Effects of onion extract containing concentrated cysteine sulfoxides on sleep quality: a randomized, double-blind, placebo-controlled, crossover study.

The objective of this randomized, double-blind, placebo-controlled, crossover study was to examine the effects of onion extract containing concentrated cysteine sulfoxides on improving sleep quality. In total, 30 healthy men and women who were dissatisfied with their sleep consumed the test food sample (onion extract tablets) for 5 days. The delta power during non-rapid eye movement sleep and the delta power per minute in the first sleep cycle increased significantly with the intake of onion extract containing concentrated cysteine sulfoxides compared with the intake of placebo. A significant decline in sleep latency was also observed. Salivary α-amylase level, a stress indicator, decreased significantly with the intake of onion extract containing concentrated cysteine sulfoxides compared with the intake of placebo. These findings indicate that onion extract containing concentrated cysteine sulfoxides alleviates stress, improves the quality of sleep and promotes smooth transition into sleep.