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The Gut Check: Unraveling the Effects of Alcohol on Gut Health

by Valerie Polley | Aug 16, 2023 | 0 comments

While enjoying a social drink occasionally likely isn’t cause for alarm, excessive alcohol intake carries several health risks, including high blood pressure and various cancers.

But what about the effect of alcohol on the gut? While we’re still learning about the effects of alcohol on the gut in humans, animal studies provide clues about how alcohol intake could harm our gut. Excessive alcohol intake is correlated with changes in the gut microbiome, inflammation in the digestive tract, increased gut “leakiness,” and impaired nutrient absorption.

Read on to learn about the different ways excessive alcohol consumption can impact your gut, plus tips for enjoying alcohol safely and responsibly.

 

The Gut Microbiome: A Balancing Act

The gut microbiome is the community of microorganisms that live in the human intestinal tract. They have numerous important functions, including the production of vitamins and essential amino acids. They also produce short-chain fatty acids (SCFAs), which fuel the intestine's cells and can influence the immune system.

Studies have uncovered links between the composition of the intestinal microbiome and different diseases, including inflammatory bowel disease (IBD), inflammatory skin diseases, autoimmune arthritis, type 2 diabetes, obesity, and atherosclerosis. In many cases, less bacterial diversity and lower overall numbers of certain bacteria are associated with developing these diseases.

Alcohol consumption can disrupt the balance of microorganisms in the gut. This is known as gut dysbiosis. One study showed that alcohol consumption led to the overgrowth of bacteria in the small intestine, where the number of microorganisms should be low. It’s possible that this occurs because alcohol impairs gut motility (the movement of food through the digestive tract).

Other studies show that there is a correlation between alcohol and changes in the ratio of “good” bacteria to “bad” bacteria, with “bad” bacteria increasing after chronic alcohol consumption in a study on mice.

While we’re still learning about how alcohol affects specific species of bacteria in the gut, preliminary findings show that excessive alcohol consumption can negatively impact your gut microbiome. So, if you’re looking to keep your gut microbiome healthy, you may want to forego that second cocktail.

 

Alcohol Absorption and Inflammation the Digestive Tract

Once swallowed, alcohol is primarily absorbed by the small intestine into the veins that collect blood from the bowels and stomach and the portal vein that leads to the liver. Once in the bloodstream, it is carried to the liver, where it is broken down by special enzymes.

Alcohol can irritate each part of the digestive tract. For example, alcohol can impair the esophagus's motility (movement). Plus, it can cause gastroesophageal reflux resulting in damage to the esophagus.

Excessive alcohol consumption can also lead to gastritis, a condition in which the lining of the stomach becomes inflamed. This chronic inflammation is recognized to have significant tumor-promoting potential, which could increase your risk of developing stomach cancer.

In addition, the gut can become inflamed due to an inflammatory response that the immune system mounts against alcohol and its metabolites (the substances or byproducts that are produced during the metabolism of alcohol).

The inflammatory response is provoked in several ways. First, alcohol may lead to an initial decrease in immune response, increasing susceptibility to gut pathogens such as bacteria and viruses. Infection by these gut pathogens then triggers an immune response and increases the production of immune cells involved in inflammation.

Since inflammation is involved in the development and progression of numerous diseases, such as cancer, heart disease, asthma, and psoriasis, avoiding things that cause inflammation can be one way of keeping our bodies happy and healthy.

 

Alcohol and Gut Permeability

The “leakiness” of the gut (also known as gut permeability) is a key component of the immune system. When it’s working properly, the gut wall is semipermeable. This means that special proteins in the gut wall prevent harmful substances from entering the gut while allowing helpful substances like nutrients and immune molecules to enter.

However, different factors can make the gut “leakier” than it should be. This allows foreign substances to travel through, which can lead to inflammation. Defects in the gut barrier have been associated with several different diseases, including celiac disease and inflammatory bowel disease.

Studies have found that alcohol can increase the “leakiness” of the gut wall. It’s thought that this happens because alcohol and its metabolites disrupt the gut wall cells and the spaces between those cells, which consist of special proteins that control the “leakiness” of the gut wall. If these special proteins are disrupted, the “leakiness” of the gut wall increases.

To protect the integrity of your gut wall, be mindful of how many alcoholic beverages you consume in one sitting. If it’s more than one or two, you may want to consider cutting back to keep your gut wall healthy.

