Are you aware of resistant starch? This beneficial fiber is gaining recognition for its role in supporting gut health, managing blood sugar and cholesterol levels, reducing inflammation, and even aiding in weight loss. Surprisingly, many individuals are unfamiliar with this nutrient, which can be found in a variety of foods. While resistant starch is commonly associated with nutrition powerhouses such as pulses, nuts, seeds, and whole grains, it can also be found in unexpected items like white bread, cold potatoes, overnight oats, underripe bananas, and reheated white rice or pasta.
Unlike most starchy carbohydrates that are digested in the small intestine, resistant starch resists this process and travels to the large intestine, where it is fermented by beneficial gut microbes.
“Once it reaches the large intestine, resistant starch undergoes fermentation,” explains Rhiannon Lambert, a registered nutritionist and author of The Fibre Formula. This unique characteristic allows it to act as a prebiotic, delivering numerous health benefits. “Gut bacteria ferment resistant starch into short-chain fatty acids (SCFAs) such as butyrate, which provide various health advantages,” Lambert adds. “These SCFAs nourish gut microbiota and help lower inflammation, which can be a contributing factor to conditions like heart disease and obesity.”
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Research suggests significant potential in resistant starch. A study involving nearly 1,000 individuals with a high genetic predisposition to various cancers, known as Lynch syndrome, led by John Mathers, a professor of human nutrition at Newcastle University, indicated that a two-year intake of resistant starch had a notable preventive effect against certain cancers. The most significant benefits were observed for upper gastrointestinal cancers, with reductions of over 60 percent in some cases.
Mathers and his team propose that resistant starch may help diminish harmful bile acids that can damage DNA and potentially lead to cancer. “The dosage used in the trial was akin to consuming a banana daily,” he noted. “Before they become overly ripe, bananas contain resistant starch that makes its way to the gut, altering the bacteria present there.”
Resistant starch promotes metabolic health and curbs hunger. It complicates the breakdown of carbohydrates into glucose, leading to a steadier blood sugar response, unlike high-sugar foods such as cakes or refined cereals. “The presence of this beneficial starch allows sugars to enter the bloodstream gradually,” Lambert states. “This helps maintain feelings of fullness and can promote improved insulin sensitivity, making it a valuable resource for weight management and type 2 diabetes control.” So, where can you find it?
Choose Overnight Oats Over Porridge
The resistant starch remains intact when oats are soaked overnight
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Oats inherently contain resistant starch; however, their preparation significantly affects the amount that remains after digestion. “Cooking oats with heat and water causes the starch granules to swell and soften through a process called gelatinization,” explains Lambert. “Consequently, more of the starch is broken down and converted into glucose.”
By soaking oats overnight instead of cooking, the resistant starch remains largely intact. “Although cooked porridge is still an excellent source of fiber, overnight oats contain slightly more resistant starch,” Lambert states.
Opt for Underripe Bananas
Firm, green bananas contain substantial amounts of resistant starch. As bananas ripen and turn brown, much of this starch is converted into sugars. “When a banana ripens to yellow, natural enzymes start to transform resistant starch into simpler sugars,” Lambert explains. “By the time a banana is fully yellow with spots, most resistant starch has been converted, yielding lower levels of this beneficial carbohydrate.”
Chill Your Potatoes and Pasta
You can increase the resistant starch content in potatoes and pasta by cooking and then cooling them in the refrigerator.
“Upon cooking, the starch granules swell and burst, leading to gelatinization, which softens the food and makes it easier to digest,” explains Alex Ruani, a nutrition researcher at University College London and chief science educator at the Health Sciences Academy. “However, when these foods are cooled, the starch molecules undergo retrogradation, rearranging into a tight, crystalline structure that’s more difficult for digestive enzymes to break down.”
This cooking and cooling method transforms foods with a high glycemic index—those that can spike blood sugar levels—into lower glycemic options, which is beneficial for blood sugar management. Cooling cooked potatoes can reduce their glycemic index by up to 25%, while rice can see reductions of up to 20%.
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Refrigerate Cooked White Rice for 24 Hours
White rice benefits from the retrogradation process of cooking and cooling. An Indonesian research team studied the resistant starch levels in white rice prepared in different methods. Freshly cooked white rice contains about 0.64g of resistant starch per 100g serving, while allowing it to cool at room temperature for ten hours may double that amount. The highest levels were obtained when white rice was cooked, then cooled in the fridge for 24 hours and later reheated, resulting in approximately 1.65g of resistant starch per 100g serving. However, caution is necessary, as rice can harbor bacillus cereus spores that survive cooking. “If rice is left out at room temperature, these spores can proliferate and produce toxins,” Ruani warns. “To retrograde rice safely, it should be cooled within half an hour after cooking, ideally at a temperature of 4°C in the refrigerator.” Never keep cooked rice at room temperature for longer than an hour; it can be stored in the fridge for 3-4 days. When reheating, ensure it is piping hot throughout.
