Resistant Starch: The Five Types, Cooled Rice, Indian Foods and What Trials Show

Resistant starch is the part of starch that is not digested in your small intestine and so reaches the large intestine, where gut bacteria ferment it. Ordinary food holds little of it: one study measured 0.64 g per 100 g in freshly cooked white rice and 1.65 g after a day in the refrigerator and reheating. Trials that report benefits have mostly given 10 to 45 g a day as a supplement, and ICMR-NIN sets no requirement for it. You are reading part of the handbook's carbohydrates section.

What is resistant starch?

It is starch that behaves like fibre. The FAO and WHO expert consultation on carbohydrates defines it as starch and starch degradation products not absorbed in the small intestine of healthy humans. Ordinary starch is split into glucose and absorbed. The resistant fraction passes on to the colon, where bacteria ferment it into short-chain fatty acids and gases. Reviews count it as a form of dietary fibre, and a 2022 paper in the Indian Journal of Medical Research classes both as unavailable carbohydrate, the kind that is not digested and may be fermented.

Because it is fermented and not absorbed as glucose, it yields less energy. The high-amylose maize product in one 2024 trial was listed at 2.8 kcal per gram, against 3.55 kcal per gram for the ordinary starch used as its control. The amount in a food is not fixed: it depends on the plant, on how intact the grain is, on cooking and on cooling.

The five types of resistant starch

Researchers sort resistant starch into five types by the reason it escapes digestion. Types 1, 2, 3 and 5 occur naturally in foods; types 2, 3 and 4 can be added to packaged foods as an ingredient. Type 3 is the one a home kitchen can change, because it forms when cooked starch cools and its chains realign, most readily near refrigerator temperature. Cooking works against type 2: once a raw potato or a green banana is cooked, most of its starch gelatinises and becomes highly digestible.

How much resistant starch do you need in India?

There is no requirement. ICMR-NIN's Nutrient Requirements for Indians, 2020, gives no figure for resistant starch; its guidance is for fibre as a whole, about 30 g for every 2,000 kcal. The WHO's 2023 carbohydrate guidance, as the WHO summarises it, gives adults a figure for naturally occurring fibre, 25 g a day, and none for resistant starch. The practical target remains fibre from whole foods.

Intake from ordinary diets is small. An analysis of 18,305 people in United States dietary surveys estimated about 4.9 g a day, with a range of 2.8 to 7.9 g depending on the food values used. A national Indian intake figure could not be found for this entry. Trials, by contrast, have given 10 to 45 g a day, usually as a purified powder.

Which Indian foods contain resistant starch?

Whole pulses, coarse grain preparations and cooled starchy foods carry the most, and fried, puffed and flaked foods the least. The 2022 Chennai study in the Indian Journal of Medical Research measured freshly cooked dishes as eaten: white chickpea sundal had 3.95 g per 100 g, broken wheat upma 3.25 g, adai 2.78 g, wheat dosa 1.95 g, sorghum idli 1.87 g, bajra roti 1.0 g and a ragi ball 0.7 g. The sundal also had the lowest glycaemic index of the twelve foods tested, 24.1.

Read the last two rows with care: the Vadodara laboratory reported dry-weight values, which are higher than the same food weighed on a plate with its water. That study also found very little in fried rice papadi (0.03 g) and corn flakes (0.28 g). The pages on Bengal gram and raw banana give the full nutrient panels, and NNWA's table of fibre in Indian foods ranks the wider group.

Does cooling rice, roti and potato really raise it?

Yes, by a measurable but small amount. In a study from Jakarta, freshly cooked white rice had 0.64 g of resistant starch per 100 g, rice left for 10 hours at room temperature 1.30 g, and rice refrigerated for 24 hours at 4 degrees C and then reheated 1.65 g. The Vadodara study saw the same direction in Indian foods stored at 4 degrees C: boiled rice went from 2.1 to 3.9 g per 100 g dry weight in 12 hours and 4.1 g in 24, chapatti from 2.9 to 3.7 g, and bajra rotla from 0.9 to 1.5 g.

Not everything responds. Puri, paratha and the other fried or shallow-fried items showed no significant change on storage, which the authors attributed to starch forming complexes with fat. For potatoes, a United States analysis of three varieties found that baked potatoes held more resistant starch than boiled ones, and chilled potatoes more than hot or reheated ones, with no difference between varieties.

What does the trial evidence say about post-meal glucose?

