Dark Chocolate Consumption Improves Fasting Glucose Levels and Blood Pressure in Overweight and Obese Persons

Almoosawi S, Fyfe L, Ho C, Al-Dujaili E. The effect of polyphenol-rich dark chocolate on fasting capillary whole blood glucose, total cholesterol, blood pressure and glucocorticoids in healthy overweight and obese subjects.

Obesity has been shown to be associated with elevated blood pressure (BP) and insulin resistance, and epidemiological studies have shown an association between high polyphenol intakes and a reduced risk of oxidative stress-related diseases such as diabetes, hypertension, and cardiovascular disease (CVD). In particular, the consumption of cocoa or dark chocolate (DC) (Theobroma cacao) has been shown to improve endothelial function, insulin sensitivity, and BP in obese persons. One underlying factor linked to these CVD risk factors is the abnormal metabolism of cortisol, and postprandial hypercortisolism has been associated with abdominal obesity, increased urinary cortisone-to-cortisol ratio, and insulin resistance. The objective of the present study was to evaluate and compare the effect of DC consumption containing two different amounts of polyphenols on fasting capillary whole blood glucose levels, total cholesterol, BP, and urinary cortisol levels in healthy obese persons.

Fourteen obese (body mass index average: 27.7 kg/m²), but otherwise, healthy men (n = 8) and women (n = 6) aged 21-50 years were enrolled in this uncontrolled, randomized crossover study, which was conducted at Queen Margaret University (Musselburgh, United Kingdom). The subjects served as their own controls and were randomly assigned to consume 20 g DC daily (Acticoa™ chocolate; Barry Callebaut; Lebbeke, Belgium) containing either 500 or 1000 mg polyphenols for 2 weeks. After a 1-week washout period, the subjects were crossed over to the alternate treatment. The subjects were advised to consume the chocolate throughout the day, so as to achieve a high steady state level, and to maintain their usual diet but to refrain from consuming polyphenol-rich foods. Before and after the intervention, fasting capillary whole blood samples were collected for the measurement of glucose and total cholesterol 12 hours after the last intake of chocolate; 24-hour urine samples were collected for the measurement of magnesium, sodium, potassium, and cortisol levels; anthropometric measures (body mass index and waist and hip circumferences) were made; and systolic and diastolic BP were measured. Fasting glucose (FG) and systolic and diastolic BP were measured weekly. The subjects were requested to complete a 3-day diet and physical activity diary.

A mixed between-within subjects analysis of variance showed a significant decrease in capillary blood glucose levels (P = 0.002), systolic BP (P < 0.0001), and diastolic BP (P < 0.0001) after the consumption of DC. However, no significant differences in FG or in BP were observed between the 500- and 1000-mg polyphenol interventions, which indicated that both doses of polyphenols had similar efficacy. No significant changes in any of the anthropometric measures, in total cholesterol, or in urinary cortisol-to-cortisone ratio, magnesium, potassium, sodium, or free cortisol were observed after either of the polyphenol interventions. Urinary free cortisone levels trended toward a reduction after both the 500- and 1000-mg polyphenol interventions; however, the change did not reach statistical significance. Energy expenditure and intakes of energy, macronutrients, and minerals did not change significantly throughout the intervention.

The results indicate that the consumption of polyphenol-rich DC decreases FG levels and BP in obese adults. These results coincide with previous findings that intakes of polyphenol-rich DC improved insulin resistance and sensitivity, FG levels, and BP in healthy,¹ hypertensive,² glucose-intolerant,³ and obese⁴ persons. The authors suggest that the main mechanism by which DC polyphenols improve glucose and BP is via the nitric oxide pathway. Furthermore, it was shown that DC containing 500 mg polyphenols was as effective at decreasing FG and BP as was DC containing 1000 mg polyphenols with similar nutrient contents, and these effects appeared to be independent of cortisol metabolism. However, only 1 of the 14 subjects was abdominally obese, the condition most associated with enhanced cortisol metabolism. Finding the minimum polyphenol dose for maximum benefits will help to reduce bitterness and increase palatability. The authors conclude that "the present study confirms previous reports of improved FG levels and BP following DC consumption" and that additional studies are needed "to identify the optimal dose of polyphenols required to improve glucose metabolism and to examine additional parameters that could be influenced by polyphenols."

—Review by Brenda Milot, ELS, American Botanical Council

References
¹Grassi D, Lippi C, Necozione S, et al. Short-term administration of dark chocolate is followed by a significant increase in insulin sensitivity and a decrease in blood pressure in healthy persons. Am J Clin Nutr. 81:611-614.

²Grassi D, Necozione S, Lippi C, et al. Cocoa reduces blood pressure and insulin resistance and improves endothelium-dependent vasodilation in hypertensives. Hypertension. 46:398-405.