Incorporate Pulses into Casseroles, Soups, and Salads
Resistant starch is integral to the structure of beans, peas, and lentils
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Pulses such as lentils, chickpeas, kidney beans, and butter beans are naturally abundant in resistant starch. The starch is encapsulated within thick, fiber-rich plant cell walls. “Since resistant starch is integrated into the structure of these legumes, they do not require cooling to enhance its levels as some other foods do,” Lambert notes. “Cooling might slightly increase resistant starch levels in pulses, but the effect is far less significant than with rice or potatoes.”
Generally, beans and pulses offer about 1-5g of resistant starch per 100g after cooking. “Fava beans have the highest content, providing 8-12g per 100g, but they are not commonly consumed in the UK,” explains Dr. Linia Patel, a researcher in clinical sciences at the Universita degli Studi di Milano and a spokesperson for the British Dietetic Association. “Warming canned or jarred beans, then allowing them to cool, yields the best results.”
Patel recommends making a large pot of dal or bean stew, refrigerating leftovers, and enjoying them with vegetables and whole grains throughout the week for balanced meals.
Consider Chickpea Pasta for an Extra Boost
Chickpea pasta is not only rich in fiber and protein but also contains substantial amounts of resistant starch, making it an excellent choice for boosting your overall fiber intake. A recent Polish study published in the journal *Metabolites* examined chickpea pasta prepared in two ways—freshly cooked and cooked, cooled for 24 hours at 4°C, and then reheated. The results revealed that freshly cooked chickpea pasta contained about 1.83g of resistant starch per 100g serving, whereas the refrigerated and reheated version doubled this amount to approximately 3.65g per 100g serving.
“Processing reduces the resistant starch content, so chickpea flour has less than whole chickpeas,” Patel cautions. “However, if you create bread from chickpea flour and freeze it, you can increase the resistant starch content that way.”
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Reheat Your Chilled Potatoes, Rice, or Pasta
If you prefer your potatoes or pasta warm, reheating them is a viable option. Researchers from the University of Surrey compared blood sugar responses of identical pasta dishes served fresh, chilled, or chilled and reheated. They found the smallest blood sugar spike occurred when the pasta was reheated after being chilled.
“The ‘cool then reheat’ approach, known as dual retrogradation, is exceptionally effective,” Ruani explains. “This method enhances starch’s resistance to digestive enzymes even beyond a single cooling session, allowing glucose to be released more gradually into the bloodstream, thus aiding in blood sugar and appetite control.”
Freeze, Thaw, and Toast White Bread
Freezing any type of bread results in increased resistant starch content. “Freezing alters the structural arrangement and makes the bread less easily digestible, thus promoting the formation of resistant starch,” Patel points out. “While the caloric impact may be minimal, the health benefits for gut health and blood sugar management are significant.”
While white bread typically isn’t the richest source of resistant starch, freezing, thawing, and then toasting it markedly enhances its levels. Research from Oxford Brookes University indicated that prepared this way, white bread exhibited a 30-40% reduction in glycemic index compared to fresh bread.
“Toasting may help stabilize the retrograded starch formed during freezing, which contributes to the lower GI effect,” Ruani adds. “Toasting fresh, unfrozen bread lowers its glycemic index by about 20%, which is a lesser effect than the frozen-then-toasted process.”
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Can Resistant Starch Promote Weight Loss?
Incorporating resistant starch can significantly aid in appetite control and weight management. “Resistant starch is lower in calories than regular starch because it isn’t fully absorbed,” Ruani explains. “It also prompts the release of appetite-suppressing hormones like GLP-1, helping you feel full longer.”
A small study published in *Nature Metabolism* in 2024 involved 37 overweight participants who consumed a daily sachet of either regular starch or resistant starch mixed with water, alongside three balanced meals monitored throughout the trial. After eight weeks, participants taking the resistant starch lost an average of 2.8kg, while there were no changes noted in the regular starch group. Additional benefits included better blood sugar control after meals and an increase in gut bacteria associated with weight loss.
How Can You Tell if You’re Getting Enough?
Currently, there are no official UK recommendations regarding how much resistant starch should be part of our diets. A sensible approach includes aiming for the daily fiber intake of 30 grams. “Resistant starch is just one element of that total fiber intake,” Lambert advises. “Instead of focusing on specific amounts, it’s more practical to incorporate foods that naturally provide it.”
Slowly introduce foods rich in resistant starch into your diet. “The key takeaway is not to fixate on a single source of resistant starch, but to base your meals around pulses, whole grains, and plant foods like nuts and seeds,” she concludes. “This way, resistant starch will naturally become a part of your diet without much effort.”
Who Should Be Cautious About Increasing Intake?
According to Patel, it’s recommended to gradually introduce foods high in resistant starch to prevent bloating. Individuals with IBS symptoms should consult a dietitian before making significant dietary changes. “Foods rich in fiber and resistant starch, such as beans and lentils, can potentially lead to bloating and gas, so it’s best to increase intake slowly,” she advises.
The Fibre Formula by Rhiannon Lambert (Dorling Kindersley, £20). Order a copy at timesbookshop.co.uk. Enjoy free UK standard P&P on orders over £25. Special discounts available for Times+ members.
