Designing a quality assurance system for dietary data in a multicenter clinical trial: Women's Intervention Nutrition Study.

Reliable dietary intake data are essential for determining outcomes in nutrition-related clinical trials. Nevertheless, systems for quality assurance of dietary intake data are often slighted in the design of such trials and not incorporated or monitored as the trials continue. The Women's Intervention Nutrition Study (WINS), a multicenter clinical trial investigating the effect of reduction of dietary fat intake together with adjuvant systemic therapy on recurrence rates in and survival of postmenopausal women with early stage, surgically treated, breast cancer, has developed a quality assurance system to minimize errors and to produce data that are complete and reliable. The system involves development of standardized procedures for data collection, a quality control program to evaluate the data collected, and continual monitoring and reevaluation. The WINS system is offered as a model for studies collecting dietary intake data, no matter how simple or complex the trial design.

Very-low-energy diets alter the counterregulatory response to falling plasma glucose concentrations.

A consequence of short-term very-low-energy diets (VLEDs) in lean subjects is reactive hypoglycemia. We therefore tested the responses of overweight women on prolonged (14 d) VLEDs. Subjects lost 4.8 +/- 0.2 kg (mean +/- SEM, n = 13, P < 0.001). Group A (n = 6) was challenged with an oral-glucose-tolerance test (OGTT) and group B (n = 7) with an oral-sucrose-tolerance test (OSTT) on days 1 and 14. In group A, mean nadir plasma glucose after the OGTT was lower on day 14, 3.75 +/- 0.16 vs 4.7 +/- 0.19 mmol/L (P < 0.01), because of an accelerated rate of glucose decline (RGD, 26.7 +/- 3.3 vs 17.2 +/- 3.9 mumol.l-1.min-1, P < 0.05) late in the OGTT. Plasma insulin was also lower (P < 0.03) and the VLED suppressed two growth hormone (GH) peaks on day 14 (P < 0.05 for each). In group B on day 14, a greater RGD was also observed late in the OSTT, 16.9 +/- 4.1 vs 6.5 +/- 2.0 mumol.L.min-1 (P < 0.03). GH peaks were also significantly suppressed. We conclude that a VLED results in altered glucose regulation late after carbohydrate loading, characterized by an accelerated decline in plasma glucose and GH suppression. Patients on a VLED may be at risk for abnormally low plasma glucose concentrations when ingesting high carbohydrate loads.