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An antioxidant is a chemical that reduces the rate of a particular oxidation reaction. Oxidation reactions
are chemical reactions that involve the transfer of electrons from a substance to an oxidizing agent. Antioxidants can slow
these reactions either by reacting with intermediates and halting the oxidation reaction directly, or by reacting with the
oxidising agent and preventing the oxidation reaction from occurring.
Antioxidants are particularly important in organic chemistry and biology. All organisms maintain a reducing environment
inside their cells and contain complex systems of antioxidants to prevent damage by oxidation. These antioxidants include
glutathione and ascorbic acid and are substrates for enzymes such as peroxidases and oxidoreductases. Low levels of
antioxidants or inhibition of antioxidant enzymes causes oxidative stress and may damage or kill cells.
Antioxidants are widely used as ingredients in dietary supplements used for health purposes such as preventing cancer and
heart disease. Studies have suggested antioxidant supplements have benefits for health, but several large clinical trials did
not demonstrate a definite benefit for the formulations tested, and excess supplementation may even be harmful.
Before discussing their role in maintaining good health, let us first clarify what antioxidants are. "Antioxidant" is a
classification of several organic substances, including vitamins C and E, vitamin A (which is converted from beta-carotene),
selenium (a mineral), and a group known as the carotenoids. Carotenoids, of which beta- carotene is the most popular, are a
pigment that adds color to many fruits and vegetables -- without them, carrots wouldn't be orange, for example. Together as
antioxidants, these substances are thought to be effective in helping to prevent cancer, heart disease, and stroke.
At the molecular and cellular levels, antioxidants serve to deactivate certain particles called free radicals. In humans, free
radicals usually come in the form of O2, the oxygen molecule. The oxygen molecule wants to be oxidized (remember that stuff
from your chemistry class?), and this oxidation process can sometimes be carcinogenic. Free radicals are the natural
by-products of many processes within and among cells. They are also created by exposure to various environmental factors,
tobacco smoke and radiation, for instance.
If allowed to go their merry way, these free radicals can cause damage to cell walls, certain cell structures, and genetic
material within the cells. In the worst case scenario and over a long time period, such damage can become irreversible and lead
to disease (e.g., cancer). This is where antioxidants come into play. Based on what you have read so far, can you guess what
role antioxidants play in the maintenance of health?
Antioxidants play the housekeeper's role, "mopping up" free radicals before they get a chance to do harm in your body.
Researchers have postulated that antioxidants prevent the possible carcinogenic effects of oxidation. Despite numerous studies
carried out on the role of antioxidants in cancer and heart disease prevention, the jury is still out as to which groups of
people, if any, benefit from taking antioxidant supplements.
Some studies have shown that smokers with diets high in carotenoids have a lower rate of lung cancer development than their
smoking counterparts whose carotenoid intake is relatively low. However, a recent study indicated that some beta-carotene
takers, primarily smokers, actually had higher death rates. Other research efforts have suggested that diets high in
carotenoids may also be associated with a decreased risk of breast cancer. Also, vitamin C has been found to prevent the
formation of N-nitroso compounds, the cancer-causing substances from nitrates and nitrites found in preserved meats and in some
drinking water.
Many researchers claim that elderly people, especially those who have reduced their food intake, frequent aspirin users, heavy
drinkers, smokers, and people with impaired immune systems may benefit from taking antioxidant supplements daily. In terms of
heart disease and stroke, it is possible that higher levels of antioxidants slow or prevent the development of arterial
blockages, a complicated process involving the oxidation of cholesterol. Moreover, antioxidants may deter the collection of
plaque on arterial walls.
Obviously, conflicting reports on the health benefits of antioxidants and beta-carotene exist. It is difficult to know what to
believe and whose advice to follow. It is best to remember that vitamin and mineral supplements should never be used as
substitutes for a healthy, well balanced diet! It is also important to note that we can "over- supplement" our bodies, taking
much more than the recommended daily value of certain vitamins and minerals. Vitamins A and E are fat soluble, meaning that
excess amounts are stored in the liver and fatty tissues, instead of being quickly excreted, creating a risk of toxicity. Your
best bet is to eat a diet rich in fruits, veggies, and whole grains. Sweet potatoes, carrots, spinach, cantaloupe, and mangoes are great sources of antioxidants.
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