Diabetes, heart attacks and cancer: a low-fibre diet increases the risk – here’s how to get the most out of fruit and vegetables

They are essential for the well-being of the digestive system and bowel function; they help reduce the risk of type 2 diabetes by regulating nutrient absorption, and they help lower the risk of cardiovascular disease and cancer. And unfortunately, we don’t eat enough of them. But above all, we throw away far too much of them, when in fact adopting a ‘root-to-tip’ approach to fruit and vegetable consumption could be a boon for our physical health as well as for the sustainability of the public health system and the environment. All at no cost. All we need to do is stop discarding the skins, stalks and seeds of our vegetables.

This simple approach is highlighted in a study by experts at King’s College London, led by Rachel Gibson (lead author Georgia Browne), published in the International Journal of Food Sciences and Nutrition. The study analysed 12 common types of fresh fruit and vegetables in the UK and concluded that the peelings were much richer in fibre in 10 out of 12 cases. In other words, we often throw away the most nutritious part of the food.

In the UK, only 4 per cent of British adults meet the recommended minimum daily intake of 30 grams of dietary fibre, consuming on average just 16.4 grams a day. At the same time, around 10 million tonnes of food are wasted every year, 36 per cent of which consists of fresh fruit and vegetables. And what about here? “The study provides interesting and relevant data, especially when we consider that fibre intake remains rather low amongst the Italian population too,” comments Daniela Martini , lecturer in Human Nutrition at the University of Milan . According to data from the latest national food consumption survey, IV SCAI, conducted by CREA, the usual fibre intake among adults aged between 18 and 64 is on average 18.6 grams per day. For just under nine in ten adults, the amount consumed is significantly lower than the nutritional target for prevention of at least 25 grams per day, as indicated by the Reference Intakes for Nutrients and Energy for the Italian population drawn up by the Italian Society of Human Nutrition”. In short: finding new ways to increase fibre intake is therefore an important issue, and making use of the edible parts of fruit and vegetables that we usually discard can make a valuable contribution, combining potential nutritional benefits with a reduction in food waste.

The study, carried out by a large team of experts from the Department of Nutritional Sciences at King’s College London and King’s Food, examined fruit and vegetables commonly used in the catering industry, such as pumpkin, peppers, broccoli, kiwis, pineapples and watermelon. In laboratory analyses, the team measured the total dietary fibre content of both the ‘root-to-tip’ components (skins, seeds, stalks) and the parts typically consumed. And it became clear that we throw away too many parts that are nutritionally ‘good’. Watermelon rind, for example, is said to contain 2.10 grams of fibre per 100 grams, roughly the equivalent of the fibre found in a slice of wholemeal bread. The rind and seeds of a pumpkin (known as ‘Nutterbut’) provide 9.25 grams per 100 grams, almost the same amount of fibre as a bowl of bran flakes. To give you an idea, just 100 grams of pumpkin skin and seeds (roughly the size of a small apple) could provide almost a third of the recommended daily intake of fibre. Something similar applies to pineapple – don’t throw away the core – whilst the opposite is true for broccoli: the florets are the part richest in fibre. However, broccoli stalks contain 28.4 per cent less fibre than the florets we usually eat: in this case, most people are already eating the part richest in fibre. “The variation in fibre content between the parts of food we consume and those that most people throw away was surprising,” Gibson commented in a statement from the organisation. The ‘root-to-tip’ components in our study accounted for between 25 per cent and 48 per cent of the product’s total weight. This means that people discard a significant proportion of the produce they buy. And these are parts of the plant that could help us make up for our dietary fibre deficiency.”

To understand how people might begin to incorporate these foods into their diet and to gain a better understanding of their attitudes towards them, researchers introduced a ‘root-to-tip’ menu at King’s College London, following a trial involving 40 people. It emerged that, in terms of perception, there is a stronger focus on nutritional wellbeing than on the environment, even though food waste contributes significantly to overall waste. But bear in mind: the effort to avoid waste and make use of fibre must begin at the food production stage and in the catering sector. “At home, we can do things like leave the skin on kiwis, use broccoli stalks in stir-fries or add pepper seeds to dishes,” says Gibson. “However, for real change aimed at reducing food waste and improving fibre intake on a large scale, it would be fantastic to see caterers and food producers explore what fruit and vegetable scraps are produced and look for ways to use them to improve the healthiness of meals.”