London: Good news for those who enjoy one or two drinks in the evening -- moderate drinking may help protect against dementia -- especially in older people, two new studies have claimed.

Researchers at the Loyola University Chicago Stritch School of Medicine reviewed 143 studies looking at the effect of drinking of around 365,000 people and found that middle- aged and older adults who drink moderate amounts -- around one to two drinks a day -- are 23 per cent less likely to develop Alzheimer's and other forms of dementia.

But heavy drinking -- defined as more than three to five drinks a day -- was linked to dementia, although the finding was not statistically significant, the researchers said.

The analysis, which calculated the risk ratio between drinkers and non-drinkers of developing dementia in studies dating back to 1977, also found that wine was more beneficial than beer, and there was no difference in the effects for men and women, the Daily Mail reported.

Study researcher Professor Edward Neafsey said: "We don't recommend non-drinkers start drinking. But moderate drinking -- if it is truly moderate -- can be beneficial."

It is unknown why moderate drinking can have a beneficial effect, but the well-known benefits of alcohol on the heart may result in better blood flow in the brain and mental functioning.

Another explanation is "sick quitters", which means that the comparison group of non-drinkers who do not get mental protection also contains heavy drinkers who quit after damaging their brain cells.

But the researchers accounted for this, by looking at studies which excluded former heavy drinkers, and they found the benefits of moderate drinking still held.

Detailing their findings in the journal Neuropsychiatric Disease and Treatment, the researchers said small amounts of alcohol may make brain cells more "fit".

Alcohol in moderate amounts stresses cells and thus toughens them up to cope with major stresses that might eventually lead to dementia, they said.

However, other things also reduce the risk of dementia such as exercise, education and a Mediterranean diet high in fruits, vegetables, cereals, beans, nuts and seeds, the researchers added.

Another review by a panel at the International Scientific Forum on Alcohol Research found that older people have most to gain from regular drinking, as long as it isn't heavy consumption.