Chronic oxidative stress impairs regular defecation. Sulforaphane (SFN) enhances anti-oxidant systems, ameliorating oxidative injury. SFN inhibits overgrowth of anaerobic microflora and protects small intestine from oxidative injury. We assessed whether daily intake of SFN-rich broccoli sprouts (BS) improves defecation in humans. Forty-eight subjects, with a constipation scoring system (CSS) >2 points, were assigned to either the BS group ( n = 24) or the alfalfa sprouts (AS) group ( n = 24), and were requested to eat 20 g daily of raw BS or AS, respectively, for 4 weeks. BS contains 4.4 mg/g sulforaphane glucosinolates (SGS), while AS contains no SGS. CSS-based questionnaires were performed to evaluate bowel habit. Stool samples were collected to evaluate intestinal microflora using a terminal restriction fragment length polymorphism flora analysis. Intervention with BS, but not AS, caused a significant decrease in the duration of attempted defecation and the total CSS score. Intervention with BS decreased the percentage of Bifidobacterium in the stool. These results suggest that daily intake of BS improves bowel habit in human subjects. Since BS treatment enhance antioxidant enzyme activities, these effects of BS appear to relate with the SFN-mediated modulation of the intestinal motility during exposure to oxidative stress. (UMIN Clinical Trial Registration Number: UMIN-000021207)