Erectile dysfunction (ED), or impotence, is the inability to get and sustain an erection that is firm enough for sexual intercourse. It is the most common form of sexual dysfunction in men, affecting more than 18 million aged 20 and older in the US.
ED can be a devastating condition for men, causing lack of self-confidence, stress and relationship problems. The majority of ED cases are caused by physical problems, including high blood pressure, overweight, obesity, diabetes and high cholesterol, though it can also be triggered by psychological issues.
The researchers of this latest study, led by Dr. David Lopez of The University of Texas Health Science Center at Houston (UTHealth), note that previous studies have hypothesized that caffeine - commonly consumed via coffee, soda and energy drinks - may improve ED, though there is a scarcity of population-based studies investigating this association.
As such, Dr. Lopez and colleagues used 2001-04 data from the National Health and Nutrition Examination Survey (NHANES) - a program of studies assessing the health and nutritional status of Americans - to investigate the role of caffeine intake in ED.
Up to 42% reduced ED risk with two to three cups of coffee daily
The data analyzed involved 3,724 men aged 20 and older whose ED status was identified during a computer-assisted interview. Of these men, 40.9% were overweight, 30.7% were obese, 51% had high blood pressure and 12.4% were diabetic.
The researchers estimated the men's caffeine intake by analyzing 24-hour dietary recall data, gathered from asking participants to report all food and beverages consumed in the past day. The caffeine sources assessed included coffee, soda, sports and energy drinks and tea.
Overall, the team found that men who consumed 85-170 milligrams (mg) of caffeine daily were 42% less likely to report ED, while those who consumed 170-303 mg of caffeine a day were 39% less likely to report ED, compared with men who consumed 0-7 mg of caffeine a day.
The team notes that the caffeine levels consumed among men with reduced risk of ED were the equivalent to drinking two to three cups of coffee a day.
In addition, higher caffeine intake was also found to reduce risk of ED in men who were overweight or obese and those who had high blood pressure - all of which are considered risk factors for the condition.
However, Dr. Lopez notes that caffeine did not lower the risk of ED for men with diabetes. "Diabetes is one of the strongest risk factors for ED, so this was not surprising," he adds.
Still, the team concludes that their findings show a reduced likelihood of ED among men with a daily caffeine intake the equivalent to consuming two to three cups of coffee a day.
While the exact mechanisms behind this association are unclear, the researchers hypothesize that caffeine induces a series of pharmacological effects that causes relaxation of both the penile helicine arteries and the cavernous smooth muscle of the penis, increasing blood flow.
The researchers point to the large, nationally representative sample included in their study as a major strength, but they admit there are some limitations.
They point out that some risk factors for ED - such as cardiovascular diseases - were not addressed. In addition, they note that since NHANES is a cross-sectional study, their findings cannot imply a causal link between caffeine intake and reduced risk of ED. As such, further studies assessing this association are warranted.