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The liver plays a significant role in maintaining the delicate balance of microbes in our gut. It does this by producing bile, a digestive juice essential for breaking down fats (1). But bile isn't just about fat digestion; it also helps prevent bacterial overgrowth. Bile is bacteriostatic, meaning it inhibits the growth of bacteria, which is particularly important in the small intestine, where bile enters the digestive system (2,3,8).
When we hear about dysbiosis, we often think of an overgrowth of "bad" bugs. While this can indeed be the case, there are other forms of dysbiosis to. One other form of dysbiosis is when bacteria grow in the wrong place (5). Even if these bugs aren't necessarily "bad," their growth in areas where they shouldn't be can wreak havoc on our microbiome and lead to digestive symptoms (5).
So, where should our gut microbes hang out?
In a healthy gut, the small intestine remains relatively "clean" in terms of microbial growth. In contrast, the large intestine is a bustling metropolis teeming with microbes. To put things into perspective, our large intestine harbors around 1000 to 100,000,000 times more microbes than our small intestine (8)!
Why the stark contrast? Well, the microbes in the large intestine play a crucial role in digestion. We humans absorb the majority of our nutrients from the small intestine, leaving mostly indigestible fiber to reach the large intestine. There our microbes feast on these leftover fiber and produce metabolites that provide us with additional nutrients (8). Alternately, if microbes migrate up the digestive tract and overgrow in the small intestine, they start competing with us for nutrients. This leads to a host of digestive issues such as gas, bloating, and diarrhea (5).
How does the liver keep microbes in check?
Each time we eat, the liver releases antimicrobial bile into the upper part of the small intestine, creating an inhospitable environment for any stray pathogens that might have survived the journey down the digestive tract (8). By making the small intestine less welcoming to microbes, bile also discourages the large population of microbes in the large intestine from venturing up into new territory (5). By the time food reaches the large intestine, most of the bile has been reabsorbed through the gut wall to be recycled by the liver, allowing the microbes to thrive without the presence of irritating bile.
But what happens when this process goes awry?
Issues with bile flow are linked to an increased risk of small intestinal bacterial overgrowth (4). Without bile to keep the small intestine "anti-bacterial," opportunistic microbes are more likely to survive the journey down from the stomach or migrate up from the large intestine and establish themselves.
So, how can we support our liver and promote healthy bile production?
The most prevalent threat to liver health today is non-alcoholic fatty liver disease (NAFLD), affecting approximately one in four people globally (9). NAFLD is characterized by the infiltration of fat into the liver, impairing its essential functions, including bile production and flow (25). If you're interested in learning more about dietary strategies to prevent and treat NAFLD, I've got a detailed post here.
Another common issue that disrupts bile flow is gallstones. Many people can have small gallstones that inhibit bile flow but don’t cause pain, allowing them to go undetected for years. The majority of gallstones form due to excessive cholesterol in our bile or an immobile gallbladder, so maintaining healthy cholesterol levels and gallbladder movement is key (10). I've covered gallstones before, with prevention strategies and what to do if you've had your gallbladder removed, so feel free to explore those resources for more information.
Foods:
High-fiber diets:
Fiber supports liver function in 3 ways.
A high-fiber Mediterranean diet has been shown to be effective in preventing and treating fatty liver disease, thereby supporting proper liver function and bile flow (9, 16).
Weight loss is a primary treatment goal in fatty liver, and fiber is one of the few foods that helps achieve this - sometimes even without reducing calorie intake! (6)
Fiber also helps our body get rid of excess cholesterol through poop - which helps prevent thick bile and cholesterol gallstones (13).
Swapping animal-based proteins for plant-based proteins:
Opting for plant proteins not only increases fiber intake but also reduces the intake of dietary cholesterol and saturated fats, which contribute to increased cholesterol in bile and gallstone formation (12). This swap is also associated with reduced the risk of developing fatty liver disease (7).
Coffee:
Good news for coffee lovers! Drinking two or more cups of coffee per day has been associated with stimulating bile flow and reducing the risk of gallstone formation (12).
Beets:
Animal studies have demonstrated the protective effects of beetroots in preventing fatty liver disease (14), and several small human studies using beetroot powder and beetroot juice also show promise (15)(16).
Turmeric:
This golden spice has been shown to stimulate bile production and excretion from the gallbladder, thereby decreasing the risk of gallstones (17). I’d recommended consuming turmeric as a spice, as well as in supplement form as curcumin (see below).
