We Love Alcohol, but the Immune System Disagrees

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Dealing with COVID-19 has made all of us obsessed with keeping our immune system nice and fit. What we eat and drink can have a real impact on it. As a recovering alcoholic, thinking about alcohol consumes a good deal of my cognitive energy. I’m also a scientist studying the immune system. So, naturally, I was wondering: How does alcohol affect the immune system?

Spoiler: It’s mostly bad for you.

There’s a solid reason why pregnant women are advised not to drink. If an expecting mother drinks while pregnant, the fetus will have problems developing a proper immune system, particularly in the lungs1. This can put the child at a higher, more than 2-fold, risk for infections. In the case of severe alcohol use, this risk can increase up to 4-fold.

In adults, alcohol abuse significantly reduces the number of T and B cells, crucial cells for fighting infections, and impairs their functions2. Alcohol also limits immune cells’ ability to migrate to where there’s an injury or infection in the body.

Excessive alcohol consumption increases the susceptibility to certain infections like pneumonia3. Heavy alcohol use is a risk factor for severe influenza, especially in the elderly over 65 years old4. It also makes you more likely to develop acute respiratory stress syndrome (ARDS), a term you might be familiar with now. This is what happens in some severe cases of COVID-19.

Alcohol creates tissue damage in the intestines and interferes with the gut microbiome, the almost-magical collection of microorganisms living in our guts and impacting many biological processes, including immunity5. Diversity of the microbiome is crucial for a robust immune system, but alcohol can negatively impact this diversity. Also, since alcohol damages the barriers in the intestines, these microbes can leak into the circulation6. When confined in the intestines, they are helpful to us. When leaked into the blood circulation, they can potentially be life-threatening.

These days, lung infections are in the spotlight. Alcohol takes a real toll on the lungs as well. It damages the lungs’ tissue lining and interferes with the function of the local immune cells, leaving the body especially vulnerable to respiratory infections7. That’s definitely not something that we would like during the respiratory pandemic we’re experiencing.

How much is too much?

Chronic alcohol use, or alcohol abuse, is clearly not good for us. What about moderate drinking? Although some studies suggest that moderate amounts of alcohol can actually be beneficial, there is skepticism, and other studies counteract the idea8. An important thing to consider is the type of drink that is consumed. I’ll explain this in more detail below. Now, let’s see what is regarded as moderate alcohol consumption. The American Center for Disease Control (CDC) defines moderate alcohol intake as 2 drinks or less in a day for men and 1 drink or less for women. Consumption above this is not recommended.

What if you’re not a chronic drinker but drink just once in a while during a wild night out with friends? Studies show that acute binge-drinking, defined as 5 or more standard alcohol drinks by men and 4 or more by women over 2 hours, has detrimental effects on the gut, lungs, liver, heart and brain, just like chronic drinking9. Binge-drinking causes more severe tissue injury in women, whose alcohol metabolism work differently, and more toxicity in the elderly.

Good news: Wine is not so horrible!

Alcoholic beverages contain ethanol, which is what is detrimental to the immune system. However, some beverages, such as wine, also contain polyphenols and antioxidants, which can be protective. For instance, in a mouse study, scientists fed the mice with ethanol or wine containing the same amount of ethanol for 8 weeks10. While the mice that drank plain ethanol experienced a decline in immune cell numbers and responsiveness against a microbial challenge, the wine-drinking mice had normal cell numbers and responses. In another study, consumption of red wine, but not beer and spirits, was associated with less common cold infections11. Another study comparing wine with gin containing the same amount of ethanol revealed that wine, but not gin, significantly reduced many inflammatory proteins after 28 days of consumption12. High levels of these proteins contribute to the dysfunctioning of the immune system, especially in the elderly.

What about vaccines?

Alcohol might impact the efficiency of vaccines, but it’s something to investigate for every specific disease and vaccine. For instance, it can interfere with the response to pneumonia vaccination, but not with hepatitis A or B vaccinations13. Interestingly, in a study with rhesus macaques, alcohol abuse negatively affected vaccine responses, but moderate alcohol use actually enhanced the production of antibodies and antiviral proteins14.

There is no clear scientific information on alcohol’s effect on COVID-19 susceptibility or the vaccines against it. However, many news outlets have been speculating about it. Knowing all we have learned about alcohol’s effects on the immune system, I would say that it’s better to avoid it for a little while until the worst of the pandemic is over. Even if it doesn’t interfere with the vaccines’ effects, wouldn’t you prefer to keep your immune system in the best shape, ready for battle?

Sources

  1. Gauthier, Theresa W. “Prenatal alcohol exposure and the developing immune system.” Alcohol research: current reviews 37.2 (2015): 279.
  2. Pasala, Sumana, Tasha Barr, and Ilhem Messaoudi. “Impact of alcohol abuse on the adaptive immune system.” Alcohol research: current reviews 37.2 (2015): 185.
  3. Sarkar, Dipak, M. Katherine Jung, and H. Joe Wang. “Alcohol and the immune system.” Alcohol research: current reviews 37.2 (2015): 153.
  4. Greenbaum, Adena, et al. “Heavy alcohol use as a risk factor for severe outcomes among adults hospitalized with laboratory-confirmed influenza, 2005–2012.” Infection 42.1 (2014): 165-170.
  5. Engen, Phillip A., et al. “The gastrointestinal microbiome: alcohol effects on the composition of intestinal microbiota.” Alcohol research: current reviews 37.2 (2015): 223.
  6. Hammer, Adam M., et al. “The first line of defense: the effects of alcohol on post-burn intestinal barrier, immune cells, and microbiome.” Alcohol research: current reviews 37.2 (2015): 209.
  7. Simet, Samantha M., and Joseph H. Sisson. “Alcohol’s effects on lung health and immunity.” Alcohol research: current reviews 37.2 (2015): 199.
  8. Andréasson, Sven, et al. “Evidence about health effects of “moderate” alcohol consumption.” Alcohol and Society 6 (2014).
  9. Molina, Patricia E., and Steve Nelson. “Binge Drinking’s effects on the body.” Alcohol research: current reviews 39.1 (2018): 99.
  10. Percival, S. S., and C. A. Sims. “Wine modifies the effects of alcohol on immune cells of mice.” The Journal of nutrition 130.5 (2000): 1091-1094.
  11. Takkouche, Bahi, et al. “Intake of wine, beer, and spirits and the risk of clinical common cold.” American Journal of Epidemiology 155.9 (2002): 853-858.
  12. Estruch, Ramon, et al. “Different effects of red wine and gin consumption on inflammatory biomarkers of atherosclerosis: a prospective randomized crossover trial: effects of wine on inflammatory markers.” Atherosclerosis 175.1 (2004): 117-123.
  13. Zimmermann, Petra, and Nigel Curtis. “Factors that influence the immune response to vaccination.” Clinical microbiology reviews 32.2 (2019).
  14. Messaoudi, I., et al. “Moderate alcohol consumption enhances vaccine-induced responses in rhesus macaques.” Vaccine 32.1 (2013): 54-61.

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