Feeding dried purple laver (nori) to vitamin B12-deficient rats significantly improves vitamin B12 status
Shigeo Takenaka1*, Sumi Sugiyama1, Shuhei Ebara2, Emi Miyamoto3, Katsuo Abe3, Yoshiyuki Tamura1, Fumio Watanabe3, Shingo Tsuyama4 and Yoshihisa Nakano2
1Laboratory of Nutrition and Food Science, Hagoromo-gakuen College, Sakai 592-8344, Japan 2Department of Applied Biological Chemistry, Osaka Prefecture University, Sakai 599-8531, Japan 3Department of Health Science, Kochi Women’s University Kochi 780-8515, Japan 4Department of Veterinary Science, Osaka Prefecture University, Sakai 599-8531, Japan
(Received 7 July 2000 ± Revised 5 October 2000 ± Accepted 3 January 2001)
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) mg/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) mmol/d) in urine, were fed the diet supplemented with dried purple laver (10 mg/kg diet) for 20 d, urinary methylmalonic acid excretion (as an index of vitamin B12 deficiency) became undetectable and hepatic vitamin B12 (especially adenosylco- balamin) levels were significantly increased. These results indicate that vitamin B12 in dried purple laver is bioavailable to rats.