Highlights
- A 12-week high-SDS diet significantly reduced the Mean Amplitude of Glycemic Excursions (MAGE) compared to a low-SDS diet (P = 0.0025).
- Participants in the H-SDS group achieved a mean HbA1c below the 7% clinical target, showing a trend toward greater reduction than the L-SDS group.
- The intervention demonstrated high feasibility with a 96% compliance rate among patients with suboptimally controlled Type 2 Diabetes.
- Modulating starch digestibility via simple culinary and dietary adjustments offers a scalable strategy to mitigate glycemic variability and cardiovascular risk.
The Clinical Challenge of Glycemic Variability
In the management of Type 2 Diabetes (T2D), clinicians have traditionally focused on glycated hemoglobin (HbA1c) as the primary indicator of long-term glycemic control. However, emerging evidence suggests that HbA1c only tells part of the story. Glycemic variability (GV)—the fluctuations in blood glucose levels, including postprandial spikes and interprandial dips—is increasingly recognized as an independent risk factor for diabetic complications. High GV is strongly associated with increased oxidative stress, endothelial dysfunction, and elevated cardiovascular risk, even in patients whose HbA1c remains within the target range.
Starch constitutes the largest source of dietary carbohydrates globally. However, not all starches are metabolized equally. Rapidly Digestible Starch (RDS) leads to swift glucose absorption and sharp postprandial excursions, whereas Slowly Digestible Starch (SDS) is digested at a more gradual rate, promoting a sustained and blunted glucose response. Controlling starch digestibility through nutritional strategies represents a promising but underutilized avenue for stabilizing GV in clinical practice.
Study Design and Methodology
The study, published in the American Journal of Clinical Nutrition (Chisbert et al., 2025), was a randomized, parallel, single-blind, controlled trial designed to evaluate the impact of starch digestibility on GV and cardiometabolic health. The trial enrolled 51 patients with T2D who exhibited suboptimal glycemic control. Participants were randomized into two groups for a 12-week intervention:
High-SDS (H-SDS) Diet
This group received commercial starchy products specifically formulated or processed to have high SDS content. Crucially, the intervention was paired with dietary and culinary counseling to teach patients how to preserve SDS during meal preparation (e.g., optimal cooking times and cooling techniques that promote resistant starch formation).
Low-SDS (L-SDS) Diet
The control group received products with lower SDS content and standard dietary advice, reflecting a more conventional approach to carbohydrate consumption in T2D.
The primary endpoint was the Mean Amplitude of Glycemic Excursions (MAGE), measured via a Continuous Glucose Monitoring System (CGMS). Secondary endpoints included other GV parameters such as the Coefficient of Variation (CV), Standard Deviation (SD), Continuous Overall Net Glycemic Action (CONGAs), and the Mean of Daily Differences (MODD), alongside HbA1c and lipid profiles.
Key Findings: Significant Reductions in Glycemic Fluctuations
The results of the 12-week trial provide robust evidence for the efficacy of SDS-focused interventions. The H-SDS group showed a marked improvement in glycemic stability across multiple metrics:
Primary Outcome: MAGE
Compared with the L-SDS diet, the H-SDS diet significantly lowered MAGE over the 12-week period {β = 30.4 [95% CI: 12.4, 48.5]; P = 0.0025}. This reduction indicates that modulating the rate of starch digestion effectively flattens the peaks and valleys of daily glucose levels, providing a more stable metabolic environment.
Secondary GV Parameters
The benefits extended to other measures of intra- and interday variability. Significant improvements were noted in the SD of glucose levels and the Coefficient of Variation. Furthermore, metrics like CONGAs and MODD—which reflect the consistency of glucose levels over different time intervals—were significantly better in the H-SDS group. This suggests that the intervention helped patients maintain more predictable glucose profiles both within a single day and from one day to the next.
Glycemic Control (HbA1c)
While both groups saw a reduction in HbA1c, the H-SDS group exhibited a trend toward a more pronounced decrease [β = 0.3 (95% CI: 0.05, 0.47); P = 0.0981]. Notably, the H-SDS group successfully brought their mean HbA1c below the 7% threshold, a critical milestone in clinical diabetes management. The lack of statistical significance in the difference between groups for HbA1c may be attributed to the relatively short 12-week duration and the modest sample size, but the clinical trend is highly encouraging.
Mechanistic Insights and Culinary Feasibility
The success of this intervention lies in the physiological behavior of SDS. Unlike RDS, which is hydrolyzed quickly in the upper small intestine, SDS is digested slowly throughout the length of the small intestine. This results in a slower rate of glucose entry into the portal circulation, reducing the demand on pancreatic beta cells and minimizing the postprandial insulin spike.
A standout feature of this study was the 96% compliance rate. Many dietary interventions fail due to the complexity or restrictiveness of the regimen. By focusing on “simple dietary and culinary recommendations”—such as choosing specific commercial products or adjusting cooking methods—the researchers demonstrated that modulating starch digestibility is a highly accessible strategy for the average patient. It does not require the elimination of carbohydrates, which is often a barrier to long-term adherence, but rather a focus on the quality and preparation of those carbohydrates.
Clinical Implications and Expert Commentary
For clinicians, these findings suggest that the “carbohydrate quality” conversation should evolve beyond the Glycemic Index (GI) to include starch digestibility and culinary techniques. While GI is a useful tool, it is often criticized for its variability based on food ripeness and meal composition. Focusing on SDS provides a more mechanistic approach to carbohydrate selection.
It is important to note that while GV improved significantly, other cardiometabolic markers such as lipid profiles and blood pressure remained similar between the two groups. This suggests that the primary benefit of SDS in this timeframe is specific to glucose metabolism. Longer-term studies may be required to determine if the reduction in GV eventually translates into measurable differences in macrovascular and microvascular outcomes.
Limitations of the study include the single-blind design and the use of provided commercial products, which may not perfectly replicate real-world environments where patients must source all their own food. However, the inclusion of culinary counseling mitigates this by empowering patients with the knowledge to make better choices independently.
Conclusion
The trial by Chisbert et al. confirms that modulating starch digestibility is an effective, feasible, and clinically meaningful strategy for managing T2D. By reducing MAGE and other GV parameters, a high-SDS diet addresses a critical gap in traditional diabetes care. For patients struggling with suboptimal control, these simple dietary and culinary adjustments can be the key to reaching recommended glycemic targets and reducing the long-term burden of the disease.
Funding and Registration
This study was supported by institutional grants and industry partnerships focused on nutritional science. The trial was prospectively registered at clinicaltrials.gov as NCT03847701.
References
- Chisbert M, Castell AL, Van Den Berghe L, et al. Optimizing glycemic variability in type 2 diabetes using simple dietary and culinary recommendations to modulate starch digestibility: a randomized controlled trial. Am J Clin Nutr. 2025;122(6):1591-1601. doi:10.1016/j.ajcnut.2025.10.007.
- Monnier L, Colette C, Owens DR. Glycemic variability: the third component of the dysglycemia in diabetes. Is it important? How to measure it? J Diabetes Sci Technol. 2008;2(6):1094-1100.
- Vinoy S, Goux A, Meynier A, Nazare JA. The interest of slowly digestible starch in type 2 diabetes management. Nutrients. 2020;12(10):3074.
