Alcohol may have a protective effect on the heart, but not the brain, a study suggests. (CBC)

Consuming even small amounts of alcohol seems to shrink the brain, researchers have found.

Moderate alcohol consumption has been linked to a lower risk of cardiovascular disease, leading researchers to investigate whether it also slows aging-related declines in brain volume.

But it turned out that people who drink more showed more brain shrinkage, Carol Ann Paul of Wellesley College in Massachusetts and her colleagues report in the October issue of Archives of Neurology.

"It's been known that people who drink a lot have a decline in brain volume. What I was looking for was a protective effect in people who drink one to seven glasses a week," Paul says.

"My expectation is that it would [be protective]. And it didn't turn out that way."

As we age, our brain volume decreases at an estimated rate of 1.9 per cent per decade, the study notes. At the same time, the brain accumulates white-matter lesions that may occur in cases of dementia and cognitive decline.

The researchers analyzed data on 1,839 American adults aged 33 to 88 who reported their alcohol consumption and had magnetic resonance imaging scans to examine brain volume, along with medical exams.

None of the participants in the continuing Framingham Offspring Study showed evidence of clinical dementia or stroke.

Participants were divided into five groups: abstainers, former drinkers, and low, moderate and high consumers.

No protective effect found

Among those who drank the most, more than 14 drinks a week, the brain was one per cent smaller on average, compared with abstainers, the researchers found, after correcting for head size, age, sex, education, height, body mass index and stroke risk.

"In contrast to studies on cardiovascular disease, this study found that moderate alcohol consumption was not protective against normal age-related differences in total brain volume," the study concluded.

"Rather, the more alcohol consumed, the smaller the total brain volume."

"The public health effect of this study gives a clear message about the possible dangers of drinking alcohol," the study's authors wrote.

Almost 38 per cent of men and more than 44 per cent of women fell into the low consumption category, having one to seven drinks per week.

While men were more likely to drink alcohol, the association between drinking and loss of brain volume was stronger in women, perhaps because women may be more susceptible to the effects of alcohol, the researchers say.

The team called for more long-term studies to confirm the findings and determine what the consequences there are for smaller brain volumes, if any.

The harmful effects of alcohol abuse include damage to the liver, brain and other organs.

With files from Reuters