First, the experts said drinking low to moderate amounts of alcohol was a good idea, that it might protect against heart disease.

Now, a study has found that such drinking has a risk: It might speed the shrinking of the brain that naturally comes with age.

The scientists found that the more people drank, the smaller the size of their brains. Even people who drank lightly -- one to seven drinks a week -- had slightly smaller brains than non-drinkers, according to the study in the Archives of Neurology.

The association was especially pronounced in women, perhaps because women's typically smaller body size renders them more vulnerable to alcohol, according to the researchers from Wellesley College, Boston University, the Framingham Heart Study and the University of California, Davis.

The gradual decrease in brain size seen as participants drank more was "slightly larger than the average decline in brain volume per year with aging."

The group studied 1,839 adults who were part of the Framingham Offspring Study, which began in 1971. The participants underwent brain scans from 1999 to 2001 and reported the number of alcoholic beverages they consumed each week.

Their brain volumes were measured as a percent of total cranial volume. Those in the lowest drinking category -- one to seven drinks a week -- had brain volumes of 78 percent of their total cranial volume, compared with 78.6 percent in abstainers. Those in the highest drinking category -- 14 or more drinks a week -- had brain volumes of 77.3 percent. Researchers computed the figures after adjusting for age, body size, weight and other factors.