The venerable recommended dietary allowances (RDAs) for vitamins
and other nutrients could soon have a strikingly different look
based on a new--and more activist--concept of what they are supposed
The past objective of the RDAs was to define the amounts of nutrients
needed to prevent nutritional deficiencies in healthy people.
The new concept is that RDAs should reflect the latest scientific
information on the role of nutrients, such as antioxidants, in
reducing 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 Institute
of Medicine's Food and Nutrition Board, which formulates the RDAs.
She spoke at a symposium celebrating the 25th anniversary of the
American Health Foundation. "Yes, we will revise the RDAs,"
Dr. Marriott said. "How, is the question."
Several approaches have been proposed for changing today's RDA
format, she said:
1. To give multiple reference values for each RDA, perhaps resulting
in a range of recommended intakes.
2. To issue several RDA reports, each aimed at different population
3. To set RDA levels with a view to disease prevention, based
on new scientific data about the role of nutrients in causing
cancer and other diseases.
Revision of the RDAs is "an open process," and comments
are invited from any interested party, Dr. Marriott said. Several
more meetings to facilitate such participation will be held, she
The nutrient requirements of older Americans will have a "high
priority" in any revision, Dr. Marriott said, but the essential
focus will be on setting guidelines for individuals in specific
medical categories rather than for groups in the mass.
How New Guidelines Might Look
An idea of what new dietary guidelines might look like was given
by Paul A. LaChance, PhD, Chairman of the Department of Food Sciences,
Rutgers University. He looked at the dietary recommendations made
by the US Department of Agriculture, whose major goal is prevention
of heart disease, and the NCI, whose goal is cancer prevention.
The diets recommended by both federal agencies are essentially
the same, Dr. LaChance said. For example, both recommend that
no more than 30% of total calories be in the form of fat, and
both advise a daily fiber intake of at least 30 g.
If the RDAs followed those dietary guidelines, the recommendation
for vitamin E would triple from its current RDA level, and vitamin
C would move from 60 mg/d to an RDA between 217 and 225 mg. There
would be little change in the B vitamin RDAs.
One important point is that the RDAs should consider interactions
between nutrients, Dr. LaChance said--a point with which Dr. Marriott
agreed. They emphasized interactions between antioxidents such
as vitamins A and C.