Insufficient Vit B12 in a Vegetarian, Vegan, Macrobiotic or Raw Food diet can cause anaemia and nervous system damage.
Therefore it is unwise to rely on the minute quanties of B12 found in miso, spirulina, nori, tempeh, barley grass and fortified foods like bread, nutritional yeast and soya milk.
Rather take a Vegan Vitamin B12 supplement . Two companies I can recommend :The mail order company Pangea http://veganstore.com/ has an excellent product VeganLife B12 Chewable Supplement 1,000 mcg tablets and in most Health Stores you can also find Solgar http://www.solgar.com/ Solgar sublingual 1,000 mcg nuggets. I can recommend both products having used them both over the years.
Please click the link below to view a very comprehensive Information Sheet about Vit B12 on the Vegetarian Societies website.