Is it good for you or bad for you? Uncorking the truth about moderate drinking
Some experts say a few drinks a week are good for you, while others argue they'll damage your health. As Covid sees many of us reaching for the bottle, here's our guide to...
MODERATE drinking – is it a curse or a cure? Tippling's reputation for helping or harming our health flips so frequently that it's enough to make anyone's head spin.
One week, positive research has careful drinkers crying ‘Cheers'. The next, scientists report an alcohol peril that has the abstainers saying ‘Told you so'.
In the latest twist, a major new US study of midlifers says drinking in moderation may be beneficial for our brains, helping to protect against dementia in old age. Researchers from the University of Georgia say they have identified what they call a ‘U-shaped relationship' between alcohol and brain health.
Consuming a little – eight units spread over a week for women; 15 for men – may slow mental decline and preserve brainpower. Exceeding this amount can damage cognitive function.
It comes as a survey published last month showed that four in 10 households in Northern Ireland and Britain are drinking more than before because of lockdown, with experts fearing a surge in alcohol-related ill-health and liver disease.
To give you an idea of how consumption adds up, a pint of normal-strength beer has 2.3 units of alcohol, the same as a 175ml glass of wine, while a small single measure of spirits counts as one unit.
The US investigators monitored nearly 20,000 men and women in their 50s, 60s and 70s for a decade, regularly assessing their ability to think, reason, remember, solve problems, make decisions and pay attention.
In the journal JAMA Network Open, they reported that people who regularly had up to two drinks a day were on average a third less likely than teetotallers to develop decreased cognitive function that could lead to dementia. Even those who drink a smaller amount of alcohol each week could benefit, their results suggest.
But why should this be? Dr Changwei Li, an assistant professor of epidemiology and biostatistics, who led the study, admits that "the mechanisms underlying the beneficial association of low to moderate alcohol consumption with cognitive function are unclear".
The picture is indeed cloudy. Dr Li adds that while some previous studies have reported that low-to-moderate drinking is statistically associated with better heart health compared with being teetotal or drinking heavily, other researchers have found that any level of drinking raises your risk of high blood pressure and stroke.
Dr Li speculates that perhaps "[alcohol's] role in cognitive function may be a balance of its beneficial and harmful effects on the cardiovascular system".
This U-shaped relationship has been seen before. In The BMJ in 2018, an analysis of the health records of more than 9,000 civil servants reported that in midlife, moderate drinkers had a lower risk of developing dementia than colleagues who were teetotal or drank more than 14 units a week.
Dr Dorina Cadar, a senior research fellow in behavioural science and health at University College London, says that consuming alcohol moderately may stimulate anti-inflammatory systems in the brain that preserve cells' longevity.
This may also protect against common problems that afflict ageing brains, including diminished blood flow caused by failing vessels; a build-up of inflammatory toxins; and the formation of plaques that are believed to cause Alzheimer's. Some plant-derived components of alcoholic drinks may also help. Dr Cadar explains: "The antioxidant effect of polyphenols [such as resveratrol], which are abundant in red wine, has been proposed to be neuroprotective."
:: Do women benefit more than men?
However, Dr Adam Sherk, a research fellow at the Canadian Institute for Substance Use Research, warns that moderate drinkers are not "insulated from harm".
They account for significant numbers of alcohol-related medical problems, according to his analysis of hospital statistics.
Writing in June in the Journal of Studies On Alcohol And Drugs, Dr Sherk reported that half of cancer deaths associated with alcohol use in British Columbia in Canada in 2014 occurred among moderate drinkers.
On top of that, about a third of all alcohol-attributable deaths there were experienced by people drinking below the Canadian government's recommended weekly limit of 10 drinks (they measure in drinks, not units) a week for women and 15 for men.
Just to confuse matters, the study did show one benefit of moderate drinking – for women only. It appears to be associated with a lower risk of type 2 diabetes, heart attack and stroke.
"This protective effect did not appear to hold for men, who experienced harm at all drinking levels," the study reported.
Dr Sherk says his results show that countries such as Canada and the UK should tighten their recommended drinking limits to mirror those in the Netherlands.
Current UK guidelines say both women and men should not drink more than 14 units spread over a week. The Dutch recommendations, however, state that it is best not to consume alcohol at all.
:: Alcohol and the link to cancer
Meanwhile, more conflicting evidence about the benefits or dangers of moderate drinking continues to emerge.
In January, for example, investigators at Johns Hopkins University in Baltimore, US, declared that drinking moderately significantly lowers people's risk of developing chronic kidney disease, compared with teetotallers.
The study of more than 12,500 people in the Journal Of Renal Nutrition found that people who consumed between eight and 14 alcoholic drinks a week had a 29 per cent lower risk of chronic kidney disease compared with teetotallers.
Even people who consumed between 15 and 20 drinks a week had a 23 per cent lower risk. Any more than that, however, and the benefit disappeared.
But, predictably, another recent study disagrees about the safety of moderate drinking. Published last December by the American Cancer Society, it concluded that light-to-moderate drinking is associated with a greater risk of developing any type of cancer.
In the study, which examined health records of more than 126,000 people, teetotallers had the lowest risk of being admitted to hospital with cancer. For the moderate drinkers, there was an almost linear association between cancer risk and alcohol consumption: the more they drank, the greater their likelihood of a cancer diagnosis.
So why is it that after years of dedicated research, we have no consistent steer about whether moderate drinking is either beneficial or perilous?
:: Why is the research so contradictory?
The problem, says a leading expert in health risks, is that the dangers and benefits of moderate drinking are so modest that they are very difficult to detect – and could equally produce positive or negative results, depending on the way in which studies are conducted.
Professor David Spiegelhalter, chair of the Winton Centre for Risk and Evidence Communication at the University of Cambridge, says: "The effects of low alcohol consumption – ie within UK government guidelines – are so small that the type of studies we can do will never be good enough to overcome random statistical noise." In other words, it's hard to detect a genuine difference.
Another problem, says Prof Spiegelhalter, is that when scientists compare moderate drinkers with teetotallers, they are not comparing ‘like with like' – the sets of people who practise either behaviour are different, so studies end up highlighting basic demographic differences rather than the health effects of modest drinking.
"One consistent finding across studies is that people who have never been drinkers tend to have different health outcomes than moderate drinkers. But this does not mean it is alcohol that is causing the difference," he explains. "There are many reasons why people don't drink, including ethical, religious or health ones.
"These mean that we can never compare like with like, even with fancy statistical methods. That is why I am deeply sceptical of any studies that use this comparison."
Prof Spiegelhalter believes we should stick with the current advice of drinking no more than 14 units a week.
Moderation in all things. It seems that with alcohol, the four wisest words in medicine still apply.
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