Vitamin B-12 content and bioavailability of spirulina and nori in rats

Abstract

The availability of vitamin B-12 from two different seafood products, nori ( Porphyra tenera) and spirulina ( Spirulina sp.), was evaluated in rats. Male weanling Wistar rats ( n = 30) were fed a vitamin B-12 deficient diet for six weeks, followed by a four-week repletion period in which the rats were supplemented with equal doses of vitamin B-12, either supplied as pure cyanocobalamin, or as dried spirulina or nori. No difference in body weight gain, relative liver, or relative kidney weight could be demonstrated between the groups in either the depletion or repletion period. Low serum, liver, and kidney cobalamin contents were measured after the depletion period using an Intrinsic Factor-based radioassay. However, no hematological abnormalities could be demonstrated in the B-12 depleted rats. After repletion, cobalamin contents of serum and kidney were significantly lower, and liver cobalamin content was higher, for both the nori- and spirulina-fed rats than for the cyanocobalamin-supplemented controls. These data illustrate that cobalamins from algae are indeed absorbed by the rat. However, the distribution pattern over liver and kidneys indicates that at least part of the cobalamins, measured by a specific radioassay, may actually be analogues.