The present study investigated the effect of apple consumption on postprandial blood glucose and insulin levels in subjects with normal versus impaired glucose tolerance. The study participants were ten healthy subjects with no glucose intolerance (normal subjects) (mean, 24.4 ± 4.8 years) and nine subjects with impaired glucose tolerance (mean, 45.2 ± 11.1 years, including 2 on insulin therapy). The test meal included white rice (148 g) and a Fuji apple (150 g). The normal subjects were randomly divided into two groups: the apple-first group, wherein the subjects consumed white rice 5 min after consuming the apple, and the rice-first group, wherein the subjects consumed an apple 5 min after consuming the white rice. Blood samples were then taken from both groups for 3 h. In addition, the subjects with impaired glucose tolerance received the same treatment as the normal subjects, with the difference being glucose level monitoring according to the order in which the apples were consumed. In the normal subjects, the Cmax of Δblood glucose and Δinsulin levels were 54.0 ± 5.0 mg/dL and 61.9 ± 7.2 µU/dL versus 46.2 ± 5.9 mg/dL and 49.8 ± 8.5 µU/dL in the rice-first and apple-first groups, respectively. The incremental area under the curve (iAUC) of insulin tended to decrease in the apple-first group. In the impaired glucose tolerance subjects, the Cmax of Δblood glucose was 75.2 ± 7.2 mg/dL in the apple-first group compared to 90.0 ± 10.0 mg/dL in the rice-first group, which was a significant difference (p < 0.05). The iAUC of blood glucose was lower in the apple-first group. Eating an apple before a meal may be a simple and effective strategy for managing the glycaemic response in individuals with impaired glucose tolerance.
Keywords: apple; impaired glucose tolerance; intake timing; postprandial blood glucose.