How does alcoholic liver disease affect the digestive system?
For thousands of years, man has produced alcohol, distilling anything that contained enough slow or fast sugars.
As a whole, excessive drinking can alter cognitive functions, increase the risk of alcoholic liver disease, cancer, and other diseases. It induces extreme bacteria growth in the small intestine and a dysbiosis of the colonic microbiota, which will become poor due to a lack of diversification.
Alcohol reduces states of fear and anxiety, fights against depression and pain, or simply brings a feeling of unlimited power.
However, these immediate beneficial effects of alcohol can be negated when alcohol dependence sets in.
Continue reading to learn all about alcoholic liver disease and its impact on our digestion.
Table of Contents
- 1 How does alcoholic liver disease affect the digestive system? Introduction
- 2 The impact of alcohol consumption on our intestinal microbiota
- 3 Excessive alcohol and its damage to the liver
- 4 Alcoholic liver disease and gut microbiota
- 5 Alcohol-induced severe liver damage affects our gut microbiota
- 6 Dysbiosis and alcohol dependence
- 7 Changes in microbiota and alcohol-related liver damage
- 8 How does alcoholic liver disease affect the digestive system? Conclusion
How does alcoholic liver disease affect the digestive system? Introduction
When alcohol consumption becomes chronic, the excess of alcoholic beverages can alter cognitive functions and memory and eventually cause brain damage leading to dementia.
It also increases the risk of accidents, cardiovascular diseases (such as heart rhythm disorders and high blood pressure), cancers (of the mouth, throat, esophagus, colon), and cirrhosis due to steatohepatitis lesions induced by alcohol toxicity on the liver.
When an individual reaches the stage of cirrhosis, the risk of liver cancer is very high. Excessive drinking is responsible for millions of deaths per year worldwide.
The physical and psychological deterioration caused by excessive alcohol consumption has many harmful consequences on the family and social life of excessive drinkers.
Furthermore, the gut microbiota creates inequalities for humans regarding the risk of alcohol dependence and severe liver damage related to excessive consumption of alcoholic beverages.
This article will uncover how alcoholic liver disease can impact our gut microbiota.
The impact of alcohol consumption on our intestinal microbiota
When an individual has a chronic excessive consumption of alcoholic beverages, this induces an abnormally high growth of bacteria in the small intestine and a dysbiosis of the colonic microbiota.
This dysbiosis will weaken the epithelial barrier and cause disorders of intestinal permeability, characterized by a decrease in bacteria of the Clostridium family, which produce butyrate (the leading supplier of energy to intestinal epithelial cells).
Therefore, it also leads to a bacterial translocation as dangerous as alcohol consumption, which will also be associated with the emergence of enterobacteria, opportunistic bacteria, and carriers of endotoxins.
The mechanisms by which alcohol causes these intestinal dysbioses are not yet known.
Excessive alcohol and its damage to the liver
Excessive alcohol consumption will lead to liver problems. But what is the role of the liver, and what are the possible injuries due to this consumption of alcoholic beverages? This is what we will discover in this section.
The liver plays a significant role in the elimination of alcohol
The alcohol we ingest is absorbed by the small intestine. The absorption speed is very fast when the stomach is empty, with a peak concentration in the blood 25 minutes after ingestion.
This peak will be later and lower if alcohol is consumed while food is ingested. The diffusion of alcohol from the blood to the brain, liver, and lungs occurs very quickly, in just a few minutes.
However, it is interesting to know that a small part of the alcohol ingested will be eliminated through breathing, sweat, urine, or breast milk.
In fact, the concentration of alcohol in exhaled air is always 1,000 times lower than in the blood. This constant ratio allowed the development of breathalyzers to evaluate our blood alcohol level while driving.
It is essential to know that alcohol is transformed before it is eliminated. In the liver, alcohol undergoes two successive transformations:
- During the first transformation, several enzymes, including alcohol dehydrogenase, transform it into acetaldehyde, responsible for many unpleasant symptoms, such as redness, excessive sweating, headaches, nausea, malaise, etc.
- Then, acetaldehyde is transformed by another enzyme, aldehyde dehydrogenase, into acetate, which will be eliminated by the kidneys and lungs.
Alcohol causes liver damage
Drinking alcoholic beverages causes liver damage. In fact, alcohol is responsible for three types of liver damage: steatosis, alcoholic hepatitis, and cirrhosis (the final stage).
This lesion is present in most people who consume alcohol in excess.
Isolated, this steatosis can be reversed without consequences if no more drinking occurs.
Alcoholic steatohepatitis is associated with steatosis lesions, inflammatory lesions close to metabolic steatohepatitis lesions.
In time, it can also cause fibrous scarring in the liver.
