Strawberry and cranberry polyphenols improve insulin sensitivity in insulin-resistant, non-diabetic adults: a parallel, double-blind, controlled and randomised clinical trial

Abstract

Plant-derived foods rich in polyphenols are associated with several cardiometabolic health benefits, such as reduced postprandial hyperglycaemia. However, their impact on whole-body insulin sensitivity using the hyperinsulinaemic-euglycaemic clamp technique remains under-studied. We aimed to determine the effects of strawberry and cranberry polyphenols (SCP) on insulin sensitivity, glucose tolerance, insulin secretion, lipid profile, inflammation and oxidative stress markers in free-living insulin-resistant overweight or obese human subjects (n 41) in a parallel, double-blind, controlled and randomised clinical trial. The experimental group consumed an SCP beverage (333 mg SCP) daily for 6 weeks, whereas the Control group received a flavour-matched Control beverage that contained 0 mg SCP. At the beginning and at the end of the experimental period, insulin sensitivity was assessed by a hyperinsulinaemic-euglycaemic clamp, and glucose tolerance and insulin secretion by a 2-h oral glucose tolerance test (OGTT). Insulin sensitivity increased in the SCP group as compared with the Control group (+0·9 (sem 0·5)×10−3 v. −0·5 (sem 0·5)×10−3 mg/kg per min per pmol, respectively, P=0·03). Compared with the Control group, the SCP group had a lower first-phase insulin secretion response as measured by C-peptide levels during the first 30 min of the OGTT (P=0·002). No differences were detected between the two groups for lipids and markers of inflammation and oxidative stress. A 6-week dietary intervention with 333 mg of polyphenols from strawberries and cranberries improved insulin sensitivity in overweight and obese non-diabetic, insulin-resistant human subjects but was not effective in improving other cardiometabolic risk factors.

Effect of daily consumption of cranberry beverage on insulin sensitivity and modification of cardiovascular risk factors in adults with obesity: a pilot, randomised, placebo-controlled study

“…In the study performed by Stull et al (18) , a 6-week intake of a smoothie with 45 g of blueberry extract powder increased insulin sensitivity by 22 %. As recently reported by Paquette et al (21) , intake of 1•84 g daily of a strawberry-cranberry powder blend for 6 weeks resulted in a lower first-phase insulin secretion response as measured by C-peptide levels during the first 30 min of the OGTT. In our study, we examined whether a cranberry beverage could improve insulin resistance, which is a risk factor for the development of diabetes.…”

Attenuation of Postmeal Metabolic Indices with Red Raspberries in Individuals at Risk for Diabetes: A Randomized Controlled Trial

“…Clinical studies using strawberries showed reduced insulin needs for managing postprandial glycemia, independent of fiber content (13). Two other trials have reported improved insulin sensitivity accessed by hyperinsulinemic-euglycemic clamp after 6 weeks of consumption of polyphenols from blueberry (28) or an extract blend of strawberry and cranberry (29). The data from the present study with red raspberries suggest improved insulin action in peripheral tissues aiding in postmeal glycemic control and apparently lasting effects over the 24-hour period, warranting follow-up in a chronic feeding design.…”

The impact of cranberry (Vaccinium macrocarpon) and cranberry products on each component of the metabolic syndrome: a review

“…The main human-interventional studies with cranberry or cranberry products considering glycemic metabolism are listed in Table 2. In sum, although nutritional intervention studies with cranberries on glucose metabolism are still scarce, some of them have shown that cranberry products may promote glucose homeostasis by reducing fasting glycemia, improving HOMA-IR, increasing insulin sensitivity, and preventing compensatory insulin secretion [44,46,47], whereas others did not demonstrate any significant change on this feature [16,48]. From these studies, it is still not possible to define if duration and consumed amount of cranberry are responsible for these controversial results.…”

“…Paquette et al [47] A parallel, double-blind, controlled, and randomized clinical trial to determine the effects of strawberry and cranberry polyphenols (SCP) on insulin sensitivity, glucose tolerance, insulin secretion, lipid profile, inflammation, and oxidative stress markers in free-living insulin-resistant overweight or obese human subjects.…”