Brittany Roman-Green is a licensed dietitian nutritionist and certified personal trainer. She is the owner of her private practice in Mountain View, California and specializes in gut and liver conditions. The contents of this article are the personal opinion of the author, and not the official position of PSC Partners Seeking a Cure. Always speak with your doctor before starting a new diet to make sure that the diet change is appropriate for your medical condition and treatment.
Diet, Gut Bacteria, and Bile Acids
Purpose of Bile Acids
Bile acids help with the digestion of dietary fat and fat-soluble vitamins including vitamins A, D, E, and K. They can also affect the rate at which our stool travels in our intestines, the strength of our gut barrier, and can regulate inflammation.
Bile Acid Metabolism and Gut Bacteria
Primary bile acids are made in the liver then travel through the bile ducts into the intestines. About 95% are recycled and return back to the liver while the remaining 5% are metabolized by gut bacteria in the colon and ultimately excreted in the stool. The bile acids in the colon are metabolized by good or bad bacteria, which can lead to creating healthy or toxic secondary bile acids. Toxic bile acids (such as chenodeoxycholic acid or deoxycholic acid) are toxic to the liver cells and are linked to increasing the risk of colon and liver cancers. Healthy secondary bile acids (such as ursodeoxycholic acid) are thought to have anti-inflammatory and anti-cancer properties that help fight off disease.1
Research suggests that people with primary sclerosing cholangitis (PSC) have a greater percentage of toxic bile acids than they should. Compared to healthy individuals, and to individuals with inflammatory bowel disease (IBD) alone, studies suggest that people who have both IBD and PSC have fewer strains of bacteria overall and more of the bad types of bacteria.2
Types of Bacteria and Diet Patterns
The same type of bad bacteria (Bacteroides) that has been discovered to be increased in people with PSC has been found to be increased in people who consume a lot of animal protein. This bacteria and other types of bad bacteria are also found to be increased in individuals who consume a westernized diet. The westernized diet is followed by a growing number of Americans and is thought to be a risk factor for many different diseases including IBD and PSC.
A westernized diet is an eating plan that includes foods that are:
- high in saturated fat (found in meat and dairy products)
- high in red meat (found in beef, lamb, and pork)
- high in junk food, added sugars, and fake sugar (artificial sweeteners)
- low in fresh fruits and vegetables
A Mediterranean diet is a plant-based eating plan that has been linked to reducing the risk for many different types of diseases. This diet has also been linked to increasing the diversity of bacterial strains and increasing the good types of bacteria in the gut.3
A Mediterranean diet is a healthy eating plan that includes foods that are:
- high in unsaturated fats (found in foods like avocado, olive oil, nuts)
- high in antioxidants (found in foods like colorful fruits and vegetables)
- high in prebiotic fiber and probiotics (found in foods like bananas, legumes, yogurt, kefir, miso)
- high in resistant starch (found in foods like rice and legumes)
Although many factors contribute to the type and amount of bacteria in our gut, what we eat can improve the diversity of bacteria as well as the percentage of good bacteria.
- Include more plant-based sources of protein into your diet. Examples include legumes, grains, nuts, nut-butters, seeds, tofu and edamame. It is important to note that PSC patients should not necessarily avoid animal-based protein altogether. Particularly as PSC progresses to more advanced stages, patients should focus on a diet rich in lean protein to avoid the loss of body mass and muscle wasting.
- Aim to consume more monounsaturated and polyunsaturated fats, found in foods like avocado, salmon, olive oil, nuts, seeds, and less saturated fats (found in foods like fatty meats, poultry skin, bacon, sausage, and whole and 2% dairy products) and trans fats (found in margarine, shortening, and some processed baked and fried foods).
- Reduce your intake of added sugars and fake sugar (artificial sweeteners)
- To bump up your intake of antioxidants and fiber, consume a wide variety of colorful fruits, vegetables, and different types of legumes
- Consume prebiotic fiber, found in foods such as bananas, legumes, and potatoes, and probiotics, found in foods such as kefir, yogurt, kimchi, miso, and tempeh. It’s even better for your gut if you consume prebiotics and probiotics together. For instance, try consuming fat-free yogurt with a banana for a snack.
Always talk to your health care provider for recommendations on the specifics of your diet.
- Gérard P. Metabolism of cholesterol and bile acids by the gut bacteria. Pathogens. 2014; 3(1):14-24. doi: 3390/pathogens3010014.
- Torres, J., Palmela, C., Brito, H., et al. The gut microbiota, bile acids and their correlation in primary sclerosing cholangitis associated with inflammatory bowel disease. United European Gastroenterol J. 2018; 6(1): 112-122. doi: 1177/2050640617708953
- Singh, R.K., Chang, HW., Yan, D., et al. Influence of diet on the gut microbiome and implications for human health. J Transl Med. 2017; 15:73. doi: 1186/s12967-017-1175-y.