Vitamin B12 has been termed the 'energy' vitamin and the scientific support for this definition is gradually growing. Its major well-established functions, however, are in the manufacture of red blood cells and the maintenance of healthy nerves.
In childhood, vitamin B12 is needed to stimulate appetite, promote growth, especially of the nervous system, and to release energy from food. It has a reputation for rejuvenating old people physically by providing energy, and mentally by preventing mental deterioration and speeding up thought processes. Throughout life it appears to help to overcome infection and provide protection against allergies and cancer.
Good food source
Significant amounts of vitamin B12 are found only in foods from animal sources, especially liver, oily fish and egg yolk.
Bacteria in the intestine can manufacture it, but it is not known to what extent vitamin B12 produced in this way can be absorbed and used. Although there have been claims that vegetarian products, such as tempeh, miso, some seed sprouts and spirulina contain good supplies of vitamin B12, this has not been confirmed by independent analysis. Some vitamin B12 is present in sea vegetables, but its chemical make-up is slightly different from animal B12, and it is not certain how active it is. Various studies have shown that vitamin B12 can be seriously deficient in children who are given a strict vegan or macrobiotic diet.
What if your intake is too low?
Vitamin B12 is only needed in very small amounts, perhaps less than 1 mcg a day, and the liver can store several years' supply. As a result, the most common reason for vitamin B12 deficiency is failure of the body to absorb it because of changes in digestion, rather than from any dietary insufficiency. Vitamin B12 deficiency causes an extremely serious condition called pernicious anaemia, when there are too few red blood cells and the spinal cord and other nerve cells can become permanently damaged. Symptoms include pallor, shortness of breath, weakness, fatigue, mental slowness, numbness, tingling and shooting pains in the limbs, clumsiness and difficulty in walking. Untreated, it can be fatal.
When extra may be needed
- If you eat a strict vegan diet
- If you are an elderly person
- During pregnancy and when breast feeding
- If you regularly consume moderate or large amounts of alcohol
- If you regularly take laxatives or antacid preparations
(Pregnant and breast-feeding women should consult a doctor, midwife, or qualified nutritional therapist b10re taking any vitamin or mineral supplemems.)
Can too much be toxic?
There is no evidence that vitamin B12 is toxic when taken by mouth as the body does not absorb enough. If administered by injection, too much vitamin B 12 can cause skin problems, but these will quickly go away once the injections have been discontinued.
Using a supplement
If you wish to take a supplement, vitamin B12 is best taken as part of a balanced B-vitamin tablet or capsule, unless your doctor or nutritional health practitioner advises otherwise.
Supplements prescribed by doctors for the treatment of pernicious anaemia are usually administered by injection.