When I tell people I am vegan, one of the first things they ask (when they've stopped laughing) is 'Do I not miss cheese?'
Then, 'Where do you get your protein?'
A far more sensible and reasonable question might be 'Are you sure you're getting enough Vitamin B12?'
Vitamins are often described as 'Things that make you Ill if you don't eat them'. They are not required in large amounts, but they are needed on a regular basis to maintain good health. Generally, they act as 'co-enzymes' - necessary for the normal functioning of various enzymes which are the protein molecules which control metabolism or body chemistry. The majority are derived from fruit and vegetables - so are not a problem for vegans. It is the various B vitamins that can be an issue - particularly B12(cobalamin). The literature about B12 is somewhat vague and confusing and it seems to me that details regarding B12 are not well understood. That said, there does seem to be a consensus that it is not possible to obtain sufficient B12 on a vegan diet without taking supplements or making sure that one's diet includes foods enhanced with added B12.
So why do we need B12? Again, the literature is not particularly clear but we seem to need it for healthy functioning of our nerves (possibly synthesis of myelin and certain neurotransmitters required for transmission across synapses), production of healthy red blood cells and synthesis of DNA, presumably during replication and the production of new cells. Also for amino acid and fatty acid metabolism. All extremely important to the normal functioning of the body!
Our requirement is estimated at 2.4μg (micrograms - mcg in the USA). The good news is that our liver will store a reasonable amount, so we do not, necessarily, have to worry about making sure it is included in our diet every day.
What happens when we are deficient in B12? Possible consequences are various - feeling tired, weak, constipated, loss of appetite and weight loss are possible. More extreme is a numbness of the extremities, loss of balance, confusion, poor memory and even depression.
B12 can only be synthesised by various anaerobic bacteria (bacteria which live in the absence of oxygen) - found in soil and also in the guts (intestines) of animals. Most animals obtain sufficient levels either as a result of consuming some soil whilst grazing, or from the bacteria in their stomachs (ruminants) or from eating their own faeces (like rabbits) - none of these are really an option for humans! It occurred to me that, if bacteria in the guts of other animals will synthesise B12, why do our bacteria not do the same? It would appear that they probably do - but in the large intestine, which is beyond the ileum, where B12 is absorbed.
However, meat and other animal products can provide adequate levels of B12 - if you are happy to eat them! Hence the problem for vegans. There also seems to be an issue regarding complications in the way in which B12 is absorbed.
To absorb B12, the lining of the stomach releases a protein, called INTRINSIC FACTOR, with which it is necessary for the B12 to form a complex to be absorbed. One reason why we might not always absorb the B12 efficiently is when we are not producing enough intrinsic factor. The most common occurence of this tends to be a condition known as PERNICIOUS ANAEMIA - usually only developed in those over 50 - when the cells producing the intrinsic factor are destroyed in an autoimmune response. This has nothing to do with the levels of B12 in the diet, but does lead to B12 deficiency.
So what about we vegans? Well it appears that we need to make sure that we are consuming foods supplemented with B12 or taking tablets. My preference (don't really like taking tablets!) is to use supplements with added B12. These include MARMITE and Meridian yeast extract - both of which have B12 added (interestingly, VEGEMITE does not have B12), fortified nutritional yeast, some non-dairy milks, moringa, spirulina or some seaweed products. The Meridian yeast extract contains fairly high levels and can easily provide the daily requirement.
NO B12 in
There is some doubt as to how well we can absorb some of these sources - so it is probably advisable to try and include several of these in one's diet on a regular (preferably daily) basis.
Thomas M Campbell (one of the co-authors of The China Study) has just published his new book - The Campbell Plan - in which he summarises his findings from a review of the available literature on B12.