Stability of vitamin B12 in the presence of ascorbic acid

Experiments were performed in two independent laboratories, each using their own meal preparations which were exactly similar in composition to the meals described by Herbert and Jacob (J. Am. Med. Assoc. 230:241, 1974), in order to check their report that incubating meals (portions of daily food intake by man) of "modest" or "high" vitamin B12 content with increasing levels of added L-ascorbic acid (vitamin C) produced increasing destruction of vitamin B12. The present studies were performed with standardized and official methods. Vitamin B12 was determined microbiologically and by radioassay method. The results showed that 1) the vitamin B12 contents of these meals were in general agreement with values calculated from the literature for the foods involved, 2) the values obtained were manyfold higher than those reported by Herbert and Jacob, and 3) there was no deleterious effect of added ascorbic acid on the vitamin B12 content of meals, contrary to their published results.