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The bioavailability of Ca is currently one of the most important topics in nutrition research and is correlated with gastrointestinal solubility. Thus, to increase the solubility of calcium, this study was undertaken to examine the effect of γ-PGA on intestinal Ca solubility. The calcium solubility increased when the amount of γ-PGA was increased, due to the inhibition of the formation of an insoluble Ca complex with phosphate. Therefore, when γ-PGA-500 (avg. MW 5,000 kDa) was added at 0.5 mg/ml, 75% of the total Ca was soluble. The amount of soluble Ca uptake in the small intestine was investigated using Balb/c mice as an animal model system. The soluble Ca uptake in the mice orally administered with γ-PGA-500 (avg. MW 5000 kDa) was significantly higher than that in the γ-PGA-100 (avg. MW 1,000 kDa)-administered mice (P<0.05). Accordingly, these results strongly support the notion that the molecular size of γ-PGA is correlated with Ca solubility. The effects of other factors, such as casein phosphopeptide and vitamin D, on intestinal Ca absorption have also previously been investigated. Therefore, it is hoped that the present observations will help clarify the role of γ-PGA in Ca solubility and its industrial application as an additive.
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