Why do so many protein bars and snacks in the UK have warnings that say "excessive consumption may produce laxative effects"?

Published 2022-12-26

To reduce sugar content and lower calories, many protein bars swap out sugar for substitutes. A common class of sugar substitutes are polyols that are poorly digestible and can cause gastrointestinal side effects.

In an effort to reduce sugar content and lower the calories contained, many protein bars and snacks swap out sugar for sugar substitutes. A common class of sugar substitutes are polyols (or sugar alcohols - contrary to the name, they are not alcoholic/do not contain ethanol). Polyols are carbohydrates that occur naturally in certain fruits and veggies but can also be manufactured (even if they are natural, in packaged foodsvthey are often refined to much greater concentrations than would naturally be found). Polyols still contain some calories but not as much as sugar - this is because they are poorly digestible and therefore can cause gastrointestinal side effects including abdominal pain, bloating, gas, and even diarrhoea. Generally you can spot polyols on an ingredient list as they will often end in "ol" (e.g., malitol, sorbitol, xylitol, etc.).

Are polyols safe

Polyols are generally considered safe (and many consider them safer than artificial zero-calorie sweeteners like sucralose or aspartame). Polyols can possible help with weight control and diabetes as a replacement for sugar but you generally want to limit daily consumption due to the laxative effects (ideally not more than one protein bar per day containing high polyol content). There is also some research that suggests that some sugar alcohols can have negative impacts on the gut bacteria / microbiome. And not all polyols are created equally - Max Lugavere, the author of the New York Times best-selling book Genius Foods (that we highly recommend for anyone looking for science-based guidance on healthy eating) suggests that the polyols erythritol and xylitol are on the safer end of the spectrum.

What do you recommend

Whilst the research on sugar substitutes is constantly evolving, the general consensus is that polyols are better for you than sugar (the NHS in the UK recommends adults limit themselves to 90g of sugar per day). With that said, ideally we would look for low sugar (less than 5g of sugar/100g) bars and snacks that contain limited amounts or polyols or artificial sweeteners (or limit yourself to the number of bars you regularly consume with high sugar and/or sugar substitutes).

Some high protein snacks in our database that do not contain polyols and are low in sugar include:

For those with a sweet tooth looking to avoid high sugar (the NHS defines as >22.5g of sugar per 100g) as well as products with polyols or artificial sweeteners, a couple of options include:

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