E-numbers / Sweeteners / E421
also: D-mannitol · Manna sugar
A naturally occurring sugar alcohol used to sweeten and bulk out foods without raising blood sugar quickly. Causes digestive effects in larger amounts.
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Sweeteners (Sorbitol, Xylitol, Aspartame, Mannitol, Acesulfame K), Gum Base, Humectant (Glycerol), Thickener (Gum Arabic), Flavourings, Emulsifier (SOYA Lecithin), Glazing Agent (Carnauba Wax), Antioxidant (BHA)
Doses above roughly 10 to 20 grams in one sitting can cause bloating, cramping and diarrhoea.
66
of the 43,325 UK supermarket foods we checked declare E421 in their ingredients
That is 0.2%, counted by its code or its name.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
Why it’s worth knowing. Doses above roughly 10 to 20 grams in one sitting can cause bloating, cramping and diarrhoea. UK and EU law requires a laxative warning on any food where polyols make up more than 10% of the product.
Mannitol is a polyol (sugar alcohol) found naturally in mushrooms, seaweed and some fruits such as olives and pineapples. Commercially it is produced by reducing fructose, either chemically or by fermentation. It has about 60% of the sweetness of table sugar and provides roughly 2.4 kcal per gram, compared with 4 kcal for sugar.
It provides sweetness and bulk without the sharp blood-glucose spike of sucrose, because it is absorbed slowly and incompletely from the small intestine. The unabsorbed portion passes to the large intestine, where gut bacteria ferment it, producing gas. This makes it useful as a low-glycaemic sweetener, a bulking agent in pressed tablets (it has a cool, pleasant mouthfeel as it dissolves), and as an anti-caking agent in powdered products.
Diabetic confectionery, sugar-free chewing gums, breath mints, hard-boiled sweets, compressed tablet supplements and some pharmaceutical lozenges. Occasionally used in ice cream and chocolate-flavoured coatings marketed as reduced-sugar. On a UK label it appears as Mannitol or E421.
Because mannitol is only partially absorbed in the small intestine, a meaningful dose draws water into the gut by osmosis and is fermented by colonic bacteria, producing gas. This produces a well-documented laxative effect. EU food law sets a threshold: any food where added polyols exceed 10% of the product must carry the statement 'excessive consumption may produce laxative effects'. In clinical studies, doses of 10 to 20 grams in a single sitting reliably trigger bloating, cramping and loose stools in most adults. People with irritable bowel syndrome are more sensitive at lower doses because mannitol is one of the fermentable carbohydrates (FODMAPs) linked to IBS symptom flares.
Single doses above 10 to 20 g produce osmotic diarrhoea in most adults; mannitol is absorbed more slowly and less completely than other polyols, making its laxative threshold lower per gram than sorbitol.
EU Regulation 1333/2008 (Annex II) requires the label statement 'excessive consumption may produce laxative effects' on foods where added polyols together exceed 10% of the finished product.
Mannitol is classified as a high-FODMAP fermentable sugar alcohol. In people with IBS, dietary restriction of mannitol significantly reduces abdominal pain and bloating scores.
Mannitol is not metabolised via insulin-dependent pathways in the same way as glucose or sucrose, so it produces a much smaller post-meal blood glucose rise. This makes it relevant to products marketed to people with diabetes. It is also poorly utilised by the oral bacteria that produce tooth-decay acids, so it is considered non-cariogenic (non-tooth-decaying). These properties are well established and not disputed.
Mannitol has a glycaemic index near zero and does not stimulate significant insulin secretion, making it suitable for diabetic food products under existing EU nutrition labelling rules.
Polyols including mannitol do not promote tooth demineralisation and are recognised as tooth-friendly by dental research bodies; the mechanism is that oral bacteria cannot readily ferment them to the organic acids that dissolve enamel.
People with irritable bowel syndrome (IBS) following a low-FODMAP diet are advised to limit or avoid mannitol, as it is a recognised FODMAP trigger. Anyone sensitive to polyols in general should check labels for Mannitol or E421. Those with fructose malabsorption may also react, since mannitol is derived from fructose.
The digestive effect of mannitol is one of the better-documented dose-response relationships in food additive science: the mechanism is straightforward osmotic chemistry and the laxative threshold is real and repeatable in studies. The effect is genuinely relevant for anyone eating multiple mannitol-containing products in a day, particularly sugar-free confectionery and gums. The FODMAP link is well supported in clinical trials for IBS patients. For people without gut sensitivities eating typical food amounts, the absorbed fraction is metabolised normally and the unabsorbed fraction behaves like other fermentable fibres. There are no credible carcinogenicity, endocrine or toxicity signals in the published record at food-relevant doses.
No. Mannitol is an approved food additive in the UK under the Great Britain Register (FSA) and in Northern Ireland under assimilated EU Regulation 1333/2008. It is permitted across a wide range of food categories.
UK and EU law requires any food where added polyols (including mannitol) make up more than 10% of the product to carry the statement 'excessive consumption may produce laxative effects'. This is because mannitol is only partially absorbed and at doses above roughly 10 to 20 grams can cause loose stools and cramping. That threshold can be reached quickly with sugar-free confectionery.
Sugar-free and diabetic sweets, chewing gum, breath mints, hard-boiled reduced-sugar confectionery, some dietary supplement tablets (where it serves as a bulking filler), and pharmaceutical lozenges. It is less common in mainstream branded food than sorbitol or maltitol.
Yes. Commercial mannitol is produced from fructose (plant-derived sugars) by chemical reduction or fermentation. No animal-derived ingredients are involved in its manufacture.
Last reviewed: 20 June 2026
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