September 18, 2002 01:22 PM ET NEW YORK (Reuters Health) - Men with fertility problems who smoke should kick the habit if they want to become dads, according to researchers. Dr. Ashok Agarwal and colleagues from the Cleveland Clinic Foundation in Ohio found that infertile men who smoked had signs of oxidative damage in their semen, which is known to reduce fertility. Oxidative damage is caused by molecules known as reactive oxygen species, which are a natural byproduct of normal body processes. Antioxidants--including vitamin C and E--can help to prevent oxidative damage. The findings, the researchers say, suggest that doctors should tell their infertile male patients who smoke to quit. To investigate whether smoking might affect oxidative stress levels and sperm quality, Agarwal and colleagues analyzed semen samples from 20 infertile smokers, 32 infertile nonsmokers and 13 healthy nonsmokers. They report their findings in the September issue of Fertility and Sterility.		The samples were subjected to standard semen analysis as well as testing for sperm DNA damage. Seminal oxidative stress was reported as a composite score of the level of reactive oxygen species and the total antioxidant capacity. Smoking was linked to a 48% increase in the level of white blood cells in semen, as well as a dramatic increase in oxidative stress levels. No significant differences in standard sperm variables or DNA damage were observed between infertile smokers and nonsmokers. However, the authors note that the harmful effects of smoking on these criteria "may be masked because of the infertility status." Any man trying to conceive should refrain from smoking, the researchers advise, but this is "particularly important for individuals experiencing infertility problems."