A Dietary Intervention High in Green Leafy Vegetables Reduces Oxidative DNA Damage in Adults at Increased Risk of Colorectal Cancer: Biological Outcomes of the Randomized Controlled Meat and Three Greens (M3G) Feasibility Trial

Green leafy vegetables (GLV) may reduce the risk of red meat (RM)-induced colonic DNA damage and colorectal cancer (CRC). We previously reported the primary outcomes (feasibility) of a 12-week randomized controlled crossover trial in adults with habitual high RM and low GLV intake with body mass index (BMI) > 30 kg/m(2) (NCT03582306). Herein, our objective was to report a priori secondary outcomes. Participants were recruited and enrolled in 2018, stratified by gender, and randomized to two arms: immediate intervention group (IG, n = 26) or delayed intervention group (DG, n = 24). During the 4 week intervention period, participants were provided with frozen GLV and counseled to consume 1 cooked cup equivalent daily. Participants consumed their normal diet for the remaining 8 weeks. At each of four study visits, anthropometrics, stool, and blood were taken. Overall, plasma Vitamin K1 (0.50 +/- 1.18 ng/mL, p < 0.001) increased, while circulating 8OHdG (-8.52 +/- 19.05 ng/mL, p < 0.001), fecal 8OHdG (-6.78 +/- 34.86 ng/mL, p < 0.001), and TNF alpha (-16.95 +/- 60.82 pg/mL, p < 0.001) decreased during the GLV intervention compared to control periods. Alpha diversity of fecal microbiota and relative abundance of major taxa did not differ systematically across study periods. Further investigation of the effects of increased GLV intake on CRC risk is warranted.

Automated summary

Increased intake of green leafy vegetables may reduce the risk of DNA damage and colorectal cancer caused by red meat. In a 12-week intervention trial, it was found that plasma Vitamin K1 levels increased, while levels of 8OHdG and TNF alpha decreased during the green leafy vegetable intervention. Further research is needed to explore the effects of increased green leafy vegetable intake on colorectal cancer risk.