Diets and Health Disease Gut and Brain Health

Effects of Carbs on the Gut Microbiome

The gut microbiome, our second brain, consists of more than 100 trillion bacteria and plays an important role in human health.1 It influences the development of chronic diseases including cardiovascular disease, neurodegenerative disorders, and cancer.2 Dietary patterns and environmental factors, rather than genetics, have the most profound effect on shaping the gut microbiota.3 These chronic diseases are on the rise in western societies and they carry a high economic and emotional burden.

NAFLD is described by the accumulation of fat in the liver not due to excess alcohol consumption. The prevalence of NAFLD is up to 30% in developed countries and nearly 10% and rising in developing nations, making NAFLD the most common liver condition in the world.4 In the United States, the National Institute of Diabetes and Digestive and Kidney Diseases estimates 30-40% of adults and 10% of children aged 2-19 are living with NAFLD.

A recent study published in Cell Metabolism found that the human gut microbiome consists of several strains of the gut bacterium Klebsiella pneumonia (K. pneumonia) which can ferment carbohydrates into high levels of alcohol and cause liver damage even in individuals who do not consume alcohol.6 K. pneumonia is normally found in the gut and has developed antimicrobial resistance.

To determine if high alcohol producing K. pneumonia is responsible for NAFLD, the team analyzed the gut microbes of 11 patients with NAFLD, 48 without NADFL (control), and 32 with non-alcoholic steatohepatitis (NASH). NASH is a type of NAFLD that causes inflammation and liver cell damage, along with increased fat deposits in the liver. They found that 61% of NAFLD patients hosted high alcohol producing K. pneumonia, while this was true for only 6.25% of the controls. The team gave oral glucose tolerance tests which measured the blood alcohol after consuming sugary food. They found that the average blood alcohol of those in the NAFLD group was more than 3.5 times that of the control group.

Your diet should take into account your gut health. In this 6-week customized meal plan, I focus on healthy foods that will nourish your gut microbiome while getting the results you want.

To test if the high alcohol producing K. pneumonia could contribute to liver damage, they introduced the bacterium to the guts of germ-free mice who do not possess a microbiome of their own and found signs of liver damage only within 8 weeks. This damage was similar to the damage observed in mice fed alcohol. A different group of mice received a fecal microbial transplant from either a person with NAFLD or from the mice who were exposed to the bacterium. In both cases, liver damage was observed just within 8 weeks.

Currently, most doctors recommend weight loss as a prevention or treatment of NAFLD. Weight loss is not one solution that fits all. It is not realistic for individuals who are at a healthy weight but are diagnosed with NAFLD due to factors not related to weight. This is also not a realistic solution for individuals who battle with eating disorders or mental health issues.

There needs to be greater emphasis on realistic and sustainable solutions that benefit the overall health of the patients. Instead of recommending weight loss, diets that are low in carbohydrates, particularly refined carbohydrates and sugars, and trans-fats should be recommended.

Despite K. pneumonia not being the only cause of NAFLD and despite not understanding the mechanisms that contribute to NAFLD, this research is ground-breaking. In the early stages, fatty liver disease is reversible. If the causes are identified sooner, liver disease can be treated or even prevented. This study also provides insight on how the gut microbiome can be studied to potentially develop therapeutics not only for NAFLD patients but for patients who are at increased risk of liver-related diseases and patients battling chronic disease.7

Check out my microbiome blog if you want to learn more about the gut!

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  1. Rinninella, E.; Raoul, P.; Cintoni, M.; Franceschi, F.; Abele, G.; Miggiano, D.; Gasbarrini, A.; Mele, M. C. What Is the Healthy Gut Microbiota Composition ? A Changing Ecosystem across Age , Environment , Diet , and Diseases. 2019.
  2. Li, E.; Bestor, T. H.; Jaenisch, R.; Shreiner, A. B.; Kao, J. Y.; Young, V. B.; Turnbaugh, P. J.; Ley, R. E.; Mahowald, M. A.; Magrini, V.; et al. Dicer (E-7): Sc-393328. Cell 2015, 69 (1), 393328.
  3. Jr, R. D. H.; Pontefract, B. A.; Mishcon, H. R.; Black, C. A.; Sutton, S. C.; Theberge, C. R. Gut Microbiome : Profound Implications for Diet and Disease. 2019, 1–40.
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  6. Yuan, J.; Chen, C.; Cui, J. Clinical and Translational Report Fatty Liver Disease Caused by High-Alcohol- Producing Klebsiella Pneumoniae Clinical and Translational Report Fatty Liver Disease Caused by High-Alcohol-Producing Klebsiella Pneumoniae. Cell Metab. 2019, 30 (4), 675-688.e7.
  7. Benedict, M.; Zhang, X.; Benedict, M.; Zhang, X. Non-Alcoholic Fatty Liver Disease : An Expanded Review. 2017, 9 (16), 715–732.
  8. Konerman, M. A.; Jones, J. C.; Harrison, S. A. Pharmacotherapy for NASH : Current and Emerging. J. Hepatol. 2020, 68 (2), 362–375.
  9. Downs, S. M.; Bloem, M. Z.; Zheng, M.; Catterall, E.; Thomas, B.; Wu, J. H. Y. The Impact of Policies to Reduce Trans Fat Consumption : A Systematic Review of the Evidence. 2017, No. 1, 1–10.
  10. Book, G. E. T. T.; Titles, F. R. The National Academies Press.
  11. Committee, N. I. H. A. ACD Working Group for Review of the Moderate Alcohol and Cardiovascular Health Trial. 2018, No. June.