NEW YORK - Light to moderate social drinking, a glass or two of wine or beer a day, can reduce the risk of developing Alzheimer's disease, according to American researchers.

After analyzing more than 140 studies dating back to 1977 and involving more than 365,000 people, scientists at Loyola University Chicago's Stritch School of Medicine found that moderate drinkers were 23 percent less likely to develop forms of dementia and cognitive impairment.

Moderate drinking is defined as a maximum of two drinks a day for men and one drink for women. "It is well accepted that a glass of wine is good for your heart and reduces coronary artery and cardiovascular diseases," said Edward J. Neafsey, a co-author of the study.

The findings show moderate alcohol consumption also produces a positive effect on the brain.

Wine was more beneficial than beer or spirits, according to the findings published in the journal Neuropsychiatric Disease and Treatment.

However, the researchers said most studies in the analysis did not distinguish between the different types of alcohol. But heavy drinking - three to five drinks a day - was associated with a higher risk of dementia.

Both Neafsey and his co-author Michael A. Collins, professors of molecular pharmacology and therapeutics, suggest that small amounts of alcohol can stress and toughen brain cells and enable them to better cope with the stresses that lead to dementia at a later date.

"It causes mild stress ahead of serious stress, which then protects the tissues and the cells," Neafsey explained.

Another theory suggests that the well-known cardiovascular benefits of moderate drinking can also improve blood flow to the brain, increasing brain metabolism.

Neafsey does not recommend non-drinkers to suddenly start drinking, and for people who do drink to enjoy their alcohol in moderation. Exercise, education and a Mediterranean diet can also reduce the risks of developing dementia.

"The key words here are light to moderate drinking," he said. "The enjoyment of a good meal with friends and glass of wine is a traditional human pleasure that most people enjoy."