Join Date: Dec 2006
Location: Italy, Europe
B12 and vegans
An exhaustive and concise review on B12 by Michale Rae in the CR forum
. This seems to be a non-dabatable issue (even the vegan societies insist on B12 supplementation in a vegan regimen)
Fortunately, nearly all major vegetarian advocacy and support organizations and authors of books on vegetarian nutrition are now emphasizing the danger of frank B12 deficiency, especially in vegetarians, and the need for a supplement. The sole serious holdout on this front is John McDougall, who continues[i] to downplay the risks of B12 deficiency associated with vegan diets, recommending supplementation only to long-term (>3 y) adherents or pregnant and lactating women, pointing to the production of B12 by colonic bacteria (despite the fact that nearly none of that B12 is produced in parts of the GI tract where it could be absorb), and at least recently[ii] promoting the illusory availability of B12 from seaweed, even after it was known that its presence was being detected because of compounds in the same cobalt-containing chemical group as the vitamin (corrinoids), picked up in nutritional analysis by the standard USP assay method because of their structural similarity to the vitamin, but lacking in bioactivity to mammals.[iii]
There are absolutely no natural, plant-based foods that contain vitamin B12. The long, tenaciously clung-to belief that there are, arises from two sources of error. The first is fecal contamination. The colonic bacteria do produce B12, but unfortunately, we absorb almost none of it: they’re making the stuff for their own use and not ours, and they live much further down in the GI tract than the major site for B12 absorption (the distal ileum), so it passes through us – and, sometimes, traces of it remain on crops where it’s been used as fertilizer. The other source of the myth of vegan B12 is that some vegan organisms (eg, many cyanobacteria (such as Spirulina ), many bacteria (including the ones used to ferment tempeh), and some seaweeds) produce various kinds of “pseudo-B12” that carry out some of the same functions as B12 for them but are useless for mammals; unfortunately, because they’re actually close chemical relatives of B12 (corrinoids), their structural similarity to the vitamin tricks the standard USP method of food analysis, leading to erroneous reporting of its presence.[iv]
Because of this, nonsupplementing vegans are often deficient in B12,[v] and despite the vitamin’s presence in eggs and dairy products, even ovolacto vegetarians’ functional B12 status tends to be poor (eg, ([vi],[vii],[viii],[ix],[x],[xi],[xii])). The main concern with such subclinical deficiency is the elevation in plasma homocysteine, a risk factor for coronary artery disease (CAD). McDougall discounts such ‘mere’ laboratory findings, and misleadingly suggests that B12 deficiency only becomes a concern when the most frank and severe of deficiency develops, complete with neurological dysfunction, but that condition represents a late and acutely dangerous stage of the disease, which is necessarily preceded by a long-term, progressive loss of the critical metabolic functions of B12. The epidemiological association of elevated homocysteine alone renders McDougall’s dismissal of ‘mere’ clinical laboratory findings irresponsible at best— especially now that a study has been completed specifically linking such mild deficiency in B12 to CAD in a predominantly vegetarian population.[xiii] There is also at least a theoretical concern that such long-term subacute deficiencies might lead to a loss of the regulation of genes by modification of methyl groups derived from B12, resulting in an elevated risk of cancer and possibly other cellular malfunction; a study investigating this possibility found such an association, but it was put into doubt by adjustment for confounding factors.[xiv]
Some vegetarian foods already contain B12 through fortification; examples include Red Star nutritional yeast, marmite, and some fortified breakfast cereals. If these foods are real staples of your diet that you eat nearly every day, and they (combined with the rest of your diet) are enough to keep you, on a representative average day, significantly over the new RDA, then that may cover your needs, but that clearly won’t be sufficient if you only eat them occasionally or as snacks or condiments, it would be irresponsible to pretend that an occasional, irregular dose will avert a long-term, subchronic deficiency.
Therefore, while B12 should be tracked in your dietary software as with all other nutrients (the IOM RDA is 2.4 micrograms for adults, except for slightly higher needs for pregnant and lactating women and some older individuals), it is prudent for all vegetarians to take a B12 supplement. A basic, common cyanocobalamin supplement is fine. Ideally, this would begin done immediately upon taking up a vegetarian diet, in which case an RDA-level dose would be quite adequate, although a somewhat higher dose may be required in older people or others with low stomach acid production due to lower absorption. [xv] However, long-term vegetarians (and especially vegans) will likely have spent several years progressively depleting the stores in their livers, and unfortunately, research (conducted in older women) suggests that just jumping back up to RDA levels under such conditions is insufficient to restore healthy B12 metabolism.[xvi]
Whatever you diet and supplement regimen, you will want to determine your actual, functional B12 status, and not just your intake levels. Fortunately, there are two very reliable and well-established tests: homocysteine and methylmalonic acid. Your lab’s reference range should do for methylmalonic acid targets. The optimal level for homocysteine remains a subject of some uncertainty, but the cutoff for increased risk of cardiovascular disease appears to be approximately 9-10 micromoles per Liter.[xvii]
This world is ruled by invisibilities or ghosts: God the Father , Christ Consciousness, the seven Spirits before the throne of God; and Satan and his legion of evil powers - Paramhansa Yogananda, Man's Eternal Quest.