Vitamin B12 is also called cobalamin because it contains the metal cobalt. This vitamin helps maintain healthy nerve cells and red blood cells. It is also needed to help make DNA, the genetic material in all cells.
Vitamin B12 is bound to the protein in food. Hydrochloric acid in the stomach releases B12 from proteins in foods during digestion. Once released, vitamin B12 combines with a substance called gastric intrinsic factor (IF). This complex can then be absorbed by the intestinal tract.
Do pregnant and/or lactating women need extra Vitamin B12?
During pregnancy, nutrients travel from mother to foetus through the placenta. Vitamin B12, like other nutrients, is transferred across the placenta during pregnancy. Breast-fed infants receive their nutrition, including vitamin B12, through breast milk. Vitamin B12 deficiency in infants is rare but can occur as a result of maternal insufficiency. For example, breast-fed infants of women who follow strict vegetarian diets have very limited reserves of vitamin B12 and can develop a vitamin B12 deficiency within months of birth. This is of particular concern because undetected and untreated vitamin B12 deficiency in infants can result in permanent neurologic damage. Consequences of such neurologic damage are severe and can be irreversible. Mothers who follow a strict vegetarian diet should consult with a paediatrician regarding appropriate vitamin B12 supplementation for their infants and children. They should also discuss their own need for vitamin B12 supplementation with their personal physician.
Who else may need a vitamin B12 supplement to prevent a deficiency?
Individuals with pernicious anemia
Anemia is a condition that occurs when there is insufficient haemoglobin in red blood cells to carry oxygen to cells and tissues. Common signs and symptoms of anemia include fatigue and weakness. Anemia can result from a variety of medical problems, including deficiencies of vitamin B12, vitamin B6, folate and iron. Pernicious anemia is the name given more than a century ago to describe the then-fatal vitamin B12 deficiency anemia that results from severe gastric atrophy, a condition that prevents gastric cells from secreting intrinsic factor. Intrinsic factor is a substance normally present in the stomach. Vitamin B12 must bind with intrinsic factor before it can be absorbed and used by your body. An absence of intrinsic factor prevents normal absorption of B12 and results in pernicious anemia.
Most individuals with pernicious anemia need parenteral (deep subcutaneous) injections (shots) of vitamin B12 as initial therapy to replenish depleted body B12 stores. Body stores of vitamin B12 can then be managed by a daily oral supplement of B12. A physician will manage the treatment required to maintain the vitamin B12 status of individuals with pernicious anemia.
Individuals with gastrointestinal disorders
Individuals with stomach and small intestinal disorders may be unable to absorb enough vitamin B12 from food to maintain healthy body stores. Intestinal disorders that may result in malabsorption of vitamin B12 include:
- Sprue, often referred to as Coeliac Disease (CD), is a genetic disorder. People with CD are intolerant to a protein called gluten. In CD, gluten can trigger damage to the small intestines, where most nutrient absorption occurs. People with CD often experience nutrient malabsorption. They need to follow a gluten free diet to avoid malabsorption and other symptoms of CD.
- Crohn's Disease is an inflammatory bowel disease that affects the small intestines. People with Crohn's disease often experience diarrhoea and nutrient malabsorption.
- Surgical procedures in the gastrointestinal tract, such as surgery to remove all or part of the stomach, often result in a loss of cells that secrete stomach acid and intrinsic factor. Surgical removal of the distal ileum, a section of the intestines, also can result in the inability to absorb vitamin B12. Anyone who has had either of these surgeries usually requires lifelong supplemental B12 to prevent a deficiency. These individuals would be under the routine care of a physician, who would periodically evaluate vitamin B12 status and recommend appropriate treatment.
Gastric acid helps release vitamin B12 from the protein in food. This must occur before B12 binds with intrinsic factor and is absorbed in your intestines. Atrophic gastritis, which is an inflammation of the stomach, decreases gastric secretion. Less gastric acid decreases the amount of B12 separated from proteins in foods and can result in poor absorption of vitamin B12. Decreased gastric secretion also results in overgrowth of normal bacterial flora in the small intestines. The bacteria may take up vitamin B12 for their own use, further contributing to a vitamin B12 deficiency.
Up to 30 percent of adults 50 years and older may have atrophic gastritis, an overgrowth of intestinal flora, and be unable to normally absorb vitamin B12 in food. They are, however, able to absorb the synthetic B12 added to fortified foods and dietary supplements. Vitamin supplements and fortified foods may be the best sources of vitamin B12 for adults over the age of 50.
Researchers have long been interested in the potential connection between vitamin B12 deficiency and dementia. A recent review examined correlations between cognitive skills, homocysteine levels, and blood levels of folate, vitamin B12 and vitamin B6. The authors suggested that vitamin B12 deficiency may decrease levels of substances needed for the metabolism of neurotransmitters. Neurotransmitters are chemicals that transmit nerve signals. Reduced levels of neurotransmitters may result in cognitive impairment. In 142 individuals considered at risk for dementia, researchers found that a daily supplement providing 2 milligrams (mg) folic acid and 1 mg B12, taken for 12 weeks, lowered homocysteine levels by 30%. They also demonstrated that cognitive impairment was significantly associated with elevated plasma total homocysteine. However, the decrease in homocysteine levels seen with vitamin supplementation did not improve cognition. It is too soon to make any recommendations, but is an intriguing area of research.
Vegetarians
The popularity of vegetarian diets has risen along with an interest in avoiding meat and meat products for environmental, philosophical, and health reasons. However, the term vegetarianism is subject to a wide range of interpretations. Some people consider themselves to be vegetarian when they avoid red meat. Others believe that vegetarianism requires avoidance of all animal products, including meat, poultry, fish, eggs, and dairy foods. The most commonly described forms of vegetarianism include:
Strict vegetarians and vegans are at greater risk of developing vitamin B12 deficiency than lacto-ovo vegetarians and non-vegetarians because natural food sources of vitamin B12 are limited to animal foods. Fortified cereals are one of the few sources of vitamin B12 from plants, and are an important dietary source of B12 for strict vegetarians and vegans. Strict vegetarians and vegans who do not consume plant foods fortified with vitamin B12 need to consider taking a dietary supplement that contains vitamin B12 and should discuss the need for B12 supplementation with their physician.
There is wide belief that vitamin B12 can be consistently obtained from nutritional yeasts. Consumers should be aware that these products may or may not contain added nutrients such as vitamin B12. Dietary supplements are regulated as foods rather than drugs, and companies that sell supplements such as nutritional yeasts fortified with vitamin B12 can legally change their formulation at any time. If you choose to supplement, select reliable sources of vitamin B12 and read product labels carefully.
When adults adopt a strict vegetarian diet, deficiency symptoms can be slow to appear. It may take years to deplete normal body stores of B12. However, breast-fed infants of women who follow strict vegetarian diets have very limited reserves of vitamin B12 and can develop a vitamin B12 deficiency within months. This is of particular concern because undetected and untreated vitamin B12 deficiency in infants can result in permanent neurologic damage. Consequences of such neurologic damage are severe and can be irreversible. There are many case reports in the literature of infants and children who suffered consequences of vitamin B12 deficiency. It is very important for mothers who follow a strict vegetarian diet to consult with a paediatrician regarding appropriate vitamin B12 supplementation for their infants and children
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