It shows a real but modest effect in single-meal tests and small average changes in longer trials. In the Jakarta study, 15 healthy adults ate the chilled and reheated rice and freshly cooked rice on separate occasions in a randomised crossover design. The glucose response was 125 against 152 mmol.min per litre, about 18 per cent lower, with a p value of 0.047. That is one meal in healthy volunteers, not a change in anyone's long-term glucose control.

For longer use, a 2021 meta-analysis of 19 randomised trials found that resistant starch lowered fasting plasma glucose by 0.09 mmol per litre compared with digestible starch, which is under 2 mg/dl. The effect was larger, 0.16 mmol per litre, at more than 28 g a day, and 0.12 after more than eight weeks. Insulin resistance by the HOMA index improved, but fasting insulin and five other insulin-related measures did not change. The authors called the effects moderate.

The 2019 pooled analysis reached a similar reading in adults who were overweight or obese: fasting insulin and fasting glucose fell, most clearly in those with diabetes. Its trials had 12 to 60 participants each, ran for 12 weeks at most, and differed from one another enough that the authors asked for the result to be taken with care. Almost all of this evidence concerns purified resistant starch, not cooled rice or roti.

What does it do in the gut?

It feeds bacteria in the colon, and what follows from that is less settled. Fermentation produces short-chain fatty acids, which enhance sodium absorption in the colon. In the 2024 Shanghai trial, 37 adults with overweight or obesity took 40 g a day of high-amylose maize starch for eight weeks alongside a supplied balanced diet. They lost a mean of 2.8 kg, their insulin resistance improved and their gut bacteria shifted, with one Bifidobacterium species tracking the change. It was a small crossover study.

Two other findings show the limits. In the CAPP2 trial, 918 people with Lynch syndrome, an inherited cancer risk, took 30 g a day or a placebo for up to four years. After up to 20 years there was no difference in cancer of the colon and rectum, although fewer other Lynch-related cancers occurred in the resistant starch group, 27 against 48. That result belongs to one inherited condition. In a hospital trial in Vellore of 48 patients with cholera, adding a resistant starch to oral rehydration solution shortened diarrhoea to 56.7 hours from 90.9. It is a research finding, not a home remedy.

A worked example: how far cooled rice gets you

The case below is illustrative and describes no real person. Take a 45-year-old shopkeeper in Kolkata who eats 150 g of cooked rice at lunch and again at dinner, 300 g a day. On the Jakarta figures, freshly cooked rice at 0.64 g per 100 g gives him about 1.9 g of resistant starch. If both servings came from rice cooked the day before, refrigerated and reheated, the figure at 1.65 g per 100 g would be about 5.0 g. The gain is roughly 3 g a day.

Now add a 100 g serving of chickpea sundal at 3.95 g, and his day reaches about 9 g. The pooled trials found their larger effect above 28 g a day. To get 28 g from chilled rice alone he would need about 1.7 kg of cooked rice, which no sensible plan would include. The fair reading is that cooled rice is a harmless habit with a small benefit, and that the sundal earns its place for its protein, fibre and low glycaemic index as much as for its resistant starch.

Common myths and mistakes about resistant starch

The most common mistake is to treat cooling as permission for a larger helping. A 150 g serving of chilled and reheated rice still delivers nearly all of its starch in digestible form: on the Jakarta figures only about 2.5 g of the serving is resistant starch.

A third error is to buy a resistant starch powder and expect the trial results. The trials gave measured doses and their average effects were small. Other pages on this site, such as the guide to eating with prediabetes in India and the article on calories in rice, put cooled rice where it belongs: one minor tactic inside a whole plate.

Side effects, safety and when to see a doctor

ICMR-NIN's 2020 table of tolerable upper limits does not list resistant starch. Its fermentation produces gases, including hydrogen, methane and carbon dioxide, so the sensible caution is to raise it gradually, as with any fermentable fibre. The Shanghai trial described 40 g a day as a relatively high dose that could be given without adverse effects, but that was a purified product under supervision. At home the larger risk is storage: cooked rice left at room temperature for hours gives microorganisms time to multiply.

Resistant starch does not replace a medicine for blood glucose, and no amount of cooled rice is a reason to stop or change a prescription. Diarrhoea with dehydration needs oral rehydration solution made as the packet directs and medical care, not an added starch. If you want to know where you stand on glucose, the diabetes risk calculator is a starting point for a conversation with a doctor, who orders and reads the tests.

Learning this subject at NNWA

Starch digestion, glycaemic index and the reading of trial evidence are part of what NNWA teaches. It is a private skill academy in Kolkata with online classes in English and Hindi, and its programmes, including the Diploma in Nutrition, prepare people to coach healthy clients and to refer anyone with a medical condition to a doctor. No NNWA course is a degree or a dietitian qualification.