© Nadin SH
June 27, 2026
Marianne Waldenfels
Cold potatoes, rice, and pasta contain more so-called resistant starch than their freshly cooked counterparts. On social media, this has become a popular tip for improving gut health, managing blood sugar, and controlling weight. But what is the science behind it?
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Cold potatoes, rice, or pasta are currently a surprising nutrition trend on TikTok and Instagram. The reason: as they cool down, a substance called resistant starch forms, which may support the gut microbiome and have a more favorable effect on blood sugar levels. But what is actually behind the hype — and how solid is the scientific evidence?
Resistant starch is the portion of starch that escapes digestion in the small intestine. Rather than being broken down into glucose, it passes into the large intestine, where it is fermented by gut bacteria. As a result, it behaves more like a dietary fiber in the body than like a classic carbohydrate.
Particularly relevant in everyday life is type 3 resistant starch, which forms after cooking and subsequent cooling.
During cooking, starch molecules swell and become more accessible to digestive enzymes. If the food then cools for several hours, components of the starch — mainly amylose and amylopectin — rearrange and form more stable structures.
This process is known as retrogradation, and it makes the starch less accessible to digestive enzymes. The effect occurs not only in potatoes, but also in rice, pasta, and other starchy foods.
The body of evidence is now considerably stronger than it was a few years ago.
The strongest overall evidence comes from meta-analyses of randomized studies. A 2021 meta-analysis of 19 randomized studies found that resistant starch can lower fasting blood sugar and improve insulin resistance, though the overall effects were moderate.
Further reviews and meta-analyses reach a similar conclusion: resistant starch can produce favorable metabolic effects, but its impact depends on a number of factors, including the type of resistant starch, the amount consumed, and the individual composition of the gut microbiome.
Context matters: the findings point to a genuine nutritional and physiological effect, but not a therapy in the strict sense.
In the large intestine, resistant starch is fermented by bacteria, producing short-chain fatty acids — primarily butyrate.
It is considered the most important energy source for cells of the intestinal mucosa and is associated with a stable intestinal barrier and anti-inflammatory processes. More recent reviews therefore classify resistant starch as potentially prebiotic.
It is often claimed that cold potatoes or rice contain significantly fewer calories than freshly cooked ones. However, it's not quite that simple.
Cooling does produce resistant starch, which the body cannot fully digest and therefore yields less usable energy than regular starch. In practice, however, the difference in calorie content is relatively small and depends on factors such as how long the food was cooled and how much resistant starch actually formed.
The health benefit, then, lies less in any meaningful calorie savings and more in the potential positive effects on blood sugar, satiety, and gut health. Those who eat cold potatoes or rice should not think of them as a weight-loss trick, but rather as a simple way to add a bit more fiber to their diet and make it slightly more metabolically friendly.
No. What matters is not whether potatoes or rice are eaten cold, but simply that they have been given enough time to cool after cooking. This alone significantly increases the proportion of resistant starch.
Gently reheating them later does not completely destroy the resistant starch either. This is practically relevant in dishes like potato or rice salad, as well as meal-prep recipes that use pre-cooked side dishes which are later reheated.
Anyone who wants to take advantage of this effect doesn't need to follow a "cold diet" — they can simply increase the proportion of resistant starch by adjusting how they prepare and store starchy foods.
Resistant starch is generally well tolerated by most people. Those who have previously eaten little fiber may initially experience bloating, a feeling of fullness, or more frequent bowel sounds. These symptoms are usually temporary and tend to subside once the gut has adjusted to the higher intake of fermentable fiber.
Resistant starch is a good example of how not only the choice of foods, but also the way they are prepared, can affect their health properties.
The existing body of research supports moderate benefits in blood sugar regulation, insulin resistance, and possibly also gut health — particularly when resistant starch is consumed regularly as part of a broader fiber-rich diet.
Cold potatoes, rice, and pasta are therefore no miracle cure. However, they can be a simple and practical way to make your diet a little more gut-friendly and to support your metabolism.