 

Alcohol and Nutrient Absorption

The main role of the small intestine is to absorb nutrients vital for human health. These nutrients are either passively absorbed or actively transported through the cells of the small intestine.

However, excessive alcohol consumption can prevent the proper absorption of many nutrients, including vitamin B1 (thiamin), vitamin B2 (riboflavin), vitamin B7 (biotin), vitamin B9 (folate), vitamin C and vitamin B12. It may also impair the absorption of the mineral zinc.

While it may be advisable to supplement these nutrients in some cases (such as in the case of thiamine deficiency in alcohol use disorder, which can cause irreversible brain damage), it’s generally best to ensure adequate absorption of these nutrients by sticking to low or moderate alcohol consumption.

 

Moderation and Gut Health

We’ve talked a lot about moderate alcohol consumption. But what does that really mean?

According to the Centers for Disease Control and Prevention (CDC), moderate alcohol consumption is a single standard drink (e.g. 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of liquor) per day for women and two standard drinks per day for men. The guidelines also note that drinking less alcohol is better for health than drinking more.

For many people, cutting back on alcohol is easier said than done. After all, it’s something we use to socialize, especially during the hot summer months.

Here are a few strategies you can use to reduce your alcohol intake while remaining social:

  • Opt for a mocktail instead of a cocktail. Most restaurants have a mocktail menu; if they don’t, they can usually alter one of the alcoholic cocktails to be alcohol-free.
  • Try alcohol-free beer, wine, or spirits. More and more online retailers are starting to sell alcohol-free versions of these popular drinks. Try one, and you might be surprised by how much you enjoy it!
  • Try agua fresca. Agua fresca is one of my favorite refreshing summer drinks. Simply blend 1 cup of ice, 1 cup of fresh fruit (strawberries work well), the juice of one lime, 2-3 mint leaves, 1 tablespoon of liquid sweetener (like simple syrup or maple syrup) and enough cold water to cover all your ingredients and blend away! It’s refreshing and easy to prepare, and you get the benefits of some added fiber from the fruit!
  • Drink kombucha. Known for its fizzy, sweet-and-sour flavors, kombucha is another gut-loving drink. Since it’s a fermented food, it contains good bacteria that may contribute to better gut health.

 

Final Thoughts

There are many ways excessive alcohol consumption can negatively impact the gut, including disrupting the gut microbiome, causing inflammation in the gut, and impairing nutrient absorption.

If you’re looking to cut back your alcohol intake, try to aim for no more than one drink per day if you’re female and two drinks per day if you’re male. Better yet, opt for an alcohol-free version of your favorite drink or sip on kombucha for its tangy flavor and dose of beneficial microbes.

If you’re struggling to reduce your alcohol consumption, working with a registered dietitian can help. Here at Blue Tree Nutrition, our dietitian can help you come up with a plan for reducing your alcohol consumption while still enjoying an active social life. Click here to get in touch and book an appointment today!

Spend any amount of time on social media these days, and you'd think protein is the answer to all your health concerns. Protein coffee, protein cereal, protein deserts…even foods that never needed protein are getting a boost.

Protein absolutely plays an important role in overall health. But when it comes specifically to gut health, fiber is the real MVP.

Why Gut Health Depends on What Your Microbes Eat

Your gut is home to trillions of microorganisms collectively known as the gut microbiome. These microbes, which include bacteria, viruses, fungi, and more, influence everything from digestion and metabolism to inflammation and immune function. 

But microbes need fuel to survive.

Unlike human cells, your gut microbes thrive on dietary fiber—not protein—as their main source of energy. When you eat fiber, your gut microbes ferment it and produce compounds that actively support health.

However, when fiber intake is low, your gut microbes are forced to rely on other sources of fuel, including protein. And that shift can change which metabolic byproducts are produced in your gut. And spoiler alert—that's not always for the better.

What Happens When You Eat Fiber

Fiber is a type of carbohydrate that resists digestion in the small intestine. Instead of being absorbed, it travels to the colon intact. 

This is where the magic happens. Your gut microbes ferment fiber, producing a variety of different compounds. Some of the most important byproducts of fiber breakdown by your microbiome are short-chain fatty acids (SCFAs).

SCFAs are incredibly beneficial for overall health. Here are just some of their benefits:

  • Nourish colon cells
  • Strengthen the gut barrier
  • Reduce inflammation
  • Support regular bowel movements
  • Maintain a healthy gut pH
  • Protect against several diseases

In other words, fiber doesn't just help you poop—it actively supports the structure and function of your gut.

