Benefits
Supports healthy insulin sensitivity
In a 4-week crossover trial in 33 adults with a large waist, 15 or 30 g/day raised insulin sensitivity in men but not in women, a result seen only after splitting by sex. In 40 women, 30 g/day raised it about 16% in those with low insulin sensitivity, with no effect in the others. A 12-week trial in 68 adults with prediabetes found no change.
Post-meal blood sugar response
In 17 adults with well-controlled type 2 diabetes, 40 g/day for 12 weeks lowered blood sugar after a test meal compared with a digestible starch, the trial's main outcome, while insulin sensitivity and HbA1c did not change. In a 6-week trial of 30 g/day in muffins, groups did not differ.
Fasting blood sugar and early insulin release
In a 4-week crossover study in 12 adults with overweight, 40 g/day lowered fasting blood sugar slightly (4.8 versus 5.0 mmol/L) and raised first-phase insulin release on an intravenous glucose test compared with a digestible starch. Insulin sensitivity, body weight and blood fats did not change.
Body weight and fat mass in adults with overweight
In a double-blind crossover trial in 37 adults with overweight or obesity eating a provided diet, 40 g/day for 8 weeks lowered weight by 2.8 kg more than a control starch, with less fat mass and waist size. This is a single trial; other Hi-maize trials of 4 to 12 weeks on usual diets found no weight change.
Food intake at later meals
In two single-day crossover studies in men, 48 g of resistant starch added to breakfast and lunch led to less food eaten at a later free-choice meal than a placebo starch, without changing hunger ratings. Over 12 weeks in adults with prediabetes, 45 g/day did not change appetite or food intake.
Mechanism of action
Resists digestion in the small intestine
The granular high-amylose starch in Hi-maize resists breakdown by digestive enzymes, so its resistant fraction reaches the colon instead of being absorbed as glucose. The product also contains digestible starch, which trials matched with a placebo starch of equal digestible carbohydrate.
Colonic fermentation and gut hormones
Gut bacteria ferment the resistant starch into short-chain fatty acids. In a 12-week trial in type 2 diabetes, the rise in the gut hormone GLP-1 after a meal was larger than with placebo, which the authors linked to the better post-meal blood sugar handling.
Fatty acid release from fat tissue
In the same 12-week trial, fasting free fatty acids were lower and their suppression by insulin was greater after resistant starch, while fasting triglycerides were slightly higher. Lower fatty acid release from fat tissue may help muscle respond to insulin.
Gut bacteria and bile acids
In the 8-week weight trial, resistant starch shifted gut bacteria, including more Bifidobacterium adolescentis, and changed bile acid levels. Mouse experiments by the same group suggested this bacterium plays a part; this route has not been confirmed in people.
Clinical trials
Randomized, double-blind, controlled crossover trial: 0 (control starch), 15 or 30 g/day of resistant starch from Hi-maize 260, with Amioca as control, both supplied by National Starch, for 4 weeks each with 3-week washouts; primary outcome insulin sensitivity on an insulin-modified intravenous glucose tolerance test. Funded by National Starch, the producer, and two authors were its employees; registered as NCT01058135. (Maki et al. 2012, J Nutr)
33 evaluable adults (11 men, 22 women) with a large waist and an average BMI of 30.6; 41 were randomized.
The overall treatment effect on insulin sensitivity was significant (p = 0.018) but differed by sex (interaction p = 0.033), so men and women were analyzed separately. In men, insulin sensitivity was higher after 15 and 30 g/day than after control (6.90 and 7.13 versus 4.66 units, p < 0.05). In women, no dose differed from control. Body weight, waist size and blood fats did not change. Flatulence above usual was reported by 33% on 30 g/day versus 9% on control, and one person withdrew because of constipation.
Randomized, placebo-controlled, double-blind crossover trial: cookies giving 15 or 30 g/day of resistant starch from Hi-maize 260, or Amioca control cookies, for 4 weeks each with 4-week washouts; insulin sensitivity by intravenous glucose tolerance test. Funded by Ingredion; one author was an Ingredion employee and two were Ingredion consultants. (Gower et al. 2016, Nutr Metab (Lond))
40 non-diabetic women aged 22 to 67 with a BMI of 20.6 to 47.4, split by baseline insulin sensitivity; 23 completed all three arms.
