Normally food, once eaten, is broken down by the body, and the components used to assemble needed nutrients. However, some compounds, called essential nutrients cannot be made in the body, but instead must be gotten from outside sources. One of these is vitamin B12, also called cobalamin. However, while vitamin B12 cannot be manufactured in the body, it is possible for any of the varieties of the vitamin to be converted into the kinds that the body can use. Vitamin B12 is needed to produce red blood cells and effects the functioning of the brain and nervous system; B12 deficiency can lead to anemia and dementia.
A person can get vitamin B12 from eating fish and shellfish, meat, eggs, and dairy products. In the United States, synthetic B12 is often added to livestock feed in the United States, making farmed meat an especially good source. That means B12 supplementation is important for vegetarians, and especially vegans—all the more so because soy, a common ingredient in vegan cooking, can actually contribute to B12 deficiency. A compound found in soy products can reduce B12 levels by, in effect, mimicking B12 despite not being useable by the body, thus distracting the B12 utilization mechanisms.
Similarly, some medical conditions can prevent the body from properly absorbing or using vitamin B12. Supplements need to be taken with the drug metformin, which is used to treat type 2 diabetes. People infected with HIV have trouble absorbing sufficient amounts of B12. Patients who have gastrointestinal illness or have had intestinal surgery may be prone to B12 deficiency. Interestingly, B12 can both cause and result from anemia.
Due to cobalamin’s role in building and maintaining brain tissue, it is necessary for cognitive functioning. B12 doesn’t boost cognition in people with normal levels of functioning, but it can prevent cognitive problems or dementia, or slow the progress of dementia in people who already have it. Overdose is nearly impossible, because the vitamin is water-soluble—an excess amount is simply removed from the body. More than half of Americans have the opposite problem: deficiency, which can cause fatigue, rapid heartbeat, stomach upset, and bleeding gums. Oral and sub-lingual supplements are usually enough to get B12 to normal levels.