UPF and our microbiome

Listen to the very classic shoegaze band, Slowdive, while you read!

Today we are going to talk about how the daily food we eat impacts our microbiome. In contrast to assumptions that we eat mostly healthy if we’re conscious, 75% of the food in the US is ultraprocessed. Ultraprocessed foods (UPFs) aren’t as complicated as food stuffed full in harmful chemicals, but simply, by definition, foods that have have one or more ingredients that wouldn’t be found in a kitchen, like chemical-based preservatives and sweeteners like high fructose corn syrup. Also contrasting to the common knowledge that UPFs are just unhealthy junk food, there is less-unhealthy UPF such as whole grain bread and yoghurt. These food have low fat and sugar and have plenty healthy nutrients, but they reduce satiety, as the industrial processing alters their structure, making them softer and easier to eat and digest. This overrides natural fullness signals and cause people to overeat. 

Some common additives in UPF include emulsifiers, artificial sweeteners, preservatives, and colorants & flavor enhancers. Emulsifiers might sound complicated, but making homemade mayo involves the emulsifying process! From egg yolks to artificial chemicals, these thickening agents could strengthen dough crumb texture, lengthen the shelf life of cream-based foods, and act as gelling agents; which make them great for pastries. Artificial sweetners are also predominant in zero-calorie foods, and they could be sweeter than sugar, so minimal amount may be added to them. While giving sweetness, they don’t raise blood sugar levels and don’t cause cavities. Preservatives make foods last longer by controlling food spoiling from microorganisms, and is cruical in a variety of foods to ensure safety.

UPFs are characterized by lower levels of beneficial bacteria like Akkermansia muciniphila and Faecalibacterium prausnitzii, and an increase in pro-inflammatory microorganisms. They are also low in prebiotic fibers needed to produce SCFAs. Specifically,  Short-Chain Fatty Acids (SCFAs) synthesis could be largely affected with the decrease of pro-inflammatory cytokine production. They are important as they are crucial systemic mediators that influence metabolism, immune function, and homeostasis. Besides this, immune modulation, such as epigenic mechanisms that promotes anti-inflammatory effects primarily through the suppression of NFkB.

Our gut is lined by a thick mucus that helps protect us against harmful bacteria, as they don’t get into the blood vessels directly. As UPFs are low in fiber, fiber deprivation could lead to the proliferation of mucus-degrading species such as Akkermansia muciniphila and Bacteroides caccae, and a decrease in fiber-degrading bacteria such as Eubacterium rectale and Bacteroides ovatus in the mucus layer. Specifically, Emulsifiers used in UPFs can prevent the growth of beneficial bacteria with anti-inflammatory properties, which can increase gut permeability and bacterial translocation directly into the bloodstream. Recent research points towards that food emulsifiers can increase intestinal permeability, alter microbiota composition, promote E. coli translocation across the epithelium and causing gut inflammation.

Irritable bowel syndrome (IBS) is a condition in the stomach that causes cramping, belly pain, bloating, gas, and diarrhea. It is often defined by visceral hypersensitivity, where the nerves in the gut overreact to normal sensations like gas or digestion. This condition is impacted by changes in the gut microbiome, which is relevant to eating UPFs. Research has shown that an 8% higher risk of IBS was associated with every 10% increment of UPF consumption. Specifically, additives as well as high-FODMAP ingredients in many UPFs are known to trigger IBS symptoms and low fiber content in a diet high in UPFs. 

Reducing the intake of ultraprocessed foods could mitigate early-onset colorectal cancer. Common emulsifiers in UPFs like Carboxymethylcellulose (CMC) and Polysorbate-80 act like soap on the gut lining, washing away the protective mucus layer. This allows bacteria to touch the colon wall, creating a state of chronic inflammation that fuels tumor growth. Further, food dyes like Red 40 (Allura Red), have been shown to incite a concealed tissue-specific inflammation in the colon and rectum, laying the groundwork for colorectal carcinogenesis, especially with a high-fat diet. There are some exceptions in UFPs in this case, such as yoghurt in women, as theircalcium and probiotics might counteract some of the processing risks.