Differential effect of polyphenol-rich dark chocolate on biomarkers of glucose metabolism and cardiovascular risk factors in healthy, overweight and obese subjects: a randomized clinical trial.
The association between excess cortisol and various parameters of metabolic syndrome including hypertension, insulin resistance and dyslipidaemia is increasingly recognised. The present single-blind randomised placebo-controlled cross-over study compared the effect of polyphenol-rich dark chocolate (DC) on biomarkers of glucose metabolism, lipid profile, and blood pressure (BP) in females with BMI ≥ 25 kg m(-2) (n = 21) and females with BMI < 25 kg m(-2) (n = 21). Volunteers consumed 20 g of DC containing 500 mg polyphenols or a placebo DC with negligible polyphenol-content daily for 4 weeks, separated by a 2-week washout period. Systolic BP and diastolic BP decreased after 4 weeks of polyphenol-rich DC. Placebo raised fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR) and salivary cortisol, an effect that was significantly different from polyphenol-rich DC which had a negligible effect on fasting insulin, HOMA-IR and salivary cortisol. Females with BMI ≥ 25 kg m(-2) responded less favourably to placebo than lean females and consequently had higher fasting insulin and HOMA-IR, in addition to a lower quantitative sensitivity check index (QUICKI) after ingestion of placebo compared to polyphenol-rich DC. No significant changes in lipid profile were observed. This study provides evidence for the metabolic benefits of consuming polyphenol-rich dark chocolate while demonstrating the possibility of adverse effects occurring with polyphenol-poor chocolate placebo.
MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK. suzana.almoosawi@mrc-hnr.cam.ac.uk
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Almoosawi
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Tsang
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Ostertag
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Fyfe
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Al-Dujaili
D000975:Antioxidants / Q000008:administration & dosage / Q000032:analysis; D015415:Biomarkers / Q000097:blood*; D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism*; D001794:Blood Pressure; D015992:Body Mass Index; D002099:Cacao / Q000737:chemistry*; D002182:Candy; D002319:Cardiovascular System / Q000378:metabolism*; D018592:Cross-Over Studies; D005215:Fasting; D005260:Female; D005938:Glucocorticoids / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D009765:Obesity / Q000503:physiopathology; D050177:Overweight / Q000503:physiopathology; D059808:Polyphenols / Q000008:administration & dosage*; D012307:Risk Factors; D016037:Single-Blind Method
D000975:Antioxidants; D015415:Biomarkers; D001786:Blood Glucose; D005938:Glucocorticoids; D007328:Insulin; D059808:Polyphenols