Do you smoke? You could be unwittingly lowering your sperm quality, a new study warns.

The research that included 20 nonsmoking men and 20 men who smoked found that that sperm of smokers has a greater extent of DNA damage than that of non-smokers.

Researchers also assessed 422 proteins in participants' sperm. One protein was absent, 27 proteins were underrepresented, and 6 proteins were over-represented in smokers. Analyses of these proteins suggest that cigarette smoking may promote an inflammatory response in the male reproductive tract.

"More and more studies are demonstrating a harmful effect of smoking on male fertility. Our results point in the direction of important semen alterations: semen of smokers presents an inflammatory nature, associated with decreased capacity of sperm to achieve fertilization and generate a healthy pregnancy," said senior author Dr Ricardo Pimenta Bertolla.

Bertolla added that in the study, sperm DNA fragmentation was increased. Other studies have proposed this to be a potentially promutagenic effect, which is to say that sperm with altered DNA may lead to health problems in the offspring.

The study appears in BJU International.