How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Resistant starch
Resistant starch, a type of starch that escapes digestion, slightly lowers blood glucose, insulin, and cholesterol, and increases stool weight. It does not protect against colorectal cancer, and its effects remain modest.
Benefits
- Blood glucose: across 19 trials, fasting blood glucose is slightly lower than with regular starch (−0.09 mmol/L), slightly more so above 28 g per day (−0.16 mmol/L).
- After the meal: replacing the refined flour of a scone with type 4 resistant starch reduced the blood glucose spike by 43 to 45% and the insulin spike by 35 to 40%.
- Insulin: in overweight adults (13 trials, 428 people), it lowers fasting insulin and glycated hemoglobin, especially in diabetics; in insulin-resistant women, 30 g per day made it about 16% more effective.
- Cholesterol: on average −7.33 mg/dL of total cholesterol and −3.40 mg/dL of LDL over 20 trials, with a clearer effect beyond 4 weeks.
- Weight: in 37 overweight people, 8 weeks of resistant starch led to an average weight loss of 2.8 kg and improved insulin resistance.
- Fewer calories: 48 g split over two meals led to eating less over 24 hours (12,603 kJ vs 13,949 kJ) in 20 young men, without changing perceived hunger.
- Gut: heavier stools (35.5 g more per day on average) and more butyrate in healthy adults; in constipated adults, type 3 starch made stools more frequent.
- Lynch syndrome: 30 g per day for up to 4 years reduced non-colorectal cancers linked to the syndrome, 27 affected people vs 48 on placebo, over up to 20 years of follow-up.
Precautions
Tolerance: a review of 39 trials (2,263 people) found it tolerated in all trials conducted in patients, and in 14 of 20 trials in healthy people who reported on it, most often at 20 to 40 g per day. Limitations: colorectal cancer: 30 g per day made no difference to risk in 918 people with Lynch syndrome, nor to the number of polyps in young people with familial adenomatous polyposis. Modest effects: in 68 prediabetic adults, 45 g per day for 12 weeks improved neither blood glucose (glycated hemoglobin −0.1%, clinically insignificant) nor insulin sensitivity. Across 22 type 2 trials, the effect on most cardiometabolic markers is limited; the trials are short (1 to 12 weeks) and small (10 to 60 people). Nothing in women already sensitive to insulin, nor in obese people without diabetes. Inflammation: interleukin 6 (−1.11 pg/mL) and TNF-α (−2.19 pg/mL) drop slightly, but C-reactive protein does not budge.
Recommended dosage
15 to 45 g per day in trials, most often 30 g; effect on blood glucose is clearer above 28 g per day.
How to take it
- Dose: 30 g per day in most trials in this profile, in the form of biscuits, muffins, or powder; 45 g per day in prediabetic adults.
- Duration: the effect on blood glucose is clearer beyond 8 weeks, and on cholesterol beyond 4 weeks.
- Starch type: type 2 (high-amylose corn, unmodified potato starch) is the most studied, generally at 20 to 40 g per day.
- On the plate: about two potatoes cooked then cooled (about 18 g of resistant starch) over a day lowered the next day's fasting blood glucose in overweight adults, without changing insulin sensitivity.
- As a replacement: it was tested in place of regular flour, at equal calories, in most blood glucose trials.
- Variable response: the rise in stool butyrate depends on your microbiota; in 20 young adults, it was strong in some and absent in others.
Did you know?
Resistant starch can reduce total calorie intake and the insulin response without altering the subjective sensation of hunger or satiety.
What the studies say
This meta-analysis reveals that type 1 and 2 resistant starches can lower postprandial blood glucose in individuals with type 2 diabetes or prediabetes. Type 2 also improved postprandial insulin response, fasting blood glucose, and fasting insulin. The addition of resistant starch as a dietary intervention could help prevent the deterioration of glycemic control.
Pugh JE, Cai M, Altieri N, Frost G. — Frontiers in nutrition (2023) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more