Health and nutrition literature is filled with warnings about molecules called free radicals, and how they can accelerate the aging process, damage cells, and initiate disease. The literature also advises us to consume foods and supplements containing substances called antioxidants to protect ourselves from free radical damage. Sometimes, the literature can be confusing because it assumes the reader has studied biology and is familiar with cellular processes. In fact, very few people have the time to investigate the subject in great detail. But they would like to get a clear idea of what the researchers are talking about.
So, what are these "free radicals," and "antioxidants" anyway why should anyone care, and what can anyone do about them? At first glimpse, the phrase "free radical" may sound like it describes a terrorist political group. In fact, free radicals are cellular terrorists. They cause damage that has been linked not only to vascular and heart problems, cancer, and other types of illness, but also to accelerating the body's natural aging processes. Free radical formation can be triggered in a number of ways chiefly, from harmful chemicals in the environment, from radiation, especially ultraviolet radiation from the sun, and sometimes they are created by the body's own metabolic processes.
The so-called Free Radical Theory of Aging and Disease has been around a relatively long time. It was formulated beginning in the 1950s by University of Nebraska biochemistry professor Denham Harmon, who put forth the notion that oxygen-based compounds called free radicals inside our own bodies cause an oxidation process similar to the rusting of metal or the browning of a cut apple.
This is because the particles called electrons in oxygen molecules, which normally travel in pairs, enter into reactions where they become unpaired and unbalanced. Electrons are tiny fragments which form part of the structure of all molecules, and provide electrical charge. The oxidation process strips away one electron, leaving the molecule in an incomplete state, so it pulls against nearby molecules in an effort to retrieve the lost electron. The process destabilizes affected cells, and ultimately creates a chain reaction whereby molecules missing one electron strip away single electrons from their neighbors.
Free radicals wreak all sorts of cellular havoc; they harm enzymes, genes, proteins, hormones, cell membranes, and play the major role in age-related deterioration. The scientist who developed the definitive test for the cancer-causing potential of a compound, Dr. Bruce Ames of the University of California at Berkeley, has estimated that the genetic material in each cell is hit 10,000 times a day by free radicals. While the cellular repair mechanisms can curb this damage, over time the cell repair mechanisms breakdown.
When free radicals attack the lipids (fats) in cell membranes, they form peroxides. This can decrease the fluidity of membranes, making them rigid, and hampering the exchange of nutrients and wastes to/from the cell. The result is similar to what happens when an oil turns rancid. Lipid peroxidation and toxicity associated with oxygen radicals have been suggested as major causes of cancer, atherosclerosis, and the aging process. It is now generally accepted that free radicals play a major role in the deposition of cholesterol into the blood vessel wall. In the arterial vessels, the main sources of free radicals are unsaturated fatty acids of the LDL cholesterol.
Antioxidant compounds prevent "free radical" type of cell damage because they protect cells and membranes from oxidation by allowing themselves to be oxidized instead. Antioxidant compounds can stop free radical damage by donating an electron to stabilize radicals and stop the electron-stealing chain reaction.
Among the most commonly recognized antioxidant compounds are vitamins C, vitamin E, and beta-carotene, as well as the mineral selenium. In recent years, certain compounds from fruits and vegetables have also demonstrated antioxidant properties. Among these compounds are:
· lycopene: found in tomatoes and red grapefruit, it contributes to the red pigment of these foods
· ellagic acid: found in walnuts, strawberries, cranberries, and blackberries
· gallic acid: found in tea, especially Chinese green tea, as well as many fruits and nuts
· garlic: this vegetable and its relatives onion and leek, have a very complex chemistry and demonstrate an even greater antioxidant capability in some tests than vitamin E
· lutein: found in spinach and collard greens
· p-coumaric acid and chlorogenic acid: found in strawberries, green peppers, and tomatoes.
The U.S. Committee on Diet and Health has advised us in recent years to eat from five to nine servings of fresh fruits and vegetables daily to improve heath. One of the reasons to eat fruits and vegetables is to take advantage of antioxidants they contain. Sadly, however, statistics indicate most Americans are not paying attention to the dietary advice.
Meantime, antioxidant compounds are also put into many processed foods as additives to preserve freshness and prolong shelf life. The Food and Drug Administration has approved 27 synthetic and natural antioxidant substances as additives. Among the natural substances is vitamin E, which, for example, when added to bacon, prevents rancidity of fats, and prevents harmful compounds called nitrosamines from forming. Among the synthetic antioxidants are the substances BHA and BHT, which are used principally to prevent rancidity in cereal and baked goods. However, the amount of BHA and BHT ingested from eating these products contributes little or nothing to the body's antioxidant defense system, and at high levels, BHT has been found in experiments to actually contribute to cancer.
In the meantime, if you are not eating enough fruits and veggies, you may want to consider some of the antioxidant supplements and formulas in your health food stores.
Susan Moyers is a writer and educator focusing on health and science
issues. Her full length book about the history and health benefits of garlic
is due to be published this fall. Phone: 813-393-5986