Gut health: foods to boost the microbiome and prevent colon cancer

Although the intestine is located inside our body, it represents the largest contact surface of the body with the outside world, covering about 400 m2. The most important functions of the intestine are nutrient absorption and excretion, but the immunological function must not be underestimated and is still largely unexplored. 80% of our immune cells are located in the intestine and act as a kind of border control at this large contact surface to the outside world. An intact intestinal barrier is indispensable for the intact function of the “intestinal immune system”. It helps to protect our body from the outside world and consists of three layers: the intestinal mucosa, the intestinal mucus and a thick layer of bacteria — the microbiome.

How does a disturbed intestinal barrier manifest itself?

The incidence of inflammatory bowel diseases (IBDs) has increased alarmingly worldwide in recent decades. Genetic predispositions but also various environmental factors are involved in the development of IBDs. Diet is the number one risk factor for the onset and severity of inflammatory bowel disease. An unfavorable diet can promote inflammation in the intestine by disrupting the microbiome, altering intestinal permeability and the mucus layer, and triggering an exaggerated immune response by facilitating the penetration of pathogens. Targeted dietary changes are therefore nowadays always included in therapeutic strategies.

Chronic inflammation increases risk of colorectal cancer

Colorectal cancer has been identified as the third leading cause of cancer-related deaths. The World Health Organization estimates that there will be 27 million new cases of colorectal cancer and 17 million deaths from colorectal cancer worldwide by 2030. The causes of colorectal cancer are diverse and include both genetic and lifestyle factors that can cause changes in the intestinal barrier. It is known that a long-term inflammatory situation in the intestine brings an increased risk of degeneration of intestinal cells, which can ultimately lead to the development of colorectal cancer.

Emulsifiers such as soy lecithin are added to ice cream, chocolate, margarine or bread to improve their consistency. Immunologist Andrew Gewirtz of Georgia State University in Atlanta wondered which foods people eat every day play a role in the development of intestinal inflammation. His recently published study suggests that emulsifiers can disrupt gut flora and contribute to the development of inflammatory bowel disease. In mouse experiments, emulsifiers caused the mice to eat more, gain weight in the form of adipose tissue and negatively alter their gut flora, making inflammation more likely.

Additives such as carrageenan, which is often used as a gelling agent, and carboxymethylcelluloses, which are commonly used in industrially processed foods (especially confectionery, creams, desserts) without maximum quantity restrictions, have also been shown to be detrimental to an intact microbiome. Here, too, there is an increased risk of inflammatory bowel disease. Therefore: better keep your fingers away from industrial food!

What foods protect the intestine?

1. Oats
   Oats are uniquely nutritious due to their composition of bioactive compounds, lipids, β-glucans and dietary fiber. In particular, the sterols it contains, the soluble fiber component of β-glucan, and bioactive compounds such as ferulic acid, avenacosylates, avenacins, and avenanthramides have a beneficial effect on the microbiome. In unprocessed form, oats help change the microbiome for the better. Scientific research found that oats lower cholesterol, regulate satiety, and may protect against cancer development in the colon.
   Oat bran from the oat kernel has a particularly anti-inflammatory effect and thus has a positive effect on inflammatory bowel diseases such as Crohn’s disease and irritable bowel syndrome. The effective (effective) dose of oats varies depending on the variety and the amount of beta-glucans contained. About 2.5 to 2.9 g of β-glucan per day has been shown to lower stool pH, alter intestinal bacteria, as well as increase their numbers. This amount is contained in about 40 to 100 g of oat bran. Oatmeal porridge with cinnamon, nutmeal and grains are a quick and delicious way to start the day healthy and gut-friendly.
2. Beetroot
   Studies see beet as a good source of nitrates and thus as a growth engine for “good” bacteria that fends off “bad” bacteria. The positive effect is explained by the inhibition of so-called imidazole propionates. These chemical compounds are suspected of promoting the growth of harmful cells (e.g. cancer cells). Beet therefore has what it takes to defend the body against cancer.
3. Red wine
   Daily red wine consumption has been linked to many health benefits. Scientists found that drinking red wine increases the number of healthy gut bacteria. This, they say, leads to improved digestion, lower cholesterol levels and the strengthening of the immune system. However, this positive effect cannot be attributed to alcohol.
   The researchers did not find any positive effect on intestinal health with other alcoholic beverages. The reason for the healing effect of red wine: the polyphenols contained in grape juice, which are also found in fruit and vegetables and bring with them plenty of antioxidants. So far, the study has only been able to establish a connection between red wine consumption and improved intestinal flora — but the exact reason for the positive effects has not been researched.
4. Berries
   Berries can have positive effects on the gut microbiome. Especially berries with high ellagitannin content (100 g of strawberry puree, frozen raspberries or frozen cloudberries) can increase the presence of special “good” intestinal bacteria such as Ruminococcaceae and Lachnospiracea. In addition, berries can help with bacterial diarrhea: 60,185 isolated berry polyphenols have been shown to weaken Salmonella by increasing the permeability of its outer membrane and leading to the death of the bacteria.

