The Recommended Daily Allowance (RDA) and Recommended Daily Intake (RDI) numbers you see on a regular basis are largely misunderstood. They’re very old guidelines created as minimum recommendations to avoid nutritional diseases like scurvy and rickets. Unfortunately, they don’t give you a lot of information about what constitutes a healthy amount of micronutrients for you. Although the RDAs have been revised occasionally, they still essentially act as minimum recommendations. They also don’t tell you anything about what you need during pregnancy, with illnesses, for times of stress, athletics, or a whole host of variables that separate your nutritional needs from the nutritional needs of your neighbors. Consider the case of Vitamin E. The RDA for Vitamin E is only about 15mg/day, or about 22IU. Yet one study found that an amount of 100-200mg/day helped endurance athletes. Another study found those who took 400IU of Vitamin E daily showed a 41% reduction in heart disease, a 22% reduction in death from cancer, and a 27% decrease in all-cause mortality.(i) It’s unlikely that you’ll get these ideal levels of vitamin E without supplements. If those numbers seem a little “out of whack” to you, then you know why RDAs and RDIs aren’t always effective measurements of the vitamins and minerals you need in your diet.
- Losonczy KG, et al, Vitamin E and vitamin C supplement use and risk of all-cause and coronary heart disease mortality in older persons: the established populations for epidemiological studies of the elderly, Amer J Clin Nutr. 1996; 64; 2:190-6.