In women with low baseline insulin sensitivity, insulin sensitivity was about 16% higher after 30 g/day than after control in the all-data analysis (p < 0.05) and tended to be 23% higher among women who completed all arms (p = 0.06). The 15 g/day dose, and either dose in insulin-sensitive women, had no effect. FDA's 2016 review noted that 51 women entered and only 23 completed all three arms with usable results.
Randomized, subject-blind crossover study: 67 g/day Hi-maize 260 (40 g resistant starch) or 27 g/day Amioca placebo, both supplied by National Starch, for 4 weeks each with a 4-week washout, followed by an insulin-modified intravenous glucose tolerance test. Funded by Diabetes UK and a Premier Foods fellowship. (Bodinham et al. 2012, PLoS One)
12 adults with overweight (average BMI 28.2).
Fasting glucose was lower after resistant starch than after placebo (4.8 versus 5.0 mmol/L, p = 0.049), and first-phase insulin secretion was higher. Fasting insulin, blood fats, body weight and waist size did not differ, and modeled insulin sensitivity did not differ. Both supplements were well tolerated.
Single-blind, randomized crossover study: 67 g/day Hi-maize 260 (40 g resistant starch) or 27 g/day Amioca placebo for 12 weeks each with a 12-week washout; primary outcome post-meal glucose tolerance. Supplements were donated by Ingredion, with no industry role in design or interpretation; funded by Diabetes UK; registered as ISRCTN10727538. (Bodinham et al. 2014, Endocr Connect)
17 adults with well-controlled type 2 diabetes.
Post-meal glucose was lower after resistant starch than after placebo (p = 0.045) and the post-meal GLP-1 rise was larger, but liver and muscle insulin sensitivity and HbA1c did not change. Fasting free fatty acids fell, while fasting triglycerides rose slightly (p = 0.039). Flatulence ratings were mildly higher.
Randomized controlled parallel trial: 45 g/day high-amylose maize starch (Hi-maize 260, named in the companion appetite paper) or an equal-calorie amylopectin starch (Amioca) for 12 weeks; primary endpoints insulin sensitivity, insulin secretion, ectopic fat and inflammation markers. Funded by the US National Institutes of Health (NIDDK); registered as NCT01708694. (Peterson et al. 2018, Am J Clin Nutr)
68 adults aged 35 to 75 with prediabetes and a BMI of 27 or more.
Insulin sensitivity, insulin secretion, glucose and insulin responses and ectopic fat did not change versus control. HbA1c fell by a clinically insignificant 0.1 percentage point (p = 0.05), and heart rate and TNF-alpha fell. A companion analysis found no effect on appetite, gut hormones or food intake.
Randomized, placebo-controlled, double-blind crossover trial: 40 g/day resistant starch as Hi-maize 260 or energy-matched Amioca control starch, both provided by Ingredion, for 8 weeks each with a 4-week washout, on a provided background diet; primary outcome body weight. Funded by Chinese public research grants, with no competing interests declared; registered as ChiCTR-TTRCC-13003333. (Li et al. 2024, Nat Metab)
37 adults with overweight or obesity in Shanghai, China.
Body weight fell 2.81 kg more on resistant starch than on control starch (95% CI 2.07 to 3.55 kg, p < 0.001), with lower fat mass, waist size and visceral fat. Insulin sensitivity on a clamp test also improved (p = 0.025). No digestive side effects were reported. The diet was provided, so results may differ with usual eating.
Acute randomized, single-blind crossover study: 80 g Hi-maize 260 (48 g resistant starch) or an energy and carbohydrate-matched Amioca placebo, split between two meals, both supplied by National Starch; food intake measured at a later free-choice meal and over 24 hours. (Bodinham et al. 2010, Br J Nutr)
20 healthy young men.
Energy intake was lower after resistant starch at the free-choice meal (5241 versus 5606 kJ, p = 0.033) and over 24 hours (12603 versus 13949 kJ, p = 0.044), with no change in hunger or fullness ratings. Post-meal insulin was lower, while glucose did not differ.
Randomized, controlled, double-blind parallel trial: muffins giving 30 g/day resistant starch from Hi-maize 260 (supplied by Ingredion) or control muffins for 6 weeks; primary objective glucose control. Funded by Texas Woman's University and Ingredion; not registered. (Maziarz et al. 2017, Nutr J)
18 healthy adults with overweight (11 resistant starch, 7 control).
Within the resistant starch group, the post-meal glucose and leptin areas fell and fasting PYY rose, but the authors reported no between-group differences in these markers, and body composition and energy intake did not change.