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High-Cocoa Polyphenol-Rich Chocolate Improves HDL Cholesterol in Type 2 Diabetes Patients


Aim  To examine the effects of chocolate on lipid profiles, weight and glycaemic control in individuals with Type 2 diabetes.

Methods  Twelve individuals with Type 2 diabetes on stable medication were enrolled in a randomized, placebo-controlled double-blind crossover study. Subjects were randomized to 45 g chocolate with or without a high polyphenol content for 8 weeks and then crossed over after a 4-week washout period. Changes in weight, glycaemic control, lipid profile and high-sensitivity C-reactive protein were measured at the beginning and at the end of each intervention.

Results  HDL cholesterol increased significantly with high polyphenol chocolate (1.16 ± 0.08 vs. 1.26 ± 0.08 mmol/l, P = 0.05) with a decrease in the total cholesterol: HDL ratio (4.4 ± 0.4 vs. 4.1 ± 0.4 mmol/l, P = 0.04). No changes were seen with the low polyphenol chocolate in any parameters. Over the course of 16 weeks of daily chocolate consumption neither weight nor glycaemic control altered from baseline.

Conclusion  High polyphenol chocolate is effective in improving the atherosclerotic cholesterol profile in patients with diabetes by increasing HDL cholesterol and improving the cholesterol:HDL ratio without affecting weight, inflammatory markers, insulin resistance or glycaemic control.



Dyslipidaemia is a risk factor for cardiovascular disease, especially in individuals with Type 2 diabetes [1]. Cardiovascular risk in Type 2 diabetes has been associated with dietary factors [2] and high intakes of refined carbohydrates such as sucrose are associated with worse glycaemic control, increased obesity and hypertriglyceridaemia [3]. Concern over the effect of sugar on glycaemia has been altered by work on the glycaemic index [4]. The concept of the glycaemic index has led to the realization that foods such as chocolate, although high in carbohydrate, and in particular sugar, may have a lesser effect on blood glucose than foods that are low in sugar, including potatoes and bread [5].

It has been hypothesized that flavonoid compounds found in foods, including epicatechins found in high-cocoa-solid chocolates, decrease the risk of death from coronary heart disease, cancer and stroke [6]. Short-term administration of dark chocolate was followed by a significant increase in insulin sensitivity and a decrease in blood pressure in healthy subjects [7]. Dark chocolate consumption has been reported to increase HDL cholesterol concentration and chocolate fatty acids may inhibit lipid peroxidation in healthy subjects [8].

Therefore, our hypothesis was that that the daily consumption of chocolate (45 g daily) containing polyphenol-rich, high-cocoa solids would improve cardiovascular risk factors when taken chronically, whilst being safe for patients with Type 2 diabetes.



This randomized, placebo-controlled, double-blind crossover study was undertaken in the Clinical Trials Unit of the Michael White Diabetes Centre, Hull Royal Infirmary, Hull, UK. All participators were screened between January 2008 and October 2008. The chocolate for the study was provided as an unrestricted gift from Nestle PTC, York and was funded through the Diabetes Research and Development fund. The study was approved by the local National Health Service Research Ethics Committee and written consent was obtained from all subjects prior to enrolment.

Twelve subjects (seven males, five females) with Type 2 diabetes [age—median (range) 68 (42–71) years)] were enrolled and completed the study. The mean duration of diagnosis of diabetes was (mean ± sd) (18 ± 5) months. Inclusion criteria were a diagnosis of Type 2 diabetes based on the World Health Organization guidelines [9]. Exclusion criteria included HbA1c greater than 9.0% (Diabetes Control and Complications Trial aligned), treatment with insulin, use of steroids, any change in use of medication in the previous 8 weeks and not having attended a structured diabetes education programme. Five of the subjects had their diabetes managed with metformin, eight were treated with statin therapy and three were treated with anti-hypertensive agents. None of the patients were on any other oral hypoglycaemic agents or other lipid-lowering medications. All of the subjects’ chronic medications were maintained at stable doses for at least 3 months prior to the start of the study.

The active product was high-polyphenol chocolate containing 85% cocoa solids (derived from a high-cocoa liquor content) compared with chocolate containing cocoa butter alone that contained no non-fat cocoa solids (cocoa liquor) (iso-calorific and macronutrient profile matched chocolate), which was low in polyphenols and that was dyed to the same colour as high-polyphenol chocolate. Individual 15-g foil wrapped bars were provided and subjects were asked to consume one bar three times daily. This would provide a total of 326 kcal for the three bars, with high-polyphenol chocolate providing 16.6 mg of epicatechins and the low-polyphenol chocolate < 2 mg. Randomization was undertaken by Nestec Ltd., with enough chocolate being given to subjects for the 8-week period. To monitor compliance, subjects were asked to return all empty wrappers, noting the time and date when it was consumed on the wrapper. Subjects were advised not to consume any other chocolate for the duration of the study; apart from this, subjects were instructed to make no further changes to their diet and lifestyle. To monitor the potential acute effects on glycaemia, and as a safety measure, all subjects were supplied with a glucometer (Glucomen; Menarini Diagnostics, Wokingham, UK) and asked to measure 7-point profiles on at least 2 days of the week on two separate weeks for each of the two intervention arms. Reassuringly, there were no significant excursions in blood glucose.

Following an overnight fast, measurement of weight and blood pressure were made and blood samples were collected at the beginning and the end of the each of the two 8-week phases. Weight was measured using calibrated weighing scales in light clothing and bare feet, fasting and with an empty bladder. Dietary recall of eating patterns to estimate energy and macronutrient intake was performed at each visit by a registered dietitian.

