A US study showing how drinking may cause Alzheimer's adds to previous evidence linking alcohol to the disease, say British experts.
It found too much alcohol damages genes that help clear the rogue proteins that form plaques in the brains of patients.
This destroys neurons - triggering memory loss and confusion. The finding could explain a growing body of evidence linking heavy alcohol consumption with dementia.
Dr David Reynolds, chief scientific officer at Alzheimer's Research UK, said: "While it is difficult to tell exactly what level of alcohol consumption begins to affect the long-term health of the brain, there is strong evidence that regular, heavy drinking increases the risk of dementia.
"This study builds on previous research implicating inflammation in the brain as the process linking alcohol use and Alzheimer's disease, the most common cause of dementia.
"The researchers highlight that alcohol may affect the activity of immune cells that cause inflammation in the brain, and leave them less able to clear away proteins that build up in cells in Alzheimer's disease.
"These are interesting findings, but as the researchers worked with cells from rats, we can't be sure how well this research reflects the effect of alcohol in people.
"The researchers exposed cells to a level of alcohol equivalent to very heavy binge drinking, and it is not clear whether this day-long procedure provides a useful insight into how cells in the brain are affected by alcohol over the course of someone's life.
"While we don't fully understand all the long-term health effects of alcohol use, not drinking to excess is linked to better brain health as well as a number of other benefits.
Dementia and alcohol consumption have been linked in thenew study
"Guidelines set out by the Chief Medical Officer advise men and women not to regularly exceed 14 units of alcohol over the course of a week."
Dr James Pickett, head of research at Alzheimer's Society, added: "We've known for some time that drinking alcohol excessively can damage the brain and increase the risk of developing dementia.
"This research highlights our brain's immune system as another potential reason for this link - but because it studied cells rather than people, it is not clear how the findings would translate to real life.
"Dementia is now the UK's biggest killer, and with no new drugs in 15 years, we are investing in dementia risk reduction research because it is vital to find ways people can protect against the disease.
"There is good evidence to suggest that a healthy lifestyle '“ drinking responsibly, exercising, eating well and not smoking '“ can help to reduce dementia risk."
The study by the University of Illinois, Chicago, is published in the Journal of Neuroinflammation.