In the supply catalog, vitamin A has a poison warning label on it. When it arrives we have to handle it very carefully. However once we mix it with filler, like cornstarch, so it is not overpowering, it becomes an essential nutrient. Too much causes liver abnormalities and birth defects, not enough causes night blindness, reproduction problems, immune system dysfunction, and other prob- lems. How do you know what is the “right” amount for you? Today, the US government’s Reference Daily Intake (RDI) is 5000 IU, 1

but is this the right amount for you? To get RDI’s, the government relies on a consensus of scientific opinion to gauge the quantities necessary to assure the performance of recognized and essential physiological functions, but one problem with this approach is: we don’t know everything about the human body. Scientific consensus is capricious; it changes as we learn more. For instance the 1968 RDA for vitamin C was 60 mg. In 1974 that changed to 45 mg., but in 1980 it went back to 60 mg. 2

What if tomorrow scientists find out that lots more would have been better? In fact there are well-documented benefits of nutrient quantities above the RDI for folic acid, vitamin B6, vitamin B12, selenium and chromium, according to Vitamin and Mineral Safety, 2nd Ed. (VM Safety3 ).

We should ask ourselves: Is there a better yardstick to measure our optimal intake, than RDI’s? Scientists may argue incessantly over “optimal”, but there is much more agreement about “too much”. Many studies vary the dosages of nutrients, and often note when adverse effects appear. The safe upper limit is therefore somewhat apparent, and government agencies are very interested in that in order to protect consumers. For instance the US Food and Nutrition Board (FNB) sets their upper limit of safety for vitamin A at 10,000 IU. The European Commission Scientific Committee on Food upper limit is also 10,000 IU. The United Kingdom Expert Group on Vitamins and Minerals Guidance Level is 5,000 IU. It should be noted that these are safe daily limits. Children in some parts of the world are given a 50,000 to 200,000 IU dose of vitamin A once every 3 to 12 months to treat and prevent deficiencies (VM Safety).