Debunking the 'Toxic' Sugar Myth: A Dietitian's Perspective

“It’s a common myth,” says Dr Emily Leeming, a dietitian at King’s College London – and one that thrives on social media. The confusion, she says, often comes from people cutting out sugary foods and feeling better. But that can be because removing ultra-processed sweet treats improves the overall quality of a diet (making more room for wholefoods). Leeming says influencers who call sugar “toxic” often see it as inherently harmful – solely responsible for weight gain, poor blood sugar control and heart problems. But in controlled studies where calorie intake is kept the same, diets high in sugar don’t appear to worsen weight loss, metabolism or key health markers. “It’s not ideal nutritionally if you’re missing out on fruits, vegetables and whole grains,” Leeming says, “but sugar isn’t in itself directly harmful in that context.” So why does sugar have such a bad reputation? It’s partly because foods high in sugar are often high in calories, which, if you’re eating over your energy needs, can lead to increases in inflammatory markers. In addition, persistently high levels of blood sugar elevate advanced glycation end product (AGEs) toxins, which are linked to ageing and diseases. “It’s chronically elevated blood sugar levels where harm can be done, rather than simply eating a bit of added sugar now and again,” says Leeming. It’s also important to note that not all sweet foods are created equal. UK guidelines recommend no more than 30g a day of “free sugars” – those added to foods such as sweets and biscuits, but also found in fruit juice. Sugars in whole fruit, however, don’t count because their sugars are contained within the fruit’s structure, and come with fibre and micronutrients. “It makes me so upset when people say, ‘Oh, you shouldn’t have that fruit because it’s high in sugar,’” Leeming adds. “That is the wrong advice.”