³Grassi D, Desideri G, Necozione S, et al. Blood pressure is reduced and insulin sensitivity increased in glucose-intolerant, hypertensive subjects after 15 days of consuming high-polyphenol dark chocolate. J Nutr. 138:1671-1676.

⁴Davison K, Coates AM, Buckley JD, et al. Effect of cocoa flavanols and exercise on cardiometabolic risk factors in overweight and obese subjects. Int J Obes (Lond). 32:1289-1296.

Buijsse B, Weikert C, Drogan D, Bergmann M, Boeing H.
Department of Epidemiology, German Institute of Human Nutrition (DIfE) Potsdam-Rehbrücke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany..

ABSTRACT: Aims To investigate the association of chocolate consumption with measured blood pressure (BP) and the incidence of cardiovascular disease (CVD). Methods and results Dietary intake, including chocolate, and BP were assessed at baseline (1994-98) in 19 357 participants (aged 35-65 years) free of myocardial infarction (MI) and stroke and not using antihypertensive medication of the Potsdam arm of the European Prospective Investigation into Cancer and Nutrition. Incident cases of MI (n = 166) and stroke (n = 136) were identified after a mean follow-up of approximately 8 years. Mean systolic BP was 1.0 mmHg [95% confidence interval (CI) -1.6 to -0.4 mmHg] and mean diastolic BP 0.9 mmHg (95% CI -1.3 to -0.5 mmHg) lower in the top quartile compared with the bottom quartile of chocolate consumption. The relative risk of the combined outcome of MI and stroke for top vs. bottom quartiles was 0.61 (95% CI 0.44-0.87; P linear trend = 0.014). Baseline BP explained 12% of this lower risk (95% CI 3-36%). The inverse association was stronger for stroke than for MI. Conclusion Chocolate consumption appears to lower CVD risk, in part through reducing BP. The inverse association may be stronger for stroke than for MI. Further research is needed, in particular randomized trials.

PMID: 20354055 [PubMed - as supplied by publisher]

Boosting brain power — with chocolate

Professor Ian Macdonald
School of Biomedical Sciences, University of Nottingham.

ABSTRACT: Eating chocolate could help to sharpen up the mind and give a short-term boost to cognitive skills, a University of Nottingham expert has found.

A study led by Professor Ian Macdonald found that consumption of a cocoa drink rich in flavanols — a key ingredient of dark chocolate — boosts blood flow to key areas of the brain for two to three hours.

Increased blood flow to these areas of the brain may help to increase performance in specific tasks and boost general alertness over a short period.

The findings, unveiled at one of the biggest scientific conferences in America, also raise the prospect of ingredients in chocolate being used to treat vascular impairment, including dementia and strokes, and thus for maintaining cardiovascular health.

The study also suggests that the cocoa flavanols found in chocolate could be useful in enhancing brain function for people fighting fatigue, sleep deprivation, and even the effects of ageing.

Ian Macdonald, professor of metabolic physiology at The University of Nottingham, used magnetic resonance imaging (MRI) to detect increased activity in specific areas of the brain in individuals who had consumed a single drink of flavanol-rich cocoa. The effect is linked to dilation of cerebral blood vessels, allowing more blood — and therefore more oxygen — to reach key areas of the brain.

Flavanols are not only found in chocolate with a high cocoa content — they are also present in other substances such as red wine, green tea and blueberries.

He presented his research at the annual meeting of the American Association for the Advancement of Science (AAAS), one of the biggest annual gatherings of scientists from all over the world.

Professor Macdonald said: “Acute consumption of this particular flavanol-rich cocoa beverage was associated with increased grey matter flow for two to three hours.

“The demonstration of an effect of consuming this particular beverage on cerebral blood flow raises the possibility that certain food ingredients may be beneficial in increasing brain blood flow and enhancing brain function, in situations where individuals are cognitively impaired such as fatigue, sleep deprivation, or possibly ageing.”

He emphasised that the level of cocoa flavanol used in the study is not available commercially. The cocoa-rich flavanol beverage was specially formulated for the purpose of the study.

Co-authors on the research were Dr Susan Francis, research associate Kay Head, and Professor Peter Morris, all from The University of Nottingham’s School of Physics and Astronomy.

Professor Macdonald is a member of the Food Standards Agency’s Scientific Advisory Committee on Nutrition, and is President-Elect of the UK Nutrition Society. His main research interests are concerned with the functional consequences of metabolic and nutritional disturbances in health and disease, with specific interests in obesity, diabetes, cardiovascular disease and exercise.

The AAAS, founded in 1848, is the world’s largest general scientific society and publisher of the prestigious international journal Science. Its annual conference draws up to 10,000 attendees.

The emerging role of flavonoid-rich cocoa and chocolate in cardiovascular health and disease

Engler MB, Engler MM.
Department of Physiological Nursing, Laboratory of Cardiovascular Physiology, University of California, San Francisco, California.

