What is the role of bile acids in healthy digestion?
Bile acids are indispensable for proper fat digestion and the absorption of fat-soluble vitamins. If you suffer from greasy stools or have had a liver disease or intestinal surgery, discuss this with your doctor, as a bile acid deficiency may be the underlying cause.
Bile acids make fat digestion possible. The liver produces them from cholesterol and stores them in the gallbladder. After a meal, they are released into the small intestine, where they disperse fat into tiny droplets, much like a soap. This allows the digestive enzymes of the pancreas to break those fats down into small building blocks that are absorbed through the intestinal wall. Without bile acids, the fat-soluble vitamins A, D, E and K cannot be properly absorbed either, which leads to health problems when deficiencies are prolonged.
After completing their work in the small intestine, bile acids are not simply excreted. The terminal section of the small intestine reabsorbs them, after which they return to the liver via the bloodstream. Only a small fraction is lost through the stool. This efficient recycling keeps the bile acid pool at a sufficient level without the liver having to start from scratch continuously. At the same time, the production of bile acids is the primary way in which the body breaks down and eliminates cholesterol.
Beyond their role as fat emulsifiers, bile acids act as signalling molecules. They activate receptors in the liver, intestines, muscles and adipose tissue, which in turn regulate the processing of fats and sugars and contribute to energy balance. This is plausible but not yet as well established as their direct role in digestion.
Gut bacteria convert the bile acids produced by the liver into what are known as secondary bile acids. This conversion influences the composition of the bile acid pool throughout the body. An unhealthy balance, in which certain secondary bile acids accumulate, has been associated with a higher risk of colorectal cancer, gallstones and other gastrointestinal diseases, although these are associations and the direct causal relationship in humans has not yet been fully proven.
When the bile acid system becomes disrupted, whether through liver disease, removal of a section of the small intestine, a high-fat diet, alcohol use or a disturbed sleep-wake cycle, fat digestion goes wrong. This manifests as greasy, foul-smelling stools, malnutrition and vitamin deficiencies. Prolonged disruption is also linked to an increased risk of fatty liver, diabetes and cardiovascular disease.
All claims are based on reviews; no randomised studies or meta-analyses were included. The role of bile acids in fat digestion and recycling is well described and classified as causal. The signalling molecule function and the association with chronic diseases are based on associations and animal studies, and are considered probable but not yet fully proven.
Does chewing slowly really help with better digestion?
Chewing well certainly helps form a smooth food bolus and increases saliva production, but whether it actually leads to better digestion in healthy people has not been demonstrated. Take your time with it, but do not expect a major health benefit if you already eat normally.
Does drinking apple cider vinegar help your digestion?
There is no research whatsoever showing that apple cider vinegar improves digestion. If you want to use apple cider vinegar for blood sugar control in diabetes, discuss this with your doctor, as good evidence is also lacking for healthy people.
Can exercise improve your gut microbiome?
Moderate regular exercise demonstrably improves your gut microbiome, but you need to keep exercising because the effect disappears when you stop. Do not overdo it: very intensive training can actually put gut health under pressure.
Does eating flaxseed help your gut?
Through its fibre and lignans, flaxseed has a plausible positive effect on the gut, but for the gut as a specific target the evidence in humans is still limited. If you want to take concrete action, opt for at least 30 grams of ground flaxseed per day.
What does eating fibre do to your gut microbiome and your long-term health?
Fibre demonstrably feeds your gut bacteria, improves stool consistency and protects the gut wall. But how your microbiome and immune system respond varies considerably from person to person.
What are the signs that your gut flora is out of balance?
There are several recognisable signals, of which abdominal complaints such as persistent pain, diarrhoea, or constipation are the best supported. If you experience prolonged bowel complaints after a course of antibiotics or an infection, discuss this with your GP.