Potatoes are a staple of the British diet. However, they have gained a bad reputation, with concerns about them spiking our blood sugar levels – which, if repeated over time, can increase the risk of diabetes.
“It depends on the type of potato and how you prepare it,” says Dr Christine Bosch, from Leeds University’s School of Food and Nutrition. She explains that while regular potatoes cause a higher spike in blood sugar than sweet potatoes, they are a valuable source of carbohydrate – a key macronutrient. Potatoes also contain fibre and polyphenols, which slow digestion, leaving you feeling fuller for longer.
Not all potatoes are created equal, however. Waxy types typically cause a smaller blood sugar spike compared with floury varieties such as Maris Piper. Bosch points out that removing the skin reduces the health benefits. “A 150g potato contains about 2g of fibre, but once peeled, that drops to 1g. The skin also contains a higher concentration of polyphenols.”
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The way we cook and serve potatoes affects their health impact too. Foods that break down into sugar more quickly tend to cause sharper blood sugar spikes. Mashed potatoes can spike blood sugar faster than whole potatoes with their skin on.
A tip for preparing potatoes to cause a lower blood sugar spike is “boiling them and letting them cool”, says Bosch. Whether you eat them cold or reheated, this lowers their glycaemic index (which ranks foods based on how quickly they raise blood sugar levels) by 30-40%, she says.
And studies have shown that eating potatoes on their own doesn’t necessarily increase the risk of diabetes. However, cooking them with lots of cream, butter, or oil can have negative effects. “Still, if you don’t overeat, it’s fine,” says Bosch.