Vitamins – How Much is Enough?
By Jon B. Pangborn, PhD
The controversy over nutritional and medical uses of vitamins continues to find its way into the news. Recently, Chicago was the location for a meeting of national scope that focused mostly on vitamin toxicities, rather than beneficial effects. Health food store operators may of may not be properly informed about the vitamin products they sell. Many consumers have the mistaken impression that, "If a little is good, then more must be better." Vitamin formulators and suppliers are partly to blame because they persist in the competitive game of one-upmanship by putting more and more in the tablet or capsule so as to attract the buyer. In fact, too much of a vitamin can produce toxicity.
The food and nutrition experts at the National Research Council – National Academy of Sciences (NAS) haven’t helped much with their "Recommended Daily Dietary Allowances." Those infamous RDA’s were not formulated on hard information about metabolic requirements. The US RDA for vitamin C, for example, is 60 mg as that is the amount observed to prevent scurvy. In Great Britain a lesser amount is recommended. Last year the US committee of experts recommended lowering the RDA for vitamin C. A recent article in The New England Journal of Medicine (M. Levine, April 3, 1986, 892-902) points out metabolic requirements for vitamin C that were never considered (or known?) by the experts; and we still don’t all the uses of ascorbate in our bodies.
Five years ago the NAS experts were commissioned to rethink the nutritional RDA’s in a study paid for by the National Institutes of Health (NIH). Their most recent effort (including lowering the vitamin C RDA) was rejected by the NAS because the study results could not be scientifically defended (Science, Vol. 230, October 25, 1985, 420-421).
It is important to realize that many individuals require more than the RDA of vitamins for optimal physical and mental functioning. Temporary or acquired illness, infections, toxic exposures, inadequate rest or diet, increased physical activities, and metabolic impairments all can cause increased vitamin needs. In some cases, chemical form of a vitamin supplement is far more important than quantity. Vitamin powders in gelatin capsules are the most easily absorbed. Some tablets are so tightly packed and "glued together" with binders that individuals with gastrointestinal dysfunctions (who probably need the vitamins) can not absorb them.
For general nutritional purposes, about 5x to about 20x the RDA for water-soluble vitamins can be beneficial and is tolerated once a day with a meal with no adverse effects. For medical purposes, therapeutic doses of water-soluble vitamins may be in the range of 25x to 250x the RDA.
Lipid-soluble vitamins A, E, and especially D should not be used at high levels. Hypervitaminosis D might occur with continuing supplementation of D at only 3 to 5x the RDA of 400 IU/day.
When high megadose levels are needed to gain therapeutic benefit, there almost always is something gone awry with the individual’s gastrointestinal function, renal function or metabolism. That individual should be under medical supervision and his or her pathological condition be diagnosed and treated. Usually it is possible to correct or improve physiological functioning and provide reasonable nutritional supplementation later.
Article from NOHA NEWS, Vol. XII, No. 1, Winter 1987, pages 2-3.