How can quitting smoking affect your gut health?

Nicotine use affects more than a third of the world’s population, either directly or indirectly, and the most common source is cigarette smoking. We are all aware of the various effects of nicotine use because the media constantly make them public. We typically talk about the cardiovascular and respiratory burden of cigarette smoking, and in some cases cancer and brain issues after chemotherapy. But what about gut health? Is it affected by smoking?

Moreover, what happens when we quit smoking? As you will see in this article, there’s a double message in smoking cessation. There are many health benefits, but your gut microbiota may also become adversly affected, which can explain common side effects that usually appear during the withdrawal stage and afterwards.

Smoking and gut health

It is no secret that smoking causes inflammatory reactions, and the cigarette smoke has many substances, each one of them carrying a different health burden. That is what usually motivates people to quit smoking.

By quitting cigarette smoking, you might reduce the incidence of the following medical conditions:

  • Oral disease: Gut health problems in smokers start in the mouth. Tobacco causes bad odor, and this annoying symptom is caused by saliva reduction in the mouth. This stimulates the growth of bacteria, and may even cause periodontal disease or darkening of the teeth, to say least.
  • Gastroesophageal reflux and associated problems: Cigarette smoking increases the incidence and severity of heartburn, reflux episodes, and other symptoms associated with gastroesophageal reflux. Cigarette substances injure the epithelium of the esophagus and cause alterations to the smooth muscle that keeps it moving.
  • Peptic ulcer and gastritis: Peptic ulcer problems are more common in smokers because tobacco smoke causes a reduction in the synthesis of prostaglandin, causing alterations in the barrier function of the stomach.
  • Altered secretions by the pancreas: Tobacco smoke increases the production of acid by the stomach while decreasing the secretion of bicarbonate by the pancreas. The acidity in the duodenum is not controlled and causes damages to the mucosa, potentially ending up in duodenal ulcers.
  • Inflammatory bowel disease: There are many studies about ulcerative colitis and Crohn’s disease in smokers. Studies have divergent opinions, showing that quitting smoking may improve the symptoms of ulcerative colitis, but it is not always a good thing in Crohn’s disease. It appears that smoking has some protective effects that prevent colonic involvement in Crohn’s disease and recurrences in ulcerative colitis, but more studies are necessary to understand the association.
  • Cancer in the gastrointestinal tract: Finally, smoking is associated with cancer, not only in the respiratory tract but in the gastrointestinal tract as well. The most common type of cancer is oral cancer, but it may also trigger esophagus cancer through a higher incidence of gastroesophageal reflux and Barrett’s esophagus, and gastric cancer.

Smoking cessation and how it affects your metabolic and gut health

By all means, we are all advised to quit smoking, and it is a common recommendation in almost every specialty. That’s because smoking is a significant cause of preventable disease and death worldwide. However, you should know about a few problems you might experience after quitting tobacco smoking, especially in your gut health and your gut microbiota.

One of the most common occurrences after quitting tobacco is gaining weight. This post-cessation weight gain is a reason why people, often women, relapse after trying to quit smoking or fail to initiate the process in the first place. The weight gain after quitting smoking can continue for up to 10 years after the last cigarette, and a significant number of patients report gaining more than 10 kilograms in a year. This weight change is commonly attributed to stress, anxiety, and other psychological factors. However, recent evidence shows that our gut health might be another plausible reason.

Research: How Smoking Affects Digestive system

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Two recent studies evaluate the gut microbiota in humans before and after smoking cessation. Both of them raise the same conclusion: the gut microbiota is radically changed after quitting tobacco smoking. According to the microbial analysis of fecal samples, there are significant increases in Actinobacteria and Firmicutes bacteria, and other healthy microbes are reduced after smoking cessation, especially Bacteroidetes and Proteobacteria species. It is not yet clear whether this change is due to smoking cessation itself or common in all smokers vs. nonsmokers, but one thing is clear: it is a potential pathway we can use to reduce the incidence of weight gain in people who want to quit smoking.

These microbial shifts may also trigger adverse events in patients with inflammatory bowel disease. In this case, they are cause by an intestinal dysbiosis, an imbalance that we can correct without any side effects by using probiotic supplements and foods.

Does it mean you should not quit smoking?

The recommendation of quitting tobacco smoking can relieve and prevent many diseases caused by nicotine use and other substances in tobacco. It leads to weight gain, which may be significant, and should be closely monitored in patients with inflammatory bowel disease. Post-cessation weight gain is probably more prevalent than reported in studies because many patients prefer not to self-report their condition, and some of them relapse and do not try to quit once again.

But even with these gastrointestinal changes and the consequences in our gut microbiota, smoking cessation is highly recommended, and the benefits always outweigh the risks. Moreover, it is possible to use probiotic supplements in an attempt to modulate the patient’s gut microbiota and prevent some of the gastrointestinal effects.


Harris, K. K., Zopey, M., & Friedman, T. C. (2016). Metabolic effects of smoking cessation. Nature Reviews Endocrinology12(5), 299.

Biedermann, L., Brülisauer, K., Zeitz, J., Frei, P., Scharl, M., Vavricka, S. R., … & Schuppler, M. (2014). Smoking cessation alters intestinal microbiota: insights from quantitative investigations on human fecal samples using FISH. Inflammatory bowel diseases20(9), 1496-1501.

MASARAT, S. (2008). Smoking and gut.

Biedermann, L., Zeitz, J., Mwinyi, J., Sutter-Minder, E., Rehman, A., Ott, S. J., … & Loessner, M. J. (2013). Smoking cessation induces profound changes in the composition of the intestinal microbiota in humans. PloS one8(3).

About Simon Bendini 78 Articles
Hello, I'm an expert in all things Probiotics. I also live and breathe what I write about: I take Probioitcs EVERY day. I want to help you discover the benefits of them too. Enjoy my humble site.

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