Why smoothies are worse for you than raw fruit – and the healthier alternatives

Fruit juices and smoothies are often seen as health foods. But a new government report has said they contain the worst kinds of sugars for causing weight gain and tooth decay. While many of us know we should cut down on sugar, dietitians and doctors increasingly split the sweet stuff into two categories – and one may be worse for our health than the other. The bad kind is called free sugars, while the not-so-bad kind is naturally found in whole fruits and vegetables, called intrinsic sugars. What are free sugars? In whole fruits, this intrinsic sugar is present inside the plant cells. Free sugars, on the other hand, have been extracted from plant cells and concentrated. Free sugars include any refined sugar that has been added to food, usually sourced from sugar cane or corn – as well as sources that might seem more “natural”, like honey or agave syrup. Many studies have found that people who consume more of these added free sugars tend to be more overweight and children have more tooth decay. On the other hand, people who eat more fruit and vegetables generally have better health. As a result, official health advice is to focus on limiting free sugars. They should give us no more than 5 per cent of our calories. In the UK we eat about twice that, on average. The big question is how advisable it is to consume sugar from fruits if they have been processed in some way. That’s the subject of the new report from the Government’s Scientific Advisory Committee on Nutrition (SACN).If fruit has been blended, crushed, pressed or sieved – as is the case with shop-bought or home-made smoothes or juices – that releases free sugars. “Where the cellular structure is likely to be damaged, all the sugars are defined as free sugars,” say the authors. But if fruit or vegetables have just been chopped, diced or grated, that leaves the cellular structure largely intact. Smoothies can still be one of your five a day. (Photo: Alexander Spatari/Moment RF/Getty) The importance of chewing Exactly why free sugars that have been released from plant cells are worse for us is up for debate. They promote tooth decay in children, but this is less of a concern for adults. While the report does not answer that question, a common claim is that free sugars raise blood sugar levels quickly. But a recent small trial contradicted this theory, showing that whole fruits and blended smoothies that contain the same amount of sugar raised people’s blood sugar levels over similar time scales. Dr Carrie Ruxton, a dietitian at fitness centre SALT St Andrews, says whole fruits must release free sugars when they are chewed up and digested by stomach acid: “Nobody swallows it whole.” But that chewing process could be advantageous, because it slows down the rate at which people consume the fruit, giving time for the body to release hormones that promote fullness. So people tend to eat less overall. “I think it’s more to do with the fact that you’re chewing it, and that takes time,” says Ruxton. Another advantage of whole fruit is that the sugar there comes packaged with other nutrients, such as fibre, vitamins and minerals. Fibre also boosts feelings of fullness. In other words, a home-made smoothie where nothing is taken out – made, for instance, from a blended banana and some berries – would retain those nutrients, although the blending would still release free sugars. On the other hand, a fruit juice – where the fruit’s liquid has been extracted – will have lost some of the fibre. No need to cut out juice and smoothies If people are concerned about the blending process releasing free sugars, and don’t like whole fruit, they could just chop up the produce into a fruit salad. The SACN report is clear that this does not release significant free sugars. Another issue with smoothies and juices, especially if shop-bought, is that they can be easy to overconsume, says Professor Ciaran Forde, a food scientist at Wageningen University & Research in the Netherlands. “If I consume an apple I know I have had the nutrient intake of a single apple,” he says. “But if I drink a litre of apple juice, I don’t have an indication of how many apples I have consumed. So, the potential to consume a large amount of sugar could be a problem.” But juices and smoothies should not be completely banned from our diets – just taken in moderation. NHS advice is that they can make up one of the recommended five portions of fruit and vegetables a day. “Either whole fruits or whole-fruit juices is likely to have a largely positive effect on nutrient intakes,” says Forde. “In a population that doesn’t consume enough fruit and vegetables, finding novel ways to increase [them] and meet consumers within their own eating pattern is probably a good thing.”