Many people routinely peel their potatoes or apples without considering the nutritional cost. Nutritional scientist Professor Tim Spector warns that discarding the skins means missing out on essential nutrients found predominantly in the outer layers of fruits and vegetables.
According to Professor Spector, the skins of apples, kiwis, potatoes, and other produce are rich in polyphenols—natural compounds that act as antioxidants, reduce inflammation, and enhance the body’s immune defenses. Research suggests these plant-derived polyphenols may have anti-aging effects and potential anticancer properties.
In his Channel 4 series What Not to Eat, Tim explains that polyphenols provide numerous health benefits: “To peel or not to peel, that is the question, and for me it is generally to avoid peeling. These defense chemicals that plants produce are concentrated in the skin and help our gut microbes flourish, boosting immunity in many ways.”
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He points out that apple skins contain up to 30 times more polyphenols than the flesh alone. Similarly, kiwi skin offers 50% more fibre than eating the fruit peeled. Potatoes boast five times the fibre when consumed with their skin intact. For those who prefer peeling, Tim suggests repurposing the discarded skins by roasting them with olive oil and seasoning to make homemade crisps.
The NHS notes that fibre in potato skins helps lower the risk of heart disease, stroke, type 2 diabetes, and bowel cancer, while also promoting prolonged feelings of fullness.
Beyond the benefits of eating unpeeled produce, Professor Tim encourages people to swap white rice with grains or pulses for improved health and weight management. Speaking to The Telegraph, he criticized the misconception that white rice is healthy, adding: “You can get a tin for about 50p, so they are incredibly good value. You don’t have to have pure carbs on your plate all the time.”
He also advocates healthier snacking alternatives such as fruit, nuts, and dark chocolate instead of sugary treats. Professor Spector has previously championed dark chocolate for its digestive health benefits, highlighting its rich polyphenol content.
On social media last year, he described polyphenols as “rocket fuel for your gut microbes,” found in foods like grapes, berries, peanuts, red wine, coffee, extra virgin olive oil, nuts, and dark chocolate. According to him, a morning coffee paired with a piece of dark chocolate fits perfectly into a polyphenol-rich diet.