Feeding dried purple laver (nori) to vitamin B12-deficient rats significantly improves vitamin B12 status

To clarify the bioavailability of vitamin B-12 in lyophylized purple laver (nori; Porphyra yezoensis), total vitamin B-12 and vitamin B-12 analogue contents in the laver were determined, and the effects of feeding the laver to vitamin B-12-deficient rats were investigated. The amount of total vitamin B-12 in the dried purple laver was estimated to be 54.5 and 58.6 (se 5.3 and 7.5 respectively) mug/100 g dry weight by Lactobacillus bioassay and chemiluminescent assay with hog intrinsic factor respectively. The purple laver contained five types of biologically active vitamin B-12 compounds (cyano-, hydroxo-, sulfito-, adenosyl- and methylcobalamin), in which the vitamin B-12 coezymes (adenosyl- and methylcobalamin) comprised about 60 % of the total vitamin B-12. When 9-week-old vitamin B-12-deficient rats, which excreted substantial amounts of methylmalonic acid (71.7(se 20.2) mu mol/d) in urine, were fed the diet supplemented with dried purple laver (10 mug/kg diet) for 20 d, urinary methylmalonic acid excretion (as an index of vitamin B-12 deficiency) became undetectable and hepatic vitamin B-12 (especially adenosylcobalamin) levels were significantly increased. These results indicate that vitamin B-12 in dried purple laver is bioavailable to rats.