In this article
- Resistant starch and skin: what resistant starch actually is
- The types of resistant starch, and where to find them
- What the research shows
- Potato starch vs green banana flour
- How long before you notice a difference?
- How to add resistant starch without overdoing it
- The honest verdict on resistant starch skin benefits
- Resistant starch and skin: your questions answered
- Sources
Cook white rice, chill it in the fridge for a day, then warm it up again, and it ends up with more than 2.5 times the resistant starch of the same rice served fresh. In a 2015 study, that chilled and reheated rice also raised blood sugar less in healthy adults.
Kitchen tricks like this are why resistant starch skin advice keeps popping up online. The idea is that this starch feeds gut bacteria, which in turn calm inflammation that can show up on your skin. Here’s what resistant starch is, what the research actually supports, and how to eat more of it sensibly.
By the numbers
- 2.5x more resistant starch in white rice that was cooked, chilled for 24 hours and reheated
- 174 adults tested three fermentable fibers for two weeks, and potato starch raised short-chain fatty acids the most
- 13 trials with 672 people found resistant starch lowered two inflammation markers, IL-6 and TNF-alpha
Resistant starch and skin: what resistant starch actually is
Most starch breaks down into sugar in your small intestine. Resistant starch is the exception: it resists digestion there and travels on to the large intestine, where it feeds the good bacteria living in your gut.
That’s why it behaves more like a fiber than a typical carb. When gut bacteria ferment it, they produce short-chain fatty acids, and three of these get most of the attention:
- Butyrate: the one raw potato starch raised most in a large two-week study of young adults.
- Propionate: in a mouse study of psoriasis-like inflammation, it calmed the skin when given on its own.
- Acetate: the third main product of fiber fermentation, made alongside the other two.
This chain from starch to bacteria to short-chain fatty acids is the link people mean when they talk about the gut skin axis. It’s a real biological route, but as you’ll see, the skin end of it hasn’t been tested directly with resistant starch yet.
The types of resistant starch, and where to find them
Cleveland Clinic describes four types. Three of them come from everyday foods, and the fourth is a manufactured ingredient added to some processed products.
Type 1: locked inside whole foods
This starch sits inside the cell walls of whole grains, legumes and seeds, so digestive enzymes can’t easily reach it. Beans, lentils, barley and oats are good everyday sources.
Type 1 comes packaged with other fibers, which makes legumes the most well-rounded resistant starch food for gut and skin.
Type 2: raw and unripe
Unripe bananas and raw potatoes contain starch granules that resist digestion in their natural form. Raw potato starch and green banana flour are concentrated versions of this type.
Type 2 is the type with the strongest human data for raising butyrate, thanks to studies using raw potato starch.
Type 3: cooked, then cooled
When starchy foods such as rice, potatoes or pasta are cooked and then cooled, some of the starch re-forms into a tighter structure that resists digestion. Cleveland Clinic suggests cooling cooked rice or pasta in the fridge overnight before reheating.
Type 3 is the easiest to add without buying anything new, because it only changes how you prepare foods you already eat.
Curious how much fiber your current meals already provide before you start adding more? Our fiber calculator gives you a quick read on a normal day.
What the research shows
There’s no published human trial that gave people resistant starch and then measured their skin. The evidence comes in three steps, each reasonably solid on its own.
Step 1: it raises short-chain fatty acids
A 2019 study in mBio gave 174 healthy young adults one of three fermentable fibers, or a regular corn starch control, for two weeks. Resistant potato starch produced the biggest rise in total short-chain fatty acids, including butyrate, while resistant maize starch and inulin didn’t raise butyrate significantly. The comparison group ate an easily digested corn starch, so the rise can’t be put down to simply eating more starch.
Responses varied a lot from person to person. People whose gut bacteria responded with more Ruminococcus bromii, especially alongside plenty of Eubacterium rectale, were the most likely to see butyrate climb.
Step 2: it can lower inflammation markers
A 2020 meta-analysis in Nutrition Journal pooled 13 randomized trials with 672 people, lasting 4 to 14 weeks. Resistant starch lowered IL-6 by about 1.1 pg/mL and TNF-alpha by about 2.2 pg/mL. TNF-alpha is also one of the signals that dropped in the inflamed skin of mice fed a fermentable fiber in a 2023 psoriasis study.
C-reactive protein didn’t change, though, and results varied widely between studies. The authors also flagged possible publication bias for the TNF-alpha result, so the effect is real but modest.
Step 3: it softens blood sugar spikes
In the 2015 rice study, healthy adults ate freshly cooked rice one morning and rice that had been chilled for 24 hours and reheated on another. The chilled rice had 1.65 g of resistant starch per 100 g versus 0.64 g, and across the 14 people with complete data, the rise in blood sugar after eating it was about 18% smaller.
Steadier blood sugar is one of the things acne and diet research keeps coming back to. Put together, these three steps make resistant starch a reasonable addition for skin inflammation, but not a proven skin treatment.
Potato starch vs green banana flour
These two powders are the most common ways people add a concentrated dose. Both are Type 2, and both lose much of their benefit with heat.
| Source | Type | What the evidence shows | Best way to use it |
|---|---|---|---|
| Raw potato starch | Type 2 | Raised butyrate most in a 174-person, two-week study | Stirred raw into yogurt, smoothies or cool drinks |
| Green banana flour | Type 2 | Almost entirely resistant in lab tests, but heat cut that to 29 to 48% | In no-cook recipes rather than baked goods |
| Cooked and cooled rice or potatoes | Type 3 | Chilled rice had 2.5 times the resistant starch of fresh rice | Cook ahead, chill overnight, reheat |
| Beans, lentils, oats, barley | Type 1 | Supply resistant starch alongside other fibers | Everyday meals, several times a week |
The green banana flour numbers come from a 2023 lab study in Frontiers in Nutrition using one Chinese banana variety. Untreated flour was nearly all resistant starch, but four different heat treatments brought it down to between 29% and 48%, so baking with it sacrifices much of the point.
