It's commonly said that moderate alcohol consumption is good for people, but no one knew why and the determination of moderate was arbitrary.

A new study of 618 Swedes with coronary heart disease and a control group of 3,000 healthy subjects lent evidence to epidemiological curve-matching. The subjects were assigned to various categories based on the amount of alcohol they consumed and were tested in order to identify a particular genotype (CETP TaqIB) that previous studies suggested played a role in the health benefits of alcohol consumption.

The results showed that moderate consumption of alcohol helps protect people  against coronary heart disease
- if they have the genotype.

"In other words, moderate drinking has a protective effect among only 15% of the general population," says Professor Dag Thelle, Professor Emeritus at Sahlgrenska Academy, University of Gothenburg.

The researchers believe that the advice frequently given about the health benefits of moderate alcohol consumption is far too sweeping.

"Moderate drinking alone does not have a strong protective effect," says Professor Lauren Lissner, who also participated in the study. "Nor does this particular genotype. But the combination of the two appears to significantly reduce the risk of coronary heart disease."

Unknown mechanisms

The genotype codes for the Cholesterylester transfer protein (CETP), which affects the 'good,' cardio-protective HDL cholesterol that helps remove excess lipids from the blood vessels. One hypothesis is that alcohol somehow affects the CETP in a way that benefits HDL cholesterol.

A second hypothesis is that alcohol contains healthy, protective antioxidants.

The researchers believe that one or both of the hypotheses may prove correct, but the mechanisms by which HDL cholesterol or antioxidants might act remain unknown.

"Our study represents a step in the right direction," Professor Thelle says, "but a lot more research is needed. Assuming that we are able to describe these mechanisms, it may be a simple matter one day to perform genetic testing and determine whether someone belongs to the lucky 15%. That would be useful to know when offering advice on healthy alcohol consumption. But the most important thing is to identify new means of using the body's resources to prevent coronary heart disease."