Smog Exposure
Protection from Pollution
From campfires to jet engine exhaust, where there's civilization, there's smog, a combination of noxious chemicals, light-as-air particles and moisture that hangs in a yellowish gray haze over cities. Smog not only makes your eyes sting and lungs twitch but can even nibble the nose off a marble statue of Ulysses S. Grant.
Smog contains a long lineup of chemical nasties, including ozone, nitrogen dioxide, sulfur dioxide and tiny particles of everything from asbestos to soot, that can settle deep in the lungs and cause general havoc. "Smog is a soup that contains a lot of stuff, and people inhale everything that's in it, a whole bunch of toxic chemicals," says Daniel Menzel, M.D., Ph.D., professor in the Department of Community and Environmental Medicine at the University of California, Irvine. "They're a significant threat to people's health."
A high concentration of or long exposure to any one of these chemicals can cause shortness of breath, wheezing, coughing, bronchitis, pneumonia, headaches, inability to concentrate, chest pain and, in some cases, lung cancer.
Smog Hurts
Breathing smog changes the way that lung cells do business, Dr. Menzel explains. In some people, the lungs become supersensitive, reacting to smog exposure with inflammation, bronchial spasms, coughing, asthma attacks or increased production of mucus.
Smog can also make lung cells vulnerable to attack by bacteria and viruses that are always in the air. Smog can kill cells, making the lungs less efficient at doing their job of gas exchange (absorbing oxygen and releasing carbon dioxide). And some of the chemicals in smog can cause genetic mutations in cells that lead to cancer in the lungs or nasal passages.
Many of the harmful interactions between the noxious substances in smog and lung cells happen during a chemical process known as oxidation. This is the same process that causes butter to turn rancid and iron to rust. Oxidation, as you might guess, is a chemical reaction that requires oxygen in order to take place, and there's plenty of oxygen in the lungs. During oxidation, free radicals, which are unstable molecules of harmful chemicals, snatch electrons from the healthy molecules that compose the cells in order to balance themselves. This starts a chain reaction of electron stealing. The end result: serious damage to cells.
The best way to deal with smog, of course, is to avoid it as much as possible. Don't run along heavily trafficked roads. Aerobic exercise makes you breathe deeply, so you draw pollutants deep into your lungs. And don't smoke cigarettes. Smoking exposes your lungs to some of the same toxins found in smog, plus it makes your lungs more sensitive to smog's effects.
If you can't avoid smog entirely, you may want to protect yourself by taking nutrients that provide a measure of internal pollution protection: vitamins A, C and E, beta-carotene and selenium.
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Food Factors
Antioxidant nutrients are your surest protection against damage from chemical exposure. But these additional dietary adjustments may help, experts say. Scratch the saturated fat. Researchers at the National Cancer Institute in Rockville, Maryland, reported a strong association between saturated fat intake and adenocarcinoma, a type of lung cancer that is most common in nonsmokers. They found that women who consumed the greatest amounts of fat, typically from hamburgers, cheeseburgers, meat loaf, cheeses and cheese spreads, hot dogs, ice cream and sausage, had six times the risk of lung cancer of those who ate the least fat. Think raw. Researchers at Yale University found that the risk of lung cancer among men and women eating lots of salad greens and other raw vegetables, along with fresh fruits, was almost half of the risk seen among people not putting these foods on their plates. |
Vitamin E Equals Protection
Vitamin E, found in wheat germ, certain vegetables, nuts, seeds and vegetable oils, is well-known both for its ability to enhance the immune system and as an antioxidant. Antioxidants offer their own electrons to free radicals, disarming those renegade molecules and protecting healthy molecules from damage.
"Vitamin E is the strongest antioxidant found in the body," Dr. Menzel explains. "It gets incorporated into cell membranes, where it shields cells from harm. It helps stop the chain reaction that starts with exposure to smog and so is very effective at limiting the amount of damage done to cells."
Researchers at Yale University School of Medicine have shown just how well vitamin E does its job in the lungs. They found that nonsmokers had only half of the normal risk of developing lung cancer if they took vitamin E supplements.
"In our study, we weren't able to determine the amounts of vitamin E that people took, but the protective effect was apparent, and it was almost as strong as the protection offered by eating lots of fruits and vegetables," says Susan Taylor Mayne, Ph.D., a research scientist in the Department of Epidemiology and Public Health at Yale University School of Medicine and the study's main researcher.