Myth vs fact
Myth: Reheating cooled rice or potatoes undoes the resistant starch.
Fact: In the rice study, the chilled rice was reheated before testing and still had 2.5 times the resistant starch of fresh rice. Cooling does the work, and a quick reheat doesn’t erase it.
How long before you notice a difference?
It depends on what you’re tracking. Gut changes come first, inflammation markers later, and skin last.
- The same day: a meal with cooled and reheated rice produces a gentler blood sugar rise.
- Around 2 weeks: the time it took raw potato starch to raise short-chain fatty acids in the mBio study.
- 4 to 14 weeks: the length of the trials that saw lower IL-6 and TNF-alpha.
- 3 months or more: a fair window to judge whether your skin looks calmer, since skin conditions naturally come and go.
Go slowly, as you would with any fiber. Adding about 5 g of total fiber per week, and starting resistant starch powders with a small spoonful, gives your gut bacteria time to adjust.
Need a gentle week-by-week routine for bringing new fibers into your diet? Our gut health guides lay it out in simple stages.
How to add resistant starch without overdoing it
You don’t need special products to eat more resistant starch. These habits cover all three food-based types.
- Batch-cook and chill: make rice, potatoes or pasta a day ahead, refrigerate overnight and reheat as needed.
- Keep legumes in rotation: beans and lentils add Type 1 resistant starch plus plenty of other fiber.
- Pick bananas a little green: slightly unripe bananas carry more Type 2 starch than fully ripe ones.
- Use powders raw: stir potato starch or green banana flour into cold foods rather than baking with them.
- Cook with starch-rich flours: Cleveland Clinic suggests chickpea flour, tapioca flour and potato starch as easy kitchen swaps.
- Mix sources: since people’s gut bacteria respond differently, a variety of resistant starches gives more of them something to work with.
Looking for make-ahead potato salads, chilled grain bowls and bean dishes that fit this approach? Our recipe eBooks are full of easy ideas.
The honest verdict on resistant starch skin benefits
Here’s where the evidence stands. Resistant starch reliably feeds gut bacteria, potato starch raises butyrate within two weeks, and trials show modest drops in two inflammation markers. Because gut bacteria respond so differently from one person to the next, your own results may not match someone else’s.
What’s missing is the final step: a trial that measures acne, eczema or skin inflammation after people eat more resistant starch. If you follow an eczema diet or manage acne through food, resistant starch is a sensible, low-risk addition rather than a replacement for anything that’s already working.
The best part is how little it asks of you. Cooling yesterday’s rice, adding beans to a salad and buying your bananas a shade greener costs nothing, and your gut bacteria will put it to use either way.
Resistant starch and skin: your questions answered
Is resistant starch good for your skin?
Possibly, but indirectly. Resistant starch feeds gut bacteria that make butyrate and has lowered IL-6 and TNF-alpha in trials, yet no study has measured skin results directly.
Does reheating rice destroy resistant starch?
No. In one study, rice chilled for 24 hours and then reheated still had 1.65 g of resistant starch per 100 g, compared with 0.64 g in freshly cooked rice.
Is potato starch or green banana flour better?
Raw potato starch has the stronger human evidence, having raised butyrate the most in a 174-person study. Green banana flour is also rich in resistant starch but loses much of it when heated.
Can resistant starch help acne?
It hasn’t been tested on acne directly. It can soften blood sugar spikes and lower some inflammation markers, both of which are relevant to acne and diet research.
Which foods are highest in resistant starch?
Unripe bananas, raw potato starch, green banana flour, cooked and cooled rice, potatoes and pasta, and legumes such as beans and lentils are among the best sources.
Does resistant starch help with eczema?
There’s no direct evidence yet. It supports the gut bacteria and short-chain fatty acids that eczema research focuses on, so it can fit into an eczema diet as one part of a varied, fiber-rich pattern.
How much resistant starch or fiber do I need for better skin?
There’s no skin-specific amount, so build up gradually toward the general fiber needs of a typical adult. Our fiber calculator shows the target that fits you.
Sources
- Cleveland Clinic Health Essentials. “Resistant Starch.” 2025. clevelandclinic.org
- Baxter NT, Schmidt AW, Venkataraman A, Kim KS, Waldron C, Schmidt TM. “Dynamics of Human Gut Microbiota and Short-Chain Fatty Acids in Response to Dietary Interventions with Three Fermentable Fibers.” mBio, 2019. doi.org
- Vahdat M, Hosseini SA, Khalatbari Mohseni G, et al. “Effects of Resistant Starch Interventions on Circulating Inflammatory Biomarkers: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.” Nutrition Journal, 2020. doi.org
- Sonia S, Witjaksono F, Ridwan R. “Effect of Cooling of Cooked White Rice on Resistant Starch Content and Glycemic Response.” Asia Pacific Journal of Clinical Nutrition, 2015. apjcn.qdu.edu.cn
- Zhang S, Zhao K, Xu F, et al. “Study of Unripe and Inferior Banana Flours Pre-gelatinized by Four Different Physical Methods.” Frontiers in Nutrition, 2023. doi.org
- Yoshida M, Funasaka Y, Saeki H, Yamamoto M, Kanda N. “Dietary Fiber Inulin Improves Murine Imiquimod-Induced Psoriasis-like Dermatitis.” International Journal of Molecular Sciences, 2023. mdpi.com
