question: Since Vitamin B12 is only found in animal products, vegetarians and vegans get it from supplements or cereals for example. But where do the cereal makers get it if not from animal products?
comment: B12 is produced by micro-organisms. Animals get it from dirt, or supplements these days. The B12 for supplements is produced industrially, in the B12 factory.
passages: Because there are few common vegetable sources of the vitamin, vegans must use a supplement or fortified foods for B intake or risk serious health consequences. Otherwise, most omnivorous people in developed countries obtain enough vitamin B from consuming animal products including meat, milk, eggs, and fish. Staple foods, especially those that form part of a vegan diet, are often fortified by having the vitamin added to them. Vitamin B supplements are available in single agent or multivitamin tablets; and pharmaceutical preparations may be given by intramuscular injection. 
   Vitamin B is mostly manufactured by industrial fermentation of various kinds of bacteria, which make forms of cyanocobalamin, which are further processed to generate the ingredient included in supplements and fortified foods. The "Pseudomonas denitrificans" strain was most commonly used . It is grown in a medium containing sucrose, yeast extract, and several metallic salts. To increase vitamin production, it is supplemented with sugar beet molasses, or, less frequently, with choline. Certain brands of B supplements are vegan.
  
  Section::::Vegan diet.:Nutrients.:Calcium.
   Animals store vitamin B in the liver and muscles and some pass the vitamin into their eggs and milk; meat, liver, eggs and milk are therefore sources of the vitamin for other animals as well as humans. For humans, the bioavailability from eggs is less than 9%, compared to 40% to 60% from fish, fowl and meat. Insects are a source of B for animals (including other insects and humans).
  
  Food sources with a high concentration of vitamin B—50 to 99µg B per 100 grams of food—include clams; liver and other organ meats from lamb, veal, beef, and turkey; mackerel;
   B is only produced in nature by certain bacteria, and archaea. It is synthesized by some bacteria in the gut flora in humans and other animals, but humans cannot absorb this as it is made in the colon, downstream from the small intestine, where the absorption of most nutrients occurs. Ruminants, such as cows and sheep, absorb B produced by bacteria in their guts. For gut bacteria of ruminants to produce B the animal must consume sufficient amounts of cobalt. These grazing animals acquire the bacteria that produce vitamin B, and the vitamin itself.
   Feces are a rich source of vitamin B, and are eaten by many animals, including dogs and cats. Lagomorpha species, including rabbits and hares, form fecal pellets in their cecum called cecotropes, which consist of chewed plant material that has been metabolized by cecal bacteria; cecotropes contain digestible carbohydrates and B vitamins synthesized by the resident bacteria. These animals ingest cecotropes which have been expelled in their feces.
  
  Section::::Sources.:Animals.
   Animal protein products are a good source of B, particularly organ meats such as kidney or liver. Other good sources are fish, eggs, and dairy products. It is suggested that vegans, who consume no animal meat or by-products, supplement their diet with B. While there are foods fortified with B available, some may be mislabelled in an attempt to boost their nutritional claims. Products of fermentation, such as algae extracts and sea vegetables, may be labelled as sources of B, but actually contain B analogues which compete for the absorption of the nutrient itself. In order to get adequate amounts of the vitamin, orally administered pills or fortified foods such as cereals and soy milk, are recommended for vegans.
   The UK Vegan Society, the Vegetarian Resource Group, and the Physicians Committee for Responsible Medicine, among others, recommend that every vegan who is not consuming adequate B from fortified foods take supplements.
  
  Foods for which B-fortified versions are widely available include breakfast cereals, soy products, energy bars, and nutritional yeast.
  
  Section::::Sources.:Supplements.
   Animals store vitamin B in liver and muscle and some pass the vitamin into their eggs and milk; meat, liver, eggs and milk are therefore sources of B.
   Vitamin B is not made by plants or animals, but by bacteria that grow in soil, feces, dirty water or laboratories, so plant foods are not reliable sources of B. The UK Vegan Society, the Vegetarian Resource Group, and the Physicians Committee for Responsible Medicine, among others, recommend that every vegan consume adequate B from either fortified foods or by taking a supplement.
   Section::::Sources.
  
  Most omnivorous people in developed countries obtain enough vitamin B from consuming animal products including, meat, fish, eggs, and milk. Vegan sources in the common food supply are rare.
  
