Italian toasted bread (‘bruschetta’) should be carefully evaluated by people with type 1 diabetes

Abstract

Several studies focused the effect on glycemic index (GI) of bread on blood glucose either in healthy individuals or in diabetes [1] since post-prandial glycemia (PPG) and glycemic variability have important impact on diabetes complications [2]. The amount and composition of carbohydrates (CHO) affects PPG, together with fibres, chemical state of the starch and food cooking. In fact, high temperature of food processing increases the starch gelatinization with an easier enzymatic accessibility, faster digestion and higher PPG [3]. Mediterranean diet is a model of healthful eating habits in diabetes for its content of starch, mainly pasta and bread. However, no data are available on toasted bread (‘bruschetta’) which is frequently present in breakfast Mediterranean diet. Thus, we evaluated in type 1 diabetes (DM1) the PPG spikes after ingestion of white and dark bread served fresh and toasted. Eighteen (12 F, 6 M) DM1 clinical outpatients, nonsmokers, without any diabetes complications or malabsorptive disorders, aged 38.4 ± 3.7 years, with HbA1c 7.2 ± 0.8% and duration of diabetes of 22.8 ± 7.8 years, were selected. All patients were treated with intensive insulin regimen with 22.1 ± 10.1 IU and 22.3 ± 7.0 IU daily of rapid (Lispro)and long-acting insulin analogue (Glargine), respectively. All patients gave their informed consent to the study protocol approved by Ethical Committee of University of Florence. During the study period of 20 days, all patients maintained their habitual diet and stable insulin therapy. Overnight fasting patients, alcohol and exercise free for 24 h, were admitted to the starting day only with capillary glycemia between 70 and 140 mg/dl. The food test, consumed with 250 ml of water in 50, consisted of 60 g of commercially available fresh wheat-refined bread (white bread: WB), whole-grain bread (dark bread: DB) and the same breads toasted for 2 min in an electric toaster. All patients consumed all four types of food test. The amount of total fibres for DB was 3.9 g for serving, whilst the amount of CHO was 40.2 and 29.4 g for WB and DB for serving, respectively. Four bread types were consumed for 5 days by each patient for total 20 days of collecting data. The patients were treated with preprandial insulin, with the own habitual doses of rapid insulin analogue. These doses were obtained during the pre-test period in order to achieve a post-breakfast glucose levels between 120 and 140 mg/dl. Figure 1 shows the glycemic responses to bread ingestion in the fasting (FPG) and PPG (2hPG) status (mean ± SD). FPG values were 104 ± 19, 105 ± 18, 106 ± 18 and 105 ± 19 mg/ dl for WB, toasted WB, DB and toasted DB, respectively. PPG levels were significantly higher than FPG, in all tests (P \ 0.05). PPG was higher with WB compared to DB with an incremental glucose response of 112.6 ± 4.2 versus 34.4 ± 20.3 mg/dl (P \ 0.001). In addition, the PPG incremental excursion between WB and toasted DB was not statistical different (112.6 ± 4.2 vs. 117 ± 13.4; P = 0.12) although a higher concentration of CHO was present in WB. Toasted WB showed the highest PPG levels (P \ 0.001), with an incremental of 168.7 ± 19.7 mg/dl, whilst the lower incremental was S. Giannini (&) G. Bardini E. Mannucci C. M. Rotella Section of Endocrinology, Department of Clinical Pathophysiology, University of Florence, Viale Pieraccini 6, 50134 Florence, Italy e-mail: s.giannini@dfc.unifi.it