Men who drink the equivalent caffeine level of two to three cups of coffee a day are less likely to have erectile dysfunction (ED), according to researchers from The University of Texas Health Science Center at Houston (UTHealth).

The results of a study published recently in PLOS ONE found that men who consumed between 85 and 170 milligrams of caffeine a day were 42 percent less likely to report ED, while those who drank between 171 and 303 milligrams of caffeine a day were 39 percent less likely to report ED compared to those who drank zero to seven milligrams a day. This trend was also true among overweight, obese and hypertensive men.

"Even though we saw a reduction in the prevalence of ED with men who were obese, overweight and hypertensive, that was not true of men with diabetes. Diabetes is one of the strongest risk factors for ED, so this was not surprising," said David S. Lopez, Dr.P.H., M.P.H., lead author and assistant professor at UTHealth School of Public Health.

According to the journal article, the suggested biological mechanism is that caffeine triggers a series of pharmacological effects that lead to the relaxation of the penile helicine arteries and the cavernous smooth muscle that lines cavernosal spaces, thus increasing penile blood flow.

In the United States, 18.4 percent of men 20 years and older have ED, suggesting that more than 18 million men are affected. Caffeine is consumed by more than 85 percent of adults, according to previous research.

Data for the study came from the National Health and Nutrition Examination Survey and ED was assessed by a single question during a computer-assisted interview. Caffeine sources in the study included coffee, tea, soda and sports drinks.