Emulsifiers

Treat emulsifiers as a label signal that a food is ultra-processed, not as a proven gut toxin: the harm case in people is unproven, and the reasons to eat less ultra-processed food stand without it.

What they are and where you find them

Two examples are carboxymethylcellulose and polysorbate 80, found in ice cream, baked goods, sauces and plant-based milks. On an ingredient list they cluster near the end with the other cosmetic additives; soy lecithin, carrageenan and polysorbate 80 are common examples.

Under the NOVA classification, the widely used but disputed way of grading how processed a food is, a single cosmetic additive such as an emulsifier is enough to put a food in the ultra-processed group.^[1]

The case against them comes mostly from animals

In animal studies, emulsifiers erode the gut's mucus layer and promote inflammation, and emulsifiers have been linked to inflammatory bowel disease and metabolic syndrome. Most of this evidence comes from animal models, cell studies or observational cohorts, with very few human randomised trials.^[2]

The proposed chain runs like this: a thinned mucus layer lets fragments of gut bacteria cross into the bloodstream, where they trip the immune system's bacterial sensors, release inflammatory messengers and drive chronic low-grade inflammation throughout the body — the pathway implicated in insulin resistance, hardening of the arteries and neurodegeneration. In animals that chain is well demonstrated. In people it is much thinner than the mechanism implies.

Diets heavy in ultra-processed food are also linked to lower gut-bacterial diversity and fewer of the bacteria that maintain the gut lining, though that comes from a narrative review rather than a systematic one.^[3]

What the human trials found

A small, high-dose study. The best-controlled early trial fed seven adults a high dose of carboxymethylcellulose for eleven days. It did disturb the gut bacteria and deplete short-chain fatty acids, the compounds gut bacteria make from fibre. But its measures of gut leakiness, the inflammatory markers in the blood and a stool marker of gut inflammation were all unchanged.^[4]

A larger trial of five emulsifiers. A 2026 trial randomly assigned 60 adults to four weeks of one of five emulsifiers or none, and found the same absence of any inflammatory signal.^[5] The one exception was a permeability signal with carrageenan (below).

Both trials were short and small. They do not show emulsifiers are harmless over years, but they do mean the "leaky gut and inflammation" story is much thinner in people than in animals.

Carrageenan: contested

Carrageenan is an additive used in plant-based milks, processed cheese and deli meats. Laboratory colitis models use a degraded form of it (poligeenan), not the food-grade additive. But in the 2026 trial, people taking food-grade carrageenan had a modest rise in gut permeability compared with their own starting level — not compared with the group given no additive — with no change in inflammatory markers.^[6]

What to do

1. Use emulsifiers as a label signal. If the end of an ingredient list carries soy lecithin, carrageenan, polysorbate 80 or similar, the food is ultra-processed, whatever the front of the pack says.
2. Cut back on ultra-processed food for the reasons that are better established, starting with sugary drinks and processed meat; see Ultra-processed food.

Further reading

• Chassaing B et al. Randomized Controlled-Feeding Study of Dietary Emulsifier Carboxymethylcellulose Reveals Detrimental Impacts on the Gut Microbiota and Metabolome. Gastroenterology 2022.^[7]
• Wellens J et al. Effect of Five Dietary Emulsifiers on Inflammation, Permeability, and the Gut Microbiome: A Placebo-controlled Randomized Trial. Clin Gastroenterol Hepatol 2026.^[8]
• Rondinella D et al. The Detrimental Impact of Ultra-Processed Foods on the Human Gut Microbiome and Gut Barrier. Nutrients 2025.^[9]