Even Moderate Drinking Linked to Leaky Gut Syndrome

alcohol increases leaky gut

Research finds that alcohol increases leaky gut.

Over a decade of research has proven that one of the things that occurs with alcoholic liver disease is leaky gut syndrome. Chronic alcohol consumption increases the gut’s permeability – called intestinal permeability. As the ethanol metabolites damage the intestines, they loosen the tight junctions of the intestines – causing liver damage.

The link between liver disease and leaky gut has been increasingly revealed in liver disease patients.

This was shown in a study of 909 alcoholic liver disease patients who entered hospitals in Spain. The researchers found that intestinal permeability was common among the liver patients, increasing the risk of fatal liver disease.

Even moderate drinking?

Can even moderate alcohol consumption can significantly increase what is called leaky gut.

The suspicion that alcohol consumption increases leaky gut was suspected as early as 1987, but made more evident by a review from the National Institute on Alcohol Abuse and Alcoholism in 1998. These researchers found that significant alcohol consumption produced damage among the intestinal membranes, producing what they referred to as endotoxemia. Their focus of attention was upon regular drinkers at 6-7 drinks a day.

What about moderate drinking, say 1-2 drinks per day?

A recent study from the Netherlands’ Wageningen University studied precisely this. They analyzed the guts of 12 healthy people before and after moderate alcohol consumption.

The study was placebo-controlled with a crossover design, meaning the subjects were tested twice each of the subjects was given either a placebo or the alcohol during their testing.

The volunteers were tested prior to alcohol consumption. Then they were divided into two groups and one group was given the equivalent of 20 grams of ethanol within 100 milliliters. This is about equal to having a 360 ml bottle of beer or 150 glass of wine – or a 45 ml shot of 80-proof whiskey. The other group in each test was given the same drink but without the alcohol.

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The researchers identified the focus of this study:

“Our aims were to determine effects of a single moderate dose of ethanol, administered intraduodenally, on 1) small intestinal and colon permeability and 2) localization and expression of TJ in duodenal biopsies.”

By duodenal biopsies, they mean that they directly sampled intestinal tissues to determine whether they had the biochemical markers of increased permeability – leaky gut.

The researchers also tested the volunteers’ active intestinal permeability before and after alcohol consumption. They utilized two urinary sugar recovery tests – commonly used to test intestinal permeability among medical researchers. More specifically, these are the lactulose/rhamnose (L/R) ratio in 0–5 h urine and sucralose/erythritol (S/E) ratio. High L/R ratios indicate leaky gut in the small intestines, while high S/E ratios indicate leaky gut in the colon.


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Prior to their alcohol consumption on each test, the volunteers had no blood-alcohol levels. After their consumption of alcohol, the volunteers’ blood-alcohol levels peaked normally and then gradually fell off. The peaks averaged 62 mg/dl and went to 11 mg/dl at three hours. These convert to .062% and .011% blood-alcohol levels, respectively.

Using the urinary sugar recovery testing, the researchers found the alcohol drink significantly increased the L/R ratio compared to the placebo groups. This indicates that moderate alcohol consumption increases leaky gut among the small intestines.

The researchers also found that the alcohol consumption significantly increased the S/E ratio for the 5 hour to 24 hour urine tests. This indicates that moderate drinking also increases leaky gut within the large intestines.

Upon further investigation via intestinal biopsies, the researchers found more evidence of leaky gut. They also saw some of the mechanisms of even moderate alcohol consumption.

The researchers found that the moderate consumption of alcohol interfered with the production of zonulin, and changed the mechanics of the intestinal cells’ integrity. This resulted in a weakening of the tight junctions, producing intestinal permeability after exposure to alcohol (scientifically referred to as ethanol). The researchers concluded:

“Administration of moderate ethanol dosage can increase both small and colon permeability. Furthermore, the data indicate a pivotal role for MAPK and its crosstalk with MLCK in ethanol-induced intestinal barrier disruption.”

Notice the word “moderate” here.

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The researchers also tested moderate ethanol levels using intestinal Caco-2 cells – human intestinal cancer cells. This provided a litmus test for the mechanisms. These laboratory tests found that moderate alcohol produced what is called MAPK activation.

What is MAPK activation?

Simply put, mitogen-activated protein kinases (MAPK) are signaling proteins that typically initiate cellular responses to stress. Their end result is often a derangement of cells – the damage of tissue systems.

And this is precisely what happens in the case of alcohol. Alcohol is not natural to the human body. So the cells respond negatively to alcohol, and this deranges the tissues. The researchers debated whether this effect was related to the oxidation that takes place in the presence of ethanol, but this is still undetermined.

What about gut bacteria?

At least part of the relationship between drinking and leaky gut relates to our gut bacteria. A Belgium study published in the Proceedings of the National Academy of Sciences found that chronic drinking produces an alteration of gut microbes.

In plainer English, alcohol damages our intestinal probiotics.

But what about ‘heart-healthy red wine’?

Yes, some research has found that alcohol consumption specifically in the form of red wine in moderate levels might provide some cardiovascular benefit. A 2015 study from Spain found this effect in comparing red wine drinkers with non-drinkers.

But the basis for this improvement is not the alcohol – it is the polyphenols such as resveratrol that exist more significantly in red grapes. This is evidenced by the fact that the healthy benefits of this study were specific to red wine.

Therefore, if you want to get the cardiovascular benefit of polyphenols like resveratrol without damaging the intestines and producing leaky gut syndrome, try eating some delicious raw red grapes. Plus, raw grapes quite simply taste sweeter.

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Besides, most of the resveratrol content in grapes are in their skins.


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Leclercq S, Matamoros S, Cani PD, Neyrinck AM, Jamar F, Stärkel P, Windey K, Tremaroli V, Bäckhed F, Verbeke K, de Timary P, Delzenne NM. Intestinal permeability, gut-bacterial dysbiosis, and behavioral markers of alcohol-dependence severity. Proc Natl Acad Sci U S A. 2014 Oct 21;111(42):E4485-93. doi: 10.1073/pnas.1415174111.

Tresserra-Rimbau A, Medina-Remón A, Lamuela-Raventós RM, Bulló M, Salas-Salvadó J, Corella D, Fitó M, Gea A, Gómez-Gracia E, Lapetra J, Arós F, Fiol M, Ros E, Serra-Majem L, Pintó X, Muñoz MA, Estruch R; PREDIMED Study Investigators. Moderate red wine consumption is associated with a lower prevalence of the metabolic syndrome in the PREDIMED population. Br J Nutr. 2015 Apr;113 Suppl 2:S121-30. doi: 10.1017/S0007114514003262.

Case Adams, PhD

Case Adams has a Ph.D. in Natural Health Sciences, is a California Naturopath and is Board Certified as an Alternative Medicine Practitioner, with clinical experience and diplomas in Aromatherapy, Bach Flower Remedies, Blood Chemistry, Clinical Nutritional Counseling, Homeopathy and Colon Hydrotherapy. He has authored 27 books and numerous articles on print and online magazines. Contact: [email protected]

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