Prof Juan Carlos Kaski, St George's University, London, UK

Evidence from several trials in recent years suggests that chocolate and cocoa flavanols may have a beneficial effect on endothelial function, blood pressure, insulin resistance and dyslipidaemia. Even harder endpoints such as incidence of stroke and cardiovascular mortality appear to be beneficially affected by chocolate consumption. (1-4)

A meta-analysis of available prospective data, by Larsson et al. using data from a prospective study of Swedish adults assessed whether chocolate consumption is associated with a reduced risk of ischaemic heart disease. The study, recently published on line in Heart (5), concluded that chocolate consumption is associated with lower risk of myocardial infarction (MI) and ischaemic heart disease.

The Swedish prospective study involving 67 640 women and men from the Cohort of Swedish Men and the Swedish Mammography Cohort represented the basis for the Larsson et al meta-analysis. They included all patients who had completed a food-frequency questionnaire and were free of cardiovascular disease at baseline. MI cases were assessed via linkage with the Swedish National Patient and Cause of Death Registers. PubMed and EMBASE databases were searched by the authors to identify prospective studies investigating the relationship between chocolate consumption and risk of ischaemic heart disease. 4417 MI cases were identified in the Swedish study. The main finding was that chocolate consumption was inversely associated with MI risk. Indeed, compared with non-consumers, the multivariable relative risk for consumers of ≥3–4 servings/week of chocolate was 0.87 (95% CI 0.77 to 0.98; p for trend =0.04). Five prospective studies on chocolate consumption and ischaemic heart disease were identified and assessed together with the Swedish study Thus the Larsson meta-analysis included a total of six studies involving 6851 ischaemic heart disease cases. The overall relative risk for the highest versus lowest category of chocolate consumption was 0.90 (95% CI 0.82 to 0.97).

There are analogies between the results of this investigation and research work carried out to assess the effects of alcohol on cardiovascular disease. Like with alcohol, moderate chocolate consumption appears to have beneficial effects on coronary artery disease and stroke. Findings in this study open new avenues for “nutraceutical” research and will most certainly make chocolate lovers very happy indeed.

References

  1. Mastroiacovo D, Kwik-Uribe C, Grassi D, et al. Cocoa flavanol consumption improves cognitive function, blood pressure control, and metabolic profile in elderly subjects: the Cocoa, Cognition, and Aging (CoCoA) Study—a randomized controlled trial. Am J Clin Nutr 2015;101:538–48.
  1. Sansone R, Rodriguez-Mateos A, Heuel J, et al. Cocoa flavanol intake improves endothelial function and Framingham Risk Score in healthy men and women: a randomised, controlled, double-masked trial: the Flaviola Health Study. Br J Nutr 2015;114:1246–55.
  1. Larsson SC, Virtamo J, Wolk A. Chocolate consumption and risk of stroke: a prospective cohort of men and meta-analysis. Neurology 2012;79:1223–9.
  1. Zhang Z, Xu G, Liu X. Chocolate intake reduces risk of cardiovascular disease: evidence from 10 observational studies. Int J Cardiol 2013;168:5448–50
  1. Larsson SC, Åkesson A, Gigante B, Wolk A. Chocolate consumption and risk of myocardial infarction: a prospective study and meta-analysis. Heart Online First, published on March 2, 2016 as 10.1136/heartjnl-2015-309203
Cardio Debate Expert Comments

There is clinical evidence mainly from observational studies that chocolate intake can reduce the risk of cardiovascular disease (1) and regular consumption of cocoa flavanoids (CF) might be effective to improve age-related cognitive dysfunction (2-5).

