Vitamin B12 or cobalamin occurs naturally in animal foods. It can also be added to food or supplements. Vitamin B12 is necessary for the formation of red blood cells and DNA. It is also a key player in brain and nerve cell function and development.
Vitamin B12 binds to proteins in the food we eat. In the stomach, hydrochloric acid and enzymes break down vitamin B12 into its free form. From there, vitamin B12 binds to a protein called intrinsic factor so that it can be absorbed further in the small intestine.
Supplements and fortified foods contain the free form of B12, so it is more easily absorbed. There are a variety of vitamin B12 supplements available. Although there are claims that some forms, such as sublingual tablets or liquids placed under the tongue that are absorbed through the oral tissues, are better absorbed than traditional tablets, research has not shown important differences. High doses of vitamin B12 tablets are well above the recommended dietary intake, but these high doses are not necessarily absorbed because sufficient amounts of intrinsic factor are also required. If you have severe vitamin B12 deficiency due to insufficient intrinsic factor (pernicious anemia), your doctor may prescribe intramuscular B12 injections.
Recommended dosage
RDA : The recommended dietary allowance for men and women over 14 years of age is 2.4 micrograms (mcg) per day. For pregnancy and lactation, the dosage is increased to 2.6 mcg and 2.8 mcg per day, respectively.
UL : The tolerable upper intake limit (UL) is the maximum daily dose that is unlikely to cause adverse side effects in the general population. There is no upper limit for vitamin B12 because there is no established toxicity level. However, some evidence suggests that supplementing at 25 mcg per day or higher may increase the risk of fractures.
Vitamin B12 and health
Cardiovascular diseases
Vitamin B12 is involved in the breakdown of homocysteine protein. High homocysteine levels are associated with an increased risk of heart disease and stroke because it may promote the formation of blood clots and excess free radical cells and may impair normal blood vessel function. A lack of adequate vitamin B12 can increase homocysteine levels.
Although epidemiological studies have found that vitamin B12 supplementation can reduce homocysteine levels, taking vitamins has not been consistently shown to reduce the risk of cardiovascular events. Therefore, the American Heart Association does not advocate the routine use of B vitamin supplements to reduce cardiovascular disease risk. However, vitamin B12 supplements may be important for some individuals with genetic variations that cause high homocysteine levels.
Vitamin B12 is involved in the breakdown of homocysteine protein. High homocysteine levels are associated with an increased risk of heart disease and stroke because it may promote the formation of blood clots and excess free radical cells and may impair normal blood vessel function. Lack of adequate vitamin B12 can increase homocysteine levels.
Although epidemiological studies have found that vitamin B12 supplementation can reduce homocysteine levels, taking vitamins has not been consistently shown to reduce the risk of cardiovascular events. Therefore, the American Heart Association does not advocate the routine use of B vitamin supplements to reduce cardiovascular disease risk. However, vitamin B12 supplements may be important for some individuals with genetic variations that cause high homocysteine levels.
Cognitive function
High homocysteine concentrations are associated with higher rates of Alzheimer's disease, dementia, and cognitive decline. Similar to cardiovascular disease, although research shows that vitamin B12 supplementation can reduce blood homocysteine levels, this does not translate into a reduction in the rate of cognitive decline. A Cochrane review of folic acid supplements and cognition (with or without added vitamin B12) did not find that supplements had a significant effect on cognitive function compared with placebo in healthy older adults or people with dementia. Another review of 14 randomized controlled trials also found no consistent evidence that vitamin B12 supplements alone or with other B-complex vitamin supplements benefit cognitive function in people with normal or impaired cognitive function. These findings do not rule out that some individuals with lower vitamin B12 levels may benefit, and more research is needed.
food source
- fish, shellfish
- liver
- red meat
- Egg
- poultry
- Dairy products such as milk, cheese yogurt and
- Fortified Nutritional Yeast
- Fortified breakfast cereal
- Concentrated soy or rice milk
Signs of deficiency and toxicity
insufficient
Measuring vitamin B12 in the blood is not actually the best way to determine if someone is deficient because some deficient people may have normal blood levels. Blood levels of methylmalonic acid (a protein breakdown product) and homocysteine are better markers that capture actual vitamin B12 activity. These values increase with vitamin B12 deficiency. It is estimated that up to 15% of the general population is vitamin B12 deficient.
