Firm, undercooked potatoes may provide a simple dietary strategy to reduce blood sugar spikes, but their effects appear to be short-lived and vary depending on the population.
Study: Minimally cooked potatoes improved glycemic response over two meals and insulin sensitivity of a mixed rice and potato meal: a randomized controlled acute trial. Image credit: Sunlight_s/Shutterstock.com
Recent research published in nutrients investigated the relationship between texture, oral processing, and starch digestibility of hard-cooked (HP) and soft-cooked (SP) potato samples. In this study, we further evaluated the acute postprandial glycemic and insulinemic responses when these potato preparations were co-ingested with rice.
Potato intake, cooking methods, and changes in blood sugar levels
The global burden of diabetes continues to grow at an alarming rate. According to current projections, this condition is expected to affect approximately 783 million people worldwide by 2045. Given that dietary carbohydrates are the main determinant of postprandial glycemia, strategic selection of starchy foods represents a modifiable and clinically relevant glycemic control goal, especially in populations with carbohydrate-based diets.
Potatoes are one of the most widely consumed starchy staple foods around the world and provide a cost-effective source of potassium, fiber, vitamin C, and antioxidants. However, their relationship to diabetes risk remains controversial, and epidemiological studies have yielded inconsistent results across pregnancy and type 2 diabetes outcomes. These discrepancies are likely due to the way potatoes are prepared and consumed.
The cooking method determines the texture of the potato and, as a result, the glycemic properties of the potato. Firm-textured potatoes, such as fried potatoes, are reported to have a glycemic index (GI) of approximately 56, while soft-cooked potatoes have a glycemic index (GI) of approximately 83. Hard-cooked potatoes are also a rich source of resistant starch (RS), which reduces postprandial blood sugar spikes and supports intestinal health. Furthermore, firmer texture prolongs oral processing and is associated with slower eating due to increased mastication. The secretion of glucagon-like peptide-1 (GLP-1) and peptide YY was increased and insulin sensitivity was improved.
Despite these insights, clinical evidence directly comparing hard-cooked and soft-cooked potato alternatives in mixed meals remains limited, particularly regarding whether RS-mediated fermentation sustains glycemic effects beyond the index meal.
Evaluation of glycemic response to potato texture in a randomized crossover trial
This study employed a randomized crossover design with three treatments: Rice as the sole staple food (RC). Firm-textured potatoes replace one-third of the available carbohydrates in rice (HP + R). Soft-textured potatoes replace one-third of the available carbohydrates in rice (SP + R).
RC consisted of 90 g of uncooked rice, while HP+R and SP+R each consisted of 60 g of uncooked rice combined with 130 g of raw potatoes cooked to hard or soft texture, respectively. The standardized dinner was the same for all groups. Taste was confirmed in a pre-trial tasting session.
Healthy female college students aged 18 to 27 years with body mass index (BMI) of 18.5 to 23.9 kg/m² were recruited. Each participant completed all three treatments in a randomized order with at least one washout day between sessions. Sessions were scheduled outside the menstrual period. The day before each trial, participants ate meals at set times, avoided sugary drinks and alcohol, and went to bed before midnight.
Light cooking provides superior blood sugar and metabolic results
Cooking method was an important determinant of starch digestibility. SP produced the highest rapidly digestible starch (RDS), but HP had the lowest. In HP, resistant starch (RS) was highest and slowly digestible starch (SDS) was lowest, indicating reduced glucose availability.
Phenol content decreased with cooking intensity. HP decreased by 38% compared to raw, while SP decreased by 55%, while the texture gradually became softer from raw to SP, with significant differences across almost all parameters.
Twenty participants completed the study without any adverse events. Both potato-based diets reduced postprandial blood glucose levels compared to the rice control, with HP+R achieving a more pronounced and sustained reduction than SP+R.
Although HP + R produced generally more stable blood glucose levels than both comparators in several variability measurements, SP + R increased blood glucose variability, with HP + R lowering insulin concentrations up to 2 h postprandial compared to RC and lower than SP + R at early time points (30–60 min).
Across key insulin parameters such as incremental area under the curve of postprandial insulin response (iAUCins), peak insulin, and postprandial insulin resistance index (HOMA-PP), HP + R showed improvements compared to the rice control and exhibited several advantages over SP + R at specific time points. It was the only diet that improved insulin sensitivity compared to control rice.
At the second meal, SP + R produced higher blood glucose levels than controls at 90 min, whereas HP + R remained similar throughout, with no difference in overall variation between groups. This indicates that HP+R alone has no clear statistically significant second meal benefit.
Over 540 min, HP+R significantly reduced total glucose exposure compared to control, whereas SP+R failed to reproduce this benefit. of Although study results showed a correlation between longer oral processing and decreased glycemic response, a direct causal relationship between meal pace has not been established. The authors suggest that starch composition likely plays a more dominant role than oral processing.
A similar pattern emerged for insulin, with iAUCins, peak insulin, and HOMA-PP all negatively correlated with meal pace, suggesting an association rather than confirming that slow eating directly improves insulin sensitivity.
Despite these metabolic differences, satiety, hunger, and appetite did not differ significantly between meal types, indicating that the glycemic effects of HP+R operate independently of subjective appetite.
conclusion
This study shows that partial replacement of rice with minimally cooked potatoes reduces postprandial glycemic and insulinemic responses in healthy women. This may be due to increased RS content and decreased glucose availability rather than texture or oral processing. However, this effect did not extend to the second meal, suggesting that fermentation-related mechanisms such as short-chain fatty acid (SCFA) production may require additional time, although this was not directly measured.
This finding was limited to young, healthy female participants and reflected an acute response to a single meal, which may limit generalizability to other populations, including people with diabetes, and long-term dietary outcomes. Although the underlying mechanisms and population generalizability require further study, these findings provide a new perspective on potato consumption patterns for glycemic control.
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Reference magazines:
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Wei, J., Fan, Z., Deng, Y., Pan, K., Shi, R., Hu, J., and Liu, B. (2026). Minimally cooked potatoes improved glycemic responses over two meals and insulin sensitivity of a mixed rice and potato meal: a randomized controlled acute trial. nutrients. 18(6)． Toi https://doi.org/10.3390/nu18060973. https://www.mdpi.com/2072-6643/18/6/973
