The Hazard of Hypervitaminosis

Hundreds of millions of people benefit from consuming the recommended daily intake of the thirteen vitamins required for human health. (There are another 16 substances that once were thought to be vitamins, and that are still sometimes advertised in supplements, but which turned out actually to be manufactured by the body itself.) Just a few hundred thousand people every year suffer diseases caused by over-consumption of vitamins, also known as hypervitaminosis, but the consequences can be serious.

• Vitamin A. The effects of overdosing vitamin A are especially well known because many of the treatments for severe, cystic acne are based on vitamin A. About 10% of women who take an overdose (more than 50,000 IU) of vitamin A during the first trimester of pregnancy bear children who do not have completely formed brain tissue. A smaller percentage of users of acne drugs based on vitamin A develop "polar hysteria," causing extreme mood swings and resulting in a risk of suicide. Smaller overdoses of this fat-soluble vitamin can cause shedding of skin and nails and nosebleeds.

READ Vitamin A and Its Effects on Immune System

• Vitamin B1 (thiamine). Vitamin B1 is the water-soluble vitamin famed as a cure for the central nervous system disorder beriberi. Excesses of vitamin B1 can also cause neurological symptoms such as unusual gait and slurred speech. Hypervitaminosis B1 is most common in gastric bypass patients who take too many B vitamin supplements.
• Vitamin B3 (niacin) overdose causes facial flushing. People who have rosacea must be careful not to consume too much niacin. As little as 500 mg of time-released nicotinic acid for two months has been known to cause hepatitis (although this complication is more likely at dosages of 3,000 mg a day and higher). Excessive consumption of niacin can also cause dry skin, diabetes, blurred vision, and headaches.
• Vitamin B6 (pyridoxine) overdoses (500 mg a day and more for several weeks or longer) sometimes cause neuropathy, loss of nerve function in the fingers and toes.
• Vitamin C is a gastric irritant in doses of more than 2,000 mg a day. Some vendors of vitamin C for cancer will tell their customers that they "need" to induce diarrhea to help treat cancer; but the only way to get enough vitamin C into the bloodstream to fight cancer is by intravenous drip. People who have iron overload disease should not take vitamin C at the same time that ehy eat a food that is high in iron, because vitamin C increases the body's absorption of iron.

READ Vitamin C and Its Effect on Immune System

• Vitamin D in tremendous excess—over 50,000 IU a day—can cause an even worse form of osteoporosis than it is taken to prevent.
• Vitamin E in overdose, over 2,000 IU a day, can cause thinning of the blood and easy bruising.
• Vitamin K in any dosage can interfere with older drugs still used as blood thinners, such as Coumadin and Plavix.

There is nothing wrong with taking the daily recommended intake of vitamins and more. But "more and more" is not necessarily better. Never take more than 1000% of any nutrients unless you are taking the form of that supplement in a dosage recommended by your physician for the treatment of a specific health condition.