Jimmy Doherty wonders what gives fizzy sweets their fizz, and swots up on his chemistry, to see if he can harness their explosive power in a rocket. In Ireland, Kate Quilton asks if a range of vitamin-enriched mushrooms could help the one in five Britons who lack vitamin D. Meanwhile, Matt Tebbutt investigates headlines that claim that raw kale may be bad for you, and finds out if our breakfast smoothies are safe.

This seasonal special reveals the delicious facts about your favourite traditional Christmas food. Jimmy Doherty heads to Sri Lanka to find out if there's anything in your Yuletide spices that can give you a dose of Christmas cheer. Matt Tebbutt visits Mr Kipling's mega mince pie factory; he asks what the difference is between raisins and sultanas, and he discovers how they get the Christmas spirit into boozy chocolates. Helen Lawal investigates whether we should score our sprouts. And Kate Quilton is wondering if the traditional Christmas dinner is a bit of a turkey, so she checks out a more decadent dish from the past: the multi-bird roast.