In this article
- What resistant starch does in an aging body
- The types of resistant starch that matter as you age
- The deeper layer: resistant starch and longevity benefits after 70
- What the research shows on beans and the aging gut
- Resistant starch and the blue zones diet
- How long before you notice a difference?
- Practical ways to eat more resistant starch for healthy aging
- Resistant starch and aging: common questions
- Sources
In a Canadian trial, adults over 70 who took potato-based resistant starch for 12 weeks saw their blood insulin fall by about 41%, along with a drop in insulin resistance. Adults aged 30 to 50 taking the same starch saw no meaningful change.
That age gap is the most interesting clue about resistant starch and longevity benefits. The effect showed up only in the older group, the people longevity research cares about most. This article covers that trial, an aging study on bean starch, what green banana flour and potato starch actually contain, and how to eat more of it.
By the numbers
- 41% reported drop in insulin among adults over 70 who took potato resistant starch for 12 weeks
- 84 adults, half over 70 and half aged 30 to 50, who completed that Canadian trial
- 20 weeks how long aging mice carrying human gut bacteria ate resistant starch from beans and lentils in a 2023 study
What resistant starch does in an aging body
Resistant starch is the part of starch that your small intestine doesn’t digest. A 2024 review in Food Science & Nutrition by Munir and colleagues describes it as the fraction that is instead fermented by bacteria in the colon.
That makes it behave more like fiber than like sugar. Here’s what the research links it to:
- Short-chain fatty acids: colon bacteria ferment it into acetate, propionate and butyrate, according to the review.
- Insulin and blood sugar: in the Canadian trial, older adults’ insulin and insulin resistance fell over 12 weeks.
- Gut bacteria: earlier work from the same trial found more Bifidobacteria in both age groups.
- Gut barrier: in aging mice, starch from pinto beans made the gut wall less leaky.
Notice the mix of evidence. Some of it comes from people, some from animals, and none of it measured lifespan directly.
The types of resistant starch that matter as you age
Resistant starch comes in five types. The review describes two that matter most at home: type 2, found in raw starch granules, and type 3, which forms when cooked starch cools.
Potato starch
Raw potato starch holds type 2 resistant starch, packed in tight granules that digestive enzymes struggle to break down. The Canadian trial used an unmodified potato starch that its makers report is about 70% resistant starch.
Participants took 30 g a day, a research dose rather than a recommendation, and reported no more bloating or gas than those on a placebo.
Potato starch is the type most tied to lower insulin in adults over 70.
Green banana flour
Unripe bananas have the highest resistant starch content of any unprocessed food, according to the 2024 review. Green banana flour keeps much of it, though the exact amount depends on how the bananas are dried.
Freeze-drying and gentle drying at about 55°C preserved the most resistant starch in studies the review cites. In one human study it describes, unripe banana flour lowered fasting insulin and improved insulin resistance markers.
Green banana flour is the type most tied to a food-based route to the same insulin effects.
Cooked and cooled starches
When cooked starch cools, its amylose chains pack into tight double helices, which the review calls retrograded starch, or type 3. This happens best around refrigerator temperature with some moisture present.
That’s why cooked starchy foods such as potatoes or rice, chilled before eating, are the everyday way to get this type.
Cooked and cooled starch is the type most tied to everyday meals rather than supplements.
Bean and lentil starch
Beans, lentils and chickpeas carry their own resistant starch. A 2023 aging study tested starch extracted from four of them, with results covered below.
Legume starch is the type most tied to the eating patterns of the longest-lived populations.
Want to see how much fiber your usual meals add up to? Our fiber calculator gives you a daily total in a minute or two.
The deeper layer: resistant starch and longevity benefits after 70
Alfa and colleagues published the Canadian trial in Frontiers in Medicine in 2018. It enrolled two groups in Winnipeg: adults over 70 and adults aged 30 to 50, with 42 in each group completing the study.
Everyone took a placebo for two weeks first. Then each person was randomly assigned to 30 g a day of the potato starch or a digestible corn starch placebo for 12 weeks.
