As the old proverb goes, an apple a day keeps the doctors away.

While there might not be scientific legs to the centuries-old phrase, the simple healthy snack is dense with fibre, vitamins, minerals and antioxidants, making it a quick lunchbox staple for children and a stalwart of the fruit bowl.

Yet, according to Professor Tim Spector (co-founder of personalised nutrition app, ZOE, and author of Food for Life and Spoon Fed), when we peel an apple, it ends up packing less of a punch.

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Tim took to Instagram to share the science behind ditching the peeler in order to reap more of a reward - and better nutrition - from the humble fruit.

"I often talk about the benefits of polyphenols, for your health and particularly for promoting the growth of beneficial gut bacteria," he said. "Polyphenols are defence chemicals so are most abundant in the skin of plants where they are needed to protect against the elements and predators. In apples, there may be around 30 times more polyphenols in the skin than the flesh (PMID: 29364189)."

Tim added that peels are often the most fibre and prebiotic rich part of the plant - and the science applies to other fruit and vegetables, too.

"Keeping the skin on your potatoes means you’ll be getting around 50% more fibre and 175% more vitamin C than if you were to peel it and eating a kiwi with the skin on triples the amount of fibre you’ll consume (PMID: 29470689)," Tim explained.

"If you’re roasting butternut squash keeping the skin on not only speeds up preparation and reduces food waste but it also means you’ll be getting even more fibre and vitamins."

Adults are recommended to get around 30g of dietary fibre each day, but according to The Association of UK Dieticians, latest figures suggest that in the UK, the average fibre intake for adults is 18g, 60% of what it should be.

So, it's time to down tools in the kitchen and leave the skin on your fruit and vegetables!

"Globally about one-third of all food is lost or wasted so any hack which makes your food healthier, saves time and helps the planet is a winner in my books. I hope this convinces you to put away the peeler," Tim added.