Larsson et al (4) followed 30,103 men in the Cohort of Swedisk Men for 10.2 years and found that high chocolate consumption (median 62.9 g/week) was associated with a lower relative risk of stroke (RR 0.83; 95 % CI 0.70-0.99) and in a meta-analysis of 5 studies, with a total of 4,260 stroke cases, the overall RR of stroke for the highest vs lowest category of chocolate consumption was 0.81 (95% CI 0.73-0.90). In a German cohort, consumption of 6 g of chocolate per day was associated with a 39% lower risk of the combined outcome of myocardial infarction (MI) and stroke, a protective effect which was partly explained by a lower blood pressure(6). In another population-based cohort study from the Stockholm Heart Epidemiology Program, chocolate consumption was associated with lower cardiac mortality in a dose dependent manner in patients free of diabetes surviving their first acute MI (7). Furthermore, the Flaviola Health Study showed that regular CF intake improved cardiovascular surrogates of cardiovascular risk in healthy middle-aged men and women (i.e. low-risk patients) (8). Based on observational evidence, higher levels of chocolate consumption were associated with a 37% reduction in cardiovascular disease (RR 0.63; 95% CI 0.44 to 0.90) and a 29% reduction in stroke compared with the lowest levels (9). Additionally, prospective cohort studies in which consuming more than 2.25 g/d of cocoa (average, 4.2 g/d) was associated with a 50% lower risk of cardiovascular mortality (10,11). Finally, a prospective cohort study of elderly women found that compared with women who rarely consumed chocolate, those who consumed chocolate frequently had a significantly lower risk of hospitalization for or death from ishemic heart disease (IHD) and heart failure and also had a significantly lower prevalence of carotid atherosclerotic plaques (12).

The potential beneficial effects of chocolate or CF intake on cardiovascular risk were related to: a) an improvement in insulin sensitivity and endothelial function; b) an increase flow-mediated vasodilation; and c) a decrease low-density lipoprotein cholesterol and triglycerides, oxidative stress, inflammation, plasma glucose, fasting insulin concentration, vascular tone and systolic/diastolic blood pressure (2-5,8,13,14).

To examine whether chocolate consumption is associated with a reduced risk of IHD, very recently Larsson et al (15) used data from two prospective population-based cohorts 67,640 women and men from the Cohort of Swedish Men and the Swedish Mammography Cohort who had completed a food-frequency questionnaire and were free of cardiovascular disease at baseline. The study found that compared with non-consumers, the multivariable RR for those who consumed ≥3–4 servings/week of chocolate was 0.87 (95% CI 0.77 to 0.98; p for trend =0.04). Compared with non-consumers of chocolate, men and women who consumed ≥3–4 servings/week of chocolate were more likely to have a university education but less likely to be current smokers, overweight and to have a history of diabetes, hypertension and hypercholesterolemia. In a complementary meta-analysis, including the Swedish study and five prospective studies recruiting 6,851 IHD cases, they showed that a high consumption of chocolate was associated with a significant 10% lower risk of IHD (RR 0.90 ; 95% CI 0.82 to 0.97), with little heterogeneity among studies. Taking the data from the Swedish study and three other studies the overall RR per 50 g/week increment of chocolate consumption was 0.95 (95% CI 0.92 to 0.98), without heterogeneity among studies. Thus, it was concluded that chocolate consumption is inversely associated with risk of MI and IHD.

Despite the interesting results, this study presents several limitations. 1) Chocolate intake was assessed with only one question from a self-administered 96-item food-frequency questionnaire (FFQ) and measured at baseline, so that the long-term chocolate intake is uncertain. 2) There was a lack of information on the most suitable type of chocolate intake (eg, dark or milk chocolate, plain, bars, snack bars, cocoa powder). Indeed, only 2 out the 6 studies included in the meta-analysis defined the type of chocolate consumption (6,16). However, there are marked differences in the amount of CF among these presentations. 3) The Larsson´s trial was not a mechanistic study and there was no information on blood glucose or plasma lipid or blood pressure levels, so that the mechanisms responsible for the observed benefit were extrapolated from other studies. 4) Although chocolate consumption may lower the IHD risk, chocolate should be consumed in moderation because of its high content in sugar, calories and saturated fat. 5) The study population comprised middle-aged and older Caucasian people and it is uncertain whether the present data can be extrapolated to younger individuals and other ethnic groups. Thus, further studies should be conducted in order to know the real benefit of moderate chocolate consumption to lower the risk of IHD. But despite all these limitations, the study of Larsson et al opened a new, much sweeter door, to reduce the risk of IHD.