The pH value makes the difference

The idea that high pH in the colon promotes colorectal cancer by encouraging the destruction of good gut bacteria was established in the early 1980s. It was shown that individuals at high risk for colorectal cancer had higher fecal pH than those at lower risk for colorectal cancer. Although few studies are available specifically on oats and other whole grains, it is generally believed that some dietary fibers stimulate the growth of beneficial bacteria and produce beneficial byproducts such as SCFAs during fermentation in the gut, which in turn lower pH.
The role of the gut microbiota in human health and disease remains an evolving area of research, with current science suggesting that gut microbiota may play an immense role in diseases such as colon cancer, diabetes and obesity. Diet also plays an important role in maintaining a healthy gut microbiota, but studying how individual dietary fibers and other components of foods affect the gut microbiota is often difficult. However, certain foods, such as whole grain oats, are unique in that they contain components that, once metabolized, favorably influence the gut microbiota.

What does a healthy gut look like?

Changes in the composition or function of the gut microbiome can have profound consequences for humans, both negative and positive. An altered microbiome associated with disease is often referred to as dysbiosis. Whether dysbiosis is the cause of disease or the effect of disease is poorly understood in most cases and requires further study to determine cause and effect.

Another important finding is that no two individuals share the same microbiome, even identical twins. In fact, healthy individuals with similar ages and demographics have very different gut microbiome profiles. This has confounded previous attempts to define what a “healthy” microbiome looks like. However, it is generally believed that an abundance of diverse gut bacteria, along with an absence of pathogenic, “bad” species, is indicative of a “healthy” gut.

In general, the more diverse the diet and the better the food quality, the more diverse the composition of the gut microbiome. This is especially true for plant foods that contain different types of fiber; the more diverse the fiber, the more diverse the microbiota. In seniors, loss of dietary diversity and quality after transition to institutional care has been linked to frailty, inflammation, and poorer life expectancy. Therefore, if you want to grow old, you need to start eating well early, and don’t stop when you get older!

Text Sources:

(1) Korczak R, Kocher M, Swanson KS. Effects of oats on gastrointestinal health as assessed by in vitro, animal, and human studies. Nutr Rev. 2020 May 1;78(5):343–363. doi: 10.1093/nutrit/nuz064. PMID: 31638148.

(2) Sandall, Alicia & Cox, Selina & Lindsay, James & Gewirtz, Andrew & Chassaing, Benoit & Rossi, Megan & Whelan, Kevin. (2020). Emulsifiers Impact Colonic Length in Mice and Emulsifier Restriction is Feasible in People with Crohn’s Disease. 12. 10.3390/nu12092827.

(3) Kristek A, Wiese M, Heuer P, Kosik O, Schär MY, Soycan G, Alsharif S, Kuhnle GGC, Walton G, Spencer JPE. Oat bran, but not its isolated bioactive β-glucans or polyphenols, have a bifidogenic effect in an in vitro fermentation model of the gut microbiota. Br J Nutr. 2019 Mar;121(5):549–559. doi:

(4) Koh A, Molinaro A, Ståhlman M, Khan MT, Schmidt C, Mannerås-Holm L, Wu H, Carreras A, Jeong H, Olofsson LE, Bergh PO, Gerdes V, Hartstra A, de Brauw M, Perkins R, Nieuwdorp M, Bergström G, Bäckhed F. Microbially Produced Imidazole Propionate Impairs Insulin Signaling through mTORC1. Cell. 2018 Nov 1;175(4):947–961.e17. doi: 10.1016/j.cell.2018.09.055. Epub 2018 Oct 25. PMID: 30401435.

(5) Thornton, J. R. „High colonic pH promotes colorectal cancer.“ The Lancet 317.8229 (1981): 1081–1083.

(6) El-Salhy, Magdy, et al. „Dietary fiber in irritable bowel syndrome.“ International journal of molecular medicine 40.3 (2017): 607–613.

(7) Chappell, A. J., et al. „Fermentation of oats (Avena sativa) by the faecal microbiota using an in vitro colonic fermentor system.“ Proceedings of the Nutrition Society 74.OCE5 (2015).

(8) Maukonen, Johanna, and Maria Saarela. „Human gut microbiota: does diet matter?.“ Proceedings of the Nutrition Society 74.1 (2015): 23–36.

(9) Bruna C S Cruz, Mariáurea M Sarandy, Anny C Messias, Reggiani V Gonçalves, Célia L L F Ferreira, Maria C G Peluzio, Preclinical and clinical relevance of probiotics and synbiotics in colorectal carcinogenesis: a systematic review, Nutrition Reviews, Volume 78, Issue 8, August 2020, Pages 667–687, https://doi-org.emedien.ub.uni-muenchen.de/10.1093/nutrit/nuz087

Image Sources:

(10) https://www.freepik.com/free-photo/raw-barley-grain-old-dark-background_13013486.htm