The Unlikely Leftover That’s Great For Your Gut

Cold, boiled potatoes may not be on the menu at the Ritz Carlton, but certain experts would have it that the dish is among the best foods you could eat–at least where your gut health is concerned.

The reason cold potatoes are so beneficial to maintaining a healthy gut environment boils down to the type of starch they contain. Uncooked, white potatoes contain resistant starch, so called because it’s resistant to digestion. “Resistant starch is important to support many aspects of our health and wellness, from gut function, digestion and absorption of nutrients, to effective immune function,” says Maz Packham, nutritionist and founder of Nourishful Nutrition. It means it passes through your small intestine into your large intestine–or colon–intact and without being broken down by the body. Its nutritional benefits are then utilized by the bacterial microbes in your colon.

When potatoes are cooked (because no one should eat them raw), the resistant starch becomes active, meaning it’s treated by the body in a completely different way: turned into glucose and then absorbed. The twist? If potatoes are cooked and then left to cool, the active starch is turned back into resistant starch, in a process known as retrogradation.

When this starch reaches your large intestine it begins to ferment, which helps to create a wealth of good bacteria in your gut. As well as increasing the number of bacteria, it also acts like a prebiotic, by feeding the bacteria that already exist. “Prebiotic foods are important to nourish and support the growth of beneficial bacteria in the gut such as lactobacillus and bifidobacteria,” explains Packham. “By helping to colonise the beneficial bacteria in our gut we can help to reduce symptoms like bloating, constipation or IBS-like symptoms.” If you consider that resistant starches and fermented fibre feed 90 percent of your cells (compared to most other foods that feed the remaining 10 percent), you’ll understand why it’s extremely beneficial to include it in your diet.

As well as improving the health of the environment in the large intestine, resistant starch impacts the body in other ways. Once digested by the bacteria, the starch forms compounds including gasses and short-chain fatty acids such as butyrate, which is a great source of energy for the cells in the colon. Keeping the colon healthy isn’t just important for improving digestion and digestive conditions such as constipation, it can also reduce the risk of colorectal cancer–the fourth most common cause of cancer death worldwide. The fatty acids that aren’t directly used by the cells in your colon then travel around the rest of the body, where they have an important anti-inflammatory role to play.

If you’re stuck for ideas around how to eat them, take Packham’s advice and combine cold cooked potatoes with other gut-friendly foods in a supercharged salad bowl. “Combining cold potatoes with kimchi makes a gut-friendly lunch option, as the prebiotic in the potatoes can act as food for the probiotic bacteria found in the kimchi,” she says. “Cold potatoes are versatile so you can throw them into your salad with your favorite choice of protein, whether it be meat or plant-based, and they will work well.”