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For Rita Powers, who served with the Army's Medical Corps during World War II, staying active means paying attention to nutrition.

A registered dietitian, she knows how important it is for people age 50 and older to eat smart.

"I drink milk and use milk products like yogurt and low-fat cheese for calcium. It's imperative to get the vitamin D with the calcium," Powers said. "I exercise every time the sun's out."

Nutritional needs change as people age, and older people need to increase some nutrients and limit others. Meeting these requirements to avoid nutrient deficiencies is a challenge since there is evidence that the body's ability to absorb and utilize nutrients decreases.

"Many older adults have chronic diseases such as diabetes, heart disease and hypertension that may necessitate following special, prescribed diets. These may be controlled in calories, sodium, fat, or carbohydrate and sugar," said Kim Pedroza, a clinical dietitian.

Older people should get the same or more nutrients on a diet that has fewer calories, she said. That requires eating more nutrient-dense foods with fewer sweets and other high-calorie and low-nutrient foods.

Here the basic nutrients with the mature adult in mind. Some are measured in milligrams, micrograms or international units.

*Calcium

Calcium plays a primary role in keeping bones healthy and reduces the risk of osteoporosis.

"Men and women 65 and over should take 1,500 milligrams of calcium each day, unless they are told not to for medical reasons," said Dr. John Saran, an internist specializing in geriatrics.

A study in the January 1998 American Journal of Clinical Nutrition suggests that without adequate calcium in the diet, treatments such as estrogen or hormone replacement therapy may be less effective. According to the study, 1,200 milligrams of calcium can help boost the benefits of hormone replacement therapy and perhaps other drug treatments. Women taking estrogen after menopause need as much calcium as women who are not taking hormones.

Calcium may even help with hearing loss. A recent study showed that women with hearing loss had 11 percent lower spinal bone density and 25 to 30 percent lower calcium intake from diet and supplements compared to women with normal hearing.

*Vitamin D

Vitamin D is needed to help absorb calcium. During the winter months, however, the elderly are at increased risk for vitamin D deficiency due to the lack of sunshine.

"The body can normally make vitamin D after an individual is exposed to the sun. Older people's skin is less efficient at converting sunlight to vitamin D. They also receive less sun exposure," Pedroza said.

Saran recommends that his patients take 400 international units of vitamin D in multivitamin form, along with an additional 400 IUs of the vitamin.

*Folic acid

Folic acid may cut the risk of heart disease. It helps reduce blood levels of homocysteine, a chemical believed to contribute to heart disease by making artery walls sticky and blocking the flow of blood through the body. The daily requirement is 400 micrograms. Folic acid can be found in beans, green vegetables and fortified grain foods such as pasta, bread and cereal.

*Vitamin B-12

Many older people produce less stomach acid.

"This can lead to a B-12 deficiency since stomach acid is needed to separate B-12 from food," Pedroza said.

A shortage of B-12 may cause declines in balance and pressure sensations, in muscle coordination and in mental ability. Vitamin B-12 is found only in foods of animal origin such as meat, fish, dairy products and eggs. In most cases, these foods can prevent a deficiency, but a doctor may recommend supplements as well.

*Vitamin E

Vitamin E is found in high-fat plant foods — soybeans, uncooked oils, nuts and the germ of whole grains. Moderate supplements were recently found to boost the immune system and protect against heart disease, cancer and even Alzheimer's disease.

Research published in the May 1997, Journal of the American Medical Association suggests mature people should take more vitamin E than what is currently recommended. Vitamin E cannot be consumed in the diet in sufficient quantities to reach optimal levels.

Saran recommends about 400 IUs of vitamin E.

*Vitamin supplements

"Take a multivitamin for seniors, which contains anti-oxidants like vitamins A, C and E, and trace minerals like selenium," Saran said. "Most also contain folic acid, which is very important for heart protection."

Pedroza doesn't routinely recommend that all elderly people take supplements.

"It depends on their diet," she said. "If it is apparent an individual is eating a lot less than he or she used to, or should, I would recommend a multivitamin and mineral supplement to help ensure that nutrient needs are being met." Individuals with limited sun exposure and poor consumption of milk products could benefit from vitamin D and calcium supplementation to minimize bone loss, she added.

"If I do recommend supplementation, I don't recommend a product that is greater than 100 percent of the RDA (recommended dietary allowances) as some vitamins, such as vitamin A, and some minerals, can be toxic in high doses."

*Sodium

"Restrict salt to help avoid hypertension, congestive heart failure and kidney disease. Choose low-sodium or sodium-free foods whenever possible," Saran said.

*Weight gain

As people age, they grow less active and their metabolism slows, so fat tends to replace the lean muscle tissue developed during younger years. This can happen even if a person stays the same weight or loses a few pounds. Pedroza works with people who need to reduce calories to manage diabetes and hypertension.

To reduce the risk of weight gain, older adults should eat smaller, more frequent meals. Saran recommends restricting carbohydrates and fat in order to reduce calories for weight loss.

*Weight loss

Losing weight can be just as harmful as gaining it. Many seniors, especially women, are pleased when they lose, but it's the last thing they should be doing. They need to maintain a stable weight for their stature and to consume enough nutrients.

"Many elderly people have difficulty consuming adequate nutrition and calories due to a poor appetite," Pedroza said. "Loss of appetite may be a side effect of many prescription drugs. It may also be the result of depression or the decrease in the sense of taste seen in the elderly."

Saran advises eating more protein, unless there is a history of severe kidney disease and a doctor has told them to restrict protein. "Sources of high-grade protein include egg whites, low-fat or fat-free dairy products, fish, and poultry," he said.

Eating well is a challenge. An older adult's overall caloric needs diminish, but nutritional needs remain as high or higher than ever before. Every bite counts, so it's crucial to eat high-quality, nutrient-dense foods.

Powers eats healthful foods by keeping the Food Guide Pyramid in mind.

"I believe in variety. I eat red peppers, green peppers, yellow peppers, all colorful vegetables," said Powers, who was recently honored by her peers for 50-plus years as a registered dietitian.

"Forget about any crazy diets."