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For children ages 1–13 years, the RDA increases with age from 0.9 to 1.8 μg/day. Because 10 to 30 percent of older people may be unable to effectively absorb vitamin B 12 naturally occurring in foods, those older than 50 years should meet their RDA mainly by consuming foods fortified with vitamin B 12 or a supplement containing vitamin B 12.
The structure of vitamin B 12 was the first low-molecular weight natural product determined by x-ray analysis rather than by chemical degradation. Thus, while the structure of this novel type of complex biomolecule was established, its chemistry remained essentially unknown; exploration of this chemistry became one of the tasks of the vitamin's chemical synthesis.
Vitamin B 12 cannot be produced by the human body, and must be obtained from the diet. [2] The body normally gets enough vitamin B 12 from the consumption of foods from animal sources. [2] Inadequate dietary intake of animal products such as eggs, meat, milk, fish, fowl (and some types of edible algae) can result in a deficiency state. [135]
In pigs it is obtained from the pylorus and beginning of the duodenum; [12] in human beings it is present in the fundus and body of the stomach. [13] The limited amount of normal human gastric intrinsic factor limits normal efficient absorption of B 12 to about 2 μg per meal, a nominally adequate intake of B 12. [14]
One of the superpowers of vitamin B12 is that it is the only water-soluble vitamin that can be stored in the human body, Kitchens points out, and it can remain stored in the liver for several ...
The National Institutes of Health recommends that the average man consume a mere 2.4 micrograms a day, which is actually the lowest daily recommended dose of any vitamin. “Vitamin B12 ...
Its main function is to absorb vitamin B 12, bile salts, and whatever products of digestion that were not absorbed by the jejunum. The ileum follows the duodenum and jejunum and is separated from the cecum by the ileocecal valve (ICV). In humans, the ileum is about 2–4 m long, and the pH is usually between 7 and 8 (neutral or slightly basic).
Vitamin B12 is a water-soluble vitamin that’s naturally present in some foods, although it’s also available as a dietary supplement and prescription medicine, according to the National ...