Longevity

Last Updated: July 1, 2003

What makes people grow old? How can we live longer? Why do members of some families seem to live longer than others? These questions have fascinated people for centuries. Now scientists who study aging, called gerontologists, are trying to answer them.

Genes now being studied may one day answer some of these questions. Genes might be considered little packets of information found in each cell in our bodies. These packets contain instructions that tell our bodies how to grow and work.

Areas of Research
Several “longevity genes” have been found in some living organisms. Scientists studying certain worms and fruit flies have found several genes that seem to control how long these creatures live. By making a change in just one of these genes, they have almost doubled the average lifespan of both fruit flies and one type of worm. Others looking at longevity genes have shown that the gene already shown to control how fast yeast cells age may do the same thing in mice. This gene is also present in humans. As interesting as this work is, it is unlikely that changing genes will be tried in humans in the near future as a way to help them live longer.

Genes alone, however, are only a part of the reason that some people live a long time. How people live may be more important. For example, does someone smoke? Do they exercise? Are they under a lot of stress? What do they eat? Some scientists think what people eat and how much they eat can lead to a longer life.

Caloric restriction is one area of research on aging. A calorie-restricted diet has 30% to 40% fewer calories than a normal diet, but it has all the needed nutrients. This diet seems to extend the life of almost every animal type in which it is studied. This diet has not been tested in humans. We do not know whether it will have the same life-extending effect in people. Conducting such a study in people is not practical because people would have trouble following such a diet.

Some scientists think that eating fewer calories lowers body temperature and changes metabolism, the breakdown of substances so that the body can easily use them. This, in turn, lessens damage to cells and slows certain other cell-damaging activities. In fact, caloric restriction seems to slow the whole process of growing older. Animals that have been on restricted diets since their youth reach adulthood later than others not on these diets. Not only do these animals seem to live longer, they also have less illness.

Although we don’t know how this works in people, scientists do know the flipside—that people who are overweight are more likely to develop certain age-related diseases such as heart and blood vessel disease, high blood pressure, arthritis, cancer, and diabetes.

Experts in aging do not expect ever to recommend such caloric restriction for people.
But these studies will help them understand aging. They may also teach us how to prevent or delay diseases that seem to come with growing older. Understanding how caloric restriction works might also help scientists develop chemicals that could imitate its effects on the aging process.

Antioxidants
Antioxidants are natural substances in foods. They may help protect you from disease by preventing the harmful effects of oxygen free radicals on your body. Oxygen free radicals are formed as cells in your body combine with oxygen to make energy. Free radicals also come from smoking or being exposed to things in the environment like radiation or sunlight. As we age, this damage may build up. According to one theory of aging, in time this build-up harms cells, tissues, and organs.

Your body’s own antioxidant defense system stops most free-radical damage, but not all. Antioxidants may prevent cataracts and heart disease, protect against damage from smoking, or boost immunity to illness.

Some antioxidants, such as the enzyme SOD (superoxide dismutase), are only useful when produced in the body. SOD pills have no effect on the body. They are broken up into different substances during digestion. Other antioxidants that come from food include:

• Beta-carotene, present in deep-colored fruits and vegetables
• Selenium, found in seafood, liver, meat, and grains
• Vitamin C, from citrus fruits, peppers, tomatoes, and berries
• Vitamin E, present in wheat germ, nuts, sesame seeds, and canola, olive, and peanut oils

How much of these antioxidants should you use, if at all? The National Academy of
Sciences is a nongovernmental group of experts involved in scientific research. They recommend what vitamins and minerals you need in your diet and how much of each. They say that there is no proof that large doses of antioxidants will prevent chronic diseases such as heart disease, diabetes, or cataracts. They did set guidelines for the safe use of some of them:
Selenium—at least 55 micro-grams (mcg) per day but not more than 400 mcg per day.

Vitamin C—at least 75 milli-grams (mg) per day for women and 90 mg for men, although smokers need more. No one should have more than 2,000 mg per day.

Vitamin E—at least 15 mg per day from food and not more than 1,000 mg per day.

Source: National Institute on Aging

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