USA guidelines recommend that women should drink no more than one alcohol unit per day, while men should not drink more than two.
The British Medical Journal published a study on the effects of moderate drinking on the brain, and the researchers were surprised by their findings. But these weren't just any Londoners - they were government employees who, about every five years since 1985, had been filling out surveys about their health habits, including how much alcohol they consumed.
Researcher says, drinking alcohol in moderate is not good for your brain.
The researchers found that moderate drinking over those 30-plus years was associated with degeneration and shrinking of the hippocampus, a region of the brain involved in memory and navigation, as well degeneration of the brain's white matter. Still, the results of moderate and light drinking were quite surprising.
Few studies have examined the effects of moderate drinking on the brain so the team of researchers set out to investigate if it had a harmful or beneficial association - or no association at all - with brain structure and function.
To study alcohol consumption in the long term, researchers looked into data acquired from 550 subjects deemed to be non-dependant on the substance.
None of those who took part were addicted to alcohol and their average age was 43.
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Brain function tests were carried out regularly and at the end of the study (2012-15), participants underwent an MRI brain scan.
Some of the previously conducted studies have linked moderate alcohol consumption with risks of cardiovascular ailments.
Moderate drinkers also showed a faster decline in language fluency - tested by how many words beginning with a specific letter can be generated in one minute - dropping 17 per cent more over 30 years than non-drinkers. Semantic fluency is tested by asking people to recall as many words in a particular category as they can within the space of 1 minute. Most notably, the heaviest drinkers were most likely to have clear shrinkage of a part of the brain called the hippocampus, a change that can precede or accompany dementia.
Compared with people who did not drink, people who drank moderately showed a three times higher risk of hippocampal atrophy.
An important caveat: The study is observational, so it can not prove cause and effect.
"My personal view", she added, "is that people should be less confident that drinking at the upper end of USA guidelines is 'safe, ' and it would be prudent to reduce their intake". Moderate drinkers were defined as those that drunk between 7 and 14 units per week for women and between 7 and 21 units for men. Many countries, including the United Kingdom, recommend lower limits for men. That being said, it is still worth promoting a public health message that encourages a reduction in drinking.
Commenting on the study, Dr Jennifer Wild, senior research fellow in clinical psychology, University of Oxford, said: "Medical science is under pressure to find modifiable risk factors for cognitive decline since dementia will be a global epidemic by 2050". Data on some individuals was missing and they said they "cannot exclude the possibility we have included some people who were alcohol-dependent at some points during the study period".