A previous article described a type of persistent organic pollutants called per- and polyfluoroalkyl substances (PFAS) 1. They have been used to keep food from sticking to packaging or cookware, make clothes and carpets resistant to stains, and create firefighting foam that is more effective. One report by the Centers for Disease Control and Prevention in the USA found PFAS in the blood of 97% of people in the USA2. PFAS can increase the risk of type 2 diabetes. They cause environmental damage and are toxic to the liver, neuroendocrine immune system, kidneys, lungs, and cardiovascular system3. They are especially dangerous to developing fetuses and children4.

They have been used in consumer products since the 1950s. They have been used to keep food from sticking to packaging or cookware, make clothes and carpets resistant to stains, and create firefighting foam that is more effective. They have a polar end group (such as COOH) and a chain of carbons with fluorine atoms attached to them in covalent bonds. Because the carbon-fluorine bond is one of the strongest, these chemicals do not degrade easily in the environment. Two of them, perfluorooctanoic acid (PFOA) and the sodium salt of perfluorosulfonic acid (PFOS), were removed from consumer products in the early 2000s. They are called legacy PFAS. They were mixed with polytetrafluoroethylene (also known as Teflon, made by Tefal) and used in non-stick cookware.

PFAS can decrease kidney function and increase the risk of kidney cancer. Relatively high concentrations of PFAS in the blood can increase total cholesterol, triacylglycerols (also known as triglycerides), and low-density lipoproteins. All of these are risk factors for cardiovascular diseases. When PFAS accumulate in blood platelets, they can promote blood clots. Inhaling PFAS can cause inflammation in the respiratory tract. Occupational exposure to relatively high amounts of PFAS increases one’s risk for lung cancer. PFAS may impair lung development. PFAS can interact with other pollutants, such as asbestos and microplastics, to become more toxic.

So, it was great news when researchers found recently that some of the bacteria found in healthy human gut microbiomes rapidly absorb, bioaccumulate, and excrete PFAS in fecal material5. This includes several species in the genus Bacteroides: B. caccae, B. clarus, B. dorei, B. stercoris, B. thetaiotaomicron, and B. uniformis. Other bacteria that remove PFAS include Odoribacter splanchnicus, Parabacteroides distasonis, Parabacteroides merdae, and Escherichia coli. These bacteria can remove PFAS even when it is present at low concentrations.

In addition, there is a healthy human gut bacterium called Akkermansia muciniphila that helps prevent obesity and several human diseases, including diabetes. It does this through a coordinated network of microbial antigens, lipids, enzymes, and metabolites, while its level increases in the gut. Recently, it was shown that it also supports antiviral immunity in the lungs when they are infected with the SARS-CoV-2 virus that causes COVID-196. That is, the gut microbiome is connected to the lungs through various signaling pathways, immune cell trafficking, and microbial metabolites. The SARS-CoV-2 virus changes the composition and diversity of the gut microbiota, making it unbalanced and unhealthy. This can lead to disruptions in intestinal barrier integrity, Changes in bacterial metabolites, the translocation of bacteria and viruses into the bloodstream, and hyperactivation of immune and inflammatory responses. These are major hallmarks of severe COVID-19. Therapeutic strategies targeting the gut microbiota include supplementation with short-chain fatty acids and probiotics, as well as fecal microbiota transplantation. They have shown promising outcomes in restoring microbial homeostasis and modulating immune responses in various infectious diseases.

A. muciniphilia is enriched in the mucus layer of the intestinal lining7. Like other healthy gut bacteria, it produces short-chain fatty acids (SCFAs) by fermenting dietary fiber. It also breaks down the glycoproteins called mucin and plays a significant role in gut barrier maintenance and immune regulation. That is, mucins are a class of proteins that are coated with many sugars. They create a physical barrier that protects epithelial cells from damage, pathogens, and irritants. Some mucins can interact with other molecules on cell surfaces, influencing cell behavior and communication. Amounts of mucin and changes in its structure are linked to various cancers, including those of the gastrointestinal tract and breast. Mucins play a role in inflammatory conditions, such as those affecting the airways (asthma, bronchitis). They can be targets for pathogens, but can also help to protect against infection. Moreover, A. muciniphilia is resistant to many antibiotics. So, the gut microbiome is partially protected from antibiotics.

Diet affects the structure, composition, and function of the human gut microbiome. The effects of diet on A. muciniphila start almost immediately after birth. A recent study investigated the impact of the breast milk-derived metabolite betaine on the overall relative abundance of A. muciniphila. Maternal betaine was found to transiently increase its abundance. Human milk oligosaccharides that are prebiotics for the neonatal gut microbiota also promote the expansion of A. muciniphila. On the other hand, eating saturated fats that are in meat decreases the amounts of A. muciniphila and other healthy gut bacteria. Dietary antioxidants, the SCFA butyrate, and complex carbohydrates found in dietary fiber increase in the relative abundance of A. muciniphila.

A higher abundance of A. muciniphila has been observed in the gut of healthy individuals relative to those with metabolic disorders, and multiple metabolic benefits, including improved glucose management, reduced body fat, and reduced inflammation, have been linked to A. muciniphila. So, dietary fiber in the Mediterranean diet and others is very healthy. Moreover, one of the best things that you can do for your health and the health of Gaia (the biosphere) is to avoid eating meat -especially mass-produced beef and pork.

Notes

1 Polyfluoroalkyl substances are toxic, persistent pollutants by R. Smith on Meer.
2 Serum Biomarkers of Exposure to Perfluoroalkyl Substances in Relation to Serum Testosterone and Measures of Thyroid Function among Adults and Adolescents from NHANES 2011–2012 by Lewis, R.C. et al. on International Journal of Environmental Research & Public Health.
3 Public Health Risks of PFAS-Related Immunotoxicity Are Real by Bline, Abigail P., et al. on Current Environmental Health Reports.
4 Public Health Risks of PFAS-Related Immunotoxicity Are Real by Sodani, Kamlesh, et al. on ScienceDirect.
5 Human gut bacteria bioaccumulate per- and polyfluoroalkyl substances by Lindell, Anna E., et al. on Nature Microbiology.
6 Akkermansia Muciniphila Primes Lung-Resident Antiviral Immunity via the Gut–Lung Axis During SARS-CoV-2 Infection by Kim, Gi-Cheon, et al. on TheLancet.
7 Health effects and therapeutic potential of the gut microbe Akkermansia muciniphila by Aja, E. et al. on Nutrients.