Roasted Barley Extract (Mugi-cha) Containing Cyclo(D-Phe-L-Pro) Prevents Lowering of the Cutaneous Blood Flow and Skin Temperature under Air Conditioning: A Randomized, Double-Blind, Placebo-Controlled, Crossover Study

摘要

Roasted barley extract (RBE), also known as mugi-cha, is a well-known healthy non-caffeinated beverage, and its health functionality has been widely reported. Our previous clinical study showed that RBE affects the cutaneous blood flow and skin temperature after cold-water immersion and that cyclo(D-Phe-L-Pro) is responsible for its effect. In this study, we investigated whether cyclo(D-Phe-L-Pro)-containing RBE prevents the decrease in the cutaneous blood flow and skin temperature. Subjects remained in the air-conditioned room while ingesting RBE or a placebo. We measured the cutaneous blood flow and skin temperature. We evaluated the effect of RBE administration by two-way repeated measures analysis of variance. A total of 15 subjects were enrolled. The change in cutaneous blood flow in the RBE and placebo groups was -0.79 +/- 0.38 and -2.03 +/- 0.35 mL min(-1) 100 g(-1), respectively (p value of 0.041). The change in the skin temperature in the RBE and placebo groups was -1.85 +/- 0.35 and -3.02 +/- 0.30 degrees C, respectively (p value of 0.001). We also did subclass analysis with cold feeling subjects. For the seven subjects who had cold sensation, the change in the cutaneous blood flow in the RBE and placebo groups was -0.48 +/- 0.58 and -2.56 +/- 0.48 mL min(-1) 100 g(-1), respectively (p value of 0.008). The change in the skin temperature in the RBE and placebo groups was -1.46 +/- 0.74 and -2.89 +/- 0.39 degrees C, respectively (p value of 0.009). Thus, RBE containing cyclo(D-Phe-L-Pro) prevents the decrease in the cutaneous blood flow and skin temperature under air conditioning.