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.

Both men and women 50 or older should step up their calcium intake from about 1,000 mg a day to at least 1,200 mg. That's a lot. An 8-oz. glass of milk contains about 300 mg, an equal amount of yogurt the same. Hard cheese and calcium-fortified orange juice are helpful, as are soft-shell crabs and the bones of small fish. The general rule applies here too: consume as much calcium as you can through food, but for many it is hard to eat sardine skeletons daily, so it's O.K. to use a supplement for a little help.

Calcium is not absorbed by the body without vitamin D. The ultraviolet rays of the sun manufacture D in the skin, but the efficiency of the factory declines with age. It drops even further if you live in the northern half of the country, where the sun is too low on the horizon half the year to help, and even lower if you keep your skin covered to protect it from cancer.

A 50-year-old needs 400 IUs (international units) of vitamin D a day, twice as much as a 30-year-old. A 70-year-old needs 600 units a day. Milk and some breakfast cereals and breads are fortified with D. However, you have to drink a quart of milk to get even 400 IUs. Again, a supplement makes sense. And because your body adjusts bone mass to the loads your skeleton is called upon to support, it is important to do weight-bearing exercises.

The presence of folate in the blood seems to lower the level of homocysteine, an amino acid that may be a cause of stroke and heart disease. A variety of foods contain folate--again including breakfast cereals as well as beans and green vegetables--and since January 1998, the Federal Government has insisted that folate be added to all flour. So it's in your bread, whether you eat it sliced, wrapped or by the baguette.

Older stomachs can lose the ability to secrete gastric acid and pepsin, so about 20% of those in their 60s and 30% of those in their 70s have trouble extracting vitamin B12 from food. B12 protects the myelin sheath around nerves, enabling electrical impulses to travel along them; a severe B12 deficiency can lead to nerve damage and eventually dementia. A daily dose of 25 mg of B12, a common component in multivitamins, is plenty.

For 50 years or so, a leading hypothesis has been that aging and disease are promoted by highly reactive molecules called free radicals. The older we get, the more free radicals are released into our systems, where they destroy tissue. The villain is oxygen. "It's oxygen's dark side," says Jeffrey Blumberg, chief of Tufts' antioxidant research lab. "In effect, we rust as we get older." But the body also has a network of defenses against free radicals, called antioxidants. Some are produced internally; others are derived from what we eat.

One of the most potent antioxidants may be vitamin E. But as Russell points out, it exists in such small quantities in food that you would have to consume nauseating food portions for maximum effect. The National Academy of Sciences, the ultimate arbiter of nutrition requirements, is studying the case for E and will report its recommendations by the end of the year. Meanwhile, according to Russell, there is evidence that as much as 200 IUs of vitamin E a day, four or more times the amount in a typical multivitamin, might provide benefits without side effects. (Through many clinical trials, vitamin E has caused no harm at the level Russell suggests, but in extremely high dosages--more than 1,200 IUs a day--it can be dangerous to those who are taking anticoagulants.)

Two other antioxidants also show promise for protection against diseases that commonly afflict the elderly. One is lutein, found in leafy green vegetables, which may help protect against degeneration of the macula in the eye, the leading cause of blindness in those 65 or older. The other is lycopene, contained in tomatoes, apricots, guava, pink grapefruit and watermelon, which may help prevent prostate cancer. Unlike E, there seems to be enough of both in a good diet to make supplements unnecessary. More tentative are the possible beneficial effects of antioxidants contained in red wine, blueberries and strawberries. Rats in the Tufts labs are feasting on extracts of those consumables to determine, among other things, whether they might improve memory.

In a couple of decades, Dr. Russell believes, it may be possible to determine each individual's genetic vulnerability and then custom-design a food and supplement pyramid to his or her particular need: every man and every woman a pharaoh.

A Matter of Proportions

Nutritionists have been heaping our plates for years with proof that we eat too much of the wrong thing. But if your anecdotal eyeballing of the nation's girth tells you that we seem to be scarfing down everything but the evidence, you are right. The U.S. Department of Agriculture surveyed American eating habits a few years ago and determined that only 12% of us have a healthy diet.

Our collective recalcitrance is easily explained, in part. Bad stuff tastes good. But beyond the obvious, says Susan Borra, director of nutrition for the International Food Information Council, consumers don't like nutritional advice. In focus groups they complain that the advice makes them feel guilty, angry and confused--that a food that is praised today will be trashed tomorrow. That accusation is unfair. Nutritionists have usually been consistent, except for an occasional dashed hope.

What is fair criticism is that the message is sometimes impossible to decipher and follow. For example, consumers tend to interpret the message "low fat" as meaning "no fat," an unachievable--and undesirable--standard. Getting 30% of your calories from fat is considered a sensibly low-fat diet by mainstream nutritionists, Borra explains. "We should change the wording to 'moderate fat,'" she says.

Also, when it comes to recommending serving sizes, nutritionists seem to live on a planet far from the one that Big Boy, Wendy's and the rest of us inhabit. To understand the scale they are working with, you must think Lilliputian. Try following the whimsical but useful guide Borra and her colleagues have developed: a serving of steak is the size of a deck of cards; half a cup is a woman's fist; a pancake is the diameter of a CD; and a baked potato is a computer mouse--without sour cream, mind you.

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