Antioxidants decrease the damage done to cells by reducing oxidants before they can damage the cell. As food produces free radicals (oxidants) when metabolized, antioxidant-rich diets are thought to stave off the effects of aging significantly better than diets lacking in antioxidants. The reduced levels of free radicals, resulting from a reduction in their production by metabolism, is thought to be a major cause of the success of caloric restriction in increasing life span.
Although there is little doubt that antioxidants are a necessary component for good health, there is considerable doubt as to the most beneficial antioxidant(s) and as to the optimal amount for results. One study of lung cancer patients found that those given beta-carotene supplements had worse prognoses. This is believed to be due to antioxidant interference with the body's normal use of localised free radicals e.g. nitric oxide for cell signalling. Due to the complex nature of the interactions of antioxidants with the body, it is difficult to interpret the results of many experiments designed to test such things. In vitro testing (outside the body) has shown many natural antioxidants, in specific concentration, can halt the growth of or even kill cancerous cells. There have been clinical studies showing specific antioxidants have a beneficial effect against certain cancers.
Nutritional antioxidants Edit
The following substances have shown positive antioxidant effects:
- Vitamin A (Retinol, also via beta-carotene) protects dark green, yellow and orange vegetables and fruits from solar radiation damage, and is thought to play a similar role in the human body. Carrots, squash, broccoli, sweet potatoes, tomatoes (which gain their color from the compound lycopene), kale, collards, cantaloupe, peaches and apricots are particularly rich sources of beta-carotene.
- Vitamin C (Ascorbic acid) is a water-soluble compound that fulfills several roles in living systems. Important sources include citrus fruits (such as oranges, sweet lime, etc.), green peppers, broccoli, green leafy vegetables, strawberries, blueberries, raw cabbage and tomatoes.
- Vitamin E, including Tocotrienol and Tocopherol, is fat soluble and protects lipids. Sources include wheat germ, nuts, seeds, whole grains, green leafy vegetables, vegetable oil, and fish-liver oil. Recent studies showed that some tocotrienol isomers have significant anti-oxidant properties.
- Selenium has been shown as early as the 1950's to have a beneficial effect in reducing the occurrence of male prostate cancer, and a recent study done by the National Health System of China have verified previous results. However, the substance must be taken in measured amounts because large doses of the element can be toxic. Good food sources include fish, shellfish, red meat, grains, eggs, sunflower seeds, chicken, garlic, and brazil nuts. Vegetables can also be a good source if they are grown in selenium-rich soils, and some nutritional supplements contain a supply of selenium.
- Coenzyme Q10 (CoQ10) is an antioxidant which is both water and lipid soluble. It is not classified as a vitamin in humans as it can be manufactured by the body, but quantities decrease with age to levels that may be less than optimal, and levels in the diet are generally low. Supplementation with CoQ10 has been clinically proven to improve the health of gums. There is evidence that CoQ10 helps protect the brain against Parkinson's disease.
- Melatonin is a natural hormone which has several biological roles in different species. It is an exceptionally effective antioxidant within the mitochondria, which are subject to extreme oxidative stress.
- Bio-flavonoids are present in many dark berries such as pomegranate, noni, blueberries, and blackberries, as well as in certain types of tea and coffee, especially green tea. Coffee is often depleted of antioxidants due to the high-temperature roasting process. Applied Food Sciences has introduced Healthy Roast, a product that remove antioxidants from the green coffee beans before roasting and then adds them back when beans are quenched. The FDA may have recently suggested that the average person should consume up to 7000 ORAC units daily, in order to reduce the risk of cancer. As this is nearly 12 servings of high-ORAC-value fruit, the use of nutritional supplements containing bio-flavonoids is likely necessary to reach this target.