A common component of the microbiota of the human gastrointestinal tract and in particular are amongst the first bacterial colonizers of the intestine.

Considered amongst the most beneficial commensal bacteria in the human gut, Bifidobacterium spp. are able to degrade monosaccharides, galacto-, manno-, and fructo-oligosaccharides, as well as some complex carbohydrates. Many of the non-digestible oligosaccharides, found as natural components in mother’s milk, select for colonization of these species which dominate the infant gut shortly after birth.

Bifidobacteria may provide health benefits directly through interactions with the host, and indirectly through interactions with other microorganisms. Bifidobacterium spp. take part in production and adsorption of vitamins, such as vitamins K and B12, biotin, folate, thiamine, riboflavin, and pyridoxine.

Bile acids are compounds that are made in the liver and stored in the gall bladder. Bile acids help with digestion of foods, particularly fat. When food is eaten, the body sends a signal to the gall bladder to contract and push bile acids into the small intestine. The bile acids mix with the food in the intestine and break down large, complex fats into small particles that can be absorbed more easily.

Bile acids are a group of molecules produced by the liver from cholesterol and play a vital role in the digestion and absorption of fats and fat-soluble vitamins in the small intestine. They are components of bile, a fluid that is released into the intestines to help break down fats. A lab panel can measure the levels of bile acids in the blood, which is an important marker for assessing liver function and health. Elevated levels of bile acids in the blood can indicate liver disease or conditions that impair bile flow, such as cholestasis. This is because when the liver is damaged or the bile ducts are blocked, bile acids can accumulate in the liver and spill into the bloodstream. On the other hand, lower levels might be seen in certain conditions affecting the production of bile acids. Therefore, measuring bile acids can help diagnose and monitor liver diseases, evaluate the severity of liver dysfunction, and guide treatment decisions. This test is particularly useful in diagnosing and monitoring conditions that affect bile acids metabolism or bile flow, providing crucial information for the effective management of liver-related disorders.

Bilirubin is a waste byproduct of the breakdown of red blood cells. Yellow in coloration, bilirubin is filtered out of the blood by the liver and excreted in stool by the intestines. Bilirubin tests are done when a disease or blockage of the liver is suspected. Direct bilirubin differs from indirect bilirubin in that it is bound to a sugar and is therefore water soluble. 

The Indirect Bilirubin test measures how much bilirubin is in your blood. It originates from the breakdown of hemoglobin in the red blood cells, but must be removed by your liver. 

Bilirubin is a yellowish pigment produced when your body breaks down old red blood cells. This process is normal and healthy—it's how your body recycles hemoglobin, the protein that carries oxygen in your blood.

Once formed, bilirubin travels to the liver, where it becomes part of bile—a fluid that helps digest fats. Bile is stored in the gallbladder and released into the small intestine during digestion. Most bilirubin is eventually removed from the body through feces (giving stool its brown color) or urine (giving it a yellow tint).

When bilirubin levels rise, it can be a sign that something isn’t working properly in the liver, gallbladder, or bile ducts. High bilirubin may lead to jaundice, a yellowing of the skin and eyes. This often occurs when the liver can’t effectively process or clear bilirubin from the bloodstream.

A bilirubin blood test helps identify liver or bile duct problems early—especially when symptoms like jaundice, dark urine, or pale stools are present.

Bilirubin is primarily derived from metabolism of hemoglobin. Only conjugated bilirubin is excreted into the urine and normally only trace amounts can be detected in urine.

Bilophila Wadsworthia is a gram negative, anaerobic, sulfidogenic bacterium resistant to β-lactam antibiotics. This pathobiont is commonly found in patients with appendicitis and it has been associated to the Western diet (high in fats and animal proteins), as well as severe malnutrition. A recent study in animals showed that a high fat diet stimulates the growth of B. Wadsworthia, which causes inflammation, dysfunction in the intestinal barrier and bile acid metabolism, hepatic steatosis and dysfunctional glucose metabolism. Interestingly, the co-administration of a probiotic strain (Lactobacillus rhamnoses) reduces the generated inflammation and limits the metabolic impairment.

Bilophila wadsworthia is a sulfate-reducing bacterium that naturally occurs in the human gut microbiome, typically in small quantities. This anaerobic, gram-negative bacillus was first isolated in 1989 and is known for its ability to thrive in bile-rich environments. While B. wadsworthia is present in 50-60% of healthy individuals, an overgrowth of this species has been associated with various health concerns. It produces hydrogen sulfide, which in excess can contribute to gut inflammation and has been linked to conditions such as inflammatory bowel disease, irritable bowel syndrome, and colorectal cancer. B. wadsworthia's growth is particularly stimulated by diets high in saturated fats and taurine-rich foods like meat and dairy products. In controlled studies, this bacterium has been shown to exacerbate metabolic dysfunctions in mice fed a high-fat diet, leading to increased inflammation, intestinal barrier dysfunction, and glucose dysregulation. The presence and abundance of B. wadsworthia in a BiomeFX report may provide insights into potential gut dysbiosis and associated health risks, especially in the context of dietary habits and metabolic health.

Biotin is required for proper metabolism of fats and carbohydrates. Biotin-dependent enzymes catalyze the addition of carboxyl groups (COO-) from bicarbonate, for use in fatty acid biosynthesis, gluconeogenesis, lipogenesis, propionate metabolism, and leucine catabolism.

Biotin, also known as Vitamin B7, is a water-soluble B-complex vitamin that plays a critical role in various metabolic processes and is commonly included in blood panel tests to assess nutritional status. It acts as a coenzyme for carboxylase enzymes, pivotal in the synthesis of fatty acids, amino acids, and the generation of glucose from non-carbohydrate sources. Biotin is essential for the proper functioning of the nervous system and plays a role in maintaining skin, hair, and mucous membrane health.

Used in alloys, electronics, batteries, crystal ware, cosmetics, flame retardants,and in antimicrobial therapy (H. pylori), antiseptic dressings, paraffin paste. Bismuth medical therapies exhibit high therapeutic effects and little side effects, though over-dosage can cause toxicity.

Very limited absorption in the GI tract. When absorbed, it binds mainly to transferrin and lactoferrin, interacts with enzymes due to a high affinity to cysteine residues, blocking the active site. Can accumulate in the kidney, lung, spleen, liver, brain, and muscles, while being eliminated in urine and feces via bile and intestinal secretions.

Fecal bismuth (Bi) provides an estimate of a recent oral exposure to the element. Bi is a non-essential element of relatively low toxicity. Absorption is dependent upon solubility of the Bi compound, with insoluble Bi excreted in the feces while soluble forms are excreted primarily in the urine. Sources of Bi include: cosmetics (lipstick), Bi containing medications such as ranitidine Bi-citrate, antacids (Pepto-
Bismol), pigments used in colored glass and ceramics, dental cement, and dry cell battery electrodes.

Several organometallic Bi compounds are used for bactericidal and fungicidal applications.

Symptoms of moderate Bi toxicity include constipation or bowel irregularity, foul breath, blue/black gum line, and malaise. Unusually high levels of Bi retention in the body may result in nephrotoxicity (nephrosis, proteinurea) and neurotoxicity (tremor, memory loss, monoclonic jerks, dysarthria, dementia). Urine elements analysis may be used to corroborate Bi absorption for a period of days or a few weeks after
the exposure.