July 14 (UPI) -- People who drink in moderation faced sobering news on Thursday from a large British research study: Even that amount of imbibing may be linked to brain changes and cognitive decline.
Specifically, drinking seven or more "units" of alcohol per week is associated with higher iron levels in the brain -- and iron accumulation is linked with Alzheimer's disease and Parkinson's disease. It also is seen as a potential mechanism for alcohol-related cognitive decline.
That's according to a study of nearly 21,000 people published Thursday in the journal PLOS Medicine.
"The significance is this is the first study showing higher brain iron -- and in turn this is associated with worse cognition -- in 'moderate' drinkers," Anya Topiwala, the study's lead author, told UPI in an email.
The "practical advice is to try to keep your drinking at low levels, and of course spreading out consumption not bingeing it," said Topiwala, senior clinical researcher in the Nuffield Department of Population Health at the University of Oxford in England.
Topiwala explained just how modest a person's alcohol intake may have to be to avoid ill health effects.
One unit of alcohol in the United Kingdom is defined as 8 grams (10 milliliters) of pure alcohol/ethanol. "So seven units is approximately two large, 250 ml., glasses of 14% wine or two to three beers a week," she said.
The study found that alcohol consumption above seven units per week was "associated with markers of higher iron in the basal ganglia, a group of brain regions associated with control of motor movements, procedural learning, eye movement, cognition, emotion, and more," according to a news release about the study.
Topiwala said she found the results surprising, adding, "I did not think we would find evidence of higher brain iron at such low drinking levels."
In fact, the study found much higher levels of drinking among the 20,965 participants, who self-reported the amounts -- a method researchers said was needed in such a large group, but conceded most likely resulted in underreporting.
Although 2.7% characterized themselves as non-drinkers, the average intake was around 18 units per week, which translates to about 7½ cans of beer or 6 large glasses of wine, according to the news release.
All of the study's participants -- who are part of a biomedical database of one-half million people in the United Kingdom called the UK Biobank -- had brain scans using magnetic resonance imaging. Nearly 7,000 also had MRI imaging of their livers to assess their levels of systemic iron.
All of the participants also completed a series of tests to assess cognitive and motor function. Their mean age was 55, and it was an even split between males and females.
In the United States, the Centers for Disease Control and Prevention points to the federal government's 2020-2025 Dietary Guidelines for Americans with respect to safe levels of alcohol intake.
The guidelines recommend that adults who choose to imbibe should "drink in moderation by limiting intake to two drinks or less in a day for men or one drink or less in a day for women, on days when alcohol is consumed."
The CDC noted that 2 in 3 adult drinkers report drinking above moderate levels at least once a month.
Topiwala said the idea of focusing on iron accumulation was interesting to her because it had not been examined in "moderate" drinkers previously.
"Plus we have medicines that can reduce iron levels in the body," she explains, "so if it is proven that iron is responsible for damage, we might have a way to reduce the damage."
Topiwala noted that researchers did not directly measure iron in the brain, but instead analyzed other aspects of the brain scan, such as changes in magnetic field that are generally linked to iron changes.