E-numbers / Sweeteners / E966
also: lactit · lactositol · lactobiosit
A sugar alcohol made from lactose, used as a low-calorie bulk sweetener. Causes a laxative effect at higher intakes.
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Eating several lactitol-sweetened products in one day can cause bloating, loose stools, or diarrhoea.
1
of the 43,325 UK supermarket foods we checked declare E966 in their ingredients
That is under 0.1%, 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. Eating several lactitol-sweetened products in one day can cause bloating, loose stools, or diarrhoea. The effect is dose-dependent and more pronounced in people with irritable bowel syndrome.
Lactitol (E966) is a sugar alcohol (polyol) produced by hydrogenating lactose, the sugar found in milk. It has roughly 40% of the sweetness of table sugar and provides about 2 kcal per gram, compared with 4 kcal for sugar. Despite being derived from lactose, lactitol itself does not contain intact lactose and does not raise blood glucose significantly because it is poorly absorbed in the small intestine.
Lactitol adds bulk and sweetness to food without the same caloric or glycaemic impact as sugar. Because it is not fully absorbed in the small intestine, it passes into the large intestine where gut bacteria ferment it. This fermentation produces short-chain fatty acids and gas, and draws water into the bowel. At low doses this is unremarkable; at higher doses it acts as an osmotic laxative, which is why lactitol is also sold as a licensed medical laxative at therapeutic doses.
Found in sugar-free and reduced-calorie versions of confectionery (chocolate, boiled sweets, chewing gum), biscuits, ice cream, and baked goods. Also used in some diabetic-targeted foods. On a label it appears as 'lactitol', 'E966', or listed under 'polyols' or 'sugar alcohols' in the nutrition panel. EU and UK law requires any food containing polyols to carry the advisory statement: 'excessive consumption may produce laxative effects'.
Lactitol's laxative action is the most consistent and well-documented effect. Because most of it is not absorbed in the small intestine, it draws water into the bowel and is fermented by colonic bacteria, loosening stools. The dose at which this becomes noticeable varies between individuals, but intakes approaching 20g per day from food have been associated with digestive symptoms in some people. At doses of 20-30g per day, the effect is reliable enough that lactitol is used as a prescription laxative.
A systematic review of polyols found that lactitol and other poorly absorbed sugar alcohols produce dose-dependent gastrointestinal symptoms including bloating, flatulence and loose stools, with substantial individual variation in threshold.
At a starting dose of 20g per day, lactitol produces a reliable laxative effect with minimal additional side effects; doses above 30g per day cause diarrhoea in most adults.
Unlike sucrose, lactitol raises blood glucose and insulin levels only minimally, because very little is absorbed intact through the intestinal wall. This makes it attractive in foods aimed at people managing blood sugar. However, the fermentation products (short-chain fatty acids) do contribute some calories and metabolic signals; lactitol is not metabolically inert.
Lactitol and other sugar alcohols produce a significantly lower glycaemic and insulinaemic response compared with sucrose, supporting their use as partial sugar replacements in dietary management of blood glucose.
Lactitol is not fermented by the oral bacteria that cause tooth decay, so it does not promote dental caries. Regulatory authorities in the UK and EU permit lactitol-containing foods to carry a 'does not promote tooth decay' claim under specific conditions.
Polyols including lactitol are not metabolised by Streptococcus mutans and other cariogenic oral bacteria, so they do not lower plaque pH to the levels that demineralise enamel.
Lactitol is produced from lactose (milk sugar), but in the finished ingredient essentially all of the lactose is converted to lactitol. Residual lactose levels are typically very low. Nonetheless, specialist dietary advice for people with galactosaemia (a rare inherited metabolic disorder affecting galactose processing) generally recommends avoiding lactitol-containing products as a precaution, because the galactose content of the residual lactose cannot always be guaranteed to be zero.
People with galactosaemia are typically advised to avoid lactitol as a precaution because it is derived from lactose and may contain trace galactose residues.
People with irritable bowel syndrome (IBS) or other functional gut disorders are often more sensitive to polyols and may experience bloating or diarrhoea at intakes well below the general population threshold. People with galactosaemia should avoid lactitol as a precaution due to its lactose-derived origin. Look for 'lactitol', 'E966', or 'polyols' / 'sugar alcohols' on the ingredients list. The mandatory advisory statement 'excessive consumption may produce laxative effects' also indicates polyol content.
Lactitol is one of the more straightforwardly characterised polyol sweeteners. Its laxative mechanism is well understood, dose-dependent, and reversible. There is no IARC carcinogen classification, no EU or UK ban, and no endocrine disruption signal. The science is not contested: the digestive effects are real, predictable, and acknowledged on the label by law. The practical question is one of cumulative dose across a day's eating. Someone who consumes two or three sugar-free products in a single sitting may cross the threshold that causes symptoms, even if each product individually seems a modest amount.
No. Lactitol (E966) is approved for use in the UK under the FSA approved-additives list and the assimilated EU Regulation 1333/2008. It is permitted as a sweetener in a range of reduced-sugar and sugar-free foods.
The threshold varies between individuals, but intakes approaching 20g per day from all sources can cause digestive symptoms including bloating, loose stools or diarrhoea in some people. At 20-30g per day the laxative effect is reliable enough that lactitol is used as a medical laxative. People with IBS may react at lower doses. Any food containing lactitol must by law carry the warning 'excessive consumption may produce laxative effects'.
Lactitol is most common in sugar-free confectionery (chocolate, boiled sweets, chewing gum), reduced-calorie biscuits, ice cream, and bakery products. It also appears in some diabetic-targeted foods and dietary supplements. On the label it appears as 'lactitol', 'E966', or within a 'polyols' or 'sugar alcohols' declaration in the nutrition information.
This depends on the certifying body. Lactitol is derived from lactose, which comes from milk, making it not suitable for a dairy-free diet. Most vegan organisations class it as non-vegan because of this milk-derived origin. Check product certification if this matters to you.
Last reviewed: 20 June 2026
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