The Food and Nutrition Board along with the Institute of Medicine have worked together to provide reference tables for all micronutrients in our diet. What are micronutrients, you ask? It’s those nutrients that we need in our diet in small amounts, hence the name ‘micro’. If you still have no idea what I’m talking about then it’s things like the entire B-vitamin complex (thiamin [B1], riboflavin [B2], niacin [B3], vitamin B6, folate, biotin, pantothenic acid, and vitamin B12), vitamin C and vitamins A, D, E and K. This also includes several key minerals we hear a good bit about such as calcium, sodium, chloride, iron, magnesium, copper, zinc, etc. A full report of these values can be located at the National Academies of Science website (http://www.nap.edu). Collectively, this report is referred to as the Dietary Reference Intake (for short it’s DRI). This system has been put into place to provide recommended intakes of the micronutrients to prevent deficiency. As you have noticed, the Dietary Reference Intakes (DRI) consists of four categories: a) the RDA or Recommended Daily Allowances, b) AI or Adequate Intake, c) EAR or Estimated Average Requirement and d) UL or Tolerable Upper Limit. Why not just use one? The easiest answer is that a constant power struggle exists so they can’t settle on one. A more thought-out reason is because these values exist for EVERYONE. While healthy, normal folks like us make up an overwhelming number of people who use them, physicians, dietitians, etc. can also use them for many specialized sick and diseased populations.
The Recommended Daily Allowances or RDA were developed to provide a dietary intake level that is sufficient to meet the requirements for 98% of the healthy individuals. So the shortest answer to the question lies with the RDAs. Make sure your daily diet is providing 100% of posted RDAs and within a 98% chance you are going to be OK. What if no RDA has been or can be established? Well this is where the others come into play. Estimated Average Requirement or EAR has been established to satisfy the needs of 50% of individuals within a particular group (could be pregnant women, ethnic group, aging, children, etc.). Adequate Intake or AI is used when no RDA has been determined. Upper Tolerable Limit or UL is the known maximum recommended intake that individuals could consume without the risk of adverse effects. So there you have it. How you decide to use them is up to you. Personally I would go with the RDAs. If you are an exercising individual that lives a fairly busy life and you may not exactly eat a great diet day in and day out, I would find a multi-vitamin you like and take it every day with food. The downside of not having enough is much worse that having too much. Overall the DRIs vary among gender, age, etc. and represent what is needed for normal individuals. As physical activity or health status change, so do your daily requirements of vitamins and minerals.