The long-held belief that drinking a glass of red wine a day can help protect against heart disease cannot be assumed for all drinkers, say researchers.
A meta-analysis done by the Centre for Addiction and Mental Health (CAMH) provides new insight into the relationship between alcohol consumption and heart disease.
"It's complicated," said Dr. Juergen Rehm, director of social and epidemiological research at CAMH.
"While a cardioprotective association between alcohol use and ischaemic heart disease exists, it cannot be assumed for all drinkers, even at low levels of intake," said Dr. Rehm.
Ischaemic heart disease is a common cause of illness and death in the Western world. Symptoms are angina, heart pain, and heart failure. Based on 44 studies, the analyses used 38,627 ischaemic heart disease events (including deaths) among 957,684 people.
"We see substantial variation across studies, in particular for an average consumption of one to two drinks a day," said Dr. Rehm.
The protective association may vary by gender, drinking patterns, and the specific health effects of interest. Differential risk curves were found by sex, with higher risk for morbidity and mortality in women.
Moreover, for any particular individual, the relationship between alcohol consumption and ischemic heart disease should not be isolated from other disease outcomes. Even at low levels, alcohol intake can have a detrimental effect on many other disease outcomes, including on several cancers.
"Even one drink a day increases risk of breast cancer, for example," said Dr. Rehm.
"However, with as little as one drink a day, the net effect on mortality is still beneficial. After this, the net risk increases with every drink."
"If someone binge drinks even once a month, any health benefits from light to moderate drinking disappear."
Binge drinking is defined more than four drinks on one occasion for women, and more than five for men.
Given the complex, potentially beneficial or detrimental effects of alcohol on ischaemic heart disease in addition to the detrimental effects on other disease categories, any advice by physicians on individual drinking has to take the individual risk constellation (such as familial predisposition for certain diseases and behavior with respect to other risk factors) into consideration.
"More evidence on the overall benefit-risk ratio of average alcohol consumption in relation to ischaemic heart disease and other diseases is needed in order to inform the general public or physicians about safe or low-risk drinking levels," the study concluded.
The study was recently published in the journal Addiction.