Yak milk improves retinoic acid-induced osteoporosis by promoting intestinal calcium absorption.

Yak milk is a unique nutritional quality milk with health-promoting benefits. In this study, we investigated the effect of yak milk on intestinal calcium absorption in mice with retinoic acid-induced osteoporosis (OP) and in the Caco-2 cell model. Results showed that compared with the model group, the apparent calcium absorption rate increased from 35.93% to 51.84% and 49.41% for the low-dose yak milk group (L-YM) and high-dose yak milk group (H-YM), respectively, and the calcium accumulation rate increased from 26.14% to 44.09% and 42.66%, respectively. However, no improvement was observed in the alendronate sodium (ALN) group. The expression of the transient receptor potential vanilloid 6 (TRPV6) calcium channel in the yak milk treatment group was 2.7 (L-YM) and 3.5 (H-YM) times higher than that in the model group, implying that TRPV6 channel was the main transport pathway in the small intestine. Furthermore, in vitro calcium absorption assays indicated that yak milk enhanced intestinal Ca2+ absorption more effectively than CaCl2 by regulating the TRPV6 channel. These data suggest that yak milk promotes calcium absorption by upregulating the expression of the TRPV6 calcium channel, thereby improving OP. This study highlights the importance of yak milk as a dietary factor for bone health.