Linus Pauling responded to this in Vitamin C And The Common Cold. I came away with the understanding that large doses of vitamin c should be taken separately, such as in the morning, before eating. I take all pills at completely separate times, especially vitamins and medications.
The effect of megadose ascorbic acid ingestion on the absorption and retention of vitamin B12 in man.
Watson WS, Vallance BD, Muir MM, Hume R.
Radiotracer B12 analogues, hydroxy- and cyano-cobalamin have been used to study the effects of megadose L-ascorbic acid (vitamin C) ingestion on vitamin B12 metabolism in man. By employing whole body counter techniques it has been shown that, while ascorbic acid can partially inactivate both the important dietary analogue, hydroxycobalamin, and the gastric secretion, intrinsic factor which is essential for B12 absorption, the rapid binding of the B12 analogue to intrinsic factor protects the hydroxycobalamin from attack. As a result, the absorption of hydroxcobalamin is unaffected by the simultaneous ingestion of 1 g ascorbic acid. The absorption of cyanocobalamin, the most stable analogue but not found in quantity in the diet, is slightly increased by ascorbic acid. Whole body retention studies on normal subjects ingesting 2 g ascorbic acid per day show no significant evidence of in vivo destruction of body B12 stores.
PMID: 7112085 [PubMed - indexed for MEDLINE]
2: Am J Clin Nutr. 1976 Jun;29(6):645-9.
Stability of vitamin B12 in the presence of ascorbic acid.
Newmark HL, Scheiner MS, Marcus M, Prabhudesai M.
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.
Interesting - and good - news. Or - actually, they are not new, and I don't know if there are newer studies commenting on the findings reported above. I have heard that neither too much nor too little vitamin C is good for B12 absorption, but it is both confusing and interesting to see that different studies come to opposite conclusions. Nothing is better if an intake of 2g vitamin C 'show no significant evidence of in vivo destruction of body B12 stores' or if 'there was no deleterious effect of added ascorbic acid on the vitamin B12 content of meals, contrary to their published results'!
I will not eat anything that walks, swims, flies, runs, skips, hops or crawls.
Re: Can too much vitamin C can destroy B12 absorption?
Hello I am new here.
I am a raw vegan following Dr. Grahams 811 program.
I have calculated my daily vitamin C intake and it is about 2000% of recomented daily dose! But all the vitamin C I eat comes from natural sources like fruits and vegetables. So I really don't hope too much vitamin C destroys B12 absoption.