In fact, the RDAs are highly controversial, and many scientists insist that current RDAs are too low. Take vitamin C, for example. A 1996 study pegged the optimal daily dose closer to 200 mg. If you're pregnant, too much or too little can cause birth defects. B-3 Doses over 2 grams may cause liver damage.
Individual thresholds vary.
Which brings us to the alleged hazards of high dosages. Supplementing your vitamin intake up to three times the RDA is generally safe. Insurance formulas, a.k.a. Look for brands that deliver at least 100 percent of the RDA in one or two pills. Insurance formulas are convenient, economical, and, compared with single-nutrient supplements, better for you.