Fasting venous blood samples were separated by centrifugation at 3000 g for 15 min at 4 °C and the aliquots stored at –80 °C within 1 h of collection. Sitting blood pressure was measured after 10 min of rest using an automated device (NPB-3900; Nellcor Puritan Bennett, Pleasanton, CA, USA). Total cholesterol, triglyceride and HDL cholesterol levels were measured enzymatically using a Synchron LX20 analyser (Beckman-Coulter, High Wycombe, UK). LDL cholesterol was calculated using the Friedewald equation. Plasma glucose was measured using a Synchron LX20 analyser (Beckman-Coulter) and serum insulin was assayed using a competitive chemiluminescent immunoassay performed using the DPC Immulite 2000 analyser (Euro/DPC, Llanberis, UK). The coefficient of variation of this method was 8%, calculated using duplicate study samples. The insulin resistance was calculated using the homeostasis model assessment method (HOMA-IR) [10]. HbA1c was measured on an HA-8140 analyser (Menarini Diagnostics). The sample size calculation was based on an estimate of the standard error of mean of the treatment difference (the difference between treatment and control measurements of plasma HDL cholesterol taken on an individual) of 0.3 mmol/l [11]. At the P < 0.05 level of significance, a sample size of 12 subjects in a crossover fashion will provide > 90% power to detect a 0.4-mmo/l change in plasma HDL cholesterol concentration.



Dietary recall suggested that the chocolate tended to replace other snack foods and there was some reduction in portion size at the subsequent meal, resulting in no significant change in energy or macronutrient intake. Compliance based on returned wrappers was 93.8%. Weight was unchanged at the end of the study 89.4 ± 6.3 kg (P = 1.00); there were also no effects on glycaemia in terms of HbA1c (P = 0.84).

The differences that were found between high-polyphenol chocolate and low-polyphenol chocolate are shown in Table 1. HDL cholesterol improved significantly (P = 0.05) and the cholesterol:HDL ratio significantly decreased (P = 0.04). This change was reflected when these data were examined as a percentage change from the initial baseline. The percentage change of the lipid profile before and after each intervention is shown in Fig. 1.







High-polyphenol chocolate has the potential to be included in the diet of individuals with Type 2 diabetes as part of a sensible, balanced approach to diet and lifestyle, with a potential reduction in cardiovascular risk and without detrimental effects on weight or glycaemic control. These benefits are in addition to the potential psychosocial benefits through liberalization of eating behaviours and reduction of food-related guilt [12].

This is the first study to report on the effects of giving chocolate to individuals with Type 2 diabetes, chronically over a period of 16 weeks. It demonstrates that feeding of high-polyphenol chocolate for 2 months can improve lipid profile, particularly through increased HDL cholesterol, whilst improving the cholesterol:HDL ratio. This shows a potential for reduction in cardiovascular risk and combined with a lack of any deleterious effects on weight, markers of inflammation, insulin resistance or glycaemic control. This appears to occur even in subjects treated with lipid-lowering therapies, indicating a beneficial additive effect through an alternate pathway. However, when the high- polyphenol chocolate intervention stopped, then those beneficial effects were reversed back to baseline.

This study differs from previous studies that have used much shorter intervention periods and have tended only to use cocoa [13]. The effect on HDL cholesterol is in accord with a study in subjects without diabetes [8] and these data indicate that this effect may be sustained. However, the mechanism of how high-polyphenol chocolate may influence this improvement in lipid profile remains unclear. It has been suggested that the polyphenols may have either an insulin sensitizing effect [7],which was not seen in this study, or that there is reduced inflammation independent of insulin action [8] through reduced lipid perioxidation, although this too was not inferred as the high-sensitivity C-reactive protein levels here did not differ between groups. It has been hypothesized that additional beneficial effects of polyphenols on the endothelium may be mediated through increasing nitric oxide levels [7].

Because of the small sample size, there is a potential for type 2 errors, although the crossover design probably served to overcome this to some extent. Being a crossover study, there was concern that subjects may have been able to tell the difference between the two preparations. Therefore, a blinded taste study was undertaken prior to the trial that showed that the subjects could not tell any difference in appearance or taste between the high-polyphenol chocolate and low-polyphenol chocolate preparations, thus avoiding the bias if one could have been perceived better than the other. The measurement of plasma polyphenols in this study was not undertaken, although this may be potentially useful in the future if dose–response studies are to be undertaken.



Consuming high-polyphenol chocolate, sweetened with sucrose, over an 8-week period improved cardiovascular risk indices by increasing HDL cholesterol without a detrimental effect on glycaemic control, insulin resistance, inflammation or weight.



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High-cocoa polyphenol-rich chocolate improves HDL cholesterol in Type 2 diabetes patients

Researchers/Authors: D. D. Mellor, T. Sathyapalan, E. S. Kilpatrick, S. Beckett, S. L. Atkin

Article first published online: 18 OCT 2010 © 2010 The Authors. Diabetic Medicine © 2010 Diabetes UK Issue, Diabetic Medicine, Volume 27, Issue 11, pages 1318–1321, November 2010

Category: Diabetes
Posted: Monday, May 30, 2011 10:59:00 AM
Views: 36440

Scientific study examined the HDL Cholesterol benefits in Type 2 Diabetes using high-cocoa polyphenol-rich (dark chocolate) concluded that dark chocolate is effective in improving HDL cholesterol without affecting weight, inflammatory markers, insulin resistance or glycaemic control. A randomized, placebo-controlled, double-blind crossover study from the Michael White Diabetes Centre, Hull Royal Infirmary, Hull, UK.