Persons on a strict vegan diet cannot obtain enough vitamin B12 from their diet to satisfy their normal daily requirement. Thus standard foods for vegans such as fruits, vegetables, nuts or legumes do NOT contain a significant amount of the vitamin. Many studies have shown that persons who convert to vegans develop sub-clinical vitamin B12 deficiency within 5 years, unless they continually take vitamin B12 supplements. Vegans should be aware that even a mild deficiency of vitamin B12 can cause anaemia, fatigue, depression, whilst prolonged deficiency can cause neurological conditions and has been associated with an increased incidence of Alzheimer's disease, multiple sclerosis and dementia. Many studies have shown vitamin B12 deficiency in persons on vegan and vegetarian diets. Several studies have shown that prolonged maintenance of a vegan diet can also lead to subacute degradation of the spinal chord, optic neuritis, optic atrophy, dimness of sight and even blindness, a condition that may be worse in those who smoke. In vegetarian and vegan diets, dietary insufficiency with vitamin B12 is further complicated by deficiencies in some essential amino acids, such as methionine. Anemia is common in vegetarian communities where not only B12 levels are low but also iron (as judged by ferritin) may be very low (Wongprachum et al, 2012; Craig, 2009)
Vegan mothers who are vitamin B12 deficient can give birth to under-weight babies, who may already have signs of spinal chord damage. Following birth babies can fail to thrive and show developmental regression and develop autism. In many cased the babies can become lethargic and lose their ability to use their muscles adequately. Some cannot sense properly and most have macrocytic anemia. In many cases, even the taking of vitamin B12 supplements by the mother cannot help the babies. Other studies have shown that babies born to vitamin B12 deficient mothers are more likely to be insulin resistant, a predisposing factor for the development of diabetes.
Vegans eventually end up with vitamin B12 deficiency and may present with various diseases associated with vitamin B12 deficiency, including motor defects (including trouble walking and unstable gait), numbness and tingling in the hands and feet, being easily fatigued, neurological conditions, subacute neuronal degeneration, poor vision and severe optic disease, confusion, incontinence plus other signs of VB12 deficiency including anorexia, swollen tongue, macrocytic anemia, jaundice, vomiting, and abdominal pain.
The development of vitamin B12 deficiency is somewhat faster in those switching to a vegan diet than those who move to a vegetarian diet, however there is still a progressive development of vitamin B12 deficiency.
Reproduced from Specker et al, 1900
Many studies have shown that children raised on vegan or macrobiotic diets have lower bone mineral density, are of smaller stature, and have delayed cognitive development when compared to age-matched children on an omnivorous diet. Technically children raised on a vegan diet could be regarded as being malnourished.
Potential foods of dietary benefit to vegetarians that contain vitamin B12 are Cheeses (3.3 ug/100 gm serving of Swiss cheese), whey powder (2.5 ug/100 gm), milk (0.46 ug/cup), yogurt (0.53 ug/100 gm), yeast extract (Marmite - there is none in Vegemite).
It is very important that vegetarians and vegans obtain adequate levels of vitamin B12 through the use of supplements. It is not possible for persons on vegan or vegetarian diets to obtain sufficient vitamin B12 to maintain healthy levels of vitamin B12 in the serum, or more importantly in the brain. The situation becomes even worse in the case of vegan mothers who gradually loose vitamin B12 stores to the developing foetus and through excretion into milk. Furthermore, supplementation should be continued during lactation in order to avoid the development of signs of deficiency that may be associated with persistent neurological problems in infants. Normal vitamin supplements do NOT provide sufficient vitamin B12 to over-come loss during pregnancy.
The use of vitamin B12 in supplements for treatment of deficiency is controversial with many studies showing no benefit being obtained from standard supplements as the amount of vitamin B12 in the standard supplements is too low, Furthermore, studies with high dose oral supplements with cyanocobalamin were not effective in restoring normal levels of homocysteine, in reversing clinical signs of deficiency, or in maintaining normal levels of serum vitamin B12 once supplements were ceased. Furthermore studies have shown that oral supplements given to VB12 deficient vegan mothers were NOT effective in restoring VB12 levels in new born babies.
Vitamin B12 injections can be administered in cases of insufficiency if it is diagnosed, however they are generally not administered post-partum.
A topical form of vitamin B12 has recently been developed which is easy to administer, contains the natural form of the vitamin and has the added advantage of providing a prolonged release of the vitamin over several days. This topical formulation is able to provide a much higher dose of vitamin B12 than oral supplements and is ideally suited for vegans, vegetarians, pregnant mothers and babies who are deficient.
Further Information on the recommended daily allowance for vitamin B12 can be found at the following web-sites:
Wongprachum et al Proxy indicators for identifying iron deficiency among anemic vegetarians in an area prevalent for thalassemia and hemoglobinoptathies. Acta Haematol 2012 127: 250-5 PMID 22572177
Craig Health effects of vegan diets Am J Clin Nutr 2009 89: 1627S-1633S PMID 19279075
Specker et al, 1990 Vitamin B12: low milk concentrations are related to low serum concentrations.... Am J. Clin Nutr 52:1073-6
Publications on vitamin B12 deficiency in Vegans can be found here
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