  Section::::Sources.:Bacteria and archaea.
   Evidence shows that vegans who are not taking vitamin B supplements do not consume sufficient B and often have abnormally low blood concentrations of vitamin B. This is because, unless fortified, plant foods do not contain reliable amounts of active vitamin B. Vegans are recommended to do one of the following dietary options: 
  
  BULLET::::- Consume fortified foods 2-3 times per day to get at least 3 micrograms of vitamin B,
  
  BULLET::::- or take 10 micrograms of B as a supplement once per day
  
  BULLET::::- or take 2000 micrograms of B as a supplement once per week
   As no animal is able to synthesize cobalamin endogenously, cobalamin should be fortified and supplemented in plant-based diets. While conventional dog foods have sources of B from their animal products (meats, organs, milk, egg, etc), vegan dog foods meet their vitamin B requirement through pure supplementation. Nutritional yeast provides a good source of vitamin B, as it is already fortified.
  
  Section::::Alternative sourcing of ingredients.:Taurine.
   Vitamin B deficiency is most commonly caused by low intakes, but can also result from malabsorption, certain intestinal disorders, low presence of binding proteins, and use of certain medications. Vitamin B is rare from plant sources, so vegetarians are more likely to suffer from vitamin B deficiency. Infants are at a higher risk of vitamin B deficiency if they were born to vegetarian mothers. The elderly who have diets with limited meat or animal products are vulnerable populations as well. Vitamin B deficiency may occur in between 40% to 80% of the vegetarian population who are not also consuming a vitamin B supplement. In Hong Kong and India, vitamin B deficiency has been found in roughly 80% of the vegan population as well. Vegans can avoid this by eating B12 fortified foods like cereals, plant-based milks, and nutritional yeast as a regular part of their diet. In addition to worries concerning those following a vegetarian or vegan diet, research has found that approximately 39 percent of the general population may have possible B12 deficiencies or difficulty with the absorption of this nutrient. Taking a B12 supplement could be beneficial to most people.
   Sunlight, fortified foods and supplements are the main sources of vitamin D for humans. Unlike plant-foods, some animal products naturally contain small amounts of vitamin D, such as salmon and other oily fish, egg yolks, some dairy products, and various organ meats. Furthermore, vitamin D3 used in some supplements and fortified foods, which has longer lasting effects than vitamin D2, is commonly animal-derived. Vitamin D2 is obtained from fungi, such as mushrooms exposed to sun or industrial ultraviolet light, offering a vegan choice for dietary or supplemental vitamin D.
  
  Section::::See also.
  
  BULLET::::- Vegetarian nutrition
  
  BULLET::::- Nutrition
  
  BULLET::::- Raw veganism
   Vitamin B is the only vitamin not present in plant sources. The largest and most complex of all the vitamins, vitamin B, is synthesized only by bacteria and some archaea species, as eukaryotes lack the enzyme. It is integral to the health and function of the nervous system, key in hematopoiesis, as well as required to synthesize methionine and catabolize propionate for energy. Grazing animals are able to obtain B when they ingest bits of soil with the grass, as the vitamin and B-producing bacteria are found in the soil and attached to the roots of the plants. After ingesting the vitamin, it is stored in the muscle and liver tissues of the animal, and subsequently passed on to the next level of the food chain.
   The ingredients in Eukanuba products contain both animal and animal by-products, which are the non-rendered lungs, spleen, kidneys, brain, livers, blood, bone, partially de-fatted low temperature fatty tissue, and stomachs and intestines freed of their contents. By-products do not include hair, horns, teeth and hoofs. Most of the ingredients come from the United States, but a limited amount of nutritional supplements are imported from countries such as China.
  
  Section::::Sponsorships.
   It is essential, therefore, that vegetarians consume adequate amounts of dietary supplements or foods that have been fortified with B, such as nutritional yeast or other yeast extracts, vegetable stock, veggie burger mixes, textured vegetable protein, soy milks, vegetable and sunflower margarines, and breakfast cereals. B used in these foods or supplements is typically grown from vegan sources (such as bacteria). Soybeans and barley seeds from plants grown in soils amended either with cow dung (which is rich in B) or with pure B had a higher B content than those grown without this supplementation. There is a patent for cultivating plants in a solution containing vitamin B so that the plant contains more B.
   BULLET::::- 1926 - George Minot shared the 1934 Nobel Prize with William Murphy and George Whipple, for discovery of an effective treatment for pernicious anemia using liver concentrate, later found to contain a large amount of vitamin B.
  
