British Journal of Nutrition

Research Article

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

Shigeo Takenakaa1 c1, Sumi Sugiyamaa1, Shuhei Ebaraa2, Emi Miyamotoa3, Katsuo Abea3, Yoshiyuki Tamuraa1, Fumio Watanabea3, Shingo Tsuyamaa4 and Yoshihisa Nakanoa2

a1 Laboratory of Nutrition and Food Science, Hagoromo-gakuen College, Sakai 592-8344, Japan

a2 Department of Applied Biological Chemistry, Osaka Prefecture University, Sakai 599-8531, Japan

a3 Department of Health Science, Kochi Women's University Kochi 780-8515, Japan

a4 Department of Veterinary Science, Osaka Prefecture University, Sakai 599-8531, Japan


To clarify the bioavailability of vitamin B12 in lyophylized purple laver (nori; Porphyra yezoensis), total vitamin B12 and vitamin B12 analogue contents in the laver were determined, and the effects of feeding the laver to vitamin B12-deficient rats were investigated. The amount of total vitamin B12 in the dried purple laver was estimated to be 54.5 and 58.6 (SE 5.3 and 7.5 respectively) ΜG/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 b12 compounds (cyano-, hydroxo-, sulfito-, adenosyl- and methylcobalamin), in which the vitamin b12 coezymes (adenosyl- and methylcobalamin) comprised about 60 % of the total vitamin b12. when 9-week-old vitamin b12-deficient rats, which excreted substantial amounts of methylmalonic acid (71.7(se 20.2) μmol/d) in urine, were fed the diet supplemented with dried purple laver (10 μg/kg diet) for 20 d, urinary methylmalonic acid excretion (as an index of vitamin B12 deficiency) became undetectable and hepatic vitamin B12 (especially adenosylcobalamin) levels were significantly increased. These results indicate that vitamin B12 in dried purple laver is bioavailable to rats.

(Received July 07 2000)

(Revised October 05 2000)

(Accepted January 03 2001)


c1 * Corresponding author: Dr Shigeo Takenaka, present address Department of Veterinary Science, Osaka Prefecture University, Sakai, Osaka, 599-8531, Japan, fax + 81 722 54 9489, email