In the world of reductionist reasoning; it is easy to sacrifice one good thing for the sake of a potential bad thing.  When it comes the debate over high fat or high fiber diets related to the microbiota-brain-gut axis this debate goes without exception

When we eat, some bile acids are converted into secondary bile acids through modification by our gut microbiome. Certain microbes, such as those in the Clostridiales order, contain bile salt hydrolase (BSH), an enzyme that transforms bile into secondary bile acids. While some of these secondary bile acids, like lithocholic acid (LCA) and deoxycholic acid (DCA), can be harmful and are associated with an increased risk of colon cancer, others, such as taurodeoxycholic acid (TUDCA) and ursodeoxycholic acid (UDCA), have beneficial effects. (Yanguas‐Casás et al., 2017) For instance, TUDCA and UDCA can cross the blood-brain barrier and reduce neuroinflammation. Research as shown receptors for these bile acids in the brain.(Xing et al., 2023)

Research has shown that higher fiber diets reduce LCA and DCA whereas higher fat diets increased UDCA and TUDCA.(Kim, 2024) So, A high-fiber diet has the benefit of lowering harmful bile acids linked to colon cancer, while a higher-fat diet may promote the production of bile acids that have anti-inflammatory effects on the brain. This highlights the complexity of nutrition: one dietary approach’s "poison" can be another’s "treasure."  Now, before you head over to McDonalds the output of fatty acids is very dependent on your microbiome and we are still learning about the effect of saturated fat compared to unsaturated fat on these bile acids. (Chadaideh & Carmody, 2021).

So, what to do?

Striking a balance through an omnivorous diet—one that includes a variety of foods in moderation—may help overcome the pitfalls of single-variable dietary approaches. If you are dealing with neurocognitive disorder its best to tamper your healthy fat intake with adequate fiber intake. Stool tests like the Gut Zoomer from Vibrant America can show your microbiome status and current production of harmful secondary Bile Acids and also blood tests are available through LabCorp to measure Serum Bile Acid Levels. Follow my Substack https://adamrinde.substack.com for more information like this;