Vitamin B12 (cobalamin)
Vitamin B12 (also known as 'cobalamin')
is a water-soluble vitamin that is closely related to folic acid. Each relies
on the other for the body to be able to use them. Vitamin B12 is essential for
the efficient metabolism of protein, carbohydrates and fats in the body and
contributes to the production of red blood cells to prevent anaemia. It also
maintains the protective cover around the nerves and promotes their growth.
Vitamin B12 is excreted though the liver and passed into the bowel. Here it is reabsorbed by the body through the intestines. Vitamin B12 deficiency usually only occurs if a person's bowel has a disorder that prevents them from reabsorbing Vitamin B12, (rather than their diet being insufficient). This is a condition called 'pernicious anaemia'. However, because Vitamin B12 is only available in meat and dairy foods, and not plant foods, vegans may also be at risk of vitamin B12 deficiency.
Vitamin B12 deficiency (although very rare) can lead to anaemia, an inflamed tongue and mouth, fatigue and the degeneration of nerves, eventually leading to permanent paralysis. Babies born to mothers who are vitamin B12 deficient are at risk of spinal cord damage and possibly a severe inability to move well. If the mother is vitamin B12 deficient while breastfeeding, her baby can also exhibit limited movement. Your paediatrician may prescribe vitamin B12 supplements to help reverse the majority of these signs, but there can be permanent learning and language delays.
Recommended Daily Intake (RDI) for vitamin B12 is about 4 to 6ug (micrograms). This can be gained easily if your diet includes meats and/or dairy products.Vegans may need to take a daily vitamin B12 supplement (as a tablet).
Overdosing. There is no evidence that you can overdose on vitamin B12, however supplementing is rarely required if your diet includes meat or dairy products. If a person is unable to absorb vitamin B12 and/or is deficient in this vitamin, supplements may need to be prescribed by your caregiver as an injection.
Conception, pregnancy and breastfeeding. Vitamin B12 assists with the healthy development of the baby's brain and nervous system. Because Vitamin B12 is only present in animal and dairy foods, pregnant women who have a vegan diet will need to have a vitamin B12 supplement. There are now some brands of soymilk that are fortified with vitamin B12. Contrary to popular belief yeast, miso (soybean paste), mushrooms and sea algae (spirulina) do not contain active vitamin B12. They may be present in these foods but they are unable to be absorbed by the body. Babies also rely on obtaining adequate vitamin B12 from their mothers through breast milk when breastfeeding. Fortified foods and/or supplements need to continue during this time.
Food sources. Only meat and dairy products naturally contain vitamin B12. This includes meat, fish, chicken, shellfish, eggs, milk cheese and yoghurt. Vegans need to eat foods fortified with Vitamin B12 such as some brands of soymilk, yeast extracts, veggie burgers and some cereals (or take supplements of about 4ug per day). Generally only small daily quantities are needed to meet the body's needs.
Vitamin B12 is destroyed by microwave cooking but may be preserved by cooking on a stovetop or in an oven.