Supplements:
Magnesium Oxide:
If constipation is a concern, addressing it should be the top priority, as regular bowel movements promote gallbladder movement and the excretion of excess cholesterol, a key contributor to gallstone formation (27, 20).
Omega 3s:
Omega 3 supplements help reduce the concentration of cholesterol in bile, thereby reducing the formation of gallstones (12).
Vitamin C:
Vitamin C supplementation has been shown to help prevent cholesterol precipitation in bile, a critical step in the formation of cholesterol gallstones (11, 12).
Curcumin:
The active compound in turmeric, curcumin, not only helps decrease liver fat accumulation but also reduces cholesterol absorption from the intestine and aids in weight loss (18).
Herbal Remedies:
Various herbal remedies, such as milk thistle, berberine, dandelion, and quercetin, have a long tradition of use to support liver health and bile flow. While most of the evidence supporting these comes from animal studies, they deserve a mention (21-29).
Promising results from animal studies:
Milk thistle has antioxidant and anti-inflammatory benefits for the liver, as well as promotes healthy bile flow (21)
Berberine helps lower cholesterol, decrease inflammation and support bile flow (21, 22)
Dandelion helps restore bile flow and prevent fat accumulation in the liver (23)
Quercetin promotes bile flow and offers protection against fatty liver disease (24)
Berberine (27), dandelion (28), and quercetin (29) are also known for their antimicrobial properties, but the research supporting these properties is mostly from petri dish studies. Because of their synergistic properties of both supporting liver health and addressing microbial overgrowth, I feel herbal remedies have a place in liver-health protocols, but it’s important to be aware of the limited human studies and to do a benefits vs. cost analysis when considering them.
In a Nutshell
Proper bile flow is crucial for maintaining a healthy intestinal microbial balance, particularly in preventing and treating small intestinal bacterial overgrowth. The key to promoting healthy bile flow lies in identifying and addressing the underlying causes, most commonly non-alcoholic fatty liver disease and gallstones. If you're experiencing digestive issues and seeking answers, don't hesitate to reach out. I help people understand their digestive health and develop personalized nutrition and supplement plans to get their gut back on track.
Sources:
Lim, R., and S. K. Y. Chang. "The Association between Gut Microbiome and Post-Cholecystectomy Syndrome and Diarrhoea: A Review." Journal of Gastroenterology & Hepatology Reports. SRC/JGHR-123. DOI: doi. org/10.47363/JGHR/2021 (2) 117 (2021): 2-5.
https://aasldpubs.onlinelibrary.wiley.com/doi/pdf/10.1002/hep.28709
Dreher ML. Role of fiber and healthy dietary patterns in body weight regulation and weight loss. Adv Obes Weight Manag Control. 2015;3(5):244-255. DOI: 10.15406/aowmc.2015.03.00068
Zhang S, Yan Y, Meng G, Zhang Q, Liu L, Wu H, Gu Y, Wang X, Zhang J, Sun S, Wang X, Zhou M, Jia Q, Song K, Borné Y, Qi L, Chen YM, Niu K. Protein foods from animal sources and risk of nonalcoholic fatty liver disease in representative cohorts from North and South China. J Intern Med. 2023 Mar;293(3):340-353. doi: 10.1111/joim.13586. Epub 2022 Nov 26. PMID: 36433820.
https://www.sciencedirect.com/science/article/pii/S2212877816300552
Parra-Vargas M, Rodriguez-Echevarria R, Jimenez-Chillaron JC. Nutritional Approaches for the Management of Nonalcoholic Fatty Liver Disease: An Evidence-Based Review. Nutrients. 2020 Dec 17;12(12):3860. doi: 10.3390/nu12123860. PMID: 33348700; PMCID: PMC7766941.
Lalitha, V., et al. "The indispensable role of herbs and other treatment strategies against gallstones." Annals of Phytomedicine 11.2 (2022): 52-64.
del Pozo, Reginald. "Diet and Gallstone." (2023).
https://www.peirsoncenter.com/uploads/6/0/5/5/6055321/258.pdf
Tehrani, A.N., Saadati, S., Yari, Z. et al. Dietary fiber intake and risk of gallstone: a case–control study. BMC Gastroenterol 23, 119 (2023). https://doi.org/10.1186/s12876-023-02752-0
https://link.springer.com/article/10.1007/s43188-019-00030-4
https://www.frontiersin.org/articles/10.3389/fnut.2023.1181706/full
https://journals.lww.com/aptb/fulltext/2020/10010/hepatoprotection_by_dandelion__taraxacum.1.aspx
https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.917414/full
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