Thursday 18 April 2013

Don't believe the hype


As a real chocoholic, I make no apologies for the crowd-pleasing subject of this post. It seems that you cannot go a week without the press carrying a miraculous headline that a food previously-labelled as bad for you now has health-giving properties, making it seemingly alright to consume as much as you wish. The two main commodities in question are arguably the two most attractive, alcohol and chocolate. This post will deal with the latter, and hopefully clarify some potentially misleading headlines.

The reason for a product so full of fat and sugar having possible health benefits comes from a group of chemicals called polyphenols, which are the result of metabolic reactions within the cocoa plant (theobroma cocoa, Latin fans). It seems that these polyphenols are often created to help a plant survive natural stresses such as extreme heat, and that these protective properties sometimes have similar benefits to humans when ingested. In the case of chocolate, the main polyphenols whose health benefits have been studied are called flavanols, proanthocyanidins and anthocyanins.1

Study evidence suggests several main health benefits of chocolate:
1.      Antioxidant content. Free radicals are a by-product of many natural reactions within human cells. These free radicals are very reactive, and as a result can cause damage to healthy cells. Antioxidants can “mop up” these free radicals, reducing the potential for cell damage, and related conditions such as cardiovascular disease. Studies have shown that long-term dark chocolate consumption can increase the antioxidant capacity of blood plasma, and decrease the oxidation of LDL cholesterol (a major contributing factor to heart disease)2, and that flavanols from a cocoa drink can inhibit oxidation markers within the blood.3
2.      Reduction of blood pressure. Dark chocolate high in flavanols have been shown to reduce blood pressure4-5. However, 2 things need to be borne in mind here. Firstly, these studies used chocolate that was especially formulated to be high in flavanols, and as we will see below, not all chocolates are created equal. Secondly, as a food chocolate is high in fat and sugar, both of which can contribute to raised blood pressure anyway.
3.      Arterial reactivity. Dysfunctional arteries with reduced flexibility are an important marker for cardiovascular disease. Arterial function is promoted by the production of nitric oxide (NO), and flavanols within chocolate have been linked with increased production of NO, resulting in greater arterial reactivity and consequently reduced risk of heart disease, stroke and related conditions.6 This study found a dose-dependent effect, i.e. the more you take in the better the effect. However, as above, greater intake of a fatty food has been linked with adverse effects such as increased CVD risk, so this result should be taken in the context of the whole diet, rather than an “eat chocolate and you’ll reduce your heart attack risk” blanket message.  
4.      Other reported benefits of cocoa-derived polyphenols include increased circulation of blood to the skin,7 increased oxygen saturation in blood to the brain during cognitive tasks8, and reduced incidence of brain disorders in long-term consumers of cocoa.9

However, these health benefits need to be taken in context for several reasons. Firstly, several of these studies use chocolate which has been specially formulated to include especially high levels of polyphenols, rather more than your average bar of Dairy Milk. Other studies have given subjects chemically-isolated polyphenols rather than whole chocolate, meaning that you can draw conclusions as to the effect of the polyphenol, but not as to its effect when taken is as a component of the whole food.

In fact, the food matrix appears to be of great importance when it comes to health benefits of chocolate. Not all chocolate is equal, with great variety in the amount of epicatechin observed in fermented beans from different regions.10 Another related issue stems from the production of chocolate from its raw bean state. The roasting, fermentation and other steps in the chocolate-making process can result in up to 85% of the polyphenols being lost or changed into unusable forms.11 With the health-giving properties of cocoa flavanols being big news, producers are trying to find new processes to increase the polyphenol content of their chocolate, but these not in general use by the industry.
Many of these studies used cocoa drinks rather than chocolate bars, and there seems to be a greater effect when the flavanols are delivered in this way rather than in the solid form. It also appears that the milk proteins in milk chocolate can bind with the flavanols within the chocolate, which can reduce how much of the flavanols you can actually absorb. This has led to the common conception that dark chocolate is the one that is “good for you.”

So what can we conclude from the wealth of scientific evidence about chocolate? We have gone from the Chocolate is GOOD for you!!!! headline to the reality which is that chocolate contains compounds which, as long as they survive the production process and are consumed in the right concentrations from the correct food delivery system without you eating too much fat and sugar, might be able to reduce your risk of certain conditions. Not as snappy or sales-orientated, but it does have the benefit of being closer to the truth.


1          Wollgast, J. & Anklam, E. Review on polyphenols in Theobroma cacao: changes in composition during the manufacture of chocolate and methodology for identification and quantification. Food Research International 33, 423-447 (2000).
2          Baba, S. et al. Continuous intake of polyphenolic compounds containing cocoa powder reduces LDL oxidative susceptibility and has beneficial effects on plasma HDL-cholesterol concentrations in humans. Am J Clin Nutr 85, 709-717, doi:85/3/709 [pii] (2007).
3          Flammer, A. J. et al. Dark chocolate improves coronary vasomotion and reduces platelet reactivity. Circulation 116, 2376-2382, doi:CIRCULATIONAHA.107.713867[pii] 0.1161/CIRCULATIONAHA.107.713867 (2007).
4          Grassi, D., Lippi, C., Necozione, S., Desideri, G. & Ferri, C. 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, doi:81/3/611 [pii] (2005).
5          Grassi, D. 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, doi:138/9/1671 [pii] (2008).
6          Monahan, K. D. et al. Dose-dependent increases in flow-mediated dilation following acute cocoa ingestion in healthy older adults. J Appl Physiol 111, 1568-1574, doi:japplphysiol.00865.2011 [pii] 10.1152/japplphysiol.00865.2011 (2011).
7          Neukam, K., Stahl, W., Tronnier, H., Sies, H. & Heinrich, U. Consumption of flavanol-rich cocoa acutely increases microcirculation in human skin. Eur J Nutr 46, 53-56, doi:10.1007/s00394-006-0627-6 (2007).
8          Francis, S. T., Head, K., Morris, P. G. & Macdonald, I. A. The effect of flavanol-rich cocoa on the fMRI response to a cognitive task in healthy young people. J Cardiovasc Pharmacol 47 Suppl 2, S215-220, doi:00005344-200606001-00018 [pii] (2006).
9          Bayard, V., Chamorro, F., Motta, J. & Hollenberg, N. K. Does flavanol intake influence mortality from nitric oxide-dependent processes? Ischemic heart disease, stroke, diabetes mellitus, and cancer in Panama. Int J Med Sci 4, 53-58 (2007).
10        Kim, H. & Keeney, P. (-)-Epicatechin Content in Fermented and Unfermented Cocoa Beans. Journal of Food Science 49, 1090-1092 (2006).
11        Visioli, F. et al. Chocolate, lifestyle, and health. Crit Rev Food Sci Nutr 49, 299-312, doi:908817344 [pii] 10.1080/10408390802066805 (2009).

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