Revised RDAs May Reflect Research on Nutrition and Disease Prevention

The venerable recommended dietary allowances (RDAs) for vitaminsand other nutrients could soon have a strikingly different lookbased on a new--and more activist--concept of what they are supposedto accomplish.

The past objective of the RDAs was to define the amounts of nutrientsneeded to prevent nutritional deficiencies in healthy people.The new concept is that RDAs should reflect the latest scientificinformation on the role of nutrients, such as antioxidants, inreducing the risk of cancer and other diseases.

That idea was a major focus of a 2-day workshop held in 1993,said Bernadette Marriott, PhD, Associate Director of the Instituteof Medicine's Food and Nutrition Board, which formulates the RDAs.She spoke at a symposium celebrating the 25th anniversary of theAmerican Health Foundation. "Yes, we will revise the RDAs,"Dr. Marriott said. "How, is the question."

Several approaches have been proposed for changing today's RDAformat, she said:

1. To give multiple reference values for each RDA, perhaps resultingin a range of recommended intakes.

2. To issue several RDA reports, each aimed at different populationgroups.

3. To set RDA levels with a view to disease prevention, basedon new scientific data about the role of nutrients in causingcancer and other diseases.

Revision of the RDAs is "an open process," and commentsare invited from any interested party, Dr. Marriott said. Severalmore meetings to facilitate such participation will be held, shesaid.

The nutrient requirements of older Americans will have a "highpriority" in any revision, Dr. Marriott said, but the essentialfocus will be on setting guidelines for individuals in specificmedical categories rather than for groups in the mass.

How New Guidelines Might Look

An idea of what new dietary guidelines might look like was givenby Paul A. LaChance, PhD, Chairman of the Department of Food Sciences,Rutgers University. He looked at the dietary recommendations madeby the US Department of Agriculture, whose major goal is preventionof heart disease, and the NCI, whose goal is cancer prevention.

The diets recommended by both federal agencies are essentiallythe same, Dr. LaChance said. For example, both recommend thatno more than 30% of total calories be in the form of fat, andboth advise a daily fiber intake of at least 30 g.

If the RDAs followed those dietary guidelines, the recommendationfor vitamin E would triple from its current RDA level, and vitaminC would move from 60 mg/d to an RDA between 217 and 225 mg. Therewould be little change in the B vitamin RDAs.

One important point is that the RDAs should consider interactionsbetween nutrients, Dr. LaChance said--a point with which Dr. Marriottagreed. They emphasized interactions between antioxidents suchas vitamins A and C.