Why Eating Fruit and Vegetable Scraps Can Boost Fibre and Cut Waste

New research by King's College London shows we should save our scraps, such as the skin on bananas and watermelons.

The study found many of the "root-to-tip" parts, which are usually discarded, contain higher levels of gut-boosting fibre than the bits we eat.

Fresh fruit and veg make up a third of the estimated 10 million tonnes of food wasted every year in Britain.

The study's Dr Rachel Gibson said: "People are discarding a significant portion of produce. These are parts of plants that could help address our fibre deficit."

Here, Grant Rollings reveals which kitchen scraps deserve to have a place on your plate.

What the research tells us about food waste and fibre

The King's College London team analysed the nutritional composition of 30 common fruit and vegetable parts that are typically thrown away - skins, leaves, stems, cores and seeds. Laboratory tests measured fibre, vitamin and antioxidant levels and compared them with the edible flesh of the same produce. In more than half of the items, the discarded portion contained at least twice the fibre of the part most consumers eat.

Britain discards roughly 10 million tonnes of food each year, according to the Department for Environment, Food & Rural Affairs (Defra). Fresh fruit and vegetables account for about one-third of that total. The waste not only represents a loss of money for households but also contributes to greenhouse-gas emissions when it ends up in landfill. By redirecting edible scraps into meals, the study suggests a dual benefit: improving public health through higher fibre intake and reducing the environmental footprint of our diets.

Why fibre matters for health

Dietary fibre supports a healthy gut microbiome, helps regulate blood sugar, and can lower cholesterol. The UK's National Health Service (NHS) recommends at least 30 g of fibre per day, yet surveys show the average adult consumes only about 18 g. This shortfall is linked to rising rates of constipation, colorectal cancer and cardiovascular disease. The King's College findings show that a modest addition of skins, leaves or seeds can close the gap without extra calories.

Carrot tops: A vitamin-C powerhouse

Carrot tops contain up to six times more vitamin C than the orange root itself and are rich in potassium, a mineral that helps lower blood pressure. The study measured vitamin C concentrations of 35 mg per 100 g in carrot leaves compared with 5 mg in the root. Potassium levels were 320 mg per 100 g in the tops versus 210 mg in the root. Because the leaves are tender when young, they can be used raw as a garnish, tossed into salads, or blended into a green-smoothie.

Banana skins: Antioxidant-rich and anti-inflammatory

Banana peels are often discarded, yet they hold a dense matrix of polyphenols that combat inflammation. The research found that the yellower the banana, the higher the antioxidant content, with a peak of 1.2 mg of total phenolics per gram of peel in ripe fruit. King's College London tested a banana-skin curry in its campus canteens, receiving positive feedback from students who reported a mild, pleasant bitterness balanced by spices. The peel can also be boiled to make a tea or dried and ground into a flour for baking.

Kiwi skins: Fibre and vitamin E in one bite

The fuzzy skin of a kiwi delivers 50 % more dietary fibre than the flesh, measured at 3.1 g per 100 g versus 2.0 g in the pulp. Vitamin E, an immune-supporting antioxidant, is 32 % higher in the skin (1.5 mg per 100 g) compared with the flesh (1.1 mg). Golden kiwis have a thinner skin, making them easier to eat whole, while the brown-furred variety works well when blended into a smoothie.

Butternut squash skin and seeds: A fibre-dense trio

An apple-sized portion of butternut squash skin and seeds supplies almost a third of the recommended 30 g daily fibre intake, providing roughly 9 g of fibre. The skin also contains vitamin C and the seeds are a source of healthy fats and zinc. The study suggests roasting the seeds with a pinch of sea salt for a crunchy snack, while the skin can be boiled and pureed into a base for pasta sauce.

Pineapple rind and core: High fibre, high caution

The outer rind and central core of pineapple hold five times more fibre than the sweet flesh, measured at 5.0 g per 100 g versus 1.0 g. They are also rich in vitamin C and manganese, an antioxidant mineral. Because the raw rind is extremely fibrous and spiky, the researchers recommend cooking it, boiling to make a nutrient-dense drink or blending into a smoothie after the flesh is removed.

Watermelon rind: Bread-level fibre in a summer fruit

Watermelon rind contains the same fibre content as a slice of wholemeal bread, about 2.5 g per 100 g. The rind is also a source of citrulline, an amino acid that may improve blood flow. The team experimented with juicing, pickling, and stir-frying the rind, finding that a quick sauté with garlic and chili yields a tender side dish that retains the fruit's natural sweetness.

Beetroot leaves: Nitrate-rich heart support

Green beetroot leaves are packed with nitrates, compounds that convert to nitric oxide and help dilate blood vessels, supporting heart health. Their iron content is comparable to spinach, at roughly 2.7 mg per 100 g. The study demonstrated that the leaves can be used raw in salads or blended into a pesto with garlic, olive oil and lemon juice for a vibrant sauce.

Broccoli stalks and leaves: Potassium and more

While most people eat only the florets, broccoli stems and leaves hold significant potassium, about 300 mg per 100 g, similar to a banana. They also provide fibre and vitamin C. Roasting the stems with a drizzle of olive oil, or blending the leaves into a creamy pasta sauce, adds texture and nutrition without waste.

How to incorporate scraps into everyday meals

Practical steps for home cooks include:

• Wash all produce thoroughly before using skins or leaves.
• Blanch tougher skins (pineapple, squash) for 2-3 minutes to soften.
• Dry and roast seeds (butternut, pumpkin) with a pinch of salt for a snack.
• Blend leafy tops into smoothies to mask any bitterness.
• Use a vegetable peeler to create thin ribbons of carrot tops for salads.

These techniques preserve nutrients while keeping preparation time short.

What the study means for policy and industry

Defra's waste-reduction targets aim to cut food waste by 20 % by 2025. The King's College findings give policymakers concrete data to support campaigns that encourage "root-to-tip" cooking in schools, hospitals and public catering. Some supermarkets are already trialing "whole-produce" sections where pre-cut skins and leaves are sold for ready-to-use recipes.

Nutritionists argue that incorporating scraps could help the UK meet its public-health goal of reducing diet-related disease burden. By increasing fibre intake without adding extra calories, the approach aligns with the NHS's Eatwell Guide recommendations.

Next steps for researchers and consumers

The research team plans to publish a detailed guide later this year, outlining specific recipes, cooking times and safety tips for each scrap type. They also intend to collaborate with food-technology companies to develop shelf-stable products, such as powdered carrot-top seasoning or banana-peel flour, that make waste-free cooking accessible to busy households.

Consumers can start today by checking the pantry for any edible parts that have been set aside, and by experimenting with the simple ideas above. As more people adopt a "root-to-tip" mindset, the collective impact could shave millions of tonnes off the national waste tally while improving public health.