PROTECTION, PREVENTION AND ANTIOXIDANTS

Under normal conditions the damaging actions of ROS are minimized by abundant protective and repair mechanisms that cells possess, including many enzymes (e.g. superoxide dismutase, catalase), and redox active molecules (e.g., glutathione, thioredoxin). In addition there are many protective substances in foods. Vegetables and fruits in particular have a broad range of protective molecules. Best known among others are the "antioxidants" and some vitamins (e.g., vitamins C and E). Many studies have demonstrated that a diet predominant in vegetables and fruits is associated with a reduced risk of several age-related serious diseases (a strong implication that they are also important in slowing the aging process). Since the vegetables and fruits that are most effective are rich in antioxidants, research has focused on the prominent antioxidants in those foods. Two strong antioxidants, lutein and lycopene, members of the carotenoids (yellow, orange and red pigments that occur widely in plants and animals often giving them a bright coloration) have received much attention as cancer preventive foodstuffs. However, the in vivo effectiveness of many food constituents (e.g., the polyphenols), is still not clear. The chemistry in vivo is highly complex, and antioxidants under unusual circumstances can become pro-oxidants. This is possible in conditions where iron or copper are not in their normal non-catalytic state, as occurs in some diseases (e.g., hemachromatosis, and iron overload) or following trauma. Thus, there is some concern about the net benefits of antioxidant supplements. The success of supplements in delaying aging or age associated diseases is still under extensive study. It seems clear at this time that protection against oxidative damage, as it relates to aging, is provided best by a diet of vegetables and fruits, not to be replaced by pills.

Preventing cancer and heart disease -- do Antioxidants help?
Epidemiologic observations show lower cancer rates in people whose diets are rich in fruits and vegetables. This has lead to the theory that these diets contain substances, possibly antioxidants, which protect against the development of cancer. There is currently intense scientific investigation into this topic. Thus far, none of the large, well designed studies have shown that dietary supplementation with extra antioxidants reduces the risk of developing cancer. In fact one study demonstrated an increased risk of lung cancer in male smokers who took antioxidants vs. male smoker who did not supplement. Whether this effect was from the antioxidants is unknown but it does raise the issue that antioxidants may be harmful under certain conditions.

Antioxidants are also thought to have a role in slowing the aging process and preventing heart disease and strokes, but the data is still inconclusive. Therefore from a public health perspective it is premature to make recommendations regarding antioxidant supplements and disease prevention. New data from ongoing studies will be available in the next few years and will shed more light on this constantly evolving area. Perhaps the best advice, which comes from several authorities in cancer prevention, is to eat 5 servings of fruit or vegetables per day.

Ongoing research studies the role of Oxygen Free radicals in cellular chemistry, cancer treatment, and in a range of diseases including ALS, Parkinson's, Alzheimer's, Atherosclerosis, Diabetes, and others. As you might expect, medical and scientific opinions about the ability of antioxidants to extend life and enhance well-being vary greatly. So, don't cut out your antioxidant vitamins, but consider taking them with a grain of salt.

Exercise and oxidative damage
Endurance exercise can increase oxygen utilization from 10 to 20 times over the resting state. This greatly increases the generation of free radicals, prompting concern about enhanced damage to muscles and other tissues. The question that arises is, how effectively can athletes defend against the increased free radicals resulting from exercise? Do athletes need to take extra antioxidants?

Because it is not possible to directly measure free radicals in the body, scientists have approached this question by measuring the by-products that result from free radical reactions. If the generation of free radicals exceeds the antioxidant defenses then one would expect to see more of these by-products. These measurements have been performed in athletes under a variety of conditions.

Several interesting concepts have emerged from these types of experimental studies. Regular physical exercise enhances the antioxidant defense system and protects against exercise induced free radical damage. This is an important finding because it shows how smart the body is about adapting to the demands of exercise. These changes occur slowly over time and appear to parallel other adaptations to exercise.

On the other hand, intense exercise in untrained individuals overwhelms defenses resulting in increased free radical damage. Thus, the "weekend warrior" who is predominantly sedentary during the week but engages in vigorous bouts of exercise during the weekend may be doing more harm than good. To this end there are many factors which may determine whether exercise induced free radical damage occurs, including degree of conditioning of the athlete, intensity of exercise, and diet.