'Root-to-tip' eating could help to boost dietary fibre whilst also helping to reduce food waste.
Most of us routinely discard the peels, skins, stalks, and seeds of fruits and vegetables when preparing meals. But new research from King's College London suggests these scraps could be a valuable source of dietary fibre, offering potential benefits for both public health and the environment.
Published today in the International Journal of Food Sciences and Nutrition, the study analysed 12 common types of fresh produce in the UK. It found that 'root-to-tip' components that are usually thrown away, including peels, skins and stalks, contained significantly higher levels of dietary fibre than the portions we normally eat in 10 out of 12 cases.
In the UK, only 4% of adults meet the recommended minimum daily intake of 30g of dietary fibre, consuming an average of just 16.4g per day. At the same time, approximately 10 million tonnes of food is wasted annually, with fresh fruits and vegetables representing 36% of this.
Dietary fibre is important for our health - it plays a crucial role in digestion, helps reduce the risk of type two diabetes and heart disease, and promotes feelings of fullness. High-fibre diets have been linked to a reduced risk of cardiovascular disease, certain cancers, and premature mortality.
Experts from the Department of Nutritional Sciences and King's Food looked at the total dietary fibre content of fruits and vegetables commonly used in foodservice settings - including butternut squash, bell peppers, broccoli, kiwi fruit, pineapple and watermelon. They compared the fibre content found in the peels, skins and stalks to that found in the parts we typically consume.
In 10 out of the 12 fruits and vegetables, the 'root-to-tip' components contained more fibre than the commonly consumed parts. For example:
- Watermelon rind contained 2.10g of fibre per 100g - roughly equivalent to the fibre in a slice of wholemeal bread.
- Butternut squash skin and seeds contained 9.25g per 100g - nearly as much fibre as a bowl of bran flakes.
- Pineapple skin and core contained 453.7% (five times) more fibre than the flesh. Eating just the skin and core from a pineapple could provide as much fibre as eating five portions of the flesh alone.
- However, broccoli stalks contained 28.4% less fibre than the florets we typically eat - so in this case, most people are already eating the more fibre-rich part.
Dr Rachel Gibson, Reader in Nutrition & Dietetics at King's and project lead, said: "The variation in fibre content between the parts of the food we consume and that most throw away was striking. The 'root-to-tip' components in our study represented between 25% and 48% of the total weight of the produce. That means people are discarding a significant portion of the produce we buy. And these are parts of the plant that could help address our dietary fibre deficit."
Dr Balazs Bajka, Senior Lecturer in Nutritional Sciences, who led the laboratory fibre testing in the study, said: "Importantly, this is not about encouraging people to eat '100g of butternut squash skin and seeds' to increase fibre intake. Rather, by making better use of the often-overlooked parts of fruits and vegetables as part of everyday meals, we have an opportunity to increase dietary fibre intake in a simple and sustainable way."
How could eating 'root-to-tip' work in practice?
To understand how root-to-tip eating could work in practice, the team adopted a 'Living Laboratory' approach across King's Food venues, launching a root-to-tip menu with dishes that use more of the plant.
Before it was launched, they tested the concept on a focus group of 40 King's staff and students. Feedback from participants revealed important barriers to root-to-tip eating, including a "mental discomfort" about eating these items, concerns about digestibility, and a lack of nutritional information online, particularly on social media, where trends rapidly change and credibility is unclear.
Georgia Browne, Research Assistant at King's and lead author of the study, said: "Interestingly, participants viewed nutritional benefits - particularly fibre content - as a stronger motivator than environmental sustainability when considering whether to adopt 'root-to-tip' eating."
The team emphasises that 'root-to-tip' eating doesn't require dramatic dietary changes, just simple modifications to food preparation. At home, this might mean leaving skins on kiwi fruit, using broccoli stalks in stir-fries, or incorporating bell pepper seeds into dishes. They say that changes are required at the food manufacturing stage or at the places we go to eat out for tangible results on health at a population level.
This isn't about perfection and this isn't about forcing people to eat unpalatable food - it's about recognising the nutritional value in components we've been conditioned to discard, which is exactly why we trialled the root-to-tip menu at King's. Even small steps towards using more of the plant can have cumulative benefits for health and the environment.
Dr Rachel Gibson
The researchers hope that future studies will look to better understand how 'root-to-tip' eating can be practically and safely implemented across diverse populations and settings.
