Biotin food sources

Fatty acids with odd numbers of carbon atoms are rare in mammals, but fairly common in plants and marine organisms. Humans and animals whose diets include these food sources metabolize odd-carbon fatty acids via the /3-oxida-tion pathway. The final product of /3-oxidation in this case is the 3-carbon pro-pionyl-CoA instead of acetyl-CoA. Three specialized enzymes then carry out the reactions that convert propionyl-CoA to succinyl-CoA, a TCA cycle intermediate. (Because propionyl-CoA is a degradation product of methionine, valine, and isoleucine, this sequence of reactions is also important in amino acid catabolism, as we shall see in Chapter 26.) The pathway involves an initial carboxylation at the a-carbon of propionyl-CoA to produce D-methylmalonyl-CoA (Figure 24.19). The reaction is catalyzed by a biotin-dependent enzyme, propionyl-CoA carboxylase. The mechanism involves ATP-driven carboxylation of biotin at Nj, followed by nucleophilic attack by the a-carbanion of propi-onyl-CoA in a stereo-specific manner. 

The best food sources of biotin (Fig. 8) include yeast, liver, soy products, rice, egg yolks, nuts, fish, and chocolate (179,180). Although many foods contain biotin, the levels are normally very low. Endogenous biotin in foods is usually protein bound in general there is more free biotin in plant-based foods than in animal-based products. 

In addition to food sources, biotin is available in pure synthetic form. 

In terms of amino acids bacterial protein is similar to fish protein. The yeast s protein is almost identical to soya protein fungal protein is lower than yeast protein. In addition, SCP is deficient in amino acids with a sulphur bridge, such as cystine, cysteine and methionine. SCP as a food may require supplements of cysteine and methionine whereas they have high levels of lysine vitamins and other amino acids. The vitamins of microorganisms are primarily of the B type. Vitamin B12 occurs mostly hi bacteria, whereas algae are usually rich in vitamin A. The most common vitamins in SCP are thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, choline, folic acid, inositol, biotin, B12 and P-aminobenzoic acid. Table 14.4 shows the essential amino acid analysis of SCP compared with several sources of protein. 

Biotin is widely distributed in foods. Beef liver, yeast, peanuts, kidney, chocolate, and egg yolk are especially rich sources. The intestinal flora synthesizes biotin. Fecal excretion reflects this enteric synthesis. Total daily urinary and fecal excretion exceeds the dietary intake. 

Sources. A balanced diet usually contains enough biotin as it is found in many foods (for example bread, egg yolks, fish, legumes, meat, dairy products, and nuts). In the intestines, bacteria produce a small amount of biotin, which may be absorbed and contribute to daily needs. "... 

Sources Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Huoride (1997) Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin 85, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (1998) EHetary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids (2000) Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001) Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005) and EHetary Reference Intakes for Calcium and Vitamin D (2011). These reports may be accessed via www.nap.edu A Tolerable Upper Intake Level (UL) is the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects to almost all individuals in the general population. Unless otherwise specified, the UL represents total intake from food, water, and supplements. Due to a lack of suitable data, ULs could not be established for vitamin K, thiamin, riboflavin, vitamin B12, pantothenic acid, biotin, and carotenoids. In the absence of a UL, extra caution may be warranted in consuming levels above recommended intakes. Members of the general population should be advised not to routinely exceed the UL. The UL is not meant to ply to individuals who are treated with the nutrient under medical supervision or to individuals with predisposing conditions that modify their sensitivity to the nutrient... 

Biotin is widely distributed in foods liver, milk, yeast, oilseeds and vegetables are rich sources. However, in some foods, much of the bound vitamin may not be released during digestion and hence may be imavailable. Studies with chicks and pigs have shown that the availability of biotin in barley and wheat is very low, whereas the biotin in maize and certain oilseed meals, such as soya bean meal, is completely available. 

The intervention of gastrointestinal proteases and peptidases transforms the protein bound forms of dietary biotin into biocytin or biotinyl-L-lysine and biotin-short peptides. In humans, it was assumed that biotinyl proteins and peptides arose from only two sources protein bound in food and degradation of endogenous biotin-containing carboxylases. 

In the organism that Is required In small amounts In food to sustain the normal metabolic functions of life. The key to this definition Is that this chemical compound must be supplied to the organism because the animal cannot synthesize vitamins. Lack of It produces a specific deficiency syndrome and supplying It cures that deficiency. An exception to this definition Is vitamin D, which can be made In the skin upon adequate exposure to sunlight. However, without adequate exposure, the animal Is dependent on a dietary source. Biotin, panthothenlc acid, and vitamin R are made by bacteria In the human Intestine, based on a symbiotic relation-ship and, thus, are not required by the human. Niacin can also be synthesized In humans from the amino acid tryptophane. 

Good sources of biotin are liver, pork, nuts, chocolate, pulses, cereals, and royal jelly, but biotin is widely distributed among all types of food and dietary deficiency is rare. However, biotin is inactivated by avidin which is present in raw egg whites and severe eczema has been reported from... 

Sources Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine Dietary Reference Intakes for calcium, phosphorus, magnesium, vitamin D and fluoride, 1997 Dietary reference intakes for thiamin, riboflavin, niacin, vitamin B, folate, vitamin Bj, pantothenic acid, biotin and choline, 1998 Dietary reference intakes for vitamin C, vitamin E, selenium and carotenoids, 2000 Dietary Reference Intakes for vitamin A, vitamin K, arsenc, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium and zinc, 2001, National Academy Press Washington, DC. 

SOURCES OF BIOTIN. Biotin is widely distributed in foods of both plant and animal origin and it Occurs in both the free state and in a form bound to protein. It occurs in the free state in fruits, vegetables, milk, and rice bran ... 

For additional sources and more precise values of biotin, see Food Composition Table F-21 of this book. 

Lamb is important in the diet, not for its appetite appeal alone, but for the essential food nutrients that it contains. It is an excellent source of high-quality protein for muscle building and body maintenance. In most cuts of lamb, the fat may be easily separated from the lean hence, the calories can be adjusted to desired levels. Lamb is one of the best sources of iron, needed for hemoglobin formation and it is rich in phosphorus, needed for bones and teeth. It is also an excellent source of vitamin B-12, vitamin B-6, biotin, niacin, pantothenic acid, and thiamin. Also, lamb muscle is easily digested, so it is included in the diet of both the young and aged. 

Biotin—Biotin is widely distributed in foods of animal origin, with liver and kidney being rich sources, followed by eggs, sardines and salmon, cheese, chicken, oysters, and pork. 

Considerable biotin Is synthesized by the micraurganisms in the intestinal iract and much ol it a absorbed, as evidenced by the fact ihai 3 lo 6 rimes more biotin Is excreted in the urine and feces than is ingested For additional sources and more precise values of biotin, see food Composition Table F-21,... 

Also called D-biotin, is one of the more recently discovered vitamins. It belongs to the group of B vitamins and is found in most foods in small amounts. The richest sources are yeast, liver and kidney. Egg yolk, soybeans, nuts and cereals are also good sources. Biotin is found in most feedsmffs because its bioavailability is low it is added to most animal feeds to improve reproductive functions and general health. 

The great majority of measurements of biotin content of foods have used bioassays. Recent publications provide evidence that the values are likely to contain substantial errors. However, some worthwhile generalizations can be made. Biotin is widely distributed in natural foodstuffs, but the absolute content of even the richest sources is low compared to the content of most other water-soluble vitamins. 

---