What is the bile?
The Bile Color
The bile in the gallbladder is yellow-green or brown due to bile pigments bilirubin and biliverdin .
The normal intestinal bacteria convert bilirubin into urobilinogen, which colors the intestinal contents (chyme) yellow, and finally into stercobilin, which colors the stool brown.
During diarrhea, the stool can appear yellow or green, because the bile passes through the intestine fast and the bacteria do not have enough time to change its original color to brown.
The bile in the vomit appears green or yellow and has a bitter taste [7,13].
Chart 1. Bile Composition
|Bile salts||Fat emulsification|
|Cholesterol||No function; the bile is the route of cholesterol disposal|
|Bilirubin||Disposal of hemoglobin from dead red blood cells|
|Electrolytes: calcium, potassium, sodium, bicarbonate, chloride||Alkalinization of the bile; functioning of bile salts|
|Vitamins B12 and D||Various functions in the intestine|
|Immunoglobulin A||Fighting against microbes in the intestine|
Chart 1 references: 3
Bile acids are produced from cholesterol in the liver cells. After the connection with the amino acids taurine or glycine they are called conjugated bile acids, and after further connection with sodium and potassium, they become bile salts .
The Bile Functions
1. Fat Emulsification and Digestion
The bile physically breaks down big particles of dietary fats into small droplets and thus makes them more digestible; this is known as fat emulsification .
Next, the enzyme lipase from the pancreatic juice chemically breaks down fat molecules (triglycerides) into fatty acids and monoglycerides, which can then pass from the intestine into the blood; this is known as fat digestion and absorption .
NOTE: The bile does not contain digestive enzymes and it does not digest fats; it only emulsifies them.
The bile also assists the absorption of cholesterol and fat-soluble vitamins A, D, E and K .
2. Disposal of Wastes
The bile enables the excretion of wastes from the body via the stool [3,4]:
- Bilirubin (from hemoglobin from dead red blood cells)
- Excessive cholesterol
- Heavy metals (arsenic, cadmium, copper, iron, lead, manganese, mercury, selenium, silver, zinc)
- Certain drugs
- Environmental toxins (organic solvents, pesticides)
3. Neutralization of Gastric Acid
The bile is alkaline (pH = 7-8), so it helps to neutralize the stomach acid that is delivered to the small intestine with food [3,4].
4. Protection of the Intestine Against Infections
Immunoglobulin A in the bile can fight microbes and thus protect the intestine against infections .
The Bile Flow
Picture 1. The bile flow
The Bile Production and Secretion by the Liver
The bile is produced in the liver cells and secreted into the small channels between them (the bile canaliculi). The bile flows out of the liver via the common hepatic duct  (Picture 1).
In adults, the liver produces 500-1,000 mL of the bile per day [3,4,5].
The following foods and herbs may stimulate the bile production in the liver but there is INSUFFICIENT EVIDENCE about the related health benefits: bitter artichoke , celery, dandelion root , gentian and wormwood , ginger , turmeric (curcumin) , fennel, green tea, horseradish, limes, Spanish black radish, whole grains and walnuts .
NOTE: The bile production in the liver can be reduced due to a severe liver disease or genetic disorder.
The Bile Storage In the Gallbladder
Between the meals, a muscular valve (the sphincter of Oddi) at the end of the common bile duct contracts and increases the pressure in the common bile duct, which forces the bile from the common hepatic duct to flow via the cystic duct into the gallbladder (Picture 1).
In the gallbladder, the bile is temporarily stored and concentrated . The gallbladder usually contains about 30-50 mL of bile .
The Bile Delivery Into the Duodenum
After meals, the gallbladder contracts and the sphincter of Oddi relaxes, which allows the flow of the bile from the gallbladder through the cystic and common bile duct into the duodenum (Picture 1).
Foods that stimulate the flow of the bile from the gallbladder:
- Foods high in fat or protein (oil, meat, fish, milk, cheese, eggs, nuts, seeds, soy products, chocolate, cakes, whey, avocado, fried foods) [14,17]
- Coffee (caffeinated and decaffeinated) 
- Turmeric (curcumin) [16,19]
Dietary factors that slow down the bile flow:
- Fasting, very low calorie diet or low-fat diet
- Alcoholic beverages 
- A gallstone or cancer in the common bile duct can obstruct the flow of the bile, which then backs up into the blood, skin and urine resulting in jaundice and dark yellow urine. At the same time, the absence of the bile in the small intestine results in the malabsorption of fats and their appearance in the stool, which appears grey and greasy (steatorrhea).
- Very low calorie diet (<800 Cal/day) can result in poor bile flow and consequently in thick bile (gallbladder sludge) or gallstones.
- Gallbladder removal or a disorder of the valve at the end of the stomach can result in the backflow of the bile from the duodenum into the stomach (bile reflux).
About 95% of the bile salts that flow via the bile into the first part of the small intestine (the duodenum) is reabsorbed in the last part of the small intestine (the ileum), taken up by the liver and secreted in the bile again . This is known as enterohepatic circulation (enteron = intestine, hepar = liver).
Similarly, about 50% of the cholesterol secreted via the bile is reabsorbed .
Certain drugs, vitamins and minerals secreted in the bile can also be partially or completely reabsorbed.
NOTE: In a disease of the last part of the small intestine or after gallbladder removal, the bile may not be sufficiently reabsorbed and may trigger diarrhea.
- Digestion and absorption of fats University of Washington
- Secretion of Bile and the Role of Bile Acids In Digestion Colorado State University
- Boyer JL et al, 2013, Bile formation and secretion PubMed Central
- Bile Encyclopaedia Britannica
- Bile Encyclopedia.com
- Kapoor VK, Gallbladder anatomy Emedicine
- Vomiting in adults NHS inform
- Valussi M, 2011, Functional foods with digestion-enhancing properties ResearchGate
- Artichoke WebMD
- Ginger National Center for Complementary and Integrative Health
- Dandelion National Center for Complementary and Integrative Health
- McMullen MK et al, 2015, Bitters: time for a new paradigm PubMed Central
- Walker GM et al, 2006, Colour of bile vomiting in intestinal obstruction in the newborn: questionnaire study The BMJ
- Wang Y et al, 2002, Luminal CCK-releasing factor stimulates CCK release from human intestinal endocrine and STC-1 cells Gastrointestinal and Liver Physiology
- Douglas BR et al, 1990, Coffee stimulation of cholecystokinin release and gallbladder contraction in humans The American Journal of Clinical Nutrition
- Rasyid A et al, 1999, The effect of curcumin and placebo on human gall-bladder function: an ultrasound study PubMed
- Marciani L et al, 2013, Effects of various food ingredients on gall bladder emptying PubMed Central
- Kasicka-Jonderko A et al, 2014, Sluggish gallbladder emptying and gastrointestinal transit after intake of common alcoholic beverages PubMed
- Dulbecco P et al, 2013, Therapeutic potential of curcumin in digestive diseases PubMed
- Cohen DE, 2008, Balancing Cholesterol Synthesis and Absorption in the Gastrointestinal Tract