There's a secret superfood in white rice and pasta: Here's how to unlock it

Naughty or nice? That's often how I think about foods packed with carbohydrates. Whole grains, like brown rice and whole wheat, fall squarely into the nice category, while white pasta and rice, well, they're more naughty.

"They're naughty, in a sense, because we digest them rapidly and that creates a fast rise in blood sugar," says nutritionist Mindy Patterson, at Texas Woman's University in Houston. They're also low in fiber and protein, compared to their whole grain cousins.

Over time, all those quick surges in blood sugar can hurt your health, Patterson says. They can contribute to insulin resistance and just leave you feeling tired.

"If we don't have these spikes and dips in our blood sugar, then we tend to have more energy and just feel better," she says. These spikes are especially problematic for people with diabetes. Over time, they can cause strokes or heart disease, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

But what if there's a way to make the naughty carbs a bit nicer? In the past decade, food scientists have figured out a way to help people digest refined carbohydrates more slowly. In the process, they've uncovered a surprise: a super nutrient hidden inside white pasta and white rice.

It's called resistant starch. Studies have found that eating more resistant starch comes with myriad health benefits. It can improve gut health, lower inflammation in your body and enhance insulin sensitivity. And for people with diabetes, it helps with blood sugar management, a meta-analysis in Frontiers in Nutrition found.

And here's the good news: You can create this supernutrient in your own kitchen. All you have to do, Patterson says, is cook the rice or pasta and then chill it.

Let's take white rice as an example. After you cook it, the little white kernels contain chains of sugar molecules, known as digestible starch. Enzymes in our saliva and stomach rapidly tear these chains apart, releasing a whole bunch of sugar into your gut. That sugar then quickly rushes into our blood.

Digestible Starch + Our Enzymes ===> Sugar

Now instead of eating the hot, steaming rice immediately after cooking, let's say you take it and put it in the refrigerator overnight (or for at least six to eight hours). Then something almost magical happens, says microbiologist Maria Marco, who chairs the Food Science Graduate Group at UC Davis.

As the hot rice cools down, some of those sugar chains transform. They stick together in a way that makes them no longer digestible.

"The chains form twisted shapes and different branches," Marco says, "and our enzymes can no longer reach them."

That means our enzymes can no longer tear the chains apart. We can't release their sugar molecules. So less sugar rushes into our blood. These twisted chains are called resistant starch (because they "resist" digestion).

Resistant Starch ===> No Sugar

So when you eat the cold, leftover rice, it doesn't typically raise your blood sugar as fast and high as the hot, freshly cooked rice, studies have found. The resistant starch passes right through our small intestine into our colon. (And if you don't like the sound of eating cold rice, keep reading — you can quickly reheat it.)

Now, if you think about it, scientists have a special name for carbohydrates that we can't digest: fiber. It's a super important nutrient that Marco says most of us don't get enough of. "It's so hard to eat enough fiber," she says. "I struggle with eating enough."

Just by cooling down the cooked white rice overnight, you've taken a food with little fiber in it and created one with a decent amount.

The same trick works with any food that contains digestible starch, including white pasta and potatoes. So a chilled potato salad (or pasta salad) won't spike your blood sugar as fast as a freshly baked potato (or a sizzling spaghetti), says Patterson.

"Just be sure to use olive oil instead of mayonnaise," she says.

The chilling trick also works with those "nice" carbs, including whole wheat pasta, oats, barley, beans and lentils — making them even healthier. "We found that lima beans have the most resistant starch of any food," Patterson said.

Like all fibers, resistant starch will help keep your bowel movements regular. But it also plays another critical role in keeping you healthy, says microbiologist Ravinder Nagpal at Florida State University. "It promotes the growth of beneficial bacteria in your lower gut."

Although human enzymes can't digest resistant starch, the microbes in our large intestines can break it apart. It's what's known as a prebiotic, or food for our microbiome.

"Resistant starch is one of their favorite foods," Nagpal says. "It's the most important starch for the health of your microbiome."

When these critters eat up resistant starch, they create smaller molecules that help our bodies in myriad ways.

"These molecules are good for our gut cells and also for overall metabolic health," he says. They reduce inflammation, boost immunity and reduce your risk of colon cancer. These molecules also help to keep you satisfied between meals, Nagpal points out. "So they help with weight management, too."

Nagpal says you don't have to eat the grains cold, you can reheat them — just do it gently, either quickly in the microwave, "or lightly fry it," he says. Don't recook it because then you'll lose a bunch of the resistant starch.

Nagpal likes to make a big batch of rice on the weekends and store it in the refrigerator.

"Each day, I take a small bowl of rice and mix it with either yogurt or my favorite veggies," he explains. "Or sometimes I lightly fry it with fish, beans, greens, peas, or whatever my favorite ingredients are available."

You can do the same with potatoes or sweet potatoes, he says. Cook them in a big batch, store them in the refrigerator, and then for a meal, cut off a piece that you want and mix it with toppings, such as cheese or sour cream.

To add resistant starch to breakfast, Nagpal says, simply soak oats or another whole grain in milk and water overnight. Don't cook them at all. "Then next morning or next day just mix it with some fruits or yogurt. This works perfectly."

So, are chilled leftovers better for you than freshly made dishes? "Yes, absolutely," Nagpal says with a chuckle. In fact, he eats them almost every day.

Edited by Jane Greenhalgh

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