ABSTRACT: Cocoa and chocolate have recently been found to be rich plant-derived sources of antioxidant flavonoids with beneficial cardiovascular properties. These favorable physiological effects include: antioxidant activity, vasodilation and blood pressure reduction, inhibition of platelet activity, and decreased inflammation. Increasing evidence from experimental and clinical studies using cocoa-derived products and chocolate suggest an important role for these high-flavanol-containing foods in heart and vascular protection.

Nutrition Reviews;64(3):109-118.

Effect of dark chocolate on arterial function in healthy individuals

Vlachopoulos C, Alexopoulos N, Stefanadis C.
Hypertension Unit and Peripheral Vessels Unit, 1st Cardiology Department, Athens Medical School, Athens, Greece.

ABSTRACT: Cocoa has been consumed for at least 2500 years, and for a long time it has been regarded as a medicine. Arterial function is of paramount importance for the proper function and integrity of the cardiovascular system. Dark chocolate and flavonoid-rich cocoa have beneficial acute and short-term effects on endothelial function and wave reflections in normal individuals, in adults with cardiovascular risk factors, and in patients with coronary artery disease. Furthermore, dark chocolate and flavonoid-rich cocoa may have a blood pressure-lowering effect. These effects can be attributed to flavonoids and are mainly mediated through increased nitric oxide bioavailability. Further research is needed to demonstrate whether these effects of chocolate on arterial function are translated into clinical benefit.

Current Hypertension Reports;8(3):205-11.

Cocoa and chocolate flavonoids: implications for cardiovascular health

Steinberg FM, Bearden MM, Keen CL
Didactic Program in Dietetics, Department of Nutrition, University of California, Davis, California.

ABSTRACT: This paper offers a review of current scientific research regarding the potential cardiovascular health benefits of flavonoids found in cocoa and chocolate. Recent reports indicate that the main flavonoids found in cocoa, flavan-3-ols and their oligomeric derivatives, procyanidins, have a variety of beneficial actions, including antioxidant protection and modulation of vascular homeostasis [balance between blood clot formation and prevention]. These findings are supported by similar research on other flavonoid-rich foods. Other constituents in cocoa and chocolate that may also influence cardiovascular health are briefly reviewed. The lipid content of chocolate is relatively high; however, one third of the lipid in cocoa butter is composed of the fat stearic acid, which exerts a neutral cholesterolemic response in humans. Cocoa and chocolate contribute to trace mineral intake, which is necessary for optimum functioning of all biologic systems and for vascular tone. Thus, multiple components in chocolate, particularly flavonoids, can contribute to the complex interplay of nutrition and health. Applications of this knowledge include recommendations by health professionals to encourage individuals to consume a wide range of phytochemical-rich foods, which can include dark chocolate in moderate amounts.

Journal of the American Dietetic Association;103(2):215-23.

Tropical fruit camu-camu (Myrciaria dubia) has anti-oxidative and anti-inflammatory properties.

Inoue T, Komoda H, Uchida T, Node K.
Department of Cardiovascular and Renal Medicine, Saga University Faculty of Medicine, 5-1-1 Nabeshima, Saga 849-8501, Japan..

BACKGROUND: Oxidative stress as well as inflammation plays a pivotal role in the pathogenesis of atherosclerosis. Although, various anti-oxidative dietary supplements have been evaluated for their ability to prevent atherosclerosis, no effective ones have been determined at present. "Camu-camu" (Myrciaria dubia) is an Amazonian fruit that offers high vitamin C content. However, its anti-oxidative property has not been evaluated in vivo in humans. METHODS: To assess the anti-oxidative and anti-inflammatory properties of camu-camu in humans, 20 male smoking volunteers, considered to have an accelerated oxidative stress state, were recruited and randomly assigned to take daily 70ml of 100% camu-camu juice, corresponding to 1050mg of vitamin C (camu-camu group; n=10) or 1050mg of vitamin C tablets (vitamin C group; n=10) for 7 days. RESULTS: After 7 days, oxidative stress markers such as the levels of urinary 8-hydroxy-deoxyguanosine (P<0.05) and total reactive oxygen species (P<0.01) and inflammatory markers such as serum levels of high sensitivity C reactive protein (P<0.05), interleukin (IL)-6 (P<0.05), and IL-8 (P<0.01) decreased significantly in the camu-camu group, while there was no change in the vitamin C group. CONCLUSIONS: Our results suggest that camu-camu juice may have powerful anti-oxidative and anti-inflammatory properties, compared to vitamin C tablets containing equivalent vitamin C content. These effects may be due to the existence of unknown anti-oxidant substances besides vitamin C or unknown substances modulating in vivo vitamin C kinetics in camu-camu.

PMID: 18922386 [PubMed - in process]