For decades there has been no shortage of advice on how the general public should eat to stay healthy. But the official recommendations have been based largely on the nutrition needs of middle-aged and younger adults, with scant focus given to people in their seventies and older. As this age group continues to grow, the lack of nutrition guidance geared specifically toward them becomes more and more of a public health lapse.

It's an especially serious issue because proper nutrition for people over 70 is "not just about staying in the pink," says Robert Russell, associate director of the USDA Human Nutrition Research Center on Aging at Tufts University in Boston. "If you get enough calcium and vitamin D, you might really be able to avoid a fracture," he says. "If you get enough folate and vitamin B6, it could be just as important for preventing heart disease as lowering cholesterol."

Helen Rasmussen, a research dietitian at Tufts's Human Nutrition Research Center, agrees, adding that avoiding micronutrient deficiencies in older years could mean avoiding anemias.

To help bring older people up to speed on their nutrition needs, Russell, Rasmussen and Tufts heart disease researcher Alice Lichtenstein have developed a food guide pyramid for people over 70. "It became obvious as we learned more about the nutrient needs of older individuals that they face unique dietary challenges," says Lichtenstein.

Probably the biggest challenge is that older people's calorie needs decrease (slower metabolism, less muscle mass, less physical activity), but their nutrient needs stay the same--and even increase in some instances. Thus, "their meals have to be of high quality. There are fewer calories to waste," says Rasmussen.

There are other concerns as well. One is dehydration. Older people's thirst mechanisms are not as finely tuned as those of younger adults; they don't necessarily feel thirsty when their bodies need liquid. Medications that flush water from the body, such as diuretics, add to the problem. Even mild dehydration that goes undetected can lead to unpleasant symptoms like headaches, but a lack of fluids can also have much more serious consequences. Medicare, the health care insurance for people 65 and older, spends $500 million a year on hospitalizations for which the principal diagnosis is dehydration, Rasmussen points out. For these reasons, the base of the pyramid reminds people 70-plus to drink at least eight cups of water (or juice or milk) a day. "It's something they really need to think about," says Lichtenstein.

Sufficient fiber (in combination with adequate fluids) also helps prevent constipation, which Russell, a gastroenterologist, says is "probably the most common complaint" among his older patients. "Oftentimes people think they're eating a good amount of fiber," he says, "but when you actually talk to them about" their food choices, "you often learn they're taking in very little--seven to eight grams." It's not until someone takes in about 20 grams of fiber a day, he notes, that it has "a laxative effect."

That's why the pyramid suggests that at least some of the choices in the "bread, fortified cereal, rice, and pasta group" be whole-grain. Whole-grain breads contain appreciably more fiber than refined white breads; brown rice has much more fiber than white; and so on. A high-fiber cereal for breakfast is most important here, too, the researchers say.

The cereal should also be fortified with vitamins and minerals to provide the biggest caloric bang for each bite. Eating a cereal fortified with vitamin B12 is a particularly good idea. Russell points out that 10 to 30 percent of people over age 60 have atrophic gastritis, a condition of insufficient stomach acid that doesn't allow them to absorb the B12 that is bound to protein in foods like meat and poultry. But the B12 in cereal is not bound to protein--cereal companies "literally spray the vitamin" onto the flakes, he says--so absorbing the nutrient from fortified cereals is not a problem.

As for the vegetable and fruit groups, the researchers recommend the whole fruit or vegetable rather than juice--again, to ensure the intake of plenty of fiber. People should also "choose deep yellow, orange, red or dark green vegetables as opposed to paler ones," says Lichtenstein. The darker the color, the more nutrients--including more of the antioxidants beta-carotene and vitamin C.

"It's not necessary that people make radical changes," she comments. "It may be something as simple as switching from iceberg to Romaine lettuce" and "tomatoes and grated carrots in salad as opposed to cucumbers and celery."

Lichtenstein notes that produce is well packaged for certain groups of older people. Peeled, shredded carrots and cut-up salads are available for those with arthritis, who can't always cut up vegetables. There are also bags of frozen fruit that you can take out just a little at a time if you live alone.

She also emphasizes that frozen and canned fruits and vegetables are as rich in nutrients as fresh, a bonus for people who may need softer versions of foods as a result of dental problems that keep them from chewing comfortably. Furthermore, since canned and frozen goods don't spoil until they're opened, you can keep a lot on hand so you don't have to go shopping for them every couple of days. (Keep fruits canned in heavy syrup to a minimum--they add calories from sugar without adding any extra vitamins, minerals or fiber.)

One group of vegetables that is important to include are the cruciferous kind--kale, cabbage, broccoli, cauliflower and the like. These items contain plant chemicals such as indoles, flavones and isothiocyanates, all thought to help prevent cancer.

As for the milk, yogurt and cheese group, older people should try very hard to consume at least three servings of these calcium-rich foods each day. They're supposed to be taking in anywhere from 1,000 to 1,500 milligrams of calcium daily but "are averaging, at most only 700 milligrams," says Rasmussen.

"We get a lot of people who feel that milk disagrees with them," Russell remarks. "Many old people just won't take milk except to add it to coffee or put a little on cereal."

Those people, in particular, he says, should try to get calcium from cheese and yogurt. The researchers also say that substituting a glass of calcium-fortified orange juice for one daily serving of dairy is okay.

When it comes to meat, poultry, fish, beans, eggs and nuts (all good sources of protein), the researchers put the emphasis on variety. For instance, they recommend fish at least once a week because of the evidence that the omega-3 fatty acids in fish lower the risk for developing heart disease. They also say that people should choose beans over meat twice weekly, largely for the fiber beans provide. (A half cup contains in the neighborhood of seven grams.) Choices include meatless chili, pasta topped with beans in sauce, and bean-based soup with salad and a piece of whole-wheat bread.

Finally, there's the flag at the top of the pyramid to remind older people that no matter how well they try to eat, they may fall short in certain nutrients, notably calcium, vitamin D, and vitamin B12. Indeed, people over 70 are supposed to get 600 International Units daily of vitamin D, and unless they drink six cups of milk, they're not likely to meet the mark. A cup of milk has 100 units, and few other foods have appreciable amounts. A multivitamin supplement will tend to contain 400 units of D, a little calcium and B12, which is important for people who don't eat B12-fortified cereal. In some cases, a pill containing just calcium and D may be in order. Your doctor can help you make the right supplement choices.

What's a Serving?

Here's how the government defines a serving:

* The grain group: 1 slice of bread; half of a bun, half a 2-ounce bagel or half an English muffin; 1 ounce of dry, ready-to-eat cereal; or 1/2 cup of cooked cereal, rice or pasta.

* The vegetable group: 1 cup raw leafy greens, 1/2 cup other kinds.

* The fruit group: 1 medium apple, pear, orange or banana; 1/2 cup small or diced fruit (like grapes or chopped pineapple); 3/4 cup juice.

* The dairy group: 1 cup of milk or yogurt; 1 1/2 ounces of cheese.

* Meat, poultry, fish, dried beans, eggs or nuts: 3 ounces of cooked lean beef, chicken or fish; 1/2 cup of cooked beans; 1 egg; or about 1/2 ounce of nuts (which are nutrient-rich but have a lot of calories for their weight).

CAPTION: Modified Food Pyramid for 70+ Adults (This graphic was not available)