|Om, nom, nom!|
Lions tear open the stomachs of their prey. The contents spill out and some are consumed by the lions. What do herbivores eat? Green vegetable matter. Being chewed by the molars of a herbivore is technically-speaking food processing. So, on to the study in the title.
See Green vegetables, red meat and colon cancer: chlorophyll prevents the cytotoxic and hyperproliferative effects of haem in rat colon.
"In both studies haem increased cytotoxicity of the colonic contents approximately 8-fold and proliferation of the colonocytes almost 2-fold. Spinach or an equimolar amount of chlorophyll supplement in the haem diet inhibited these haem effects completely. Haem clearly inhibited exfoliation of colonocytes, an effect counteracted by spinach and chlorophyll. Finally, size exclusion chromatography showed that chlorophyll prevented formation of the cytotoxic haem metabolite. We conclude that green vegetables may decrease colon cancer risk because chlorophyll prevents the detrimental, cytotoxic and hyperproliferative colonic effects of dietary haem."
It's a rat study (experiments on humans are unethical), but there's Heme and Chlorophyll Intake and Risk of Colorectal Cancer in the Netherlands Cohort Study. Finally, there's Associations between Red Meat and Risks for Colon and Rectal Cancer Depend on the Type of Red Meat Consumed.
So, always eat greens with your red meat. A tablespoonful of cooked spinach is all you need.
EDIT: I just found Red meat and colon cancer: should we become vegetarians, or can we make meat safer?
"For instance, promotion of colon carcinogenesis in rats by cooked, nitrite-treated and oxidized high-heme cured meat was suppressed by dietary calcium and by α-tocopherol, and a study in volunteers supported these protective effects in humans."
As dietary calcium binds to haem iron, this suggests that other binding agents would work e.g. phytates (in whole grains) and tannins (in tea).
α-tocopherol is a fat-based antioxidant. Vitamin E supplements contain D α-tocopherol.