References

  1. Zhang Z, Xu G, Liu X. Chocolate intake reduces risk of cardiovascular disease: evidence from 10 observational studies. Int J Cardiol 2013;168:5448-50.
  2. Desideri G, Kwik-Uribe C, Grassi D, et al.Benefits in cognitive function, blood pressure, and insulin resistance through cocoa flavanol consumption in elderly subjects with mild cognitive impairment: the Cocoa, Cognition, and Aging (CoCoA) Study. Hypertension 2012;60:794–801
  3. Hooper L, Kay C, Abdelhamid A, et al. Effects of chocolate, cocoa, and flavan-3-ols on cardiovascular health: a systematic review and meta-analysis of randomized trials. Am J Clin Nutr 2012;95:740–51.
  4. Larsson SC, Virtamo J, Wolk A. Chocolate consumption and risk of stroke: a prospective cohort of men and meta-analysis. Neurology 2012;79:1223–9.
  5. Mastroiacovo D, Kwik-Uribe C, Grassi D, et al. Cocoa flavanol consumption improves cognitive function, blood pressure control, and metabolic profile in elderly subjects: the Cocoa, Cognition, and Aging (CoCoA) Study—a randomized controlled trial. Am J Clin Nutr 2015;101:538–48.
  6. BuijsseB, Weikert C, Drogan D, et al. Chocolate consumption in relation to blood pressure and risk of cardiovascular disease in German adults. Eur Heart J 2010;31:161623.
  7. JanszkyI, Mukamal KJ, Ljung R, et al. Chocolate consumption and mortality following a first acute myocardial infarction: the Stockholm Heart Epidemiology Program. J Intern Med 2009;266:248–57.
  8. Sansone R, Rodriguez-Mateos A, Heuel J, et al. Cocoa flavanol intake improves endothelial function and Framingham Risk Score in healthy men and women: a randomised, controlled, double-masked trial: the Flaviola Health Study. Br J Nutr 2015;114:1246–55
  9. Buitrago-Lopez A, Sanderson J, Johnson L, et al. Chocolate consumption and cardiometabolic disorders: systematic review and meta-analysis. BMJ2011;343:d4488.
  10. Buijsse  B, Feskens  EJ, Kok  FJ et al. Cocoa intake, blood pressure, and cardiovascular mortality: the Zutphen Elderly Study. Arch Intern Med2006;166 (4) 411- 417
  11. Janszky  I, Mukamal  KJ, Ljung  R et al. Chocolate consumption and mortality following a first acute myocardial infarction: the Stockholm Heart Epidemiology Program. J Intern Med2009;266 (3) 248- 257
  12. Lewis JR, Prince RL, Zhu K, et al. Habitual chocolate intake and vascular disease: a prospective study of clinical outcomes in older women. Arch Intern Med 2010;170:1857–8.
  13. Heiss C, Keen CL, Kelm M. Flavanols and cardiovascular disease prevention.Eur Heart J2010;31:2583–92.
  14. Grassi 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 2008;138:1671–6.
  15. Larsson SC, Åkesson A, Gigante B,et al. Chocolate consumption and risk of myocardial infarction: a prospective study and meta-analysis. Heart Online First, published on March 2, 2016 as 10.1136/heartjnl-2015-309203
  16. Kwok CS, Boekholdt SM, Lentjes MA, et al. Habitual chocolate consumption and risk of cardiovascular disease among healthy men and women.Heart 2015;101:1279–87.

I saw a bumper sticker the other day, it said Save the planet – it's the only one with chocolate on it!  Being a chocolate lover myself I wholeheartedly subscribe to this tenet and was delighted to read Professor Juan-Carlos Kaski’s account of the recent clinical studies showing that chocolate consumption reduces CV risk.  If reasons were needed to indulge in the dark confection, then this is the one I would choose.

However, I doubt these data will have nutraceutical companies rushing to their marketing departments to support development of new marketable supplements.  It simply exercises our short-term memory of the research literature on plant flavanols [1].  Such extracts derived from a variety of sources including dark chocolate were shown to be beneficial through their anti-oxidative and anti-inflammatory effects.

It is interesting to note that dietary intake of a modest amount of dark chocolate may have beneficial effects on, not only cardiovascular disease, but also on hypertension during pregnancy, and recent studies have demonstrated that extract of Theobroma cacao was able to increase cell viability whilst reducing inflammatory response during pre-eclampsia [2].

If music be the food of love… then chocolate is certainly the love of food…but there is without doubt a cautionary tale in the other part of that well known Shakespearean quote… play on, give me excess of it that surfeiting the apatite may sicken and so die.  So, all things in moderation then, we don't want to become an obesity statistic.

References

[1]         He F, Pan QH, Shi Y, Duan CQ. Chemical synthesis of proantocyanins in vitro and their   reactions in aging wines, Molecules. 2008 Dec 4;13(12):3007-32.

[2]         Rahayu B, Baktiyani SC, Nurdiana N.  Theobroma cacao increases cell viability and reduces IL-6 and sVCAM-1 level in endothelial cells induced by plasma from preeclamptic patients, Pregnancy Hypertens. 2016 Jan;6(1):42-46.