What changed in the older group
- Blood glucose: fell about 7%, a significant change compared with placebo.
- Insulin: fell about 41%, a significant change.
- Insulin resistance: improved on two standard measures, HOMA-IR and QUICKI.
- Inflammation markers: TNF-alpha and CRP were raised in the older adults and didn’t improve on either starch.
The mid-age group showed no significant changes in glucose, insulin or insulin resistance. The authors concluded the starch “may be part of an effective strategy to reduce insulin resistance” in older adults.
Why the age difference matters
The same dose did something in people over 70 that it didn’t do in people in their 30s and 40s. That suggests the benefit may depend on where you start, and older metabolism may have more room to improve.
The trial excluded anyone with prediabetes or diabetes, so it says nothing yet about those groups.
Reasons for caution
The trial was small. It was funded partly by MSPrebiotics Inc., which supplied the starch and paid some of the lead author’s conference costs.
Myth vs fact: “Reheating cooled potatoes or rice destroys the resistant starch”
Myth: once you warm leftovers, the resistant starch that formed in the fridge is gone.
Fact: the 2024 review notes that cooking doesn’t easily break apart retrograded amylose, which can need temperatures of up to 170°C to come undone.
What the research shows on beans and the aging gut
Kadyan and colleagues tested bean starches in a 2023 study in Frontiers in Nutrition. They used mice about 60 weeks old, colonized with gut bacteria pooled from five human donors aged 50 to 55.
All mice ate a high-fat diet. Some also got 5% resistant starch from pinto beans, black-eyed peas, lentils or chickpeas, and one group got inulin for comparison, for 20 weeks.
- Pinto bean starch: reduced gut permeability in both males and females.
- Lentil starch: raised the anti-inflammatory signal IL-10 and lowered TNF-alpha in females.
- Chickpea starch: increased gut bacterial diversity in females.
- Blood sugar: chickpea and lentil starch partly blunted glucose rises after meals in males.
Many effects appeared in only one sex, and several were borderline. It’s a mouse study, so it points to mechanisms rather than proving benefits in older people.
What the evidence adds up to
One small human trial showed better insulin markers in adults over 70, and one mouse study showed gut changes from bean starch. That’s an encouraging start for fiber and longevity research, but no study has yet linked resistant starch to longer life in people.
Resistant starch and the blue zones diet
Long-lived populations eat a lot of the foods that carry resistant starch. Buettner and Skemp’s 2016 review in the American Journal of Lifestyle Medicine describes beans as the cornerstone of most centenarian diets in the world’s blue zones, with meat eaten only about five times a month.
The same paper cites a Danish twin study suggesting that genes explain only about 20% of how long we live. That puts daily habits, like a bean-heavy anti aging diet, in a strong position.
The authors work for Blue Zones LLC, a company built around these findings, so their account is observation rather than proof. Still, it lines up with the bean starch work above.
Looking for a calm, week-by-week way to add beans and other gut-friendly foods? Our gut guides set out a plan that builds slowly.
How long before you notice a difference?
It depends on what you’re measuring. Digestion adjusts quickly, while the insulin changes in the trial were measured after 12 weeks.
- First few days: gut bacteria start fermenting the new starch, and in the Canadian trial gas and bloating were no worse than on placebo.
- 2 to 4 weeks: starch-rich foods added one at a time start to feel routine.
- 12 weeks: insulin and insulin resistance had improved in adults over 70.
- Years: any effect on fiber and lifespan from resistant starch is still untested.
Add it gradually. Raising your fiber by about 5 g per week and drinking extra water helps your gut adapt.
Practical ways to eat more resistant starch for healthy aging
These steps lean on food first, with the trial evidence in mind:
- Cook once, eat cold or reheated: chill cooked potatoes, rice or pasta to form type 3 resistant starch.
- Make beans and lentils a habit, following the blue zones pattern and the bean starch research.
- Try green banana flour in baking or smoothies as a food-based source.