Acute alcoholic hepatitis
This hepatitis is observed during excessive consumption of alcoholic beverages in individuals who are often malnourished and have reduced their diet while drinking heavily.
Very often, and without specific symptoms apart from jaundice, this disorder can manifest as fever and significant fatigue.
Alcoholic hepatitis is of variable severity. Indeed, one can go from moderate hepatitis that will heal in several weeks to severe forms, which are sometimes fatal.
Repeated alcoholic hepatitis causes the accumulation of fibrosis scars in the liver and can eventually lead to cirrhosis.
This is the final stage of alcoholic liver disease and is responsible for the complications and the large number of liver cancers.
Alcoholic liver disease and gut microbiota
Due to excessive alcohol consumption, the gut microbiota will be very abnormal in patients with cirrhosis.
The gut microbiota will become poor, not very diversified, and characterized by an abnormally strong bacterial proliferation in the small intestine, by an increase of Bacteroides and bacteria of oral origin.
Several colonies of opportunistic bacteria not present in the normal state will multiply in the gut microbiota of people with cirrhosis.
This dysbiosis will also be accompanied by an increase in the synthesis of acetaldehyde by the intestinal bacteria, which increases the risk of colonic cancer.
Alcohol-induced severe liver damage affects our gut microbiota
Some people point out a great inequity between human beings regarding addiction and toxicity on the liver during excessive consumption of alcoholic drinks.
Several studies have been performed that have changed the understanding of the mechanism of steatotic liver injury.
Indeed, in this research, germ-free mice exposed to alcohol developed more severe liver damage than normal mice. This result shows that the gut microbiota of normal mice protects them, at least in part, from alcohol-induced liver damage.
Studies in humans also point in this direction. They revealed that the gut microbiota of heavy drinkers without alcoholic hepatitis lesions was different from the microbiota of patients with alcoholic hepatitis.
The differences were apparent and involved many families of bacteria. Two hypotheses could explain the difference between these two groups of sick people:
- The first hypothesis is that severe dysbiosis is the consequence of alcoholic hepatitis.
- Conversely, the second hypothesis is that intestinal dysbiosis favored alcohol-related liver damage.
An experiment was carried out to decide between these two hypotheses.
In two groups of germ-free mice exposed to alcohol, the researchers transplanted either the flora of excessive drinkers without serious liver damage or the flora of patients with severe alcoholic hepatitis.
This experiment showed that, with equal exposure to alcohol, mice that received the intestinal flora of drinkers with severe liver damage developed:
- marked inflammatory lesions of the liver,
- dysbiosis of intestinal permeability disorders, and
- bacterial translocation.
While the mice that received the flora of the drinkers without liver damage did not develop severe liver damage or intestinal permeability disorder.
Therefore, this experiment has affirmed the determining role of intestinal dysbiosis and intestinal permeability disorders in the occurrence of severe liver damage in excessive alcohol drinkers. This is the answer to ‘How does alcoholic liver disease affect the digestive system?’
It also opens up new possibilities in treating and preventing alcohol-induced liver damage.
Dysbiosis and alcohol dependence
The pleasure centers at the center of drug addiction
In the 1950s, researchers tried to identify the functions of different brain areas in rats by implanting electrodes.
The rats could activate these brain areas themselves only by pressing a lever that gave them a small amount of electricity in the electrodes.
The researchers were testing an area involved in alertness when they were surprised to see that one of the rats subjected to the experiment had a very unusual behavior. He kept coming back to the lever to stimulate his electrode.
After verification, the electrode had been poorly positioned in this animal and stimulated a brain area different from the tested area.
The experiment was then reproduced on more rats by placing the electrode in the new area, and the results were incredible.
The rats were constantly pulling the lever to the point of neglecting their meals, and the mothers forgot their infants, while reducing their sleep periods. These behaviors are reminiscent of the behaviors of individuals suffering from drug addiction.
These researchers had just discovered the pleasure centers located in the deep part of the brain in the limbic system specialized in emotions.
Later, other works also allowed to identify within the limbic system, next to the “all pleasures” area, numerous pleasure areas specialized in the satiety of hunger, thirst, or sexuality.
The pleasure centers are activated by a neuromediator, dopamine, which is secreted abundantly in these centers at the very moment when the idea of pleasure reaches our minds.
These centers provide a reward in exchange for a beneficial action for our body, such as eating or drinking. The reward is provided by the secretion of endogenous morphines, called endorphins, which are opioid substances secreted by the brain.
Therefore, the repetition of the actions reinforces the reward, and the addiction circumvents the system to reward the taking of the drug.
Close to the pleasure centers and located on the emotional circuit, brain structures have been discovered whose stimulation will cause an opposite effect to that of the pleasure centers, the aversion centers.
By playing with the balance between reward and aversion, our brain can regulate our behaviors for the good of our health. If this balance is solid, the occasional use of addictive substances such as alcohol will not induce strong dependence.
