Merck Manual

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Looking for the Fountain of Youth

Looking for the Fountain of Youth

Everyone wants to know how to stay young and live longer. Researchers are looking at genes, cells, hormones, eating patterns, and other factors for clues about what causes aging and how to prevent or slow it. Research has identified three strategies that may help people live longer:

People who exercise are healthier than those who do not. Exercise has many established health benefits: improving and maintaining the ability to do daily activities, maintaining a healthy weight, and helping prevent or postpone disorders such as coronary artery disease, cancer, diabetes, cognitive decline, and early death. Of all types of exercise, endurance exercises (eg, walking, cycling, dancing, swimming, low-impact aerobics) have the most well-documented health benefits for older people. Exercise programs that are more strenuous than walking may include any combination of 4 types of exercise: endurance, muscle strengthening, balance training (for example, tai chi), and flexibility. Depending on the person’s medical condition and fitness level, people should be able to select activities they enjoy but should be encouraged to include all 4 types of exercise.

People who eat a low-fat diet that includes lots of fruits and vegetables are healthier than people who eat more fat and starch. Also, people who live in Mediterranean countries and consume a so-called Mediterranean diet seem to live longer. This diet is generally thought to be healthier than northern European and American diets because it consists of more grains, fruits, vegetables, legumes, nuts, and fish and less red meat. In addition, the main fat consumed is olive oil. Olive oil contains many vitamins and is monounsaturated rather than saturated. Monounsaturated fats do not increase cholesterol the way saturated fats do. There is now randomized trial evidence that a Mediterranean diet reduces heart attacks, strokes, cardiovascular death, and development of diabetes. Accordingly, most experts recommend adhering to this diet.

Following a low-calorie diet for a lifetime may lead to longer life, possibly because it slows the body’s metabolism, reduces the number of certain damaging substances in the body, or both. These damaging substances, called free radicals, are by-products of the normal activity of cells. The damage done to cells by free radicals is thought to contribute to aging and to disorders such as coronary artery disease and cancer. But no studies to test whether a low-calorie diet could prolong life have been done in people.

These three strategies would require a major change in lifestyle for most people. Consequently, many people look for other, less demanding ways to prevent or slow aging. For example, they may look for other ways to manage free radicals. Substances called antioxidants can neutralize free radicals and in theory help prevent damage to cells. Vitamins C and E are antioxidants. So some people take large amounts of these vitamins as supplements in the hope of slowing the aging process. Other antioxidants, such as beta-carotene (a form of vitamin A), are sometimes taken as supplements. In theory, using antioxidants to prevent aging makes sense. However, doctors now realize the body sometimes uses free radicals in beneficial ways—for example, as part of the immune defense system. Thus, there is also reason to think that taking large amounts of antioxidants may not be helpful, and there is some evidence that high doses of vitamin E may be harmful. In any case, no studies have shown that antioxidants taken as supplements prevent or slow aging. Also, there is direct evidence that antioxidants taken as supplements do not protect against disorders such as heart attack, stroke, or cancer, nor do they increase lifespan. Also, such supplements have not been proved to be harmless.

Levels of some hormones decrease as people age. Thus, people may try to delay or slow aging by taking supplements of these hormones. Examples are testosterone, estrogen, DHEA (dehydroepiandrosterone), human growth hormone, and melatonin. But there is no evidence that hormonal supplements have any effect on aging, and some of them have known risks. Also, some experts believe that decreases in certain hormone levels may actually prolong life by slowing the body’s metabolism.

Some people believe that Eastern practices, such as yoga, tai chi, and qigong, can prolong life. These practices are based on the principle that health involves the whole person (physical, emotional, mental, and spiritual) and balance within the body. The practices may include relaxation, breathing techniques, diet, and meditation as well as exercise. They are safe for older people and probably make them feel better. But whether these practices prolong life is difficult to prove.