The Journal of Nutrition Vol. 127 No. 2 February 1997, pp. 378-378
Copyright ©1997 by the American Society for Nutritional Sciences

LETTER TO THE EDITOR:
Comments on the Paper by Rauma et al. (1995)

Dear Dr. Visek:

I wish to note strong doubts about the conclusion of A.-L. Rauma et al. (1995) that some algae are potentially adequate sources of vitamin B-12 for vegans. These authors found that vegans consuming nori or chlorella algae had average serum vitamin B-12 concentrations twice as high as vegans not eating these foods. On this basis they concluded that "some seaweeds consumed in large amounts can supply adequate amounts of bioavailable vitamin B-12." Their seemingly safe, implied assumption is that serum vitamin B-12 levels measure vitamin B-12 adequacy. But surprisingly, for algal sources of vitamin B-12, this assumption is questionable at best.

Rauma et al. did not cite an important study by Dangelie et al. (1991). The latter group studied the effect of algae supplements in vegan children with hematological signs of vitamin B-12 deficiency such as elevated mean corpuscular volume-(MCV) and other signs. Like Rauma et al., they found that supplemental vitamin B-12 from these sources (nori and spirulina) clearly raised plasma levels of vitamin B-12 (in three of five subjects). But surprisingly, the poor hematological status not only failed to improve, it further deteriorated in all five subjects after 1 to 5 mo. In contrast, hematological status improved in six other deficient vegan children given fish or a cobalamin supplement. These unexpected results cast strong doubt on the implied assumption of Rauma et al., and on their claim to have "demonstrated clearly that excess consumption of some seaweeds can preserve the body vitamin B-12 status."

Dagnelie et al. (1991) concluded, "It seems unjustified to advocate algae and other plant food sources of vitamin B-12 because its bioavailability is questionable." (Bioactivity might be a better word here, in viewof the raised plasma levels.) How can algal sources of vitamin B-12 raise plasma levels, but fail to reverse hematological signs of deficiency? Speculation centers on the plentiful vitamin B-12 analogs known and postulated to be in algal sources (Dagnelie et al. 1991 and 1994).

Until easier methods may be found, it seems that the "gold standard" for the adequacy of vitamin B-12 from algae must be the ability to reverse deficiency signs. All vegans studied by Rauma et al. had normal (MCV), so they could not apply this strict standard. Clearly we need more testing of vitamin B-12 from algae in B-12-deficient subjects. So far apparently no alga has met this gold standard, and two algae have failed to meet it in initial testing.

Donald R. Davis
Biochemical Institute
University of Texas
Austin, TX 78712

FOOTNOTES

Manuscript received 24 June 1996. Revision accepted 28 August 1996.

LITERATURE CITED

• Rauma A. -L., Törrönen R., Hänninen O., Mykkänen H. Vitamin B-12 status of long-term adherents of a strict uncooked vegan diet ("living food diet") is compromised. J. Nutr. 1995; 125:2511-2515
• Dagnelie P. C., van Staveren W. A., van den Berg H. Vitamin B-12 from algae appears not to be bioavailable. Am. J. Clin. Nutr. 1991; 53:695-697[Abstract/Free Full Text]
• Dagnelie, P. C. & van Staveren, W. A. (1994) Macrobiotic nutrition and child health: results of a population-based, mixed-longitudinal cohort study in the Netherlands. Am. J. Clin. Nutr. 59(suppl): 1187S-96S.

0022-3166/97 $3.00 ©1997 American Society for Nutritional Sciences