How gut bacteria protects your liver health

Healthy Aging

Fiber helps gut bacteria make the good stuff

In this series, we are catching up on the latest peer-reviewed C15:0 science that has been published during 2023.

This week, let’s talk about a new study published in Nature Microbiology, which investigated how dietary fiber protects against a liver disease called nonalcoholic steatohepatitis (aka NASH).

What is NASH?

First, let’s start with nonalcoholic fatty liver disease (aka NAFLD). NAFLD is a metabolic disease, in which excess fat is present in the liver. This condition is on the rise, with a staggering 1 in 3 people having NAFLD globally. NAFLD can progress to NASH, which involves inflammation, angry liver cells, and liver scarring. NAFLD and NASH are becoming the leading causes of liver transplants and liver cancer.

Dietary fiber is linked to a lower risk of NASH.

A review by Perez-Montes et al. covers studies linking dietary fiber to healthier gut bacteria (also called our microbiome), both of which have been associated with improved metabolism – including people with NAFLD.  Among various dietary fibers, inulin may be particularly beneficial to gut health. Because of these links, Wei et al. performed a number of studies to try and figure out how dietary fiber (especially inulin) improves metabolism and protects against NASH.

Sleuthing for fiber’s liver-protecting benefits.

• Which part of fiber is beneficial? To find out how fiber helps to improve metabolic and liver health, Wei et al. gave mouse models of NAFLD/NASH either inulin or cellulose. After 4 weeks, various measurements of metabolic, liver and immune health, as well as changes in gut microbes, were compared among the different treatment and control groups.
• Which gut microbe is beneficial? Based on the findings above, Wei et al. then provided the same mouse models a big dose of associated gut bacteria and measured the same health indices.
• Which molecule is beneficial? Finally, the team evaluated which molecules were produced by good gut microbes – and then gave that molecule to the same mouse models.

Here’s what they found.

• Inulin is beneficial. Compared to the cellulose and control groups, the inulin (fiber) group had improved insulin resistance, reduced body weight, and alleviated NAFLD (including less liver fat, lower liver enzymes, lower inflammation, and less liver fibrosis). Not bad, right?
• Parabacteroides distasonis is beneficial. Wei et al. tested three interesting gut microbes associated with the inulin-treated group: Parabacteroides distasonis, Bacteroides acidifaciens, and Bacteroides uniformis. Of these, only P. distasonis improved various aspects of NAFLD and suppressed NASH.
• Pentadecanoic acid (C15:0) is beneficial. Finally, Wei et al. showed that P. distasonis uses inulin to make (…ta dah!) C15:0. And that C15:0 was the molecule that explained the NASH-ameliorating benefits of fiber. Specifically, supplementation of C15:0 in the same mouse models of NASH resulted in the following:
  • Lower liver enzymes
  • Lower inflammation
  • Lower oxidative stress

Further, the authors concluded that C15:0 also restored gut barrier function.