Background: A variety of foods have been studied in relation to colorectal cancer risk. There is research on certain foods that cause colon cancer or have a protective factor against it but there is limited research comparing diets. While the literature indicates a benefit to the Mediterranean diet in reducing the risk of colon cancer, studies on a low-carbohydrate diet, such as the Atkins or ketogenic diets, and the incidence of colorectal cancer are less common. Therefore, this study aims to compare the Mediterranean diet and a low-carbohydrate, high-fat diet in relation to colorectal cancer risk.
Methods: A PubMed literature search for relevant articles was conducted through August 2020 to identify potential links of the Mediterranean diet and low-carbohydrate, high-fat diet to colorectal cancer with preference being given to articles after 2015. Preference were given to studies that were systematic reviews, meta-analyses, randomized controlled trials, and cohort studies, but case control studies were accepted. The studies included had to be human studies that reported risk estimates and measures of variability (95% confidence intervals). Seventeen pertinent articles were retrieved and they served as the basis for this clinical review.
Results: There are no studies comparing Mediterranean and low-carbohydrate diets specifically. While specific diets are not compared, the foods and food groups that are key to both diets have been studied in relation to colon cancer risk. A Mediterranean diet focuses on fish, poultry, unsaturated fats, whole grains, fruits, vegetables, nuts, and legumes. A low-carbohydrate diet focuses on low-carbohydrate, high fat, and moderate protein with a variation in grams of carbohydrates consumed daily. Fish, red meats, poultry, eggs, oils, full-fat dairy, non-starchy vegetables, berries, nuts, and seeds are allowed while starchy vegetables and fruits, legumes, and whole grains are restricted.
Studies suggest that red meat can increase colorectal cancer risk. Fish may be a protective factor against CRC. There is no association between CRC and poultry. Whole grains, cereal fiber, and dairy products may decrease the risk. It is suggested that cruciferous vegetables may decrease CRC risk, but no consensus was obtained for fruits or fats. Studies suggest that the Mediterranean diet can decrease the risk of colon cancer.
Conclusion: Studies suggest that the Mediterranean diet reduces colorectal cancer risk. No studies on a low-carbohydrate diet and colorectal cancer are known. If a person is participating in a low-carbohydrate diet, they should be aware of which foods can increase risk of colon cancer and modify the diet to avoid these, specifically limiting the amount of red meat and finding other ways to receive a protein source. The two diets need to be directly compared to determine if the risk of colorectal cancer is more effectively reduced with the Mediterranean diet than a low-carbohydrate diet.
McGeown C. Mediterranean Diet versus a Low-Carbohydrate Diet in Reducing Colorectal Cancer Risk. University of Lynchburg DMSc Doctoral Project Assignment Repository. 2021; 3(2).
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