B12 deficiency can arise if any of the stages of metabolism are not completed. For example B12 malabsorption may occur if surgery has been performed on the digestive system (such as a gastrectomy or ileal resection) or in the case of gastrointestinal disorders such as Crohn's disease (8). In autoimmune diseases the body’s normal responses to molecules perceived as foreign invaders (such as bacteria and viruses) go wrong and the body attacks itself. A condition called pernicious anaemia may result from an autoimmune disease that targets the cells that produce intrinsic factor, this condition is characterised by large immature red blood cells. Pernicious anaemia is most common in older people. It affects about 1 in 8,000 people over the age of 60. It is more common in women than in men and in people with fairer colouring. Symptoms of anaemia include tiredness, shortness of breath and palpitations. In some more serious cases symptoms may include soreness of the tongue, weight loss, paling skin colour, diarrhoea, and poor resistance to infections. In extreme cases there may be a tingling sensation in the fingers and toes, muscle weakness and confusion.
Additional causes include stomach infections with the bacterium Helicobacter pylori, the single-celled parasite Giardia lamblia or the parasitic worm Enterobius vermicularis These parasites can interfere with normal B12 absorption by competing with the host organism (that could be you!) for the B12 present in the diet.
The total number of people estimated to have B12 deficiency varies widely; this is largely due to how B12 deficiency is defined. The discrepancy in the figures reflects how B12 deficiency may go undiagnosed as symptoms are subtle and may not be noticed. A recent review reported that B12 deficiency is estimated to occur in anything between five and 60 per cent of the general population of industrialised countries . This suggests B12 deficiency is a problem for meat, poultry and fish eaters as much as anyone else. Indeed it may be worse for them as they do not actively seek out fortified foods and the B12 they consume is bound to animal protein. However, in 2004 a UK government survey suggested that only two per cent of men and four per cent of women had a serum vitamin B12 concentration below the limit of the normal range (1). Vitamin B12 deficiency does however occur frequently in the elderly , indeed it has been estimated that up to 40 per cent of elderly people suffer B12 malabsorption due to atrophic gastritis; inflammation of the stomach leading to a reduction in acid production
More rarely, B12 deficiency may occur among people whose diets lack any B12. This type of deficiency is very rare but the consequences can be extremely serious especially for infants. Furthermore, when vitamin B12 is absent from the diet, deficiency may take some time to occur as stores in the liver are used up. The authors of a recent review of studies on B12 deficiency agree that nutritional deficiency of B12 is rare among healthy adults in industrialised countries and estimate that deficiency caused by lack of B12 in the diet only accounts for five per cent of all cases seen.
Homocysteine
Since the early 1990’s the amino acid homocysteine has become the subject of much interest among the scientific community. Evidence suggests that homocysteine damages the lining of blood vessels and enhances blood clotting. Elevated concentrations of homocysteine in the blood have been linked to Furthermore, the study acknowledged that the actual intakes of an increased risk for heart disease and stroke. Some studies B12 and calcium might now be higher because the number of suggest it may have an even more important role in determining foods fortified with B12 has increased in recent years. It may be the health of individuals than cholesterol (2). Homocysteine is that vegetarians and vegans have gained an advantage in that they converted into the amino acid methionine in the presence of are used to routinely consuming B12-fortified foods and are B12. In the same reaction, methyltetrahydrofolate is converted therefore less likely to experience B12 deficiencies associated with to folate which is used in the synthesis of DNA. This entire age-related gastrointestinal conditions. reaction relies on sufficient supplies of B12, B6 and folate. In B12 deficiency, the amount of homocysteine in the body can Numerous studies now demonstrate that any actual deficiencies of escalate to potentially dangerous levels and has been linked to a B12 in a vegetarian or vegan diet are usually due to poor meal range of disorders including depression, dementia, damage to planning (20). While vitamin B12 may be the nutrient most likely the inner lining of the artery walls and may be a trigger for to be missing from a vegetarian or vegan diet, meat remains an heart disease. While increased homocysteine levels have been observed in vegetarians and vegans they do not occur in those ensuring an adequate B12 intake of three micrograms per day. Whereas elevated homocysteine levels are not uncommon among meat eaters due to a low folate intake (2), and tend to increase in the elderly for reasons discussed above. Interestingly a recent study showed how a daily serving of breakfast cereal fortified with folic acid, B6 and B12 not only contributed to the plasma status of these vitamins but significantly reduced homocysteine concentrations in a randomly selected group of relatively healthy 50-85 year olds (14), these were not vegetarians or vegans!How is B12 Deficiency Diagnosed and Treated?