Doctors who recommend vitamin E suggest that you take 600 international units a day. This amount is considered safe, but it's more than you can get from even the best food sources. Research indicates that the Daily Value of vitamin E, 30 international units, is not enough to offer optimum smog protection, Dr. Menzel says.
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Prescriptions for Healing
For healthy lungs, avoid smog-filled areas and supplement your diet with these nutrients, which some doctors recommend as protection against air pollution. Nutrient Daily Amount Beta-carotene 25,000 international units Selenium 50-200 micrograms Vitamin A 5,000 international units Vitamin C 1,200 milligrams Vitamin E 600 international units MEDICAL ALERT: Selenium in doses exceeding 100 micrograms daily can be toxic and should be taken only under medical supervision. If you are taking anticoagulant drugs, you should not take vitamin E supplements. |
Orange Aid for Air Pollution
Vitamin C is another well-known antioxidant. Like vitamin E, it helps stop free radical chain reactions.
Vitamin C helps maintain healthy lung function both in the general population and in people with asthma, say researchers at Harvard Medical School. They found that people who were getting at least 200 milligrams of vitamin C (about three oranges' worth) a day did best on tests that measured their lungs' capacity to expand and draw in oxygen.
"This study demonstrates, for the first time, that high dietary intake of vitamin C-rich foods is associated with improved levels of pulmonary function," says study co-author Scott Weiss, M.D., associate professor of medicine and associate physician in the Channing Laboratory at Brigham and Women's Hospital in Boston. "Getting enough vitamin C may prove to play an important role in reducing your risk of chronic lung disease."
Here again, usual dietary amounts may not be adequate protection, Dr. Menzel says. Researchers who recommend nutritional therapy to offset the effects of smog exposure suggest that you get about 1,200 milligrams of vitamin C a day. That amount is considered to be within the safe range, but it does require taking supplements.
Vitamins C and E work together in the lungs, and Yale University researchers have shown that a combination of the two helps keep lung tissue healthy. In one study, people who took daily supplements of 1,500 milligrams of vitamin C and 1,200 international units of vitamin E built up levels of a protective protein that prevents enzymes released during inflammation from destroying the lung's elastic properties. People with emphysema, for instance, who've lost lung elasticity from years of cigarette smoking, struggle for every breath.
Treat Your Lungs to a Carrot
The research evidence that's piling up about the protective effects of beta-carotene looks more and more like a cornucopia of fruits and vegetables. Those that contain beta-carotene, the yellow pigment found in carrots, cantalope and other orange and yellow fruits and vegetables, apparently help shield lungs from air pollution. "In population studies, foods rich in beta-carotene seem to offer strong protection against lung cancer, even among nonsmokers," says Dr. Mayne.
Unfortunately, a highly publicized 1994 study of male Finnish smokers found that 20 milligrams (about 33,000 international units) of supplemental beta-carotene a day did not reduce the incidence of lung cancer. Does that mean you shouldn't take beta-carotene to help protect your lungs from smog?
Some researchers feel that this study tested amounts of beta-carotene that were too little and given too late. They believe that there are still plenty of good reasons to get enough of this nutrient, Dr. Menzel says. Both beta-carotene and vitamin A (beta-carotene is converted to vitamin A in the body) help keep cells on track as they grow and divide and so help prevent genetic mutations that can lead to cancer, he explains.
Most experts recommend getting beta-carotene from foods rather than supplements, as foods contain many other substances that may also be important for cancer prevention. Dr. Menzel suggests that people get about 25,000 international units of beta-carotene a day from foods or supplements. That's roughly the amount found in one cup of chopped, cooked spinach, 11Ž4 large carrots or 2½ large sweet potatoes. Some doctors also recommend taking the Daily Value of vitamin A, which is 5,000 international units.
Selenium Shields Cells
Medical researchers round out their antipollution prescriptions with the mineral selenium. "Selenium is needed in the body to activate glutathione peroxidase, an important antioxidant enzyme that helps keep lung tissue elastic," Dr. Menzel explains.
Doctors recommend getting from 50 to 200 micrograms of selenium daily from foods and supplements. Studies show that most people get about 108 micrograms a day from foods. (Rich sources of selenium include grains, seeds and fish.) So it's probably not necessary to take a supplement. If you do take a supplement, don't exceed 100 micrograms daily without medical supervision. In high amounts, selenium can be toxic.