The Effects of Adlay Tea Intake on Immune Homeostasis and Vascular Endothelial Function in Healthy Adults: A Randomized, Double-Blind, Parallel-Group Comparative Study

Excessive immune response and inflammation are associated with an increased risk of various diseases. In particular, excessive myeloperoxidase (MPO) activity in neutrophils causes inflammatory reactions and lifestyle-related diseases. Adlay has a long history of being used as a traditional Chinese medicine. Polyphenols present in adlay seeds are expected to have the effect of suppressing excessive immune and inflammatory responses. Here, we conducted a randomized, double-blind, parallel group, placebo-controlled study was conducted to evaluate the suppressing effects of adlay seeds extract on excessive immune responses. One hundred and twenty adults participated in the study and they were equally divided into an adlay tea intake group and a placebo group. MPO activity was significantly elevated in the placebo group after 8-wk ingestion, while no significant change was observed in the adlay group. Vascular endothelial functions improved in the adlay group, especially in subjects over 40 y old. These results indicate that adlay tea intake may suppress an excessive immune and inflammatory responses, and improve arterial stiffness. Since caffeic acid, p-coumaric acid, and ferulic acid detected in adlay tea are known to inhibit MPO activity, these polyphenols may be the major functional molecules. Collectively, adlay tea is considered to have a preventative effect against lifestyle-related diseases through improving vascular endothelial function by effects to maintain immune homeostasis of the contained polyphenols. This trial was registered at University Hospital Medical Information Network Clinical Trials Registry (UMIN000032263).