To Your Health

Why are the amounts of vitamins in most pills so much higher than the RDA?

Q. Why are the amounts of vitamins in most pills so much higher than the RDA? Isn't more than 100% of the RDA wasted?

A. The use of vitamins in amounts considerably greater than the recommended daily allowance, or RDA, is known as "megavitamin therapy." There are several reasons for making available a vitamin pill with more than 100% of the RDA. For some clinical nutritionists, even the concept of a "recommended daily allowance" by whatever name (RDA. USRDA. RDI, DRI, %DV, etc.) is flawed because these recommendations cannot be applied to individuals.

Vitamins are used in the body as necessary helpers, or "cofactors," for the various enzymes that convert food into energy and carry out a multitude of other essential metabolic tasks. In order to do this, a particular enzyme will bind to specific vitamin cofactors. Flooding the body with an excess of vitamin cofactors may increase the ability of the enzyme and cofactor to bind together and function properly. About 50 diseases are known to result from genetic mutations that reduce the ability of an enzyme to bind to its vitamin cofactor, and it is likely that there are hundreds if not thousands that are yet unknown.

A specific genetic mutation may be present in less than 1% of the population, but there are so many genes that every person has at least one mutation that will affect their nutritional requirement for a nutrient. The amount of that nutrient supplied by diet alone will not fully satisfy a requirement that may be five to 50 times normal, and health will be compromised to the extent that the requirement is not met. Given the enormous safety factor of water-soluble vitamins, a vitamin pill with 50 times the normal amount of these vitamins is likely to help some people and not harm anyone.

For megavitamin therapy to be a reasonable choice, the safety factor of the nutrient used must be very large. You have probably noticed that only water-soluble nutrients such as B-vitamins, vitamin C, acetyl L-carnitine, lipoic acid, and such like are normally supplemented in extremely large amounts. Many nutrients, specifically fat-soluble vitamins, most minerals, fatty acids, and amino acids, have such low safety factors that supplements in the range of five to 10 times the RDA should only be done under the supervision of a trained professional. One of the B-vitamins, folic acid, is limited by federal law to about twice the RDA, because it can mask the usual signs and symptoms of vitamin B-12 deficiency. Vitamin B-12 deficiency can be life-threatening if left untreated, plus some women find that large amounts of folic acid provoke some breast tenderness.

There are also unethical reasons for vitamin products to have very high amounts of selected vitamins. Some supplement producers "pad" their product labels with very large amounts of inexpensive vitamins and then skimp on the amounts of costly vitamins. When a supplement producer sees that biotin costs 1,000 times more than riboflavin, there is a great temptation to use plenty of riboflavin but the smallest amount of biotin that can be managed. Thus it pays to buy from a reputable company that bases the amount of each vitamin on scientific research rather than on economics alone.

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