Exploring The Importance Of The Gut-Liver Connection

The human liver and digestive tract are connected via the hepatic portal system.

One of the many physiological consequences of this “gut-liver” connection is that the health of the gut microbiome directly influences the health of the liver.

The gut-liver connection at least partially explains why we regularly see microbiome dysbiosis in fatty liver disease and that interventions that target the gut microbiome, such as pre- and probiotics, generally lead to improvements in liver health parameters.

It’s also true that yogurt consumption may reduce one’s risk of fatty liver disease and that introducing probiotic yogurt into the diet of someone with a fatty liver was demonstrated in a controlled trial to reduce liver enzyme levels.

So what should someone with a fatty liver do with all of this wonderful scientific insight? 

We’re about to find out!

Why The Microbiome Matters So Much 

The connection between the gut microbiome and fatty liver disease goes beyond the fact that people with a fatty liver are more likely to have microbiome imbalances.

This liver-gut connection actually evolves based on the severity of the disease, as per a landmark 2016 study out of the Hepatology journal, which determined that people with more severe forms of fatty liver had different microbiome profiles than people with less severe forms of the condition.

The work in that particular paper noted that the gut bacteria most responsible for carbohydrate and fat metabolism were most affected in more severe fatty liver disease.

Given that fatty liver disease is a condition characterized by improper carbohydrate metabolism (think insulin resistance) and improper fat metabolism ( think fat getting stored where it shouldn’t be), these findings are extremely insightful.

It’s also important to acknowledge that the gut microbiome plays a significant role in bodily inflammation because a balanced, healthy gut microbiome produces compounds known as SCFAs [short-chain fatty acids] with a pronounced anti-inflammatory effect. In contrast, an imbalanced microbiome is more likely to produce inflammatory compounds known as LPSs [lipopolysaccharides].

Of course, inflammation damages the liver directly over time but also worsens insulin resistance, which can, in turn, promote further liver fat storage.

So now that we know that the microbiome plays a big role in fatty liver disease and that probiotics can help fight against a fatty liver, it’s time to explore how we might choose the right bacteria for the job.

Probiotics For Fatty Liver – The Evidence

In 2020, the European Society For Clinical Nutrition & Metabolism (ESPEN) published a comprehensive guideline relating to all aspects of nutrition for liver disease.

Given that fatty liver disease is the most common liver condition globally, it was a prominent topic within the publication with probiotic use designated its own section within the report.

ESPEN suggested that the strongest evidence for the benefit of probiotic use in fatty liver was a statistically significant reduction in liver enzymes [AST, ALT, gGT], although they noted that some studies also demonstrated probiotics' potential to reduce liver fat storage, insulin resistance, and inflammatory markers.

These are, to say the least, highly desirable changes for people living with a fatty liver, especially those who may not be able to tap into the benefits of dietary changes or physical activity in the most optimal manner.

Probiotics For Fatty Liver –  Which To Choose?

In January 2023, the Medicine journal published a meta-analysis of 21 studies on the use of probiotics for fatty liver disease.

They concluded that probiotic use demonstrated the potential to contribute to the reduction of liver enzymes and liver fat storage while supporting reductions in blood sugar and blood fat levels.

But what does this comprehensive study teach us about which probiotic to use and for how long?

It’s not the easiest question to answer, but allow me to provide some insights.

#1 Duration

The available studies on probiotic use for fatty liver disease range mostly in duration from 4-24 weeks.

Based on the duration analysis from the review discussed above, it appears that taking probiotics for 12 weeks or longer is the optimal duration for conferring the most benefit.

#2 Species

The types of bacteria used varied across studies, but most studies used multi-strain (2-14 different types) probiotics containing members of the Lactobacillus, Bifidobacterium, and Streptococcus family.

Some of the specific bacteria that came up in multiple studies include Bifidobacterium longum, Lactobacillus bulgaricus and Streptococcus thermophilus.

#3 Dose

Most studies in this area used a total probiotic dose ranging up to 30 billion CFU [3 × 1010 CFU] per day. 

Nowadays, most probiotics on the market have their CFU total on the package, which essentially refers to the “amount” of healthy bacteria in the product.

Putting It All Together

While no one “needs” to take a probiotic on their journey to fight back against a fatty liver, the overwhelming reality is that probiotics represent the most studied and effective supplement for this purpose.

The dual goals of today’s article were to help you understand WHY science shows this to be the case and HOW you can leverage the science to your health's benefit.

Hopefully, I’ve been able to achieve both.

As with any supplement, consult a healthcare provider to ensure it is right for you.

1. _{Bischoff, S. C., Bernal, W., Dasarathy, S., Merli, M., Plank, L. D., Schütz, T., & Plauth, M. (2020). ESPEN practical guideline: Clinical nutrition in liver disease. Clinical nutrition (Edinburgh, Scotland), 39(12), 3533–3562. https://doi.org/10.1016/j.clnu.2020.09.001} 
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3. _{Nabavi, S., Rafraf, M., Somi, M. H., Homayouni-Rad, A., & Asghari-Jafarabadi, M. (2014). Effects of probiotic yogurt consumption on metabolic factors in individuals with nonalcoholic fatty liver disease. Journal of dairy science, 97(12), 7386–7393. https://doi.org/10.3168/jds.2014-8500} 
4. _{Zhang, S., Fu, J., Zhang, Q., Liu, L., Lu, M., Meng, G., Yao, Z., Wu, H., Xia, Y., Bao, X., Gu, Y., Sun, S., Wang, X., Zhou, M., Jia, Q., Song, K., Wu, Y., Xiang, H., & Niu, K. (2020). Association between habitual yogurt consumption and newly diagnosed non-alcoholic fatty liver disease. European journal of clinical nutrition, 74(3), 491–499. https://doi.org/10.1038/s41430-019-0497-7} 
5. _{Zhou, X., Wang, J., Zhou, S., Liao, J., Ye, Z., & Mao, L. (2023). Efficacy of probiotics on nonalcoholic fatty liver disease: A meta-analysis. Medicine, 102(4), e32734. https://doi.org/10.1097/MD.0000000000032734}