Vitamin B12

B12 is part of the vitamin B complex which is essential for the prevention of pernicious anaemia. The RDA is only one microgram which is easy to obtain from meat, fish, poultry, eggs, cheese and all animal-based foods. It is absent from virtually all plant foods except yeast extracts and fermented soy products, though it is often added to fortified breakfast cereals. For this reason vegetarians and especially vegans should always take a daily supplement.

In order for the body to utilise B12 a substance called 'intrinsic factor', produced by the lining of the stomach, is essential and the failure to produce enough is a common cause of pernicious anaemia. This condition used to be fatal but was first treated successfully with injections of liquidised raw liver - the richest source of B12 - but in modern medicine B12 itself can now be injected.

This vitamin is also needed for the production of a fatty substance called myelin, which forms a protective sheath covering all the nerves in the body. Deficiency of B12 reduces the amount of myelin and as this is needed for the rapid transmission of nerve impulses, can also result in serious neurological problems. Another function of this nutrient is the production of special enzymes which work together with folic acid. This means that it's also an essential requirement for the normal growth of babies during pregnancy and breastfeeding.

Enough vitamin B12 is stored in your liver to last around two years but unless you continually replace what you're using, the reserve runs out, your bone marrow doesn't make enough healthy blood cells and the consequence is anaemia. Chronic fatigue, pale skin (especially inside the eyelids), loss of concentration, short term memory, mood swings, sore tongue, loss of appetite, nausea, breathlessness and general weakness of arm and leg muscles can all be signs of B12 deficiency. Although the RDA is only one microgram it's sensible to aim for 2 micrograms for children under 12, 3 micrograms for over 12's, 5 micrograms for adults. As B12 is best absorbed in the presence of other vitamins it's more effective as part of a multivitamin and mineral supplement than taken singly, unless prescribed by your health practitioner. The contraceptive pill, sleeping pills, some anti-diabetic drugs and excessive amounts of alcohol can all reduce absorption.


BEST SOURCES

Liver - this is by far the richest source and just a teaspoonful of lamb's liver provides 4 micrograms. One portion a week will make sure that you're never deficient.

Lamb's liver
B12 content: 83 mcg / 100 g
Percentage of daily requirement: 800% from an average portion
B12 score: 10/10

DUCK - although often regarded as a fatty bird, wild duck has hardly any fat at all and even the supermarket variety are fine if you roast them on a trivet so all the fat ends up in the pan, or alternatively use skinned duck breasts with the fat removed - ideal grilled or used in a stir fry

B12 content: 3 mcg / 100 g
Percentage of daily requirement: 555% from an average portion
B12 score: 10/10

ROAST BEEF SANDWICH
B12 content: 3 mcg / 100 g
Percentage of daily requirement: 150% from an average portion
B12 score: 10/10

GRILLED PLAICE
B12 content: 2 mcg / 100 g
Percentage of daily requirement: 260% from an average portion
B12 score: 10/10

SCRAMBLED EGGS
B12 content: 2.1 mcg / 100 g
Percentage of daily requirement: 250% from 2 eggs scrambled
B12 score: 10/10

VEGETARIAN CHEDDAR
B12 content: 1.2 mcg / 100 g
Percentage of daily requirement: 60% from average portion
B12 score: 6/10

SOYA CHEESE
B12 content: 2.5 mcg / 100 g
Percentage of daily requirement: 125% from average portion
B12 score: 10/10

MARMITE - although many vegetarians think of Marmite as their source of B12, the amount it contains is small, the amount you use is small and the salt content is extremely high - half a gram per teaspoon. It can be a useful addition but isn't an alternative to supplements for vegetarians and vegans.
B12 content: 1 mcg / 100 g
Percentage of daily requirement: 5% from 1 teaspoon
B12 score: 1/10