The Journal of Nutrition Vol. 127 No. 2 February 1997, pp. 380-380
Copyright ©1997 by the American Society for Nutritional Sciences

LETTER TO THE EDITOR:
Reply to the Letters of Davis and Dagnelie

Dear Dr. Visek:

Our article "Vitamin B-12 status of long-term adherents of a strict uncooked vegan diet ("Living Food" Diet) is compromised" (Rauma et al. 1995) has raised questions whether serum concentration of vitamin B-12 can be used as an indicator of the body status of this vitamin in vegans, and whether vegans can rely on seaweeds providing bioavailable vitamin B-12.

In our study, the status of vitamin B-12 in the eaters of "living food" was examined by measuring serum concentration of vitamin B-12 using commercial test kits (Bio-Rad, Diagnostics Group, Hercules, CA, and Kodak, Clinical Diagnostics Ltd, Amersham, UK) based on competitive protein-binding (CPB). The main finding of the present study was that 57% of the vegans had serum vitamin B-12 concentration below the reference range. CPB is a routine method for screening vitamin B-12 deficiency in clinical laboratories worldwide, and according to Herbert (1994), a low total concentration of serum vitamin B-12 is an indicator of deteriorated vitamin B-12 status, not merely of a short-term negative balance. According to Schneede et al. (1994) concentration of vitamin B-12 in plasma also correlates well with other more sensitive indicators of cobalamin deficiency, such as methylmalonic acid and homocysteine. This association however, may, not hold at high serum vitamin B-12 concentrations in vegans who consume seaweeds, due to presence of possible nonactive analogs of vitamin B-12. In our study, only three vegan subjects had serum concentration of vitamin B-12 above the mean of the control group (311 pmol/L). Therefore, most vegans in the present study had low concentration of serum vitamin B-12 regardless whether the method measured inactive or active analogs. The average consumption of seaweeds by the eaters of "living food" diet did not maintain serum concentration of vitamin B-12.

We agree with Dr. Davis and Dr. Dagnelie that we may not have measured the true bioavailability of vitamin B-12 obtained from nori and chlorella seaweeds by vegans, but merely the ability of these seaweeds to raise or maintain serum vitamin B-12 concentration. However, the vegans in the present study did not suffer from any hematological abnormalities associated with vitamin B-12 deficiency. The mean (±SD, range) erythrocyte mean cell volume (MCV) was, in the "living food" eaters 86 (± 3, 79-92); and in their matched omnivorous controls, 88 (±4, 76-95). Distribution of the MCV values in these groups overlapped, and all MCV values were within the normal range (76-96 fL).

We do recommend that eaters of the "living food" diet do not rely on seaweeds as a source of vitamin B-12, due to possible nonactive analogs of vitamin B-12 and high content of iodine in some seaweeds. We regret that our conclusions may have lead to misinterpretation in this respect. However, the Finnish eaters of the "living food" diet participating in this study started to supplement their diet after finding out their low vitamin B-12 status.

Anna-Liisa Rauma
Hannu Mykkänen
Department of Clinical Nutrition
University of Kuopio

Riitta Törrönen
Osmo Hänninen
Department of Physiology
University of Kuopio
P.O. Box 1627
FIN-70211 Kuopio
Finland

FOOTNOTES

Manuscript received 20 August 1996. Revision accepted 12 September 1996.

LITERATURE CITED

• Herbert, V. (1994) Stating vitamin B-12 (cobalamin) status in vegetarians. Am. J. Clin. Nutr. 59 (suppl): 1213S-1222S.
• 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
• Schneede J., Dagnelie P. C., van Staveren W. A., Vollset S. E., Refsum H., Ueland P. M. Methylmalonic acid and homocysteine in plasma as indicators of functional cobalamin deficiency in infants on macrobiotic diets. Pediatr. Res. 1994; 36:194-201[Medline]

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