Ask a Scientician

About a week ago Janelle posted this question:

How do they come up with the recommended daily allowance for the various vitamins and minerals?

I initially tried doing some research and didn’t find much in the way of an interesting answer. Unfortunately in the intervening time I haven’t been able to expand my research on the subject. As a result this is going to be a short answer that mainly comes from Wikipedia.

The RDA was developed during World War II by Lydia J. Roberts, Hazel K. Stiebeling and Helen S. Mitchell, all part of a committee established by the U.S. National Academy of Sciences in order to investigate issues of nutrition that might “affect national defense.”

The allowances were meant to provide superior nutrition for civilians and military personnel, so they included a “margin of safety.” Because of food rationing during the war, the food guides created by government agencies to direct citizens’ nutritional intake also took food availability into account.

The Food and Nutrition Board subsequently revised the RDAs every five to ten years. In the early 1950s, USDA nutritionists made a new set of guidelines that also included the number of servings of each food group in order to make it easier for people to receive their RDAs of each nutrient.

For the current recommendations the following guidelines are used:

• Estimated Average Requirements (EAR), expected to satisfy the needs of 50% of the people in that age group.
• Recommended Dietary Allowances (RDA), the daily dietary intake level of a nutrient considered sufficient to meet the requirements of nearly all (97–98%) healthy individuals in each life-stage and gender group.
• Adequate Intake (AI), where no RDA has been established, but the amount established is somewhat less firmly believed to be adequate for everyone in the demographic group.
• Tolerable upper intake levels (UL), to caution against excessive intake of nutrients (like vitamin D) that can be harmful in large amounts.
• The RDA is used to determine the Recommended Daily Value (RDV) which is printed on food labels in the U.S. and Canada.

This does not really answer the question about how the regulations were developed, but covers the history of the way we came about the guidelines.

I can follow up with information about specific nutrients if desired, but this is well out of my area of expertise and requires some research. I dislike having Wikipedia as my sole reference, but it’s a place to start.