It is widely known that alcohol can negatively affect your overall health and wellbeing when consumed in excess. In relation to gut health, too much alcohol use is particularly damaging to the gastrointestinal (GI) system, adversely influencing the gut microbiome, intestinal lining integrity, immune function, and the gut-liver axis. These alcohol-induced impacts are thought to cause inflammation throughout the body and contribute to various associated disease states [1-7]. This article will explore the interactions through which sustained alcohol consumption disrupts the delicate gut equilibrium and promotes local and systemic inflammation.
Why is Gut Inflammation Bad?
Before we explore the various ways alcohol can incite intestinal inflammation, it's critical to understand why inflammation is bad for the body in the first place.
Some of the outcomes of untreated chronic intestinal inflammation include:
Increased intestinal permeability
Impaired nutrient absorption
Diarrhea and digestive issues
Increased cancer risk
Exacerbation of IBD 
Alcohol and the Gut Microbiome
The human GI tract is home to trillions of microorganisms, including bacteria, viruses, and fungi, collectively termed the “gut microbiome.” Under normal conditions, this complex community aids digestion, facilitates nutrient absorption, and supports immune function. However, chronic excessive alcohol consumption can severely disrupt this intricate balance, causing overgrowth of potentially harmful microbes [2, 4, 5, 7].
Several studies demonstrate that when compared to moderate drinkers and non-drinkers, alcoholics have an increased abundance of detrimental bacterial strains (such as proteobacteria) and decreased levels of beneficial microbes (such as Bifidobacterium and Lactobacillus) [2, 4, 5, 7]. One study found that alcoholics have 2-5 times more proteobacteria than light drinkers or controls . Proteobacteria produce highly inflammatory endotoxins called lipopolysaccharides (LPS), while commensal organisms like Bifidobacterium generate anti-inflammatory short-chain fatty acids (SCFAs). This imbalance between inflammatory and anti-inflammatory microbes can incite intestinal inflammation.
Alcohol also permits normally suppressed bacteria like Klebsiella, Escherichia, and Candida fungi to propagate and dominate the microbial landscape [2, 7]. The oral microbiome of alcoholics is also enriched with bacteria like Prevotella, Streptococcus, and Veillonella that may migrate to colonize the gut and increase intestinal inflammation .
In addition to bacterial alterations, alcohol influences microbial metabolite production by reducing the production of both SCFAs and long-chain fatty acids (LCFAs). Research shows that alcoholics have reduced fecal SCFAs, which help maintain the intestinal barrier, and Butyrate-producing bacteria like Faecalibacterium. Additionally, alcohol has shown to decrease levels of LCFAs which can support the growth of beneficial microbes [5, 7]. Taken together, the sum of alcohol’s effects cultivates an intestinal environment conducive to inflammation.
Alcohol’s Effect on the Intestinal Barrier
In addition to disrupting microbial communities, alcohol also directly damages the intestinal barrier, potentially leading to increased permeability of the intestinal lining, known as “leaky gut” . This barrier consists of epithelial cells bound together by tight junctions and coated with a protective mucus layer, which ordinarily prevents gastrointestinal contents from entering into circulation. When this protective layer is compromised, it allows bacteria and other inflammatory substances to pass through the intestinal wall into the bloodstream. Instead of being securely confined within the gut, these substances spread, causing inflammation throughout the body.
Alcohol and the Immune System
Excessive alcohol also impedes immune cell function in the intestine, severely undermining the gut’s capacity to regulate bacteria and other microbes. Alcohol suppresses antimicrobial peptides that normally restrict bacterial overgrowth in the gut , and broadly suppresses the activity of various intestinal immune cells, including lymphocytes and neutrophils, hindering efficient bacterial clearance . Specifically, alcohol can inhibit lymphocyte and neutrophil function in the intestinal mucosa  and may also reduce zinc levels required for immune cell development . This impairment enables harmful bacteria to extensively propagate, damaging your gut’s natural immune defenses and leaving the body more susceptible to diseases.
Alcohol and the Liver
The liver is significantly impacted by alcohol-induced intestinal inflammation since gut contents drain directly into it via the portal vein. Alcohol metabolism also chiefly occurs within liver cells, directly exposing them to alcohol’s toxic effects .
When the intestinal barrier is compromised, bacteria like proteobacteria and inflammatory products like LPS escape the gut and enter portal circulation destined for the liver . Once in the liver, this influx activates specialized immune cells called Kupffer cells, triggering inflammation and damage. Kupffer cells drive inflammation and over time, chronic gut-derived inflammation can catalyze the progression of alcoholic liver diseases like hepatitis, fibrosis, cirrhosis, and even liver cancer .
Systemic Consequences of Alcohol Consumption
Chronic intestinal inflammation and “leaky gut” have detrimental impacts extending far beyond the liver. For instance, alcohol-related bacterial products such as LPS and fungal β-glucans and inflammatory cytokines entering the bloodstream can act on the brain by crossing the blood-brain barrier.
Intestinal inflammation is also linked to various GI cancers as well as distal digestive tract malignancies . Furthermore, alcohol is known to exacerbate inflammatory bowel diseases like Crohn’s and colitis .
Additional systemic effects may stem from vitamin and mineral deficiencies due to intestinal inflammation. Chronic heavy alcohol use commonly leads to deficiencies in critical micronutrients like vitamin A, B vitamins, vitamin C, zinc, and selenium, which are essential for immune function and antioxidant activity . Impaired nutrition and absorption induced by intestinal inflammation also contribute to these commonly observed deficiencies in alcoholics.
Alcohol may also suppress acetylcholine, a vagus nerve-stimulating neurotransmitter influencing gut motility and secretion . These neuroendocrine effects likely underlie common alcohol-related GI complaints like diarrhea.
Reducing Intestinal Inflammation
Given alcohol's extensive detrimental impacts on nearly all facets of intestinal health, an important avenue of research is looking into potential interventions that might reduce these effects and restore gut equilibrium. Some preliminary clinical studies provide provisional evidence that certain dietary modifications, supplements, and medications may help rebalance the gut microbiome and reinforce intestinal integrity.
For example, early trials indicate probiotic foods containing beneficial bacterial strains of Lactobacillus and Bifidobacterium could help increase intestinal populations of these microbes in alcoholics thus aiding in diversity . Prebiotic fibers that promote protective microbial growth may also hold therapeutic promise. If you are interested in learning about the positive impact of probiotics and prebiotics, check out our blog, where we cover these topics and a wealth of others related to gut health.
Various treatments for mitigating alcohol-related pathologies are a growing are of research as well. Medications like gut-targeted antibiotics may rectify alcohol-related dysbiosis and leaky gut, and fecal microbiota transplantation could help reset microbial populations in alcoholics  . However, larger rigorous clinical trials are required to verify the efficacy and safety of these gut-targeting interventions.
In summary, chronic excessive alcohol consumption adversely affects nearly every facet of intestinal health, including the resident microbial community structure and function, intestinal barrier integrity, immune defenses, and gut-liver signaling. These alcohol-induced disruptions potentiate both local and systemic inflammation that may underpin various associated diseases. Further research into these complex interactions will be key to developing therapies that can counteract the far-reaching detrimental impacts of alcohol on gut and overall health. With this in mind, it’s important to consume alcohol in moderation and ideally infrequently.
If you’re curious to see how alcohol can impact your symptoms and microbiome, look no further than the Injoy app and microbiome test (available on our Shop). Connect with GutChat, our dedicated gut-health AI ChatBot, or reach out directly to a team member at email@example.com to get started on your gut health journey.