A healthy diet is the cornerstone of a healthy gut microbiome. Many of us know that most processed foods offer little in the way of nutrition compared to the abundance of sugar, unhealthy fats, chemicals and additives they contain. Processed food have been linked to obesity, metabolic syndrome, cancer, heart disease and autism/neurological behavioral changes. New research is adding to the reasons you don’t want a diet high in processed food. Turns out our gut bacteria don’t like processed food either.
Processed foods are usually loaded with sugar and unhealthy fats such as hydrogenated oils or trans fat. With little nutrition, high in sugar, chemicals, additives and unhealthy fats, most processed foods provide our bodies and our gut microbiome little to run on. The gut microbiome relies on the fiber in our diet to ferment into butyrate for fuel.
A recent study showed that a two week change in diet has a notable impact on the gut microbiome. Researchers compared African-Americans eating a standard American diet to South Africans eating a traditional diet. The traditional diet is much higher in fiber while the Western diet is higher in industrial fats, refined carbohydrates, and animal proteins. Researchers gave the Africans a Western diet for two weeks, and the African-Americans a traditional African diet for two weeks. The gut microbiome changed dramatically in this short time. The healthy gut microbes that make butyrate increased 2.5 fold in the Americans on the African diet, whereas butyrate levels dropped by 50% when the Africans switched to the Western diet. Researchers also found greatly increased markers of intestinal inflammation after the two week Western diet while the inflammatory markers in the American guts dropped after two weeks on a traditional diet. (1) This study is a prime example of the impact that food has on our gut microbiome, dramatically impacting our overall health. Our microbiome is intimately tied to the food we eat and processed food is not only empty nutrition but it actually changes the balance of beneficial bacteria in the gut.
A diet high in processed foods exposes the gut bacteria to an array of chemicals, additives, fillers, binders, emulsifiers and more that irritate the gut lining. This irritation can lead to leaky gut or intestinal permeability. Tight junctions hold the bases of the cells that line the gut together so that food cannot enter the bloodstream. They do a great job when they are functioning properly but they can also lose integrity and become permeable under inflammation. The inflammatory cytokines that are released in response to irritation promote the loss of integrity of the tight junctions and promote the intestinal permeability in leaky gut. Research has shown how the chemical emulsifiers in processed food changes the diversity of the gut microbiome for the worse. Emulsifiers in food have been shown to promote bacterial translocation across epithelial cells. Now they have been shown to increase the inflammatory state of the gut. (2)
Researchers fed mice two very commonly used emulsifiers, polysorbate 80 and carboxymethylcellulsose, comparable to amounts found in processed foods. They found that mice that consumed the emulsifier had changes pro-inflammatory changes in the gut microbiota. The pro-inflammatory microbiota had an enhanced capacity to infiltrate the dense mucus layer that lines the intestine, which is normally harbors few bacteria. (2) The mucin layer houses the gut microbiome and acts as a barrier to the lining of the gut. Disturbances in the mucin layer affects the balance of beneficial bacteria and makes it easier for the gut to get inflamed.
Researchers found that these altered bacteria initiated chronic colitis in mice genetically prone to this condition, due to altered immune systems. While in mice with normal functioning immune systems, emulsifiers induced low-grade intestinal inflammation and metabolic syndrome. So even in healthy subjects with normal immune systems the emulsifiers caused inflammation that led to metabolic syndrome. (2) While this research needs to be reproduced in humans, in combination with the other strikes against processed foods this research is compelling.
The associations between several chronic diseases and processed foods have already been made. Add that to this new research which highlights the impact processed food has on the gut microbiome and it becomes clear that we need to make an effort to limit processed foods in our diets. A varied diet packed full of whole foods or processed foods with minimal ingredients that can be easily recognized is the best foundation for a healthy gut microbiome.
– Dr. Catherine Clinton
(1) O’Keefe, S. J. D. et al. Fat, fiber and cancer risk in African Americans and rural Africans. Nat. Commun. 6:6342 doi: 10.1038/ncomms7342 (2015).