  BULLET::::- 1929 - William Castle demonstrated that gastric juice contained an "intrinsic factor" which when combined with meat ingestion resulted in absorption of the vitamin in this condition.
  
  Section::::Other animals.
  
  Ruminants, such as cows and sheep, absorb B synthesized by their gut bacteria. Sufficient amounts of cobalt and copper need to be consumed for this B synthesis to occur.
  
  Section::::Other animals.:Epidemics.
   and crab meat.
  
  Section::::Sources.:Plants and algae.
  
  Natural sources of B include fermented plant foods, such as tempeh, nori and laver, a seaweed. Many other types of algae are rich in vitamin B, with some species, such as "Porphyra yezoensis", containing as much cobalamin as liver. Methylcobalamin has been identified in "Chlorella vulgaris". In all cases of plant foods which contain B, the vitamin is produced by bacterial fermentation or by bacterial symbiosis with various species of algae.
  
  Section::::Sources.:Fortified foods.
   Vitamin B is included in multivitamin pills; and in some countries grain-based foods such as bread and pasta are fortified with B. In the U.S. non-prescription products can be purchased providing up to 5,000µg per serving, and it is a common ingredient in energy drinks and energy shots, usually at many times the recommended dietary allowance of B. The vitamin can also be a prescription product via injection or other means. Tablets have sufficiently large quantities of the vitamin such that 1% to 5% of the free crystalline B is absorbed along the entire intestine by passive diffusion.
   Generally, humans need 2.4 to 3 micrograms of vitamin B each day. Although some argue that developing a disease from B deficiency by following a sensible diet is extremely rare (less than one chance in a million), there are cases to suggest that vegetarians and vegans who are not taking vitamin B supplements or food fortified with B do not consume sufficient servings of B and have abnormally low blood concentrations of vitamin B. This is because, unless fortified, plant foods do not contain reliable amounts of active vitamin B.
   Vegan sources of vitamin D include ergocalciferol and synthetic or plant sources of cholecalciferol. Mushrooms are a good plant source of natural ergocalciferol, especially after being exposed to UV-B light. Cholecalciferol in vegan dog food can be synthetic or naturally derived from lichen, a non-animal source of D3.
  
  Section::::Alternative sourcing of ingredients.:Vitamin B.
   B is produced in nature only by certain bacteria and archaea; it is not made by any animal, fungus, or plant. It is synthesized by some gut bacteria in humans and other animals, but humans cannot absorb the B made in their guts, as it is made in the colon which is too far from the small intestine, where absorption of B occurs. Ruminants, such as cows and sheep, absorb B produced by bacteria in their guts.
   Vitamin B is one of eight B vitamins; it is the largest and most structurally complex vitamin. It consists of a class of chemically related compounds (vitamers), all of which show physiological activity. It contains the biochemically rare element cobalt (chemical symbol Co) positioned in the center of a corrin ring. The only organisms to produce vitamin B are certain bacteria, and archaea. Some of these bacteria are found in the soil around the grasses that ruminants eat; they are taken into the animal, proliferate, form part of their gut flora, and continue to produce vitamin B.
   Vegetarians may get vitamin B from eggs and dairy products (milk, cheese, etc.); for some, this is adequate, while others may still remain B-deficient. More broadly, according to the Academy of Nutrition and Dietetics, even the form of vitamin B sourced from animal products is protein-bound and not as easily digested as supplements, especially as people age, and therefore B supplementation is recommended for everyone over the age of 50. Pregnant and lactating vegetarian mothersand breastfed infants if the vegetarian mother's diet is not supplementedshould also use supplements, whether B-pills, B-injections, or B-fortified foods, if they don't get adequate vitamin B from animal products like eggs or dairy.
  
presuppositions: B12 is only found in animal products.
corrections: B12 is produced by micro organisms.
raw_presuppositions: B12 is only found in animal products. B12 is only found in animal products.
raw_corrections: B12 is produced by micro organisms. B12 is produced by micro organisms.