For the year 2020, colorectal cancer has been featured as the third most common type of cancer globally, accounting for at least 1.93 million new cases, with greater incidence found within the male population. Broadly speaking, the incidence of this cancer type assumes a steady upward trend worldwide. Adenocarcinomas represent the great majority (98%) of cancers found within in the large intestine. But how exactly does this cancer type arise? Where does it come from? There may be both genetic and environmental influences on the development of this cancer type. There may be mutations of specific genes that lead to the unintentional and uncontrolled over proliferation of cells in that region of the gut, turning what was initially a physiological process of cell growth and development into a pathological one. Apart from genetic mutations, diet may also play a critical role as part of the environmental influence. In fact, as a modifiable risk factor, diet may significantly contribute to help lower the risk of colorectal cancer. Specifically, there may be an association between the consumption of high-fibre diet and lower risk of colorectal cancer. But why is this so? How exactly does dietary fibre act to hold its protective function against colorectal cancer? It does this through several mechanisms. The dietary fibre, is that part of the carbohydrate family that remains undigested and that passes to the large intestine, being subject to possible fermentation by the beneficial gut bacteria. Of this part of the carbohydrate family, there is the soluble and insoluble portions of dietary fibre and each portion play their role in assuming and maintaining a protective function within the gut. We see these forces taking place now. Dietary fibre and insulin levels Foods may carry a combination of different carbohydrate types (mono or di – saccharides, oligosaccharides and poly – saccharides). Some of these smaller sugar units contained in the food, such as those found as mono and di-saccharides may easily get absorbed in the small intestine. The Soluble fibre component, however, may form a gel with the water in the small intestine and this gel serves to act as a barrier, preventing or slowing the absorption of the smaller glucose units in the small Intestine. This is one mechanism through which dietary fibre works to keep the blood glucose levels at considerably moderate levels. Insulin is a hormone responsible for taking up the glucose into cells and thus lowering the glucose levels in the blood stream. Dietary fibre may work to optimize this process of glucose uptake as insulin becomes more sensitive to the glucose and so the dietary fibre facilitates more readily, the process of glucose being taken up into cells and lowering the glucose level within the blood. This is yet another means by which the glucose level in the blood is being controlled, and in fact, this mechanism helps to improve glucose tolerance. Once the glucose level becomes reduced in the blood, it also means that the demand for insulin is reduced and so less insulin is being released into the blood stream. Why this is important is that insulin may play a role in cellular proliferation. Greater levels of insulin floating around in the blood stream may generate outcomes that may lead to the alterations in signalling pathways that may result in cellular proliferation, a process that may lead to tumour and subsequent cancer formation. Key Points: So, this is what we know so far about the dietary fibre: -Soluble fibre makes gel with water to slow glucose absorption in small intestine -improves insulin sensitivity and process of glucose uptake into cells, thereby improving glucose tolerance -decreases the demand for insulin in the blood, consequently inhibiting pathways that may lead to cellular proliferation, and hence cancer formation So, we can see here, how dietary fibre works to keep the blood glucose levels controlled and also, we can see the connection between the control of blood glucose and its power to reduce risk of cancer. We can also see the soluble fibre at play and its power in the protection from excess glucose absorption in the small intestine. Dietary fibre and the Fermentation process Apart from the control of blood glucose and insulin levels as a mechanism to influence risk of cancer, beneficial micro-organisms found in the large intestine may use dietary fibre as a substrate to generate a by-product that may also help to reduce the risk of cancer. That is, the fermentation process that occurs with dietary fibre by certain beneficial bacteria is an additional mechanism that may positively influence the risk of cancer. One such substance that is generated from this fermentation process is butyrate. Butyrate is a Short Chain Fatty Acid (SCFA) that is produced in the presence of micro-organisms, The table below details some of the micro-organisms that inhabit the large intestine and that take part in the fermenting action on the dietary fibre to produce butyrate. These micro-organisms may also cross-feed with Bifidobacterium as players in the fermenting action.
