Vitamins: A Few Reminders

By Salvador Quiroz

Vitamins are not nutrients in themselves, as many people think but organic compounds whose role is to help in the absorption and utilization of foodstuffs. Without them, we’d die, but such small amounts are usually required that deficiency states are now very rare. Indeed, in first-world countries, vitamin excess disorders are more common.

Excessive consumption of vitamins can occur due to unusual dietary practices or, more commonly, deliberate ingestion. Vitamins, in general, are divided into the water-soluble kind, and the lipid or fat-soluble kind. Water-soluble vitamins are eliminated in the urine, so toxicity is rare. But fat-soluble vitamins—vitamins A, D, E, and K—are stored in the body, so toxicity may result.

Vitamin A and Carotenes—Carotenemia results from excessive ingestion of principally carrots and other colored fruits and vegetables, but it only causes harmless yellowing of the skin.

Chronic toxicity from hypervitaminosis A occurs after ingestion of 25,000 units or more daily for long periods. It’s characterized by bone and joint pain, hair loss, dryness and fissures in the lips, weight loss, low-grade fever, itchy skin, and an enlarged spleen. Relief is prompt upon discontinuation of the vitamin.

Vitamin E—Relatively large doses of vitamin E have been taken by some for extended periods without apparent harm. But in others, a state of malaise, gastrointestinal complaints, headaches, and possibly hypertension have occurred. Vitamin E can counteract vitamin K absorption and prolong blood-clotting time in patients taking anticoagulants (blood thinners).

Vitamin K—Large amounts of vitamin K can block oral anticoagulants’ effects. Some think it can even induce a greater tendency to form blood clots, dangerous for embolism-prone persons.

Vitamin D—Vitamin D regulates the absorption and the use of calcium in our body. Hypervitaminosis D can lead to hypercalcemia (high levels of calcium in the blood), which could lead to cardiac arrest, bone disease, and the formation of kidney stones.

Pyridoxine—Most adults can consume up to ten times the RDA of 2 mg pyridoxine per day without adverse effects. Excessive amounts, however, may cause an irregular gait, numbness around the mouth, clumsiness, and loss of balance. A dose of 25 mg per day can counteract some medications used to control Parkinson’s disease and/or epilepsy.

Vitamin C—Use of vitamin C in large amounts (one gram or more per day) to prevent colds is unwarranted and probably unwise. Long-term use of ascorbic acid in these doses can interfere with the absorption of vitamin B12, enhance estrogen levels in women, produce high levels of uric acid, and predispose one to the formation of oxalate kidney stones.

Niacin—This vitamin causes release of histamine, which can cause severe flushing, itching, gastrointestinal disturbances that mimic gastritis, and may aggravate asthmatic conditions. It can also increase pyridoxine levels in blood.

If we are going to take vitamin supplements, let’s be informed and do it reasonably.

Dr Salvador Quiroz, Internal Medicine and Kidney Disease, Hospital H+, Graduated from the Mayo Clinic. Tel: 152 2329.

 

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