Diets For Life

When the first food pyramid--an easy-to-digest graphical hierarchy of what we should be eating--was introduced in 1992, it seemed broad enough to cover everyone. Since then, however, variations have proliferated: pyramids just for children, for vegetarians, Southerners, Native Americans, Italians, Chinese, Indians, Mexicans and so on. Dietitians have created for us a virtual Nile Valley of nutrition.

They're not finished. And the newest monument, constructed by Tufts University's Human Nutrition Research Center on Aging, may be the most significant so far. It's designed for those who are 70 or older, but the authors point out that anyone 50 or older should heed its recommendations as well.

Conventional wisdom used to teach that in matters of nutrition, people 50 or older are like other adults, only a little less so. Their metabolism is slower, so they require less food. But the advance of science often leads to complexity rather than simplicity, and it has become clear that although older bodies burn fewer calories than younger ones, they actually require bigger helpings of nutrients. Older bodies absorb nutrients from food less efficiently than younger ones. Aging bodies continue to need not just nutrition but also aerobic exercise to preserve cardiovascular health and weight-bearing exercise to prevent bone loss and build muscle.

There are important distinctions between young and aging bodies, of course. At 50 or so, when women reach menopause, the loss of estrogen accelerates the deterioration of bone mass. Nothing so dramatic happens to men at that age, but psychologically it's a good opportunity to get them to modify their diets. It is hard to get a 30-year-old male to change his eating habits to reduce his risk of prostate cancer 20 or 30 years hence. But a 50-year-old, aware that men not much his senior are dying, is more likely to pay attention.

The most surprising recommendation in the new pyramid is the use of vitamin and mineral supplements, a departure from the doctrine that healthy people should get all they require from a well-balanced diet. Dr. Robert Russell, one of the Tufts authors, observes how difficult it is to get enough of some vitamins from the most conscientious diet. "Vitamin E in high dosages may help prevent some cancers and cardiovascular disease," he says. "To get that much from your diet, you'd have to consume 1 1/2 quarts of olive oil a day."

Co-author Alice Lichtenstein goes along with his conclusion somewhat reluctantly. "I hate to see the emphasis taken away from food," she says, adding that the benefits of a high dosage of vitamin E are not yet proved. She and other colleagues point out that food, unlike pills and extracts, contains trace elements that may have benefits not yet recognized. What they fear is encouraging the habit of chasing a handful of pills with a Slurpee and a bag of popcorn and calling it a well-rounded meal. Russell and Lichtenstein are not fighting, but their emphases are a little different. Russell stresses that one must get vitamins, Lichtenstein that one must eat. They agree that the most intelligent course is to get the maximum vitamin and mineral intake you can from food--then use supplements. Name-brand multivitamins sold at pharmacies cover most of the shortfall.

The pyramid for older people is slimmer than that for the young, reflecting the need for fewer calories, not fewer nutrients. Because his metabolism is slower, a 50-year-old man requires fewer calories to hold his weight at, say, 170 lbs. than he did when he was 30, even though he continues to exercise at the same pace. Eight glasses of water or other fluids (except alcohol and caffeine) make up the base of the new pyramid. Younger adults need the same amount, but they don't have to be told to drink. Thirst tells them. As people age, though, the thirst signal can fade and fail to warn of dehydration.

Older people need to consume more fiber than younger people because the muscles in the lower intestinal tract become less responsive and need bulk to keep working. If the muscles fail to do their job, the intestines can develop diverticulitis, an inflammation of the intestinal wall.

Bone mass peaks around the age of 20 and declines over the years, so much that elderly bones can fracture easily. The consequences are not merely casts and crutches: about 25% of people with fractures of the hip die within a year because of complications, says Dr. Michael F. Holick, chief of endocrinology, nutrition and diabetes at Boston University medical center, and another 25% spend the rest of their life in nursing homes.

Osteoporosis is thought of as a woman's disease. Women are generally smaller than men and have less bone mass to begin with. They tend to consume less calcium and vitamin D over a lifetime, and in menopause their bodies stop producing bone-protecting estrogen. So when they reach their 70s, many women begin to suffer fractures. Men are not likely to reach that stage until they are in their 80s, and because comparatively few men have lived to be octogenarians, their risk has been more theoretical than real. But as men live longer, osteoporosis will be a major problem for both sexes.