A new meta-analysis examines the controversial relationship between protein intake from our diet and the risk of developing colorectal cancer.
Colorectal cancer, which includes both colon and rectal cancer, is one of the most common types of cancers that are able to metastasize, which is when cancer travels to different sites in the body. This cancer causes significant mortality in the Western world and has also been on the rise in China. Factors that influence the risk of developing colorectal cancer are thought to include pollution, diet, and lifestyle changes. Many experts consider diet as a major risk factor for colorectal cancer, but mixed results have come from studies correlating protein intake and colorectal cancer. Some studies observe a beneficial effect from eating less protein, whereas others witness lower risk of colorectal cancer from high protein consumption. In addition, some studies see no effect of protein intake on the risk of developing colorectal cancer.
A recent meta-analysis, which compiles data among several studies, was published in World Journal of Surgical Oncology and examines the relationship between dietary protein intake and colorectal cancer risk. An extensive and systematic approach narrowed down possible articles until they were left with 13 relevant studies. The articles that were chosen had to have sufficient data and the right type of patients being studied. For example, some criteria for the review included: subjects were over 18 years of age, protein intake had to be categorized into at least two groups, and the outcome of interest was colorectal cancer. The 13 articles comprised 21 separate studies, which were vetted to ensure sufficient quality.
The authors first tried to determine whether protein intake could impact colorectal cancer risk by comparing the cancer risk of the lowest protein intake group to the highest protein intake group. No difference was observed, however. Another question of interest was whether the subgroups of protein intake played a role. It was determined that neither dietary animal protein nor vegetable protein intake affected colorectal cancer risk. Further analysis also confirmed that there was no obvious publication bias, which would skew towards either more positive or negative results being published.
Overall, this report indicated no significant association between colorectal cancer risk and dietary protein intake. More studies are required to strengthen this claim, as knowledge on whether diets should be changed in order to decrease colorectal cancer risk is crucial. Diet and lifestyle changes are one of the cheapest and most preventative ways to decrease cancer risk. By obtaining additional evidence on the relationship between protein intake and cancer risk, doctors and patients will be better able to make informed decisions on their diet.
Written by Branson Chen, BHSc
Reference: Lai R, Bian Z, Lin H, Ren J, Zhou H, Guo H. The association between dietary protein intake and colorectal cancer risk: a meta-analysis. World Journal of Surgical Oncology. 2017 Sep 8;15:169.