However, regular and heavy alcohol consumption will disrupt normal brain function and force the brain to find a new equilibrium considering the effects of alcohol itself.
Once this balance has been achieved, it has become essential to maintain the intake of alcoholic beverages.
For this reason, the pleasure centers will reward drinking despite the difficulties that may arise, such as lack of money, loss of job, or loss of driver’s license.
In addition, the patient will also be drawn into a more complicated and more destructive addiction.
Studies have shown that a depletion of the microbiota induced in mice by antibiotic treatment can increase the activity of reward circuits by reinforcing cocaine addiction.
The restoration of a dense and diversified intestinal microbiota will be accompanied by a return to the normal activity of these circuits.
In humans, an intestinal dysbiosis is associated with alcohol dependence, characterized by:
- a depletion of the microbiota,
- a deficit in butyrate-producing bacteria, and
- an enrichment in pro-inflammatory bacteria that are partly of oral origin.
One study investigated the relationship between bowel abnormalities and symptoms before and after three weeks of abstinence in heavy drinkers.
Disorders of intestinal permeability and bacterial translocation, initially present in some patients, regressed completely after weaning.
Alcohol-dependent individuals were characterized by the presence of chronic inflammation with higher elevations of pro-inflammatory cytokines in the blood.
Moreover, at the psychological level, these people had more marked psycho-behavioral signs such as:
- difficulties concentrating, and
- episodes of brutal, powerful, and irresistible desires for alcohol that experts call “craving.”
Craving is a sign of strong addiction and a risk of relapse after withdrawal. Depression and anxiety were associated with increased cytokines in the blood resulting from bacterial translocation and immune system activation.
In summary, the dysbiosis caused by excessive alcohol consumption will weaken the intestinal barrier favoring bacterial translocation and the appearance of inflammation.
These abnormalities are one of the mechanisms involved in depression and anxiety.
The various studies carried out on mice and the findings in humans suggest that these anomalies are likely to modify the functioning of the reward circuits and, beyond that, reinforce alcohol dependence.
Other studies have shown that administering a prebiotic or performing a fecal transplant in mice exposed to alcohol protects them from liver damage and restores a healthy microbiota.
In humans, randomized trials have tested treatments designed to modify the intestinal microbiota by taking probiotics or by fecal transplants.
These trials are few in number, but their encouraging results make it possible to deepen this line of research.
Randomized, placebo-controlled research has tested probiotics in patients with alcohol-related complications.
A study was carried out on about 60 patients with psychiatric disorders related to excessive consumption of alcoholic beverages. One-third of them had alcoholic hepatitis.
This study revealed a reduction in intestinal dysbiosis and an improvement in liver function in patients who received a probiotic containing the bacteria Bifidobacterium bifidum and Lactobacillus plantarum.
Another study tested two bacteria (Bacillus subtilis and Enterococcus faecium) in 100 people who were ill and hospitalized for alcoholic hepatitis.
Compared to the patients who received a placebo, the patients who received the probiotic were characterized by improved liver balance and decreased inflammation and endotoxemia.
Therefore, this research suggests that the dysbiosis responsible for alcohol-induced liver damage is accessible to probiotics, with a beneficial effect on liver blood balance and signs of inflammation.
However, they have not shown any long-term benefit on the length of hospitalization, regression of liver damage, or survival of patients.
Tip: If you’ve been prescribed antibiotics and probiotics simultaneously, check our this post to maximize the effect of both: How Should Probiotics Be Taken with Antibiotics? Gut Protection Insights
Several studies have been conducted regarding fecal transplantation and its relationship to alcohol-induced liver damage.
In this research, fecal transplantation via jejunal tube was repeated daily for one week:
- A study was done on eight patients whose liver function improved after transplantation. The latter would also have reduced the populations of dangerous bacteria in the intestinal microbiota.
- Another study compared fecal transplantation to drug treatments for alcoholic hepatitis or nutritional measures in men with alcoholic hepatitis.
- This study showed that fecal transplantation was associated with better survival of several months in patients. Regression of intestinal dysbiosis was not observed in patients who did not have fecal transplantation.
However, it should be kept in mind that these studies are not sufficient to affirm the effectiveness of fecal transplantation in the survival of patients with severe alcoholic hepatitis.
How does alcoholic liver disease affect the digestive system? Conclusion
Excessive consumption of alcoholic beverages can lead to an imbalance in our intestinal microbiota.
In addition, drinking alcohol excessively has harmful consequences on our liver. For example, it can cause severe and even fatal diseases such as cirrhosis and cancer.
Alcoholic liver disease in particular significantly affects the digestive system.
It is essential to drink alcohol in moderation to avoid the harmful effects that excessive alcohol consumption can have on our bodies.