Alcohol and muscles: what is the real cost?

“Does having a beer after a workout undo all the benefits?” This is one of the most frequently asked questions at the gym, and the honest answer is more nuanced than the categorical “yes” we often hear. Alcohol does have an effect on muscle – this has been measured, and the mechanism has been identified. But the extent of this effect depends very much on the amount consumed, and large population studies reveal a real surprise.

How alcohol affects muscle-building signals

After a weight-training session, your muscles activate a signalling pathway called mTORC1 — this is what triggers muscle growth. A 2017 study asked fit men and women to drink alcohol immediately after their session, and measured this signalling pathway.

In men, signalling (phosphorylation of mTOR and S6K1) was higher with the placebo than with alcohol, 3 hours after exercise. In women, however, no significant effect of alcohol was observed. This is the first key point to note: on this specific point, the two sexes do not respond in the same way.

A scientific review from 2022 confirms the mechanism whilst refusing to oversimplify it: alcohol can counteract the increase in mTORC1 signalling caused by weight training, but the effect depends on dose, gender, diet and fitness level.

In chronic drinkers, the effect is quantified

The data is clearest among people who have been drinking heavily for a long time. A 1991 study directly measured the rate at which muscle produces protein in six people with alcoholism.

Muscle protein synthesis is running at around half the reference values. A 2015 review explains why: alcohol primarily impairs protein synthesis, both at rest and in response to anabolic stimuli (nutrients, muscle contraction), by reducing the activity of mTOR kinase.

Added to this is an acceleration of muscle breakdown: a 2014 study showed, based on human muscle biopsies, an increase in autophagy — the muscle breaks itself down more quickly — accompanied by a significant reduction in muscle cross-sectional area as seen on CT scans.

And what about recovery after a tough session?

Here again, the results differ according to gender — and that is troubling.

In the 2012 study, the explanation put forward is interesting: the loss of strength is not solely due to the muscle itself, but to a reduction in nerve control. The brain is less effective at activating the damaged muscle.

The surprising finding: large-scale population studies

If alcohol damaged muscle tissue at any dose, we would expect drinkers to be more likely to be sarcopenic — that is, to lose more muscle as they age. Two meta-analyses have looked into this. They did not find this to be the case.

The authors of the 2016 study state this explicitly: their findings do not support the view that alcohol consumption is a risk factor for sarcopenia in people aged 65 and over. An odds ratio of less than 1 even indicates a lower prevalence of sarcopenia among drinkers.

How does this fit in with biology? We need to tread carefully on both counts. These meta-analyses bring together observational studies in which people who drink are compared with those who do not — without knowing why. Among older people, those who have stopped drinking altogether are often those who are already unwell, which may skew the comparison. The authors of the 2022 study themselves point out that confounding factors such as smoking and dietary habits require further investigation. The only clear and unfavourable finding concerns those under 65.

What about testosterone?

In this respect, the findings are consistent with biological evidence. A 2006 study of 46 men with alcohol abuse problems found significantly low plasma testosterone levels, as well as reduced levels of the hormones that regulate it (LH and FSH). And the longer the abuse had been going on, the lower the testosterone levels were.

So, what about a beer straight after exercise?

A common concern relates to hydration. A 2015 study caused 16 active men to become dehydrated through exercise in the heat, and then gave them either mineral water or up to 660 ml of beer followed by water. The result: the beer had no adverse effect on body weight, blood parameters, fluid balance or urinary output.

In other words, when consumed in moderation and with water, a post-match beer does not hinder rehydration. This says nothing, however, about its effect on muscle building.

In summary

The most accurate interpretation of this literature is neither ‘one beer ruins your workout’ nor ‘alcohol has no consequences’. Rather, it is this: the mechanism is real and dose-dependent; it mainly affects men in the available studies; and it becomes clearly evident when consumption is chronic and heavy.

And if you want to know what really matters when it comes to building muscle, start with sets, reps or time under tension.

Every figure in this article is taken from the studies listed below, summarised on the basis of their abstracts alone. Please be aware of the doses: several studies focus on chronic and heavy consumption, or even on people with alcohol dependence, and do not apply to occasional consumption. Meta-analyses on sarcopenia are observational and do not establish a cause-and-effect relationship. This is for information purposes only and is not a substitute for medical advice. If you are concerned about your alcohol consumption, speak to a doctor.