Even one glass of wine a day can increase your dementia risk. Photo / Getty Images
With scientists finding links between alcohol and a raised risk of dementia, here’s what you need to know about your weekly drinking habit.
After a night of heavy drinking, you might spare a worried thought for your liver. But what about the impact on your brain? In a study published recently about alcohol and brain health, scientists found clear links between alcohol and a raised risk of dementia.
“I don’t think the brain features in most people’s thinking about alcohol at all,” says Dr Anya Topiwala, who studies the effect of alcohol on the brain at the University of Oxford. “Maybe it’s because the message about a glass of red wine a night being good for the brain has propagated – it’s what we all want to believe.”
However, her latest research, published in BMJ Evidence Based Medicine, has firmly debunked this belief. After looking at data from around 560,000 patients in the UK, she found that drinking any amount of alcohol – even one glass a day – increases the risk of dementia.
“I can’t see a mechanism by which a small amount of alcohol will protect the brain. When we’ve done in-depth studies using brain imaging, we haven’t found that at all. We found no protective effects. We only found harmful effects.”
So, just how much are our drinking habits harming our brain?
As soon as alcohol passes our lips, it starts to be absorbed. First in our mouth, then throughout the rest of our digestive system. This includes going through the liver and into the bloodstream. Within five to 10 minutes, it reaches the brain.
This is down to ethanol molecules, the type of alcohol in beer, wine and spirits, being so small. “Although there’s a barrier between our blood and the brain [that protects harmful substances from getting in], ethanol can easily diffuse through,” Topiwala explains.
If you drink more than seven units per week – the equivalent of three 175ml glasses of wine or three pints of 4% beer – it leads to changes in the anatomy of the brain. “People have smaller brains, literally,” she says. “We noticed this in their hippocampus – the part of the brain that is really important for memory. It is also one of the earliest regions affected by Alzheimer’s.”
Drinking seven units a week, which is half the recommended upper limit in the UK, also lowers levels of grey and white matter – tissue that makes up the brain. “If you think of brain cells as electrical cables, the white matter is the outer cable and the grey matter is the wire inside those cables,” says Dr Topiwala. “We’ve found that the white matter – the quality of that insulation around the wires – is lower in people who drink seven units or more per week.”
While studies are yet to confirm the exact cause of these effects, scientists believe alcohol is killing our brain cells, forcing the organ to become smaller and damage how it functions.
One study from Topiwala and her colleagues, which looked at drinking habits and memory test results among 550 people over a 30-year period, found that people who had more than seven units a week had a faster memory decline. “They had to name as many words as they could within a minute, beginning with a specific letter. It’s quite a hard task that engages the front part of your brain for problem solving. Those who had more alcohol got worse faster.”
Each of these findings are dose-dependent, she explains. “The more you drink, the worse it gets [in terms of brain shrinkage, less white matter and cognitive test results]. We can detect these changes at seven units but the effect is more dramatic as alcohol intake increases.”
An additional worry that kicks in when people drink more than 14 units per week (around six 175ml glasses of wine or six pints of 4% beer) is higher brain iron markers, Dr Topiwala says.
Iron accumulates in people’s brain as part of ageing but research suggests that alcohol can further fuel this process. This is bad news, as it is thought the mineral damages brain cells and exacerbates cognitive decline. Too much iron in the brain has also been linked to Alzheimer’s and Parkinson’s.
“The more you drink, the more you get iron in your blood, liver and brain, which then leads to memory problems,” Dr Topiwala explains.
Topiwala and colleagues have found that iron accumulated in the basal ganglia at 14 units per week – the brain region responsible for movement. Those with higher iron levels in this part of the brain were slower at completing problem-solving tasks, results showed. “We can start seeing this effect at 14 to 21 units per week and then it’s even more extreme at 21 to 28, and alcoholics have the highest levels of all,” she adds.
Women who drink more than 28 units a week (12 175ml glasses of wine or 12 pints of 4% beer) and men who have more than 35 (16 175ml glasses of wine or 16 pints of 4% beer), over a period of five years, are at risk of a type of irreversible brain damage called Korsakoff syndrome, Topiwala says.
“It’s thought to be down to a thiamine deficiency (also known as vitamin B1),” she explains. Alcohol prevents the gut from absorbing enough of the vitamin, which brain cells need to work properly, meaning too much is lost through urine.
This can lead to a specific type of brain inflammation, called Wernicke encephalopathy. “People who are very deficient can become confused, develop abnormal eye movements and unsteady walking,” she says. “If they are not treated quickly with thiamine, it can progress to Korsakoff syndrome, which is essentially a severe dementia.”
“People who have been drinking heavily can get this in their 40s or 50s and end up in nursing homes,” Topiwala says. “But you have to be drinking really quite heavily for that – above 28 units for women and 35 for men over a period of five years.”
“Alcohol is a toxin for your brain and it basically just kills brain cells, so it’s just how much you’re willing to do that,” says Dr Topiwala. “I have one small glass with dinner a few times a week. For me, that’s the kind of balance that seems right. We all accept some risk in our life. If you want zero risk from alcohol on your brain, don’t drink anything.”
Cutting out binge drinking behaviour can also help. “It’s certainly worse to binge,” she says. “It’s thought that the repeated cycle of soaking your brain in alcohol and then withdrawing from alcohol is worse than steady exposure.”
But, ultimately, don’t kid yourself that moderate drinking won’t harm your brain health. “Whatever you can do to cut down is going to help you,” Topiwala adds.