Beta-carotene (top) and other carotenoids from vegetables provide the body with half as much vitamin A (bottom) as previously thought. © Dennis Kunkel Microscopy.

WASHINGTON, DC—Recent recommendations from an Institute of Medicine panel on dietary requirements for adequate vitamin A intake have stirred controversy among nutrition researchers and supplement manufacturers.

Robert Russell, MD, chair of the Institute’s panel on micronutrients, outlined the vitamin A recommendations during a press briefing in December. The briefing marked the release of the panel’s report on dietary reference intakes for micronutrients: vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. The last such report was in 1989.

The most provocative and confusing aspect of the new recommendations centered around vitamin A, and the Institute’s conclusion that carotenoids from fruits and vegetables are not converted to vitamin A in nearly the amounts previously thought. Despite this, the Institute held back on recommending vitamin A supplementation.

The panel actually lowered its recommended dietary allowance (RDA) for vitamin A slightly—from 1,000 micrograms per day to 900 micrograms per day for men, and from 800 micrograms per day to 700 micrograms per day for women. At the same time, the panel concluded that getting these levels from carotenoids found in green leafy vegetables and darkly-colored fruits is not as easy as once believed.

“We determined that the provitamin A carotenoids from fruits and vegetables provide half the vitamin A activity as previously reported by the Food and Nutrition Board in 1989,” Dr. Russell said. “This means that provitamin A carotenoids in fruits and vegetables provide the body with half the amount of vitamin A as previously thought.”

This does not mean that people will have to eat twice as many fruits and vegetables to meet their vitamin A requirement, Dr. Russell hastened to add. But “individuals, especially vegetarians, whose main source of vitamin A comes from provitamin A carotenoids in fruits and vegetables, will need to make sure they choose enough deeply colored green, yellow, and orange fruits and vegetables to meet their vitamin A requirement.” He insisted that the requirements can be met without taking vitamin supplements.

Recommended daily allowances or adequate intakes followed by tolerable upper intake levels (in parentheses) for selected vitamins. Adapted with permission from National Academy of Sciences, courtesy of National Academy Press. To view the Institute’s full report, go to: www.nap.edu/books/0309072794/html/.

Not surprisingly, supplement industry leaders disagree. Phil Harvey, PhD, director of science and quality assurance for the National Nutritional Foods Association, a group of health food and supplement manufacturers, said it was “misguided” of the panel to suggest that most people can meet the requirement without taking supplements.

“People are already not getting enough fruits and vegetables,” said Dr. Harvey, in Newport Beach, Calif. “Surveys continually show that people are not meeting the recommendation of a minimum five servings a day.” And people would get more vitamin A from a supplement than they would from eating the fruits and vegetables, he added.

This is precisely what worries Institute of Medicine panelists. On the one hand, panel members are concerned about deficiency, but on the other, they are equally wary of vitamin A overloading. “We are concerned about any supplement containing pre-formed vitamin A over and above our recommendations,” said Dr. Russell. “The upper level recommendation for vitamin A is based on case reports of liver disease in people who take 4,500 units, with a safety factor built in so that it (the RDA) comes down to 3,000 mcg.”

John Weisburger, PhD, senior member of the American Health Foundation, a research institute in Valhalla, N.Y., said he was disappointed that no mention was made of the need to take vitamin A—whether in pill form or in food—at the same time that they are ingesting fats.

“If you take a vitamin A pill in the morning when you’re eating a low-fat breakfast, it ends up in the toilet; it is not absorbed,” said Dr. Weisburger in an interview. “If you do take supplements, you should take them with your main meal, where you are likely to have a little fat, like olive oil, in your food.”

Alan Gaby, MD, professor of therapeutic nutrition at Bastyr University, Kenmore, Wash., and a practicing physician, said the Institute’s concerns about vitamin A deficiency in vegetarians is well-founded. He frequently sees vegetarians who show physical signs of vitamin A deficiency, such as bumps on the back of the arms. The bumps clear up when they take vitamin A supplements.

“There is evidence of wide variation in the absorption of beta-carotene, as well as variation in the ability of people to convert beta-carotene into vitamin A,” he said. “I will often recommend that vegetarians take pre-formed vitamin A rather than have them eat more carotenoids. I’m not convinced that all vegetarians will be sufficient in vitamin A no matter how many fruits and vegetables they eat.”

On the other hand, Leslie Bonci, RD, a spokeswoman for the American Dietetic Association, said she is concerned about people getting too much vitamin A in supplements. “There are a tremendous amount of supplements that contain much more vitamin A than the average person needs,” said Ms. Bonci, who works as a dietitian at the University of Pittsburgh Medical Center. “The message is, don’t go for the pill, but boost your fruit and vegetable intake.”

Ms. Bonci agreed with Dr. Weisburger that adding fat to a food with carotenoids will increase the amount of vitamin A that is absorbed. “Cooking spinach in a little olive oil increases the bioavailability of vitamin A in the body. A trail mix with dried apricots and nuts is also a perfect way of getting vitamin A. But if there’s no recognizable source of fat [with the carotenoid], we’re not getting all the benefit.”