Effects of <i>Bacillus subtilis</i> Var. Natto Products on Capillary Blood Flow in Healthy Subjects with Peripheral Coldness: A Double-Blind, Placebo-Controlled, Randomized Parallel Study

Abstract

Purpose: NKCP®, a natto-derived dietary food supplement whose main component is bacillopeptidase F produced by Bacillus subtilis var. natto, has antithrombotic, fibrinolytic, and pressure-lowering effects, and also is suggested to improve peripheral coldness. However, existing data are based on subjective evaluations with no scientific basis about the effects on peripheral coldness. Therefore, we aimed to investigate the effectiveness of NKCP® for peripheral coldness by measuring changes in blood flow using a laser doppler rheometer and biochemical indices. Patients and Methods: This was a double-blind, randomized, controlled study of individuals aged 30 - 70 years who complained of subjective symptoms of cold hands and feet. They were randomly divided into the NKCP® group and the placebo group to receive NKCP® 250 mg once daily and dextrin 250 mg as placebo once daily, respectively. The experiment lasted 8 weeks, with an intervention period of 4 weeks and a washout period of 4 weeks. Results: One-month intake of NKCP® significantly increased blood flow rate for 1 min between 4 and 5 minutes after the end of cold loading compared to that before feeding (p = 0.038). Also, analysis of the 5-minute blood flow rate before and after 4 weeks of feeding showed a significant improvement in the NKCP® group (p = 0.007), although there was no significant difference in the placebo group (p = 0.215). Furthermore, the 5-minute blood flow at 4 weeks after the end of feeding was significantly improved compared to that before feeding in the NKCP® group (p = 0.049). Therefore, the effect continued for at least 1 month after discontinuation of administration. Conclusions: It is possible that NKCP® intake effectively improves blood flow in subjects with peripheral coldness. Therefore, continuous intake of NKCP® is expected to reduce the symptoms of peripheral coldness. In the future, it needs to investigate whether the effect of increasing blood flow after ingestion of NKCP® is effective in improving the symptoms of peripheral coldness.