What is RDA

Just What is RDA

RDA stands for Recommended Dietary Allowances. This was a norm established by the predecessor of what is now the United States Food and Drug Administration (FDA) during World War II, intended to provide guidelines for how much of certain nutrients a normal, healthy person required to stay fit and healthy -- an obvious concern in times of war. Bear in mind, these were tough days with many foods being scarce at best best due to the massive war effort, prompting many families to make sometimes drastic changes to their diets.

While food availability and nutritional habits changed after the war, the RDA stayed up to date by reviewing its guidelines at least once a decade to reflect those changes. The RDA had specific classifications to distinguish the varying needs of different age groups and genders, making it a groundbreaking initiative in its day.

What is RDI

RDI, the Reference Daily Intake, is the practical implication of the RDA established above. That means you get a yard stick against which you can compare say the vitamin C content of a food product -- 20 mg vs. the recommended 60 mg -- and quickly determine whether you need additional vitamin C sources to meet your minimum requirements for the day.

This, in combination with later laws that require practically all food packages to display easy-to-read nutritional information, has made it easier to identify suitable foods and compose a more well balanced diet. After all, what is RDA if not a tool for overall healthier living? If you don't buy the importance of these little nutritional levels, try sticking to a diet while traveling abroad. While some European or Asian food manufacturers volunteer basic info about total calories and perhaps fat content, it is rare to see an indication of sodium (salt) content -- a key concern for those suffering high blood pressure and certain heart conditions, for example.

What is DRI

Of course, any discussion about RDA and RDI wouldn't be complete without DRI, the Dietary Reference Intake. Created by Institute of Medicine (IOM) of the US National Academy of Sciences in 1997, this is very similar in nature to the older RDI. Many recommendations are similar, but one important difference is the introduction of a more varied approach instead of just RDA (which remains an important part of the puzzle).

Instead of one-size-fits-all, DRI now also has recommendations for Estimated Average Requirements (EAR), which aims for the nutritional needs of half of that age group, Adequate Intake (AI), which lacks RDA but is a close guess, and Tolerable Upper Level (UL) which basically cautions about overdosing on nutrients that can be potentially toxic in excess quantities.

To illustrate this evolution, please see the current recommendations for vitamins, with RDI, DRI and UL firmly established:

It is also interesting to track the changes in RDA over the years; this chart examines the development over the last few decades:

Source: Council for Responsible Nutrition