Resistant Starch
Summary
Resistant starch effects on blood sugar are small and inconsistent. A meta-analysis of 22 RS2 trials (670 people) found lower triglycerides in healthy people but no effect on most metabolic measures, and 45 g a day for 12 weeks did not meaningfully improve glucose control in prediabetes. FDA rates the type 2 diabetes evidence as limited.
Key facts
- FDA allows a qualified claim on certain foods linking high-amylose maize resistant starch to type 2 diabetes risk, stating the evidence is limited; FDA also counts high amylose starch (RS2) as dietary fiber on labels[5][6]
- About 7 g to 40 g of RS2 per day in the trials FDA reviewed, and 45 g per day in a 12-week prediabetes trial; 3 to 12 weeks[5][2]
- The FDA claim petition was submitted on behalf of Ingredion, maker of Hi-Maize; the 12-week prediabetes trial was NIH-funded[5][2]
- 2 graded human outcomes on this page
- October 10, 2026
How it works
ProposedResistant starch reaches the colon undigested, where gut bacteria ferment it. Proposed metabolic effects run through slower glucose release and fermentation products, but human trials show inconsistent changes in insulin sensitivity.[5][1]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Metabolic health | Grade C | Mixed | Meta-analysis · n = 670 · 2019 | 1 row |
| Blood sugar | Grade C | No effect | RCT · n = 68 · 2018 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Weight, glucose and blood lipids | Mixed | Grade C | Meta-analysis · n = 670 · 2019 Healthy adults and people with overweight, metabolic syndrome, prediabetes or type 2 diabetes (22 RCTs) Form: Type 2 resistant starch (RS2) · Dose: At least 8 g per day · Duration: 1 to 12 weeks RS2 lowered triglycerides slightly in healthy people (-0.10 mmol/L) and body weight in people with type 2 diabetes (-1.29 kg), but these results leaned on a few small studies; there was no effect on any other metabolic outcome. | 31398841 (opens PubMed)Source [1] |
| Glucose control and cardiometabolic risk factors in prediabetes | No effect | Grade C | RCT · n = 68 · 2018 Adults aged 35 to 75 with prediabetes and BMI of 27 or more (US) Form: High-amylose maize starch (RS2) vs rapidly digestible amylopectin starch · Dose: 45 g per day · Duration: 12 weeks HbA1c fell by a clinically insignificant 0.1% (P = 0.05); insulin secretion, insulin sensitivity and glucose curves were unchanged. Heart rate and TNF-alpha fell; ectopic fat and other risk factors did not change. | 30010698 (opens PubMed)Source [2] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| High-amylose maize starch (RS2) | Varies[1][2][5] | Not digested in the small intestine; fermented in the colon.[5] | Flatulence was higher at 30 g/day of RS2 than with control starch in one trial reviewed by FDA, and one participant withdrew because of constipation.[5] | Glucose and metabolic trials at 7 to 45 g/day |
| Other resistant starch types (RS3, RS4, potato starch) | Varies[4] | No absorption data in our sources.[4] | Not reported separately in the abstracts.[4] | Included in glycaemic meta-analyses; type 1 resistant starch was excluded from one |
Studied doses
Doses studied in human trials ranged from about 7.4 g to 40 g of RS2 per day in the trials FDA reviewed, for 3 to 12 weeks; a separate 12-week prediabetes trial gave 45 g of high-amylose maize starch per day.[5][2]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Diabetes medicinesRCTNot studied together in the trials cited here; anyone on glucose-lowering medicine should check with a clinician before adding large fiber or starch supplements.[2]
Who should be careful
- People prone to gas or bloating
- Flatulence was higher with 30 g/day of RS2 in one trial, and one participant withdrew with constipation.[5]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Safety
Resistant starch is a food starch; the main side effects are digestive.
How to read the label
- Label dose vs clinical doseTrials reviewed by FDA gave about 7.4 to 40 g of RS2 per day, and a 12-week prediabetes trial gave 45 g; the FDA letter says the evidence does not support any recommended daily intake.[5][2]
- Starch weight vs resistant starchHigh-amylose maize starch is only partly resistant (the FDA claim requires at least 50% RS2), so check grams of resistant starch, not total starch.[5]
- Fiber on the labelFDA allows high amylose starch (RS2) to be declared as dietary fiber on Nutrition and Supplement Facts labels.[6]
Cost per studied dose, without the sales pitch
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Cost per studied dose
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Frequently asked questions
Does resistant starch lower blood sugar?
Only slightly, if at all: pooled trials found a small drop in fasting glucose, but a 12-week trial of 45 g/day in prediabetes found no meaningful change in glucose control.[4][2]
What does FDA say about resistant starch?
FDA allows a qualified claim for high-amylose maize resistant starch and type 2 diabetes risk on certain foods, stating that the scientific evidence is limited.[5]
Is resistant starch a fiber?
FDA allows high amylose starch (resistant starch 2) to be declared as dietary fiber on food and supplement labels.[6]
How much resistant starch was studied?
About 7.4 g to 40 g of RS2 per day in the trials FDA reviewed, and 45 g per day in a 12-week prediabetes trial, for 3 to 12 weeks.[5][2]
Does resistant starch cause gas?
It can: flatulence was higher at 30 g/day of RS2 than with control starch in one trial.[5]
Sources
- [1]Metabolic Effects of Resistant Starch Type 2: A Systematic Literature Review and Meta-Analysis of Randomized Controlled Trials.. Nutrients, 2019. meta-analysis
- [2]Effect of 12 wk of resistant starch supplementation on cardiometabolic risk factors in adults with prediabetes: a randomized controlled trial.. Am J Clin Nutr, 2018. RCT
- [3]Meta-analysis indicates that resistant starch lowers serum total cholesterol and low-density cholesterol.. Nutr Res, 2018. meta-analysis
- [4]Effects of resistant starch on glycaemic control: a systematic review and meta-analysis.. Br J Nutr, 2021. meta-analysis
- [5]Petition for a Health Claim for High-Amylose Maize Starch (Containing Type-2 Resistant Starch) and Reduced Risk Type 2 Diabetes Mellitus: letter of enforcement discretion (December 12, 2016). U.S. Food and Drug Administration (FDA), 2016. guideline
- [6]FDA Issues Guidance, Science Review, and Citizen Petition Responses on Dietary Fiber (constituent update, June 14, 2018). U.S. Food and Drug Administration (FDA), 2018. guideline
What changed
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.
- Adversarial review pass: every evidence row re-read against its whole PubMed abstract. Official sources opened: FDA letter of enforcement discretion for high-amylose maize starch and type 2 diabetes (December 12, 2016) and FDA dietary fiber constituent update (June 14, 2018); no NIH ODS or NCCIH page covers resistant starch. Meta-analyses without a participant total in the abstract (29914662, 32959735) are cited in insights and FAQ only. Industry ties: Ingredion submitted the FDA claim petition; the 2018 prediabetes trial was NIH-funded (PMC6134290); 31398841 has no funding statement in PubMed. Retraction, expression-of-concern, erratum and withdrawn checks on all cited PMIDs: none flagged. Page set indexable.