- Use potato starch as an ingredient, not a cure, since the trial tested it in a specific group for 12 weeks.
- Keep the rest of your diet varied, since resistant starch is one fiber among many.
- Give it at least 12 weeks, matching the length of the trial.
These legumes and grains carry plenty of fiber alongside their starch, with values from the Dietary Guidelines for Americans:
| Food | Serving | Fiber (g) | Why it’s here |
|---|---|---|---|
| Lentils, cooked | 1/2 cup | 7.8 | Starch tested in the aging mouse study |
| Chickpeas, cooked | 1/2 cup | 6.3 | Starch tested in the aging mouse study |
| Navy beans, cooked | 1/2 cup | 9.6 | Blue zones staple |
| Black beans, cooked | 1/2 cup | 7.5 | Blue zones staple |
| Green peas, cooked | 1 cup | 8.8 | Starchy legume |
| Pearled barley, cooked | 1/2 cup | 3.0 | Whole grain to cook and chill |
Some people should adjust:
- IBS or a sensitive gut: start with small servings of cooled potatoes or rice before trying powders.
- Diabetes or prediabetes: the trial excluded these groups, so work with your care team and keep taking any medicines as prescribed.
- A very low-fiber diet now: add one resistant starch food at a time.
Want ready-made ideas for potato salads, bean bowls and overnight grain dishes? Our recipe eBooks are full of them.
Resistant starch and aging: common questions
Does resistant starch help you live longer?
No study has shown that in people yet. A 12-week trial found lower insulin and insulin resistance in adults over 70 taking potato resistant starch, and a mouse study linked bean starch to a healthier gut.
Is potato starch good for older adults?
It may be. In a Canadian trial, adults over 70 taking 30 g a day of potato resistant starch saw insulin fall by about 41%, with no more gas or bloating than placebo.
What is green banana flour?
It’s flour made from unripe bananas, which have the highest resistant starch content of any unprocessed food. Drying method matters, and freeze-drying keeps the most.
Does cooling cooked potatoes increase resistant starch?
Yes. As cooked starch cools, its amylose chains pack together into type 3 resistant starch, which is hard to break apart even when reheated.
Why did resistant starch help older adults but not younger ones?
The researchers didn’t pin down a reason. One possibility is that older adults had more room to improve, since mid-age adults in the same trial showed no change.
Are beans a good source of resistant starch?
Yes. Starch from pinto beans, black-eyed peas, lentils and chickpeas changed the gut in aging mice, and beans are the cornerstone of blue zones diets.
How much resistant starch do I need for healthy aging?
The trial tested 30 g a day of a potato starch, which is a research dose, not a target. A varied diet that covers most of a typical adult’s daily fiber needs is a good base. Our fiber calculator shows the target that fits you.
Sources
- Alfa MJ, Strang D, Tappia PS, et al. “A Randomized Placebo Controlled Clinical Trial to Determine the Impact of Digestion Resistant Starch MSPrebiotic on Glucose, Insulin, and Insulin Resistance in Elderly and Mid-Age Adults.” Frontiers in Medicine. 2018. frontiersin.org
- Munir H, Alam H, Nadeem MT, et al. “Green banana resistant starch: A promising potential as functional ingredient against certain maladies.” Food Science & Nutrition. 2024. pmc.ncbi.nlm.nih.gov
- Kadyan S, Park G, Singh P, Arjmandi B, Nagpal R. “Prebiotic mechanisms of resistant starches from dietary beans and pulses on gut microbiome and metabolic health in a humanized murine model of aging.” Frontiers in Nutrition. 2023. frontiersin.org
- Buettner D, Skemp S. “Blue Zones: Lessons From the World’s Longest Lived.” American Journal of Lifestyle Medicine. 2016. pmc.ncbi.nlm.nih.gov
- U.S. Department of Agriculture and HHS. “Food Sources of Dietary Fiber.” Dietary Guidelines for Americans, 2020. dietaryguidelines.gov
