When it comes to liver health, is it best to abstain completely from alcohol regularly for short periods, as in the Japanese concept of “liver holidays?”Or should we try to spread our drinking out evenly across the week with no breaks? Dr Erik Skovenborg examines the latest medical research.
In Japan, it is widely believed that persistent heavy drinking can damage the liver; therefore, “liver holidays”—abstaining from alcohol for two or more days each week—are considered important for general health and for maintaining the function of the liver. However, limited epidemiologic evidence supports the concept of liver holidays. A recent meta-analysis of drinking the same amount of alcohol daily or non-daily retrieved five studies of moderate quality and found daily drinking associated with a significant increase in risk of liver cirrhosis compared to non-daily drinking, with pooled relative risks of 1.71 for men and 1.56 for women.1
The mechanisms that underlie the observed association are unclear. In the liver, alcohol is oxidized to acetaldehyde by alcohol dehydrogenase, and acetaldehyde is then broken down into acetate that is used as calorie energy for the body. Acetaldehyde, a highly toxic substance, is considered a mediator of alcoholic liver damage. One possible explanation for the suggested benefit of liver holidays is that non-daily alcohol consumption allows the liver time to recover after each episode of drinking.
Your liver at work
Your liver is estimated to have more than 500 different functions, and metabolizing the alcohol in your drinks is one of them. The rate of disappearance of alcohol (milligrams of alcohol per 100ml body water per hour) is determined by your amount of body water and drinking habits. First, a calculation of body water: Men: weight (kg) x 0.68 = body water (liter). Women: weight (kg) x 0.55 = body water (liter). On average, a moderate drinker can break down 15mg alcohol per 100ml body water per hour. Here are different examples of the influence of drinking habits.2
Related
• Light to moderate drinker, drinking on an empty stomach: 10–15mg/100ml/h
• Light to moderate drinker, drinking with a meal: 15–20mg/100ml/h
• Heavy drinkers and alcoholics: 25–35mg/100ml/h
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The rate of alcohol metabolism for a moderate drinking man (weight 80kg x 0.68 = 56.4l body water) having a daily large glass of wine (150ml) with his dinner would be 19mg/100ml/h = 0.19g alcohol/liter body water/hour = 0.19g x 56.4 = 10.7g alcohol/hour. And the metabolism of 150ml wine (13.5% ABV) = 20ml alcohol = 16g alcohol will thus be finished in 1.5 hours. Accordingly, for each 24 hours, the moderate drinking man’s liver has a holiday of 22.5 hours.
Fatty liver disease and binge drinking
Ethanol is a nutrient with a caloric value about 7kcal per gram, so a large glass of wine contributes to approximately 112 calories of acetate. The alcohol-derived calories are produced by the liver at the expense of the metabolism of normal nutrients, because the alcohol in your glass of wine will be oxidized preferentially over the foods on your plate. Alcohol metabolism promotes accumulation of fat in the liver mainly by substitution of acetate calories for fatty acids as the major hepatic fuel. A healthy liver contains a small amount of fat, and fat buildup only becomes a “fatty liver” problem when it reaches more than 5 percent of your liver’s weight.
A study of moderate red wine consumption in healthy students found that consumption of 33g alcohol per day in men and 16g per day in women for three months did not induce MRI-measured steatosis (fatty liver) in single subject, indicating that people sticking within the UK alcohol guidelines (no more than 14 units of alcohol a week, spread across three days or more) should not be at risk of developing fatty liver disease.3
The flip side of liver holidays
The flip side of liver holidays during the week is weekend binge drinking. The National Institute on Alcohol Abuse and Alcoholism defines binge drinking as a drinking pattern that brings blood alcohol concentration to ≥ 0.08 percent. For a typical adult, this pattern corresponds to consuming ≥5 drinks (male), or ≥4 drinks (female), in about two hours. The Finnish population-based Health 2000 Study found binge-drinking frequency associated with liver-disease risk after adjustment for average daily alcohol intake and age. The hazard ratio for binge drinking monthly was 2.26 and for binge drinking weekly 3.45.4
The meta-analysis authors acknowledge the conflict between liver holidays and binge drinking. “The existing research on patterns of drinking indicates that it is better to drink a fixed volume of alcohol spread over as many drinking days possible and to avoid heavy episodic drinking occasions altogether. Such advice is in conflict with the advice to avoid daily drinking.” Thus, they propose a distinction between heavy and non-heavy drinkers. “For heavy drinkers, with risks for alcohol use disorders and liver cirrhosis, drinking-free pause days should be recommended. For non-heavy drinkers, the best advice may be to spread out the drinking so that the least number of grams of pure alcohol per day is consumed.”
Notes
1. Drug Alcohol Review 42 (2023), pp.119–24.
2. British Medical Journal 330 (2005), pp.85–87.
3. Annals of Medicine 43:7 (2011), pp.545–54.
4. Liver International 37 (2017), pp.1373–81. ▉
