Four beers a day is enough to stunt annual growth of developing brains by almost 47%
A study at Oregon Health & Science University (OHSU) of alcohol's effect on rhesus macaque monkeys has shown nasty effects on developing brains. Each gram of alcohol per kilogram of body weight (the human equivalent of four beers a day) reduced the rate of brain growth by nearly 47 percent per year.
The researchers noted a significant decline in the rate of growth of the brain, cerebral white matter and subcortical thalamus, using MRIs to measure brain growth in adolescent and young adult monkeys that voluntarily consumed ethanol or alcoholic drinks. Alcohol intake, diet, daily schedules and health care were precisely measured.
This study was an attempt to follow up on previous studies that had shown alcohol's effect on brain development in humans – but the human studies were based on potentially unreliable self-reporting of alcohol intake by underage drinkers, instead of precise measurements. Christopher Kroenke, Ph.D, an associate professor in the Division of Neuroscience at OHSU's primate center, said this study eliminated any vagueness around this point: "our measures pinpoint alcohol drinking with the impaired brain growth."
The study also managed to determine the normal rate of brain growth in rhesus macaques in late adolescence and early adulthood at about 1 mm per 1.87 years – so a reduction of 0.25 mm of growth per year represents a 46.75 percent decline in heavy alcohol users. That's a heavy price to pay for the human equivalent of four beers a day, an amount that many college kids might call a light day's drinking.
Funded by the National Institute on Alcohol Abuse and Alcoholism of the National Institutes of Health, the study made no claims about any long-term effects on mental function or learning, but is planning to address these questions in further research.
The team's research was published in the journal eNeuro.
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It would be interesting to see how a few thousand years of 'selection for people who can developmentally cope with alcohol' has changed the effect in humans.