Carbs in bread, pasta and rice have long taken the blame for causing weight gain, diabetes and heart disease.
But popping white bread in the freezer could help reverse those health harms, dietitians have revealed.
White bread, along with pasta and rice, is filled with refined carbohydrates, carbs that have been ultra-processed to strip out vital nutrients like fiber.
Refined carbs trigger spikes in blood sugar, which stresses the pancreas and causes it to overproduce insulin, eventually leading to diabetes.
Without fiber, white bread and other sources of refined grains pass through the digestive system faster, which prevents fullness and leads to more cravings in a shorter amount of time.
Freezing bread, however, triggers a process called retrogradation, which causes molecules in starches, carbs in bread, to harder and become harder to digest.
This resistant starch, unlike refined carbohydrates, is not broken down as glucose, so it does not raise blood sugar levels. Like fiber, it promotes fullness and leads to less eating throughout the day overall.
And the benefits are not exclusive to bread. Recent studies also show rice, pasta and potatoes also gain resistant starch when cooked and then cooled after.
Dietitians have revealed putting white bread in the freezer may lead to fewer blood sugar spikes and promote weight loss (stock image)
Avery Zenker, a registered dietitian and medical writer in Canada, told HuffPost: ‘Resistant starch slows the absorption of other carbohydrates into the blood. Because less of the carbohydrates in the food are absorbed, the impact on blood sugar is more blunted, reducing blood glucose and insulin spikes.
‘This supports steady energy throughout the day, helps prevent sugar crashes and promotes feelings of fullness.’
Starch, a carbohydrate found in bread, absorbs moisture when cooled.
Zenker explained that starch is made up of two glucose polymers: amylose and amylopectin. The heat that comes from baking bread disrupts hydrogen bonds that keep starch molecules together, making amylose and amylopectin easier to digest.
But when it cools or is put in the freezer, retrogradation starts.
Zenker said: ‘During retrogradation, some of the starch molecules realign and form new crystalline structures that are more difficult for the body to digest and absorb, hence their name, “resistant starch.”
‘Fresh-baked white bread contains about 0.5 to 1.7 percent resistant starch by weight. After cooling or freezing and thawing, this might increase to one to three percent.’
Resistant starch has been linked to a host of health benefits, namely weight loss. A 2024 study in the journal Nature Metabolism, for example, found that people who consumed resistant starch for about eight weeks lost six pounds more than those in the control group.
It was also linked to lower levels of inflammation and insulin resistance, both of which lower the risk of diabetes.
Studies also show that cooling down pasta or rice after cooking may reduce glucose spikes (stock image)
Daily Mail previously enlisted the help of a dietitian to analyze the health properties of five different types of bread
A small study in the European Journal of Clinical Medicine also found that toasting bread after freezing and defrosting it led to a lower glucose response than not freezing it first, which the researchers believe was due to the process forming resistant starch.
Experts recommend freezing bread for at least 12 to 24 hours to start the retrogradation process, though it can stay fresh for three to six months.
Zenker said: ‘Indirectly, resistant starch may impact satiety and blood sugar by increasing GLP-1 production in the gut.’
GLP-1 is a hormone naturally found in the gut that weight loss drugs like Ozempic and Wegovy mimic, which has been shown to reduce hunger and cravings by slowing digestion.
The benefits may also extend to other sources of refined carbs. One 2022 study found that cooled and reheated rice led to a 30 percent lower rise in blood sugar compared to rice that was freshly cooked.
However, Zenker still recommends consuming refined carbs in moderation and opting for whole grains when possible.
‘It’s important to note that the benefit of resistant starch is small, so moderate portions still matter,’ she said.