When you transition to a vegan diet, non-vegans will always question where you're going to get your protein and calcium. Those who are slightly more informed about nutrition will often caution you that you will become vitamin B-12 deficient, since the best sources of vitamin B-12 are liver, milk, and fish.
Well, there may be a real reason to be concerned, at least with regard to B-12. Data from a small study at Oxford shows that people with lower levels of B-12 in their blood suffered from brain shrinkage six times more often than those with high levels of B-12. (Note: none of the 107 people in the study were actually B-12 deficient.) Okay, so your brain is a little smaller, since we only use around 10% of our brains anyway, this shouldn't be a big deal, right? Apparently not. Shrinkage is usually associated with the development of dementia. That's scary! Since vegetarians, and vegans especially, don't consume liver, milk, or fish, we're at an increased risk of suffering from brain shrinkage. See BBC News Health, and the University of Oxford's press release on B-12.
Why else is vitamin B-12 important?
In the body, B-12 helps the bone marrow regenerate red blood cells and has been credited with protection against heart disease and mental deterioration. Adequate B-12 in the diet is necessary to keep down levels of homocysteine in the blood. Homocysteine is a toxic amino acid produced in the breakdown of animal protein and has been identified as a risk factor for arterial disease and heart attack.
In children, B-12 deficiency can cause severe abnormalities of growth and mental retardation. In adults it causes pernicious anemia, a dangerous condition marked by weakness, apathy, lightheadedness, shortness of breath, fatigue, numbness in the arms and legs, loss of balance, and mental changes, all reversible if B-12 is supplied. Untreated, the symptoms can become permanent.
So how do we, as vegans, ensure that we get adequate vitamin B-12? There's B-12 in nutritional yeast (make sure to read the label), fortified soy milk, fortified cereals, and vitamins.
Fermented soya products, seaweeds and algae have all been proposed as possible sources of B12. However, analysis of fermented soya products, including tempeh, miso, shoyu and tamari, found no significant B12.
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.
The current nutritional consensus is that no plant foods can be relied on as a safe source of vitamin B12.
Source: The Vegetarian Society
So it looks like we have to ensure that we supplement our diets with B-12. Here are two slightly different recommendations on supplementation:
Vitamin B12: Although this is found naturally only in foods from animal sources, you can get sufficient amounts from fortified breakfast cereals, fortified soy beverages and some types of brewer's yeast. Still, I recommend taking a supplement of 50-100 micrograms of B12 in the form of a good multivitamin, sublingual tablet, nasal spray or gel.
Source: Dr. Weil.com on Becoming Vegan
Vegans who choose to use a vitamin B12 supplement, either as a single supplement or in a multivitamin should use supplements regularly. Even though a supplement may contain many times the recommended level of vitamin B12, when vitamin B12 intake is high, not as much appears to be absorbed. This means in order to meet your needs, you should take a daily vitamin B12 supplement of 5-10 micrograms or a weekly vitamin B12 supplement of 2000 micrograms (4).
Source: Vegetarian Resource Group
Note: there is no tolerable upper intake level for vitamin B-12 because of its low toxicity. There have been no toxic or adverse effects associated with large intakes of vitamin B-12 from food or supplements in healthy people.
Anyway, this is definitely something to take seriously. We'll be keeping our eyes open for additional research on vegan/vegetarian B-12 issues. In the meantime here are some links to help keep you informed on sources of B-12 in the vegan diet.