are vegetarians nutrient starved – vitamin B12 (part 5 of 5)
B12 is the only vitamin that is not recognised as being reliably supplied from a varied wholefood, plant-based diet with plenty of fruit and vegetables, together with exposure to sun. B12 is produced by “good” bacteria which are found in the soil and on plants. Every herbivore in nature gets its supply of B12 from consuming these bacteria on the plants they eat. These bacteria then make homes in the gut of the herbivores that eat them. Carnivores get their B12 by consuming the organs and thus the bacteria from their herbivore prey.
Vitamin B12 is needed for cell division and blood formation. Neither plants nor animals make vitamin B12. Bacteria are responsible for producing vitamin B12. Although recommendations for vitamin B12 are very small, a vitamin B12 deficiency is a very serious problem leading ultimately to anemia and irreversible nerve damage.
Fermented soya products, spirulina, an algae available as a dietary supplement in tablet form, and nori, a seaweed, have both appeared to contain significant amounts of B12 after analysis. However, it is thought that this is due to the presence of compounds structurally similar to B12, known as B12 analogues. These cannot be utilised to satisfy dietary needs. Assay methods used to detect B12 are unable to differentiate between B12 and it’s analogues, Analysis of possible B12 sources may give false positive results due to the presence of these analogues.
Researchers have suggested that supposed B12 supplements such as spirulina may in fact increase the risk of B12 deficiency disease, as the B12 analogues can compete with B12 and inhibit metabolism.
Bacteria present in the large intestine are able to synthesise B12. In the past, it has been thought that the B12 produced by these colonic bacteria could be absorbed and utilised by humans. However, the bacteria produce B12 too far down the intestine for absorption to occur, B12 not being absorbed through the colon lining.
Although some vegans may get vitamin B12 from inadequate hand washing, this is not a reliable vitamin B12 source.
Dairy products and eggs (if the vegetarian in question is an egg-eater) can be a source of B12, although sterilization can destroy some or all of the B12 available. Many soy milks and cereals are fortified with B12. Finally, there are B12 supplements. Alternatively, since B12 is produced by ‘good’ bacteria found in the soil that plants grow in, to ingest the vitamine you can just go eat dirt.