Good news carb lovers: Pasta, rice, and potatoes could be great for your health. They just have to be cooled down first.

• Carbs aren't known as a traditionally healthy food, but they transform when chilled.
• Cooling pasta, potatoes, and rice changes their structure and turns them into resistant starches.

It turns out some leftovers kept in the fridge overnight may be great at promoting gut health.

Leena Hilakivi-Clarke, a professor of food science and nutrition at the University of Minnesota, says that foods like pasta, rice, quinoa, and potatoes are sources of a special type of dietary fiber called microbiota-accessible carbohydrates, also known as MACs.

While "all fiber is good," Hilakivi-Clarke said, MACs "are particularly good" for boosting gut health because of the way they influence your gut microbiome. Think of them as a natural prebiotic.

Most of your starchy faves don't have high levels of MACs right out of the pot. But you can transform pasta, potatoes, quinoa, and rice into gut-healthy foods just by leaving them in the fridge. Here's how it works.

Turning regular foods into resistant starches

It might not seem like rice, potatoes, and pasta have many health benefits. But that's because when eaten fresh, their gut-helping properties haven't been unleashed yet.

Cooling these carbs in the fridge turns them into "resistant starches," a special type of dietary fiber with key health benefits.

When they're cooled, the starches in these foods are restructured in a process called "starch retrogradation." After this restructuring, the now-resistant starches become harder to digest — even if they're heated up again. This allows them to get to your large intestine where they can feed the bacteria housed there, supporting your gut health.

Resistant starches are a type of MAC

One of the health benefits of resistant starches is they are a type of MAC — those natural prebiotics that Hilakivi-Clarke said can boost gut health.

MACs are a type of fiber that allows "gut bacteria to produce lots of different metabolites that help the body," said Hilakivi-Clarke. "They help the immune system, they help the metabolic pathways in cells."

These cooled, starchy foods could be particularly good for people with diabetes

Hilakivi-Clarke said when her husband was diagnosed with prediabetes, he thought he would no longer be able to eat rice or pasta. But since cooked and cooled rice and pasta turn into MACs, Hilakivi-Clarke said it's actually "good for you."

Research backs this up — a study from 2019 found that resistant starches can improve insulin resistance and glucose levels for diabetic patients.

Another review from 2020 found that eating more resistant starch could help prevent the development of type 2 diabetes and obesity.

Now Hilakivi-Clarke and her husband can still enjoy these foods together — just one day later.