Scientists investigated the connection between the Western diet, gut microbiota, and cancer development in a review paper published in the journal Seminars in Immunology.
Background
A complex interplay of modifiable factors, such as diet, lifestyle, and environment, greatly raises the chance of cancer development. These factors, however, are modifiable in order to reduce the chance of cancer.
A healthy diet includes modest amounts of saturated fat, sugar, sodium, and cholesterol. However, the typical Western diet includes a high proportion of these unhealthy food items.
According to research, maintaining a Western diet can raise the risk of a variety of diseases, including cardiovascular disease, diabetes, obesity, and certain cancers. Diet is known to affect gut microbiota composition as well as immunological, neurological, and hormonal functions as a primary source of microbial-derived compounds.
Important elements of the Western cuisine
The Western diet is rich in saturated fat, refined carbohydrates, salt, sugar, and dietary additives, all of which are linked to a variety of health problems.
Fat
Fat is a calorie-dense dietary component that comes in three varieties: unsaturated, trans, and saturated fats. While unsaturated fat has many health advantages, trans and saturated fats raise the risk of a variety of health complications. Many processed items in the Western diet are high in trans and saturated fats.
According to studies on healthy adults, consuming a high-fat diet for 6 months produces substantial changes in gut microbiota composition, resulting in reduced short-chain fatty acids and increased production of secondary bile acids. A high-fat diet also raises pro-inflammatory genes in the gut microbiota, resulting in mild systemic inflammation.
Animal studies have shown that changes in gut microbiota caused by a high-fat diet decrease the mucosal immune response, increase the pro-tumor immune response, and increase the proliferation of gut epithelial cells and stem cells. All of these variables contribute to the development and progression of intestinal cancer.
The accumulation of Gram-positive bacteria in the liver caused by a high-fat diet, combined with dysregulated bile acid metabolism, can result in the development of a senescence-associated secretory phenotype in liver cells. These events are jointly accountable for the development of liver cancer.
Changes in microbiota caused by a high-fat diet can raise lipopolysaccharide biosynthesis and systemic levels, increasing the chance of breast, prostate, and esophageal cancer.
The fiber in the diet
Dietary fiber is a plant-based dietary component that is semi-digestible and aids in digestion and excretion. The partial fermentation and breakdown of dietary fibers in the gut by microbiota results in the production of different short-chain fatty acids. Because the Western diet includes far fewer plant-derived dietary fibers, following this dietary pattern may result in lower production of beneficial microbial metabolites.
Chronic inflammation and ulceration of the colon (ulcerative colitis) is a major risk factor for the development of colorectal cancer. Patients with ulcerative colitis who ate a high-fiber, low-fat diet had lower inflammation and microbiota dysbiosis, as well as an increased abundance of beneficial microbes in the intestine.
Animal studies have revealed that dietary fiber-induced short-chain fatty acid butyrate synthesis is linked to enhanced anti-inflammatory, anti-tumor, anti-proliferative, and pro-apoptotic effects. These variables work together to lower the risk of intestinal tumorigenesis.
A high-fiber diet was found to benefit change gut microbiota composition and microbial metabolite levels, leading to an increase in dendritic cells and cytotoxic natural killer cells and subsequent induction of anti-tumor response in a lymphoma mouse model.
Long-term fiber consumption can sometimes raise cancer risk. A highly soluble, fermentable fiber diet, for example, has been shown to induce gut microbiota dysbiosis in insulin-resistant obesity-prone mice, increasing the risk of liver cancer development.
Excessive production of microbial fiber fermentation byproducts can raise the risk of cancer. Short-chain fatty acid acetate is one such by-product, which the liver uses in lipogenesis, resulting in non-alcoholic fatty liver disease and obesity.
A low-fiber diet can also decrease microbial carbohydrate fermentation and short-chain fatty acid synthesis, increasing the risk of colorectal cancer.
Carbohydrates
Many processed foods with easily digestible carbohydrates are found in the Western diet. Because of their capacity to raise blood glucose levels, these foods have a high glycemic index.
A low carbohydrate diet has been shown in studies to decrease Gram-positive bacteria and butyrate production in the small intestine and colon, resulting in less polyp formation. This type of low glycemic index carbohydrate also lowers DNA breakdown and colon cell proliferation.
Carbohydrate diets high in resistant starch have been shown to alter gut microbiota composition, resulting in greater formate and lactate production and reduced propionate production. These factors, taken together, lower the chance of pancreatic cancer.
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Consumption of dietary sugar carbohydrates such as fructose and sucrose has been linked to an increase in obesity, which in turn has been linked to an increase in the chance of colorectal cancer. Furthermore, fructose can increase fat accumulation in the liver, increasing the chance of non-alcoholic fatty liver disease and liver cancer.
Other nutritional elements
The Western diet is loaded with salty processed and ultra-processed goods. A high-salt diet has been shown to decrease the risk of certain cancers by inducing gut microbiota-mediated anti-tumor immunity, which is characterized by an increase in natural killer cells.
A high-cholesterol Western diet has been linked to dysregulated bile acids and indole derivatives, which can all raise the risk of liver cancer.
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Emulsifiers, which are commonly found in processed foods, are possibly harmful components of the Western diet. By disrupting gut microbiota and inducing low-grade inflammation, these components can raise the risk of intestinal carcinogenesis.
According to the current scientific literature, key components of the Western diet can greatly modulate gut microbiota composition, which can increase the risk of various types of cancer.
