In an era when sugar is widely seen as enemy No 1, sugar-free drinks and treats, sweetened with low-calorie additives, promise guilt-free sweetness. Some people deliberately choose low-sugar options in the hope of losing weight or managing diabetes; others just enjoy the taste. But even if you aren’t seeking them out, it’s hard to avoid artificial sweeteners. In 2021, researchers looked at foods for sale in Hong Kong and found that sweeteners were present not just in products where you would expect them, such as sugarless chewing gum, but also in salad dressings, breads, instant noodles and many crisps. Sweeteners have become such a common part of our diet that environmental scientists have started looking for traces of them – particularly acesulfame potassium, which passes through the body largely undigested – as a marker for human waste in lakes and rivers.