac status, sexual potency, or longevity in individuals with normal blood levels of Vitamin B (tocopherols).
A number of vitamins affect the production of blood or its proper coagulation. Vitamin K is present in most edible vegetables, particularly the green leafy ones. A similar vitamin is also produced by intestinal bacteria. The gradual accumulation of vitamin K levels in a newborn baby explains easily why ancient recommendation for an eight-day circumcision was made to the Jews. Hemorrhagic disease of the newborn as well as in adults is prevented by proper blood levels of this vitamin. Vitamin B12, folic acid, and iron are also closely related to blood production and have been discussed in Chapter 4, dealing with the circulatory system.