Men who drink 14 or more drinks a week are 20 per cent more likely to develop prostate cancer, according to an international review co-authored by a University of Victoria researcher.

The results, published in Molecular Nutrition and Food Research, provides more concrete evidence of the link between alcohol and prostate cancer - a link that has remained controversial.

Tim Stockwell, director of the University of Victoria's Centre for Addictions Research of B.C., along with research teams from the U.S. and Australia reviewed 35 previously published studies that linked drinking and the risk of developing prostate cancer.

The studies that Stockwell and his colleagues examined included "cohort studies", which measure people at one point in time and then re-measure them later to see if their drinking, smoking or exercise is associated with the incidence of disease.

The other type included were "case-control studies," in which researchers compared patients who already had the disease to people who didn't in order to compare differences.

Since the current literature on the link between prostate cancer and alcohol was mixed and inconclusive, the researchers hoped that combining the results of the 35 studies would offer the larger numbers that would lead to clearer results.

They found that case control studies were more likely to find the relationship, while cohort studies were less likely, which explains why different conclusions were reached by other researchers, the authors of this review say.

When all types of studies were combined, however, the authors concluded: "Men who drink two or more standard drinks a day (or 14 drinks a week) or more have about a 20 per cent greater chance of developing prostate cancer."

The prevalence of prostate cancer is higher in Canada than the U.S., and higher in both countries than in Australia, the researchers said; but the reasons are not entirely clear.

Prostate cancer is the most common cancer among Canadian men and one in seven Canadian men will develop the disease during his lifetime. In Australia, one in nine men will develop it and in the U.S., it is the second leading cause of cancer death among men.

Stockwell said it may be that since prostate cancer typically kills men who are middle-aged and older, there are higher incidences of the disease in countries with longer life expectancies.

The authors point out that prostate cancer risk increases at the same ages that alcohol is thought to have a "protective effect" for heart disease. Men who drink two or more drinks a day might take this into account if they are consuming alcohol to prevent heart attacks.

"Further research is needed to examine more carefully the balance of health risks and benefits for different types of disease from drinking alcohol at different levels," the authors said.

In previous papers, the authors have also questioned the evidence supporting the view that moderate drinking protects against heart disease.