So, what are the benefits that can be derived from the product of the fermentation process? Generally, butyrate may be considered a preferred source of energy to support the cells lining the large intestine and may confer generally good gut health. However, it is worth noting that this is not always the case. In fact, cancerous cells actually opt for glucose over butyrate as their favoured energy source. Additionally, butyrate may inhibit any inflammatory processes occurring in the gut region and they also act as a protective barrier in the large intestine. Furthermore, butyrate may promote cell differentiation and regulated cell death for those cells that may be damaged. In this way, it slows the pathway of cell proliferation that may have ultimately led to tumour growth and cancer formation within the colorectal region. These actions work to protect the cells lining the large intestine from DNA damage, thus contributing to lowering the risk of colorectal cancer. The insoluble portion of the dietary fibre acts to attract water into the gut lumen. This action may serve various functions. Apart from stool bulking, the diluting action reduces the chances and time available for cancer causing substances to make contact with the gut lining, therefore lowering the risk of colorectal cancer. Food Sources: Dietary fibre is less energy dense but more nutrient dense. Sources may include whole grain foods, fruits and vegetables. Note: Whole grains are those cereal grains that remain clothed with their germ and bran layers. Not only do they carry high fibre content but they also are embellished with other nutrients that confer health benefits. Fruits and vegetables may play an even greater role in the prevention of colorectal cancer. This may be as a result of other nutrients that may be present in these foods, such as phytochemicals (eg. polyphenols) and vitamins (A, C and E). These additional nutrients act as anti-oxidants and have anti-inflammatory and anti-carcinogenic properties that work with the dietary fibre to further provide that protective function against cancer formation. Conclusion In conclusion, we take note that colorectal cancer has taken a prominent position as far as its incidence in the last year and there is a rising trend moving into the future. We have also identified diet playing a key role as a lifestyle risk modifier in the prevention of colorectal cancer. We have dived deeper into the understanding of the dietary fibre and how exactly it exerts its influence as a protective player against colorectal cancer. Finally, we have identified whole grains, fruits and vegetables as powerful sources of dietary fibre that may protect against colorectal cancer. References
Ferlay J, Ervik M, Lam F, Colombet M, Mery L, Piñeros M, et al. Global Cancer Observatory: Cancer Today. Lyon: International Agency for Research on Cancer; 2020 Vargas AJ, Thompson PA. Diet and nutrient factors in colorectal cancer risk. Nutr Clin Pract. 2012 Oct; 27(5):613-23. Aune D, Chan DS, Lau R, Vieira R, Greenwood DC, Kampman E, Norat T. Dietary fibre, whole grains, and risk of colorectal cancer: systematic review and dose-response meta-analysis of prospective studies. BMJ. 2011 Nov 10; 343():d6617 Autumn G Hullings, Rashmi Sinha, Linda M Liao, Neal D Freedman, Barry I Graubard, Erikka Loftfield, Whole grain and dietary fiber intake and risk of colorectal cancer in the NIH-AARP Diet and Health Study cohort, The American Journal of Clinical Nutrition, Volume 112, Issue 3, September 2020, Pages 603–612, https://doi.org/10.1093/ajcn/nqaa161 Donohoe DR, Collins LB, Wali A, Bigler R, Sun W, Bultman SJ. The Warburg effect dictates the mechanism of butyrate-mediated histone acetylation and cell proliferation. Mol Cell. 2012;48(4):612-626. doi:10.1016/j.molcel.2012.08.033 Rivière A, Selak M, Lantin D, Leroy F, De Vuyst L. Bifidobacteria and Butyrate-Producing Colon Bacteria: Importance and Strategies for Their Stimulation in the Human Gut. Front Microbiol. 2016;7:979. Published 2016 Jun 28. doi:10.3389/fmicb.2016.00979 Masrul M, Nindrea RD. Dietary Fibre Protective against Colorectal Cancer Patients in Asia: A Meta-Analysis. Open Access Maced J Med Sci. 2019;7(10):1723-1727. Published 2019 May 30. doi:10.3889/oamjms.2019.265 Riccardi G, Rivellese AA. Effects of dietary fiber and carbohydrate on glucose and lipoprotein metabolism in diabetic patients. Diabetes Care. 1991 Dec;14(12):1115-25. doi: 10.2337/diacare.14.12.1115. PMID: 1663443 Source: Björck I, Elmståhl HL. The glycaemic index: importance of dietary fibre and other food properties. Proc Nutr Soc. 2003 Feb;62(1):201-6. doi: 10.1079/pns2002239. PMID: 12749347 Tabernero M, Serrano J, Saura-Calixto F. Dietary fiber intake in two European diets with high (copenhagen, Denmark) and low (Murcia, Spain) colorectal cancer incidence. J Agric Food Chem. 2007 Nov 14;55(23):9443-9. doi: 10.1021/jf072146o. Epub 2007 Oct 12. PMID: 17929892 Matthias B Schulze, Simin Liu, Eric B Rimm, JoAnn E Manson, Walter C Willett, Frank B Hu, Glycemic index, glycemic load, and dietary fiber intake and incidence of type 2 diabetes in younger and middle-aged women, The American Journal of Clinical Nutrition, Volume 80, Issue 2, August 2004, Pages 348–356, https://doi.org/10.1093/ajcn/80.2.348
0 Comments
Leave a Reply. |
Archives
July 2022
TOPICS |