In June 2022 a new study was published that looked into the relationship between eating a plant-based diet and the risk for cancers of the digestive system. This meta-analysis included 49 previous scientific papers, specifically case-control and cohort studies, that had examined the effects of a plant-based diet on cancers of the gastrointestinal system. This research included over three million participants. (1)
Note: Cohort studies follow a group of people over time. Case-control studies compare people that have an outcome such as digestive cancer to those that do not. In this research, these two study types were analyzed separately due to their differing study methods. (1)
For the purposes of this investigation a plant-based diet consisted of (1);
A diet excluding all meat, meat products, seafood and food of animal origin
A diet characterized by a higher consumption of fruits, vegetables, legumes, and nuts rather than animal products.
The results were as follows (1);
Among the cohort studies, eating a plant-based diet was linked to…
- 24% lower risk for colorectal cancer
- 18% lower risk for colon cancer
- 16% lower risk for rectal cancer
- 29% lower risk for pancreatic cancer
- 19% lower risk for stomach cancer
- 39% lower risk for liver cancer
Among the case-control studies, eating a plant-based diet was linked to…
- 33% lower risk for colorectal cancer
- 35% lower risk for pancreatic cancer
- 42% lower risk for stomach cancer
- 39% lower risk for liver cancer
- 36% lower risk for pharyngolaryngeal cancer
Other interesting details considered during this study; (1)
- Participants lived in North America, Europe and Asia and plant-based diets were protective for digestive cancers in all of the different continents and cultures.
- The participants of some of the cohort studies were Seventh Day Adventists whose culture leads them to eat a predominantly plant-based diet, avoiding alcohol and tobacco, getting regular exercise and good sleep and placing importance on their faith and community. The Adventists in this study showed a 46% lower risk of developing digestive cancer compared to a 17% lower risk for the non-Adventist plant-based eaters.
- This research included an exploration into whether a diet needed to consist of exclusively plant-sourced foods. Could it be made up of predominantly but not completely plants and still be effective against digestive cancers? Accordingly, plant-based dietary patterns were placed into two categories, either a pure plant-sourced diet or a diet that was primarily plant-sourced. Results showed that both of these diet types were similarly protective against digestive system cancers and the researchers concluded that it is not necessary to adopt a purely plant-based diet to receive these benefits. (1) They noted that dietary recommendations from the WCRF (World Cancer Research Fund) suggest that eating meat should be limited to no more than three portions per week (to a maximum of 350 to 500 grams of meat weekly) and the diet should contain at least 30 grams of fiber and five servings (at least 400 grams in total) of a variety of non-starchy vegetables and fruit every day. (2)
The authors of this investigation outlined probable mechanisms for these positive effects on digestive cancers. (1)
- Plant-based diets are anti-oxidant and anti-inflammatory. They can reduce oxidative stress (an imbalance between the production of harmful free radicals that can damage DNA and their elimination by protective antioxidants) which can prevent chronic inflammation, a major factor in the development and progression of malignant tumors. (3,4,11)
- Plant-sourced foods are rich in the vitamins, minerals and phytochemicals that regulate inflammatory processes in the body. These natural antioxidants are protective against cancer. Examples are fiber, sulfur compounds, Vitamin C and E, carotenoids, polyphenols, anthocyanins, flavonoids, lignans and phenolic acids. Only plants contain these beneficial compounds. (5,6)
- Fiber accelerates the movement and fermentation of food particles within the digestive tract and reduces the time that the food stays in the intestines. The resultant reduction in exposure of the intestinal walls to carcinogens may be the reason that fiber is associated with lower risks of digestive cancers. (7)
- The processes by which insulin and insulin-like growth factors (IGFs) regulate carbohydrate and energy metabolism are associated with cancer risk. Excess IGF comes from eating animal protein. Studies show that the more animal protein consumed, the higher the circulating IGF-1 in the bloodstream. Conversely, eating plant protein lowers IGF-1 levels (8,9).
- There is evidence that suggests that the effects of a plant-based diet on the microbiome in the intestine is linked to reduced tumors of the digestive tract. (7,10)
And so, the scientific data keeps on coming in. It is very clear that your lifestyle can have profound effects on your health. What you choose to do is up to you.
1 Zhao, Y., Zhan, J., Wang, Y., Wang, D. The Relationship Between Plant-Based Diet and Risk of Digestive System Cancers: A Meta-Analysis Based on 3,059,009 Subjects. Front Public Health. 2022 Jun 3;10:892153. Doi: 10.3389/fpubh.2022.892153. PMID: 35719615; PMCID: PMC9204183.
3 Halliwell, B. The antioxidant paradox: less paradoxical now? Br J Clin Pharmacol. (2013) 75: 637–644. 10.1111/j.1365-2125.2012.04272.x
4 Diakos, C.I., Charles, K.A., McMillan, D.C., Clarke, S.J. Cancer-related inflammation and treatment effectiveness. Lancet Oncol. (2014) 15: e493–503. 10.1016/S1470-2045(14)70263-3.
5 Subramaniam, S., Selvaduray, K.R., Radhakrishnan, A.K. Bioactive compounds: natural defense against cancer? Biomolecules. 2019; 9: 758. 10.3390/biom9120758.
6 Hever, J., Cronise, R.J. Plant-based nutrition for healthcare professionals: implementing diet as a primary modality in the prevention and treatment of chronic disease. J Geriatr Cardiol. 2017; 14: 355–368. 10.11909/j.issn.1671-5411.2017.05.012.
7 Gonzalez, C.A., Salas-Salvado, J. The potential of nuts in the prevention of cancer. Br J Nutr. 2006; 96(Suppl. 2): S87–94. 10.1017/BJN20061868
8 Ngo, T.H., Barnard, R.J., Tymchuk, C.N., Cohen, P., et al. Effect of diet and exercise on serum insulin, IGF-I, and IGFBP-1 levels and growth of LNCaP cells in vitro (United States). Cancer Causes Control. 2002 Dec; 13(10): 929-935.
9 Pollak, M. Insulin and insulin-like growth factor signalling in neoplasia. Nat Rev Cancer. 2008 Dec; 8(12): 915-928. Doi: 10.1038/nrc2536. Erratum in: Nat Rev Cancer. 2009 Mar ;9(3):224. PMID: 19029956.
10 Singh, R.K., Chang, H.W., Yan, D., Lee, M., Ucmak, D., Wong, K., et al. Influence of diet on the gut microbiome and implications for human health. J Transl Med. 2017; 15: 73. 10.1186/s12967-017-1175-y.
11 Reuter, S., Gupta, S.C., Chaturvedi, M.M., Aggarwal, B.B. Oxidative stress, inflammation, and cancer: how are they linked? Free Radic Biol Med. 2010 Dec 1; 49(11): 1603-1616. Doi: 10.1016/j.freeradbiomed.2010.09.006. Epub 2010 Sep 16. PMID: 20840865; PMCID: PMC2990475.
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