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

Abstract

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/m2 (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 TNFα (−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.

Microbiome modulation in the prevention and management of colorectal cancer: a systematic review of clinical interventions

“…Dietary changes focused on increase of vegetable consumption or Mediterranean diet, in high-risk volunteers, did not produce alterations of microbiota, although they showed an effect on reducing markers of DNA toxicity [50,51].…”

Plasma and fecal zonulin are not altered by a high green leafy vegetable dietary intervention: secondary analysis of a randomized control crossover trial

“…The M3G feasibility trial was conducted from July 2018 to December 2018. Detailed methods have been previously described [ 32 , 34 ]. Participants were recruited from July to September 2018 and researchers obtained written consent prior to post-screening data collection.…”

“…Samples were sealed and immediately placed in the participant’s freezer until their next appointment. Fecal water was isolated as previously described [ 32 ]. Fecal and serum zonulin levels were determined using a competitive enzyme-linked immunosorbent assay kit (ELISA) (Immunodiagnostik AG, Berlin Germany, Cat.…”

“…#DY870-05 and #DY3694). Vitamin K was analyzed via liquid chromatography–mass spectrometry as previously described [ 32 ].…”

“…This intervention was designed to reduce the colonocyte damage associated with heme in red meat by increasing GLVs high in fiber and chlorophyll; intended to reduce colorectal cancer risk. Chlorophyll can bind to heme and reduce the cytotoxic effects while the prebiotic fiber can improve the microbiome which can influence inflammation and the health of the colonocytes [ 32 ]. Though zonulin is present only in the small intestine, we hypothesized that this intervention may also decrease zonulin and reduce intestinal permeability.…”