Strawberry and cranberry polyphenols improve insulin sensitivity in insulin-resistant, non-diabetic adults: a parallel, double-blind, controlled and randomised clinical trial.
Br J Nutr 2017;
117:519-531. [PMID:
28290272 PMCID:
PMC5426341 DOI:
10.1017/s0007114517000393]
[Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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)×10−3v. −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.
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