LAUSR

BACKGROUND Kombu has highly bioavailable magnesium (Mg) compared to other edible seaweeds, probably because Kombu contains a factor enhancing Mg absorption. However, a considerable amount of Mg is lost during industrial and cooking processes of Kombu. We hypothesized that thinly shaved Kombu (TSK), a Japanese traditional Kombu product, is a suitable Mg source for daily diets because TSK hardly loses Mg during processing. Rats were fed diets containing TSK or magnesium oxide (MgO) to satisfy 25%, 50%, 75%, or 100% Mg requirements. We determined the relative Mg bioavailability of TSK compared to MgO and examined factors affecting Mg bioavailability in TSK. RESULTS The relative bioavailability of Mg in TSK compared to MgO was calculated as 92.3%, 111.4%, and 87.2% from apparent absorption, urinary excretion, and femoral concentration of Mg, respectively. The ultrafiltrable Mg concentration was lower in the cecal content of rats given TSK than those given MgO. However, the mRNA expression of TRPM6, an Mg channel responsible for Mg absorption, was higher in the cecum of rats given TSK than those given MgO. CONCLUSION Enhancement of TRPM6 expression in the large intestine negates the low bioaccessibility of Mg in TSK, and thus TSK shows comparable Mg bioavailability to MgO. This article is protected by copyright. All rights reserved.