Might that morning glass of orange juice or vitamin tablet be more important for women than men? It is too soon to say, but for reasons that remain unclear, new study findings suggest that women experience more oxidation–a process suspected of increasing the risk of heart disease, stroke and several other diseases–than men. Vitamin C and other antioxidant vitamins can counteract this process.
Oxidative stress is the accumulation of cell-damaging substances called free radicals. This stress can be caused by outside factors, such as cigarette smoking, or by factors on the cellular level. Damage caused by oxidative stress is thought to contribute to the aging process and to many diseases. To confirm the role of oxidation in the development of disease, many large studies have measured the dietary intake of antioxidants, such as vitamin C. But few studies have gauged the extent of oxidative damage in people.
That is exactly what a team led by Dr. Gladys Block of the University of California at Berkeley has done. They measured oxidative damage in 298 healthy adults who ranged in age from 19 to 78. The study included 138 cigarette smokers, 92 nonsmokers and 68 people who reported exposure to secondhand smoke.
The researchers measured levels of two substances–malondialdehyde and F2- isoprostanes–that are markers of oxidative damage. These byproducts are produced after fatty substances called lipids are oxidized.
Based on levels of these markers, oxidative damage was significantly more extensive in women than in men, according to a report in the American Journal of Epidemiology. In fact, female sex was a more powerful predictor of oxidative damage than smoking.
The higher level of oxidative damage in women was unexpected, and the researchers do not have a good explanation for it. At first, Block and her colleagues thought that the higher percentage of body fat in women might be to blame, but when they accounted for body mass index (BMI)–a measurement that considers both weight and height–women still had higher levels of oxidation.
The finding of higher levels of oxidative stress in women is particularly interesting, according to the authors, “in view of the fact that women have been found to be at greater risk of lung cancer than men exposed to similar levels of cigarette smoke.”
People with higher levels of a substance called C-reactive protein–a marker of inflammation that has been linked to heart disease–also tended to have more oxidative stress, the researchers report.
In contrast, oxidative stress was lower in people who ate the most fruit as well as in those who had higher blood levels of vitamin C and carotenoids–pigments in fruits and vegetables that the body uses to make vitamin A, Block’s team found.
However, neither smoking, age, alcohol use nor other dietary factors affected levels of oxidative stress. Likewise, a form of vitamin E called alpha-tocopherol did not seem to influence oxidative stress, the report indicates.
SOURCE: American Journal of Epidemiology 2002;156:274-285.