Vitamins C AND E Seems To Provide Protection For Endurance Athletes' Airways

Vitamins C AND E Seems To Provide Protection For Endurance Athletes' Airways

Relatively low levels of ozone (<120micrograms/m3) can affect lung function in endurance athletes, making it more difficult to bring large volumes of air into thelungs (Respiratory Effects of Low-Level Photochemical Air Pollution in Amateur Cyclists,"  American Journal od Resp. Crit. Care Medicine,  vol. 150, pp.962-996, 1994). As a result, exercise scientist have searched for years to find ways to minimize ozone-related respiratory problems in athletes.

Ozone, also known as O3, is actually an unstable form of oxygen. If you have been even mildly interested in atmospheric science and air pollution over the past few years, you are well aware that there is "good ozone"  and also "bad ozone" in the earth's atmosphere. The "good ozone" occurs naturally in the upper atmosphere, approximately 10  kilometers above the earth. There, it forms a protective layer which helps to shield the earth from the harmful rays of the sun.

At ground level, however, the very same gas becomes "bad ozone." Ground-level ozone can harm human lung tissue, crops, and manufactured materials. The ground-level O3 is formed when nitrogen oxides and reactive organic gases (hydrocarbons) react chemically in the presence of sunlight. Nitrogen oxides, of course, are produced by fuel-burning engines; reactive organic gases are released by motor vehicles, solvents, a variety of different consumer products, and petroleum-processing plants.

Ground-level ozone tend to induce bronchoconstriction (narrowing of the airways), which decreases air flow into the lungs and potenially limits oxygen delivery to the blood. Even though endurance athletes have well-trained respiratory systems, they are quite prome toozone-induced problems. That's because athletes can maintain very high ventilation rates for prolonged periods of time - and thus drag more ozone into their lungs, compared to "couch potatoes". In addition, the "mouth breathing" (instead of routine nasal breathing) associated with heavy exercise takes away one of the body's key lines of defense against ozone - the trapping of ozone molecules in the nasal membranes, which prevents the irritating gas from reaching the lower air passages. If you live in or near an urban area, it's likely that ozone is having at least some impact on your respiratory function when you train and race.

What can you do to protect yourself from ozone's effects? Theorizing that antioxidants might help control ozone-related damage to the airways, researchers in Mexico City recently gave "antioxidant cocktails" to street workers exposed to fairly high levels of ozone. These cocktails contained vitamin C, vitamin E, and beta-carotene, and they did indeed have a protective effect on lung function in the workers (:Antioxidant Supplementation and Respiratory Function among Workers Exposed to High Levels of Ozone," American Journal of Respiratory Crit. Care Medicine, vol. 158, pp. 226-232, 1998).

                                                  Dutch Cyclist, Ozone, and Vitamins C and E

These workers were not exercising hevily, however. Would a similar cocktail have a beneficial effect in endurance athletes - even at lower ambient levels of ozone? To find out, researchers at Wageningen Agricultural University and the Netherlands Institute of Health Sciences in the Netherlands recently divided 38 Dutch cyclists (35 males and three females) into two groups: Members of one group received a daily dose of 500mg of vitamin C and 100 mg of vitamin E, while cyclists in the second group ingested only a placebo. The study was carried out in a "double-blind" manner (neither researchers nor athletes initially knew who was actually getting the potentially protective vitamins).

During the study, the cyclists worked out and competed in their usual manner. Average workout duration was 104 minutes, and mean workout heart rate was 141 beats per minute, but race pulse rates ascended to an average of 173 bpm. The athletes' lung functions were checked after workouts and races ( a total of 380 different tests were performed). Ozone concentrations were moderate; average ozone level was 77 micrograms/m3, and he range ws 14-186 micrograms/m3; this corresponds roughly with an average of .055 ppm and a range going up around .12 ppm ("Double- Blind Intervention Trial on Modulation of Ozone Effects on Pulmonary Function by Antioxidant Supplements," American Journal of Epidemiology, vol. 149, pp. 306-314, 1999).

Blood levels of vitamin E shot up about 48 percent in the supplement group, and plasma vitamin C rose by 4 percent; concentrations of two vitamins were essentially unchanged in placebo cyclists. When the researchers looked at average ozone levels during the eight hours before testing, they unearthed an interesting fact: As ozone levels increased, the amount of air the athletes could force out of their lungs in one second and the quantity of air they could exchange with the enviroment decreased in the placebo group - but were unchanged in the vitamin-ingesting cyclists. In other words, the vitamins seemed to protect cyclists from losses in respiratory function associated with ozone exposure.

For example, when ozone levels increased by about 100 micrograms/m3, the placebo riders could force 95 ml less air out of their lungs during a forced exhalation, while the drop-off for the supplementers was only 1 ml. C and E seemed to be reducing the extent of bronchoconstriction.

It's unclear what effects these differences would have on performance times, but it's clear that the C and E supplementation helped keep the athletes' airways more open and should have made intense exercise feel more comfortable. In a separate study, subjects took daily vitamin C (250mg), vitamin E (100mg), and a vegetable-based cocktail for two weeks, after which they were exposed to ozone levels of 800 micrograms/m3 (.4ppm) during two hours of exercise. During this period of exercise and ozone exposure, decrements in lung functioning were modest in the supplementers, compared to individuals who took in only a placebo ("The Role of Dietary Antioxidants in Ozone-Induced Lung Injury in Normal Human Subjects, " American Journal of Respir. Crit. Care Medicine, vol. 157 (supplement): A195, 1998).

But, do you really need to worry about ozone's effects on your lungs? After all, isn't it true that air quality is getting better?

Well, ground-level ozone levels are dropping. For example, last year ozone levels in the Los Angeles area exceeded California state standards on "only" 114 days. While that might seem like a lot, it was down from an average of 242  over the limit days 20 years ago.

Health advisories - when ozone soars above .15ppm and everyone is advised to avoid vigorous outdoor exercise - were in effect on "just" 43 days in Los Angeles 1998, down from 184 outrageous days in 1977, and there were "only" 12 "stage-1 Episodes", when ozone levels rocket above .20 ppm and people start getting really sick.

In other words, the air is getting cleaner, but in major urban areas like Los Angeles it still contains enough ozone to produce problems. Even the Dutch countryside, which is not notorious for its severe air pollution, contained air with enough ozone to interfere with respiratory function in the Dutch cyclists described above. Unless you live in a pristine wilderness, taking vitamin C and E to protect your lungs seems to be a fairly reasonable thing to do. It won't neccessarily help you attain a new PR, but it should have at least some positive influence on airway function.