Vitamin B12 deficiency may be diagnosed by measuring the levels of serum B12 or by measuring the levels of homocysteine; which can accumulate to high levels in the absence of B12. However, high homocysteine levels can also be caused by folate or vitamin B6 deficiencies. Conventionally vitamin B12 deficiency is treated with a course of intramuscular injections. A B12-like compound called hydroxocobalamin is injected into the muscle every two to four days. Around six injections are given to build up stores of vitamin B12 in the liver. Blood tests are given periodically to monitor the success of the treatment .Vegetarians, Vegans and Vitamin B12 Deficiency
Several reports single out vegetarians, and particularly vegans, as a high risk group for vitamin B12 deficiency. One extensive UK study described the nutrient intakes of over 65,000 people including 33,883 meat-eaters, 10,110 fish-eaters, 18,840 lacto-ovo vegetarians and 2,596 vegans . This EPIC-Oxford cohort currently includes the largest number of vegetarians than any comparable study in the world. The study concluded that vegans had the highest intakes of fibre, vitamin B1, folate, vitamin C, vitamin E, magnesium and iron, and the lowest intakes of retinol, vitamin B12, vitamin D, calcium and zinc. But this does not necessarily mean they were deficient in any of these nutrients.Summary
- B12 helps make fatty acids, DNA, red blood cells and helps the nervous system work.
- The UK government suggest an RNI of one-and-a-half micrograms of B12 per day.
- B12 is made by microorganisms in the soil and water. It is consumed in the diet and taken to every cell in the body, plants do not contain B12.
- Plant-eating primates such as the gorilla (and our human ancestors and many people in developing countries) obtain a plentiful supply of B12 from their consumption of plants due to the presence of insects and bacterial contamination of their plant foods and water.
- B12 is in red meat, fish, poultry, eggs and dairy products; and in fortified foods: veggie burger mixes, yeast extracts, margarines, breakfast cereals and soya milks; or supplements.
- Fermented soya foods and seaweeds do not provide a reliable source of B12.
- B12 from meat is bound to animal protein and so is more difficult to absorb than in its natural unbound form produced by bacteria.
- B12 deficiency can lead to serious health problems especially in the very young.
- B12 deficiency tends to increase with age; up to 40 per cent of the UK’s meat eating elderly population suffers from low B12 due to a reduction in their ability to absorb this vitamin.
- Nutritional deficiency of B12 is rare among healthy adults in industrialised countries.
- A lack of B12, B6 and/or folate can lead to raised homocysteine levels which have been linked to heart disease and stroke; this can affect meat eaters, vegetarians and vegans.
- B12 deficiency may be treated by a course of injections.
- B12 intakes among vegans are thought to be increasing, reflecting the increase in the number of B12-fortified products available (and a raised awareness). This will undoubtedly confer an advantage on vegans in later life who are used to ensuring B12 is present in their diet.
- You can obtain three micrograms of B12 per day by consuming a wide range of fortified foods.
- A well-planned and varied vegetarian or vegan diet including B12-fortified plant-based foods not only meets our requirements but provides a healthier and safer source of vitamin B12.
(published with permission in writing from:http://www.vegetarian.org.uk/)
