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When a placebo is not a 'placebo': a placebo effect on postprandial glycaemia
John L Sievenpiper1, Adish Ezatagha, Anamaria Dascalu
1Risk Factor Modification Centre, St Michael's Hospital and Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
Aims:
Placebo effects in clinical trials remain uncertain. To investigate a placebo effect on acute postprandial plasma glucose, we conducted a follow-up investigation on a previous study.
Methods:
The effect of placebo (9 g encapsulated cornstarch +500 ml water, taken at -40 min) on the plasma glucose response to a 75-g oral glucose tolerance test (OGTT) was assessed in a previous study in 12 healthy subjects (gender, five male, seven female; age 27 +/- 6 years; body mass index 24 +/- 3.4 kg m(-2)). This was compared with the effect of a water control (500 ml water taken alone at -40 min) on the same outcome in the same subjects in a follow-up study.
Results:
Cornstarch placebo decreased plasma glucose area under the curve during the 75-g OGTT by 28% [Delta (95% confidence interval) -63.3 min mmol(-1) l(-1) (-218.33, 91.66), P < 0.02] compared with the water control (P < 0.05).
Conclusions:
Postprandial plasma glucose outcomes may be vulnerable to placebo effects.
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