UK households have been advised not to throw away leftover bread by Professor Tim Spector, co-founder of the Zoe app and Professor of Genetic Epidemiology at King's College London. In a new Instagram post, he shared a health tip that also applies to potatoes and pasta.
Freeze your bread for better health
Spector told his 775,000 followers: "I've got a hack for you. You've got to start freezing your bread. Next time you have a bit of leftover bread, don't just throw it away. Stick it in the freezer because it will be healthier when it comes out. And the reason is because the starch in the bread gets converted by that cold into resistant starch."
He explained that this process changes the starch so it is not absorbed early in the gut, but instead travels to the lower colon where it meets gut microbes and acts like fibre. "And it's treated like fibre," he said. "So the same thing applies to potatoes and pasta, and you can improve both of those just by keeping them in the fridge or the freezer and reheating them afterwards. So if you want to fiber max your bread, store it in the freezer."
Scientific backing
The post's caption notes that freezing bread changes the structure of some starch through retrogradation, turning it into resistant starch. This starch resists digestion in the small intestine, reaching the colon where gut microbes ferment it, producing beneficial compounds that support the gut lining. It also states: "Because less total starch is converted into immediate glucose, freezing bread can also lead to a smaller blood sugar rise than eating the same slice fresh."
The caption advises: "The quality of the bread still matters, try to choose a wholegrain or authentic sourdough where possible. But if you regularly eat bread, freezing it, and even better, toasting it straight from frozen, is a simple habit that can give your gut microbes a little more to feed on."
Supporting evidence
The Good in Bread website cites a 2007 study suggesting freezing white bread could lower its glycaemic index, especially when toasted after defrosting, with similar results in 2017 and 2023 studies. The Conway Medical Center in America also explains that resistant starch ferments in the large intestine, producing short-chain fatty acids that support gut health, reduce inflammation, and may benefit the immune system.
Freezing bread offers two benefits: better blood sugar control and a healthier gut microbiome.