Factors that may cause vitamin B12 deficiency:
- Avoid animal products. People who do not eat meat, fish, poultry, or dairy products are at risk for vitamin B12 deficiency, since vitamin B12 only occurs naturally in animal products. Studies show that vegetarians have lower blood levels of B vitamins. Therefore, people who follow a vegetarian or vegan diet should include vitamin B12 fortified foods or vitamin B12 supplements in their diet. This is especially important for pregnant women because the fetus needs adequate vitamin B12 for neurological development and a lack of vitamin B12 can cause permanent nerve damage.
- Lack of intrinsic factors. Pernicious anemia is an autoimmune disease that attacks and may destroy intestinal cells, resulting in the absence of intrinsic factor, which is essential for the absorption of vitamin B12. If vitamin B12 is deficient, other types of anemia and nerve damage may result. Even high-dose B12 supplements won't solve the problem because intrinsic factor cannot be absorbed.
- Not having enough stomach acid or taking medications that reduce stomach acid. A more common cause of vitamin B12 deficiency, especially in older adults, is a lack of stomach acid, which is needed to release vitamin B12 from food. An estimated 10-30% of adults over the age of 50 have difficulty absorbing vitamin B12 from food. People who regularly take acid-blocking medications to treat gastroesophageal reflux disease (GERD) or peptic ulcers (such as proton pump inhibitors, H2 blockers, or other antacids) may have difficulty absorbing vitamin B12 from food. These drugs slow the release of stomach acid or reduce the production of stomach acid. In theory, this prevents the vitamin from being released into its free, usable form in the stomach. However, studies have not shown an increased prevalence of vitamin deficiencies in people using these medications. Anyone who uses these drugs long-term and who is at risk for vitamin B12 deficiency for other reasons should be closely monitored by a doctor. They may also choose to use fortified foods or supplements containing vitamin B12 because these forms are generally well absorbed and do not require stomach acid.
- Intestinal surgery or digestive disorders that cause malabsorption. Surgery that affects absorption in the stomach, where intrinsic factor is produced, or in the ileum (the last part of the small intestine), where vitamin B12 is produced, increases the risk of deficiency. Certain diseases, including Crohn's disease and celiac disease, can negatively affect the digestive tract and also increase the risk of vitamin D deficiency.
- Drugs that interfere with absorption. Long-term use of metformin, a common drug used to treat type 2 diabetes, is closely associated with vitamin B12 deficiency and reduced folate levels because it blocks absorption, which may lead to increased homocysteine levels and risk of cardiovascular disease. Proton pump inhibitors and histamine blockers, used to reduce stomach acid, are also associated with lower vitamin B12 levels.
Signs of deficiency may include:
- Megaloblastic anemia - A condition in which red blood cells are larger than normal in size but smaller than normal in number; this occurs due to insufficient or malabsorbed vitamin B12 in the diet
- Pernicious anemia - a type of megaloblastic anemia caused by a lack of intrinsic factor leading to inability to absorb vitamin B12
- fatigue, weakness
- Nerve damage, causing numbness and tingling in the hands and legs
- memory loss, confusion
- Dementia
- frustrated
- epileptic seizure
toxicity
Vitamin B12 is a water-soluble vitamin, so any unused amount is excreted in the urine. In general, taking a 1,000 mcg oral tablet daily to treat a deficiency is considered safe. The Institute of Medicine says there are no adverse effects from healthy people taking excess vitamin B12 from food and supplements. However, it is important not to start taking any type of high-dose supplement without first consulting your doctor.
did you know?
- Vitamin B complex supplements are often touted for boosting energy levels and mood. People who are deficient in B-complex vitamins may experience an increase in energy levels after taking supplements, as the vitamin is directly involved in the production of healthy blood cells and can correct anemia if present. However, there is no evidence that people without vitamin deficiencies benefit from taking additional B vitamins.
- People on a vegan diet are often told to add brewer's or nutritional yeast to supplement vitamin B12. However, yeast does not naturally contain this vitamin and is only present if it is added. Note that some brands (but not all) contain B12.
- Nori (nori) is a dried edible seaweed used in sushi rolls and is sometimes promoted as a plant source of vitamin B12. It does contain small amounts of active vitamin B12, but the amount varies depending on the type of seaweed, and some don't. Therefore it is not considered a reliable food source.
