Dietary factors and the risk of gastric and colorectal cancers: A Mendelian randomization study.

Dietary factors can significantly affect the development of gastric and colorectal cancers; however, observational findings on the impact of micronutrients and macronutrients on the risk of gastric and colorectal cancers are inconsistent. It is crucial to clarify these relationships to create nutritional recommendations for cancer prevention. A two-sample Mendelian randomization investigation was performed to examine the impact of circulating levels of 15 micronutrients (such as vitamin A, folate, vitamin B6, vitamin B12, vitamin C, vitamin D, vitamin E, β-carotene, calcium, copper, iron, magnesium, phosphorus, selenium, and zinc), along with adjusted relative macronutrient intake (including protein, carbohydrate, sugar, and fat), on the risk of gastric and colorectal cancers. Genetically predicted relative protein intake is significantly associated with the risk of colorectal cancer (odds ratio [OR] 95% confidence interval [CI] = 0.41 [0.24, 0.69]; P = .0007). Evidence suggests that genetically predicted macronutrients, such as carbohydrate (OR 95% CI = 1.88 [1.13, 3.14]; P = .0154), and micronutrients, such as vitamin C (OR 95% CI = 0.81 [0.69-0.94]; P = .008) and vitamin B12 (OR 95% CI = 1.16 [1.04, 1.28]; P = .006), may also influence the risk of colorectal cancer. Evidence suggests that intake of sugar (OR 95% CI = 0.47 [0.24, 0.90]; P = .02), and vitamin C (OR 95% CI = 0.78 [0.62, 0.99]; P = .04) may influence the risk of gastric cancer. However, no significant associations were observed between other nutrients and gastrointestinal malignancy. Taken together, these findings suggest that the intake of protein, carbohydrate, sugar, vitamin C, and vitamin B12 may influence the risk of gastric and colorectal cancers. However, further in-depth studies are needed to confirm this.