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United States Department of Agriculture

Agricultural Research Service

Some foods provide benefits beyond basic nutrition
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Huawei Zeng

The tenet “Let food be thy medicine and medicine be thy food,” espoused by Hippocrates nearly 2,500 years ago, is receiving renewed interest.

It is known that all foods are functional because they provide basic nutritional needs such as carbohydrates, proteins, minerals and others. But some foods are providing certain physiological benefits beyond that of meeting basic nutritional needs. Research data suggest that some of these foods, as part of an overall healthful diet, have the potential to delay the onset of many chronic diseases such as cancer and cardiovascular diseases. These observations have led to continuing research aimed at identifying specific bioactive components in foods, such as antioxidants, which may be responsible for improving and maintaining health.

Humans and other animals use oxygen in the air to make energy to fuel the various functions required for life. Energy formed by using oxygen is needed by our hearts to beat and pump blood to organs, by our lungs to bring in oxygen and release our waste gas into the air and by our intestines to absorb the nutrients that we obtain from food. Thus, we are aerobic creatures because of our dependence on oxygen to function.

A natural and key byproduct from the use of oxygen is the production of very reactive chemical products called “free radicals.” These chemicals are very reactive with adjacent compounds in organs. While the body has its defenses against oxidative stress, these defenses are thought to become less effective with aging as oxidative stress becomes greater. If we lack the capacity to meet the increased demand to neutralize free radicals formed during exercise, then tissue damage may occur. This condition is called oxidative stress.

Oxidation, or the loss of an electron, sometimes can produce reactive substances known as free radicals that can cause oxidative stress or damage to the cells. Antioxidants, by their very nature, are capable of stabilizing free radicals before they can react and cause harm, in much the same way that a buffer stabilizes an acid to maintain a normal pH. Because oxidation is a naturally occurring ‘process within the body, a balance with antioxidants must exist to maintain health.

Research suggests there is involvement of the resulting free radicals in a number of degenerative diseases associated with aging, such as cancer, cardiovascular disease, cognitive impairment, Alzheimer’s disease, immune dysfunction, cataracts and macular degeneration. Certain conditions, such as chronic diseases and aging, can tip the balance in favor of free radical formation, which can contribute to ill effects on health.

We often hear that “an ounce of prevention is worth a pound of cure.” Many foods contain antioxidants that detoxify or neutralize free radicals. Selenium, zinc, copper, manganese, folic acid and vitamins A, C, E and B-6 are key antioxidants. Lean meat, fish, dairy products, cereals and seeds provide selenium, zinc, copper and manganese, which the body incorporates into the active site of neutralizing enzymes. Vitamins C, E and beta carotene react directly with free radicals and eliminate them. Broccoli, cabbage and other green vegetables are rich in vitamin C. Vegetable oils, whole grains, nuts, seeds, and wheat germ are good sources of selenium and vitamin E. Carrots, sweet potatoes, pumpkin, squash and spinach supply beta carotene, while tomatoes and processed tomato products provide lycopene.

Fresh fruits and vegetables clearly are vitamin-rich foods. Antioxidant research continues to grow and emerge as new bioactive components of food are identified. Reinforced by these research data, the underlying findings are that antioxidants obtained from food sources and consumption of antioxidants is thought to provide protection against oxidative damage and contribute positive health benefits.

For examples, because tomatoes and processed tomato products are rich in lycopene, they may contribute to maintenance of prostate health. Berries, grapes, tea, chocolate and apples are rich in flavonoids and are likely to boost your cellular antioxidant reserves, contribute to brain function and to heart health. Whole grains may reduce risk of coronary heart disease and cancer and may contribute to reduced risk of diabetes.

Thus, to be beneficial to human health, current recommendations are to consume a varied diet with at least five servings of fruits and vegetables per day and six to 11 servings of grains per day, with at least three of those being whole grains. In addition, such healthful diets also can contribute significantly to reducing obesity, a risk factor for cancer and other diseases.


Last Modified: 1/7/2009
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