The Different Types of Fiber (And Why They All Matter)

You might be surprised to learn that not all fiber works the same way. Soluble fiber, which dissolves in water to form a gel-like substance, slows digestion, helps regulate blood sugar, lowers cholesterol, and, in some cases, acts as fuel for your good gut microbes. The fiber that can act as fuel for your gut microbes is called prebiotic fiber, and you can think of it as fertilizer for your gut microbiome. 

In contrast, insoluble fiber does not dissolve in water, but adds bulk to stool, helping promote gut regularity and speeding up the transit of waste through your digestive tract.

Both types of fiber are needed for a healthy gut, but soluble fiber is typically "gentler" on digestion and can be especially helpful for people with IBS.

What Happens When Protein Reaches the Colon

Protein is essential for muscle repair, immune function, and hormone regulation, and most of it is digested and absorbed in the small intestine. However, when large amounts of protein (especially protein from animal products) reach the colon, your gut microbes break it down through fermentation. Unlike fiber fermentation, protein fermentation produces compounds that can negatively affect gut health.

Byproducts of protein fermentation can include ammonia, hydrogen sulfide, phenols, and indoles. In large amounts, these compounds have been linked to gut barrier irritation, increased inflammation, unfavorable changes in gut microbiome composition, and a potential increase in colorectal disease risk.

This doesn't mean protein is harmful, but it highlights that a high-animal-protein, low-fiber diet shifts microbial activity toward less beneficial metabolic pathways. In other words? The extremely popular carnivore diet is not a good choice for gut health. Overall, it's best to focus on plant-based sources of protein, which studies show can improve gut microbiome composition. 

Why Fiber Matters More Than Protein for Gut Health

From a gut health perspective, fiber has several advantages over protein:

  • Feeds beneficial microbes
  • Produces anti-inflammatory compounds
  • Supports stool consistency and transit
  • Improves microbial diversity

Most people meet or exceed the recommended protein intake, but fall dramatically short on fiber intake (some studies suggest that as many of 95% of people in the United States don't reach the recommended fiber intake).

The National Academy of Medicine recommends that women aim for around 25 grams of fiber per day, while men should target about 38 grams per day.

Simple Ways to Increase Fiber Intake

Increasing your fiber intake doesn't require a complete diet overhaul. Small, consistent changes tend to work best, especially if you have a sensitive digestive system.

Instead of removing foods from your diet, focus on adding fiber where you can or switching to higher fiber options:

  • Toss canned beans or chickpeas into salads
  • Add chia or ground flax seeds to your yogurt
  • Include at least one plant food at every meal
  • Switch to whole wheat or fiber-enriched pasta
  • Choose rolled oats instead of sugary breakfast cereals
  • Cook and cool starchy foods like potatoes, rice, and pasta before eating to naturally increase resistant starch (a type of prebiotic) content

To avoid digestive problems, increase your fiber intake slowly by 2-3 grams per day, and ensure you're drinking plenty of fluids to keep things moving smoothly. To increase the diversity of fiber you're providing to your microbes, aim to eat 30 different plant foods (which include fruits, vegetables, legumes, nuts, seeds, herbs, and spices) per week.

The Bottom Line

Protein is essential for overall health, but when it comes to gut health, fiber plays the starring role. It feeds your beneficial gut microbes, strengthens the gut linking, and produces anti-inflammatory compounds that help keep your digestive system running smoothly. Meanwhile, diets high in protein but low in fiber may encourage metabolic byproducts linked with less favorable gut outcomes.

If your priority is improving gut health, the evidence consistently points in one direction. Eat more fiber, and your gut microbes will thank you. If you're struggling with increasing your fiber intake, a dietitian can help. Click here to get in touch with us at Blue Tree Nutrition and learn about how we can support your journey to better gut health.

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Hello, I am

Valerie

My name is Valerie Polley. I am a Indianapolis-based registered dietitian and owner of Blue Tree Nutrition. I consult with clients both local and far away.
I have a bachelor’s degree in nutrition from Purdue University and I have been practicing for 20 years.
I thoroughly enjoy helping clients through their gut health journey. I see a range of GI issues including, but not limited to celiac disease, IBS and SIBO. I also specialize in the FODMAP elimination diet.

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