"Normal" drinking for the New Scientist group ranged from 10 units of alcohol per week — the equivalent of about eight 12-ounce bottles of regular-strength beer — to 80 units, or 64 beers, per week. Those numbers may seem high, but in Britain, where drinking is a national pastime, the group's supervising doctor told them none were problem drinkers. (Incidentally, Britain's National Health Service recommends no more than 14 to 21 alcohol units per week.)

The results of these changes were significant enough to make you put down your pint and take notice.

Dr. Rajiv Jalan, a liver specialist at the Institute for Liver and Digestive Health at University College London, analyzed the findings. They revealed that liver fat, a precursor to liver damage, for all of those in the study who gave up drinking fell by at least 15 percent, and almost 20 percent for some.

Abstainers also saw their blood glucose levels — a key factor in determining diabetes risk — fall by an average of 16 percent. It's the first study to show such an immediate drop from going dry, says Dr. James Ferguson, a liver specialist at Queen Elizabeth Hospital Birmingham in England, who was not involved in the experiment.

Overall, Ferguson says, the evidence is convincing but not all that surprising.

"If you take time off from alcohol, it's going to be beneficial for your liver from the reduction of fat," he tells The Salt. "People always forget the amount of calories in alcohol, so if you take a month off, and you usually consume 20 units, you're going to lose weight and fat. It's a massive reduction in calories. "

The main causes of excessive fat in the liver are obesity and excessive alcohol consumption. Alcohol changes the way the liver processes fat, resulting in more fat cells that can cause inflammation, leading to liver disease.

But Ferguson warns that a dry January could trigger the same sort of negative boomerang effect as do restrictive diets: First you abstain, then you binge to make up for it. He questions whether a dry January leads to a wetter-than-normal February.

Beyond that, there's the question of whether and how much these improvements last in the long run. Ferguson takes a sobering view.

"I don't think taking one month a year off alcohol makes any difference," he says. "It's more important to cut back generally."

In fact, The British Liver Trust doesn't endorse a dry January, saying the tradition is "medically futile" and encourages alcohol abuse the rest of the year. Instead, the Trust suggests staying off the sauce two or three days every week, allowing the liver to recover regularly.

Copyright 2014 NPR.

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