The effect of cigarette smoke is not only bad for your lungs, but your gut microbiota also suffers significant damage.
The intestinal microbiota is the collection of microorganisms present in our intestine. Its balance can be altered by many environmental factors such as eating habits, the consumption of drugs (such antibiotics) and toxins, including cigarette smoke (1,2).
Nicotine is known to be inhaled into the lungs and rapidly absorbed from the lung alveoli, but it is also absorbed through the skin and gastrointestinal tract. Once nicotine is absorbed it can exert multiple favourable and unfavourable physiological effects, such as increasing metabolic rate, suppressing appetite, regulating body weight and / or influencing neural activities (3). In addition, exposure to cigarette smoke raises the intestinal pH, which possibly benefits some bacteria, allowing them to thrive and cause dysbiosis of the intestinal microbiota (4).
Specifically, toxic compounds contained in cigarette smoke can cause biochemical reactions and elevate concentrations of pro-inflammatory factors in the blood (5,6). Furthermore, the toxins from cigarette smoke ingested in the gastrointestinal tract induce dysbiosis of the microbiota through different mechanisms, such as antimicrobial activity and regulation of the intestinal microenvironment (7).
For all these reasons, smoking not only damages our lungs, but also causes many changes to our intestines, such as the microbiome composition and functioning, permeability of the mucosa, and alterations in the immune response of the mucosa. All these changes contribute to the development of serious diseases (8,9). Current epidemiology has shown that patients with chronic lung diseases have a higher prevalence of intestinal diseases (10). In addition, lung and intestinal diseases demonstrate many overlapping changes, such as common risk factors, reduced mucus, increased permeability, and low expression of certain proteins. The reason for these shared effects is that the respiratory and gastrointestinal epithelia have the same embryonic origin and show structural similarities (11). Clinical studies have shown that lung disorders may be implicated in intestinal diseases through underlying mechanisms, such as the lung-intestine axis (4).
So, if you need another reason to quit smoking: it will also greatly benefit your gut health!
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