E-numbers / Thickeners & emulsifiers / E434
also: Polyoxyethylene sorbitan monopalmitate · Tween 40 · POE (20) sorbitan monopalmitate
A synthetic emulsifier made from sorbitol, fatty acids and ethylene oxide, used to blend oils and water in processed foods.
Scan a barcode to check a food for polysorbate 40. NutraSafe Pro · £6.99/month · iOS
Regular intake of polysorbates may disrupt gut bacteria and weaken the gut lining.
Why it’s worth knowing. Regular intake of polysorbates may disrupt gut bacteria and weaken the gut lining. A human clinical trial found emulsifiers in this family altered gut microbiome composition in healthy adults.
Polysorbate 40 (polyoxyethylene sorbitan monopalmitate) is a synthetic emulsifier produced by reacting sorbitol with palmitic acid and then treating the product with ethylene oxide. It belongs to the polysorbate family, which also includes the more common polysorbates 20, 60 and 80. It is a viscous, water-miscible liquid.
It acts as an emulsifier by reducing surface tension at oil-water interfaces, allowing them to form stable, uniform mixtures that would otherwise separate. It also acts as a solubiliser and dispersant, helping oil-soluble vitamins and flavourings dissolve evenly in water-based products.
Used in ice cream and frozen desserts to improve texture and prevent ice crystal formation, in baked goods to extend shelf life and improve crumb structure, in salad dressings, sauces, and some dairy desserts. Less widely used than polysorbate 80, it appears on ingredients lists as 'polysorbate 40' or 'E434'.
The polysorbate family has been studied for effects on gut bacteria and the intestinal lining. Animal studies showed polysorbate 80 reduced populations of bacteria associated with gut health and increased bacteria with pro-inflammatory properties. A 2025 human placebo-controlled trial confirmed that polysorbate 80 consumption altered gut microbiome composition in healthy adults compared to a control group. Because polysorbate 40 shares the same structural class and mechanism, researchers treat the findings as relevant across the group, though most direct data comes from polysorbate 80.
In a human placebo-controlled randomised trial, sixty healthy participants who followed an emulsifier-free diet were then given polysorbate-80 or a control; microbial composition was affected by treatment, with pro-inflammatory shifts observed.
Direct exposure of human gut microbiota samples to polysorbate 80 decreased Bacteroides dorei and Akkermansia, taxa associated with anti-inflammatory potential, while increasing microbial groups with pro-inflammatory capacity.
Maternal polysorbate 80 intake in animal models retarded intestinal development, disrupted the intestinal barrier, and caused low-grade intestinal inflammation in offspring.
Some studies suggest polysorbates can increase mucus layer permeability, potentially allowing bacteria to come into closer contact with the gut wall. This has been proposed as a mechanism linking emulsifier intake to low-grade intestinal inflammation. The evidence is strongest in animal and in-vitro models; the clinical significance in humans at typical food-exposure levels is not yet established.
Polysorbate 80 increased mucus viscosity with smaller pore sizes, which could accelerate bacterial movement through the mucus layer and modify interactions between the bacteria and the gut lining.
EFSA reviewed the polysorbate group in 2015, including E434. The key long-term study in rats found no adverse effects at doses far above realistic dietary exposure, and EFSA set a group acceptable daily intake for polysorbates collectively. No carcinogenicity signal was identified in the regulatory review.
EFSA's ANS Panel set a group ADI of 25mg/kg body weight per day for polysorbates 20, 40, 60, 65 and 80 collectively, based on a rat carcinogenicity study where the no-observed-adverse-effect level was 2500mg/kg body weight per day.
People with inflammatory bowel conditions such as Crohn's disease or ulcerative colitis may wish to reduce emulsifier intake given the mechanistic gut-lining evidence, though this remains a precautionary position rather than a clinical guideline. Look for 'polysorbate 40' or 'E434' on the ingredients list.
The gut microbiome research on polysorbates is active and growing. Most of the direct experimental data comes from polysorbate 80 rather than polysorbate 40 specifically, and researchers typically discuss a class effect. A 2025 human trial did show microbiome changes in healthy people given polysorbate 80 at doses achievable through diet, which moves this beyond animal-only evidence. How much of this translates to real-world harm, and at what intake level, is not yet resolved. The regulatory ADI is based on traditional toxicology endpoints and was set before the gut microbiome evidence emerged; regulators had not re-opened the file as of mid-2026. This is a genuinely open question in food science.
No. E434 is authorised for use in the UK under assimilated EU Regulation 1333/2008 and is listed on the FSA's approved-additives register. It has not been restricted or banned.
Research on the polysorbate family, particularly polysorbate 80, shows effects on gut bacteria composition and intestinal permeability in animal studies and at least one human trial. Polysorbate 40 shares the same chemical class and mechanism. The clinical significance at typical food-exposure levels is not yet established, and the evidence is stronger in animal models than in humans.
E434 appears in some ice creams, frozen desserts, baked goods, salad dressings and emulsified sauces. It is less common than polysorbate 80 (E433). It will appear on the label as 'polysorbate 40' or 'E434' in the ingredients list.
The raw material is palmitic acid, which can be derived from either plant sources (typically palm oil) or animal fat. The final polysorbate 40 molecule does not itself contain animal protein. Some vegans avoid it due to potential animal-derived feedstocks and the environmental concerns around palm oil, but it is not universally considered non-vegan. Check with the manufacturer if this matters to you.
Last reviewed: 20 June 2026
It's the only app that does thisUKJaneK
You Need This AppGmac2005
Best AppGK getting skinny UK App Store reviews
NutraSafe reads the label and puts every additive into plain English, with the source, right in the app.
NutraSafe Pro · £6.99/month · iOS
