High quality, hypoallergenic supplements are available with a little research. If you are unhappy with one product, try another, write to supplement companies about what's in their formula, or ask a trained nutrition-oriented practitioner.
Nutrients offer safe and effective treatment for many conditions. But don't assume that the larger the dose, the better they are. All substances, even water, can be harmful at high enough
levels. Some vitamins and minerals cause acute poisoning taken in massive amounts. Lower, but still excessive, levels taken for weeks, months or even years may lead to chronic toxicity.
It is difficult to determine vitamin and mineral toxicity levels partly because it's unethical to perform these kind of experiments on people. We usually rely on animal research while taking into account physiological and biochemical differences between us and the species
tested. (Many people consider it unethical to conduct studies on animals as well).
Occasionally information is collected when a population inadvertently consumes too much of a nutrient. For example, boron overdose was studied early in the century when sodium borate was a common food preservative (5). Although rare, individual cases of nutrient poisoning also appear in the medical literature. All of this data helps direct where toxicity levels should be set.
We also need to remember that nutrients come from a number of sources besides supplements and foods. Fluoride is added to our water, toothpaste, and is used in dental care. Vitamin D is provided mainly by sun exposure and is artificially added to milk. Iodine,
initially added to salt to prevent goiter, is now found in contaminated dairy products, breads and pastries, some artificial colorings, some produce, fish, and seaweed. There are now reports of excess iodine causing goiter in England, Wales, Central China, Australia, Japan, and the U.S. (6,7,8). So toxicity levels may be lower than expected if you are getting a particular nutrient from many sources.
Generally speaking, water soluble vitamins specifically the Bs and C are relatively nontoxic. The fat soluble vitamins including A, D, E and K have more defined levels of toxicity. There are, of course, exceptions. There have been no reported cases of toxicity using vitamin E. Whereas the odd case of problems with vitamin B6 has occurred. Side effects from too much B6 typically involve neurological symptoms such as tingling in the limbs and an unsteady gait (9).
When megadoses of vitamins and minerals are used nutrients begin to act in a pharmacological rather than a physiological manner. This type of prescribing is best left in the hands of health care experts. Also, don't assume that every mineral and vitamin needs to be supplemented. Iron, although found in many multiple formulas, should only be supplemented where indicated such as iron deficiency anemia. Excess iron over a period of time may increase your risk of heart disease, cancer, SIDS, and diabetes (10).
The science and art of nutrition is complex. There are many factors to consider particularly when taking vitamins and minerals supplements. Be smart. Use the services of a well trained and credible nutritionist or other knowledgeable health care provider who can show you how to take nutrients safely and effectively.
- Subcommittee on the Tenth Edition of the RDAs, Food and Nutrition Board, Commission on Life Sciences, National Research Council. Recommended Dietary Allowances (10th ed). Washington, DC: National Academy Press, 1989.
- Diplock AT. Antioxidant nutrients and disease prevention: an overview. American Journal of Clinical Nutrition 1991;53: 189S-93S.
- Czap A. Is your polyplasdone kollidon with your solka-floc? Townsend Letter.
- Brandstetter RD, Conetta R, Glazer B. Lactose intolerance associated with Intal capsules (letter). The New England Journal of Medicine 1986;315(25): 1613-14.
- Nielsen FH. Facts and fallacies about boron. Nutrition Today 1992 May/June;27(3): 6-12.
- Pennington JAT. A review of iodine toxicity reports. Journal of the American Dietetic Association 1990;90: 1571-81.
- Mu L, et al. Endemic goitre in central China caused by excessive iodine intake. The Lancet 1987, August 1: 257-8.
- Barker DJP, Phillips DIW. Current incidence of thyroitoxicosis and past prevalence of goitre in 12 British towns. The Lancet 1984, September 8: 567-70.
- Dolphin et al (eds). ®)9¯Vitamin B6: Pyridoxal Phosphate.®):¯ Volume 10: John Wiley & Sons, 1986, pg 595.