Vitamin B7, or biotin, has many important functions in the body. Biotin is an essential component of many enzymes that break down substances in the body, including fats, carbohydrates and amino acids.
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Vitamin B7, or biotin, is a water-soluble.
Vitamin B7 plays an essential role in many processes, especially in protein-synthesis and cell reproduction. It cannot be synthesized by mammalian cells, and must therefore be obtained from external sources. It is bound to proteins in foods and becomes available for use after it is released through the action of a specific enzyme, known as biotinidase.
Sources of vitamin B7:
Biotin can be found in a variety foods because it is naturally bound to dietary proteins. The highest levels can be sourced from liver (27-35 micrograms—mcg—per 85 g of liver), egg yolk (13-25 mcg per yolk), and avocado (2-6 mcg per fruit), and yeast (14 mcg per 7g of yeast). Other sources include whole-grain cereals, bananas and some vegetables such as cauliflower.
Biotin is synthesised by some strains of bacteria, yeast, mould, algae, and some plant species. In fact, other than ingested biotin, many bacteria that normally colonise the small and large intestines—the colon—synthesise biotin. However, despite some studies alluding to a positive result, it is uncertain whether biotin released by enteric bacteria is absorbed by humans in any meaningful amounts.
Biotin is an essential component of many enzymes that break down substances in the body, including fats, carbohydrates and amino acids. It also plays an essential role in many processes, especially in protein-synthesis and cell reproduction.
It cannot be synthesized by mammalian cells, and must therefore be obtained from external sources. It is bound to proteins in foods and becomes available for use after it is released through the action of a specific enzyme, known as biotinidase.
Vitamin B7 deficiency:
Although biotin deficiency is very rare, low biotin levels are observed amongst people who smoke, have undergone rapid weight loss, who have had long-term tube feeding or are malnourished.
Those who have a diet that is devoid of biotin over an extended period run the risk of deficiency, for instance infants who are fed formula lacking in biotin. Similarly, a long-term consumption of raw egg whites can cause deficiency, because they contain an antimicrobial protein, known as avidin, that can bind biotin, thus preventing its absorption. This can simply be avoided by cooking the eggs, as this denatures avidin, rendering it susceptible to digestion, allowing the body to absorb the biotin.
There is some evidence that diabetes could cause low biotin levels, and certain types of liver disease are known to increase the requirement for biotin.
The rapidly dividing cells of the developing foetus require biotin for synthesis of essential enzymes; hence, the biotin requirement increases during pregnancy. Current research indicates that a substantial number of women develop low biotin levels (i.e. deficiency) during normal pregnancy, but it is not known whether this might increase the risk of congenital anomalies and this is an area of concern and investigation.
Biotin deficiency can also arise in people who have a specific inherited condition, such as absence of the enzyme biotinidase. The absence of biotinidase prevents biotin from being released, and intestinal absorption will be impaired. In these cases oral supplementation with 5-10 milligrams of biotin per day is sometimes required, although smaller doses are often sufficient.
Symptoms of deficiency:
Reduced urinary excretion of biotin have been validated as indicators of biotin deficiency status, but there is no good laboratory test for detecting low biotin levels in blood. A deficiency is therefore usually identified by its symptoms.
Low blood levels of biotin can cause hair loss (alopecia), thinning of the hair, as well as loss of hair colour. Other symptoms include a red, scaly rash around the eyes, nose, mouth and genital area. Neurological symptoms in adults include depression, tiredness, lack of interest, hallucinations, nausea, and tingling in the arms and legs.
There is evidence that individuals with hereditary disorders of biotin deficiency also have impaired immune system function and an increased susceptibility to bacterial and fungal infections.
The recommended dietary intake of biotin is expressed as an Adequate Intake (AI), rather than a Recommended Dietary Allowance (RDA). The daily AI is 8–12 mcg for children, 30 mcg for adults including pregnant women, and 35 mcg for breast-feeding women. There is no indication that those above 50 years of age have an increased requirement for biotin.
If dietary biotin intake is not sufficient, a daily multivitamin-mineral supplement will generally provide an intake of at least 30 mcg of biotin per day, which may help treat low blood levels of biotin.
Although preliminary evidence suggests that taking biotin by mouth for up to a year may help strengthen brittle nails, larger placebo-controlled trials are needed to assess the efficacy of high-dose biotin supplementation for this treatment.
Biotin is available as a single-nutrient supplement in various doses and is often included in B-complex and multivitamin-mineral (MVM) supplements. Many MVM supplements contain 30 mcg of biotin.
Biotin is not known to be toxic, and is well tolerated when used within recommended amounts. Furthermore, no toxicity of excess biotin intake has been described. For example, there were no associated adverse effects when people with no known biotin metabolism disorders were given daily doses up to 5 mg over the course of two years. Oral biotin supplementation has been well tolerated in doses up to 200 mg per day—nearly 7,000 times the AI—in people with hereditary disorders of biotin metabolism.
Long-term anticonvulsant (anti-seizure) therapy may also increase the dietary requirement for biotin, because anticonvulsant drugs can interfere with the intestinal absorption and renal re-absorption of biotin. Long-term treatment with some antibiotics, such as antibacterial sulfonamide drugs, may decrease bacterial synthesis of biotin.
Some medications are changed and broken down by the liver, and these should usually not be mixed with biotin supplements. This is because biotin might increase how quickly the liver breaks down the medications, thus decreasing their effect. It is therefore important to talk to your healthcare provider before starting a biotin supplement if you take any medications that are broken down in the liver.
Biotin and vitamin B5 taken together can each reduce the body's absorption of the other.
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