how do ultra processed foods harm your gut?

Not all foods are created equal, and one group in particular has been getting a lot of attention lately: UPFs, or ultra processed foods.

So what are they exactly, and why should you care?

What are UPFs?

Ultra processed foods are items that go through lots of industrial processing and often contain ingredients you would not find in a home kitchen such as preservatives, emulsifiers, flavourings and artificial sweeteners. They are made to last longer on shelves and enhance taste. Think: packaged snacks, fizzy drinks, instant noodles, and ready meals.

Why are UPFs bad for the gut?

Your gut is home to trillions of microbes that support digestion, nutrient absorption, and even your immune system. When everything is in balance, these microbes produce protective compounds and help keep inflammation at bay. But research shows that eating lots of UPFs can change both the composition of the microbiome and the way it functions. This shift may set the stage for long-term health issues, starting in the gut but spreading throughout the body.

Here’s how:

• They disrupt the microbiome
  UPFs are full of additives, preservatives, and emulsifiers. Studies show these can upset the balance of gut bacteria, encouraging the growth of strains linked to inflammation while reducing overall diversity. A less diverse microbiome means fewer protective microbes doing their job to keep your gut healthy.
  

• They reduce SCFAs
  Normally, your gut microbes break down fibre to produce short chain fatty acids (SCFAs). These are powerful compounds that strengthen the gut lining, help regulate inflammation, and protect against disease. Research has found that eating UPFs lowers SCFA production, which weakens this natural defence system.
  

• Sweeteners can weaken the gut barrier
  Some studies on healthy adults have shown that sweeteners like sucralose and aspartame can harm gut cells at high levels. Even at lower levels, they may make the gut lining more “leaky” by reducing the proteins that keep it intact. A leaky gut barrier can let more unwanted substances slip through, which can trigger immune responses and inflammation.
  

• They are high in saturated fat
  UPFs often contain lots of added fat to improve flavour and texture. Eating too much of these fats has been linked to higher levels of harmful bacterial toxins in the blood, changes in insulin sensitivity, and fat build-up in the liver and other tissues. Over time, this does not just affect the gut, but also increases the risk of chronic conditions like obesity, diabetes, and heart disease.
  
  

What Can You Do To Support Your Gut?

In today’s world, it is almost impossible to avoid processed foods altogether. From quick snacks to convenience meals, they are part of everyday life. That is why focusing on supporting your gut can make such a difference.

One effective way to do this is with a synbiotic which combines probiotics and prebiotics.

• Probiotics are live, beneficial microbes that help restore balance in the gut. Certain strains, such as Lactobacillus rhamnosus and Bifidobacterium longum, have been studied for their ability to reduce gut inflammation, support the gut lining, and increase microbial diversity. These functions are particularly important when the microbiome has been disrupted by a diet that is lower in fibre and higher in processed ingredients.
  

• Prebiotics are non-digestible fibres that act as food for probiotics and other beneficial bacteria. One of the best studied is fructooligosaccharides (FOS). FOS selectively stimulates the growth of good bacteria like Bifidobacteria, boosting their ability to produce short chain fatty acids (SCFAs). SCFAs play a crucial role in nourishing the cells of the intestinal lining, regulating inflammation, and keeping the gut environment stable.
  

References

Rondinella, D., Raoul, P. C., Valeriani, E., Venturini, I., Cintoni, M., Severino, A., Galli, F. S., Mora, V., Mele, M. C., Cammarota, G., Gasbarrini, A., Rinninella, E., & Ianiro, G. (2025). The detrimental impact of ultra-processed foods on the human gut microbiome and gut barrier. Nutrients, 17(5), 859. https://doi.org/10.3390/nu17050859

Spiller, A. L., da Costa, B. G., Yoshihara, R. N. Y., Nogueira, E. J. Z., Castelhano, N. S., Santos, A., De Freitas, M. B., Magro, D. O., & Sassaki, L. Y. (2025). Ultra-processed foods, gut microbiota, and inflammatory bowel disease: A critical review of emerging evidence. Nutrients, 17(16), 2677. https://doi.org/10.3390/nu17162677