Pizza Leavening and Postprandial Glycemia in Type 1 Diabetes (LEAVEN)

Pizza is a typical food from Southern Italy. Its consumption is spreading worldwide. However, eating pizza is often challenging for type 1 diabetes patients due to its high glycemic index and the sustained and prolonged postprandial hyperglycaemia. Therefore, modifications of the composition and manufacturing processes able to improve the effects of pizza on postprandial blood glucose response would be well accepted.

The purpose of this study is to compare in patients with type 1 diabetes the postprandial glucose response to the consumption of three types of pizza, obtained with different leavening techniques.

Patients with type 1 diabetes treated with continuous subcutaneous insulin infusion for at least 6 months and HbA1c less than 8.0%, will be recruited at the diabetes care unit of the Federico II University teaching hospital.

The intervention will be preceded by a one-week run-in period during which participants will undergo continuous glucose monitoring (CGM) to optimize basal infusion rate and insulin-to-glycemic load ratio. Then, according to a randomized crossover design, participants will consume at home at dinner-time in random order in three different days over a 3-week period:1) a long-leavened (60 h) pizza composed of sourdough and a flour mix; 2) a short-leavened (5 h) pizza composed of sourdough and a flour mix; 3) a traditional pizza composed of brewer's yeast and refined wheat flour. Over the three experimental weeks, participants will undergo CGM, wearing their sensors 7 days/week.

The pizza- meals will be similar in energy content and macronutrient composition. The pizza dough will be prepared in a specialized factory and kept under vacuum until use. Participants will be also provided with tomato sauce and extra-virgin olive oil in the exact amount needed to prepare pizza.

The test meal will be postponed in case of premeal blood glucose levels outside the 90-150 mg/dl range or a rapid decrease/increase of glucose levels (above 1 mg/dl per min) during the previous 60 min according to CGM measurement, Pre-meal insulin doses, will be calculated based on the individual insulin-to-glycemic load ratio and will be the same on all three occasions.

At the end of the experimental period, data from CGM and insulin pump will be downloaded by dedicated informatics platforms. Participants will use the CGM system integrated with their insulin pump, i.e., the one they are accustomed to.

The primary outcome will be the postprandial blood glucose incremental area under the curve (AUC). The secondary outcomes will be blood glucose peak and time to blood glucose peak. Both primary and secondary outcomes will be evaluated by general linear model for repeated-measures ANOVA .

The results of this study will allow the optimization of insulin therapy based on the different characteristics of pizza, in patients with type 1 diabetes mellitus treated with insulin pump. This will improve glycemic control and quality of life of these patients and reduce their risk of developing chronic diabetes complications. These complications involve severe disability for patients and huge costs for the community. Moreover, considering the large consumption of pizza, the identification of changes in its composition determining a more advantageous postprandial metabolic profile could also bring benefits to the health of the general population, reducing the incidence of chronic diseases such as type 2 diabetes.

Inclusion criteria

• Treatment with continuous subcutaneous insulin infusion for at least 6 months
• HbA1c less than 8.0% (64 mmol/mol)

Exclusion criteria

• Pregnancy
• Celiac disease
• Serious microvascular and macrovascular diabetes complications including autonomic neuropathy possibly influencing gastric emptying
• Any other chronic or acute disease apart diabetes seriously affecting health status