Overview of scientific evidence for chocolate health benefits

The potential health benefits of consuming chocolate have only recently been discovered. Laboratory studies and observational and small scale experimental studies on humans have found that chocolate consumption lowers blood pressure and may also have other positive health effects. There are several bioactive compounds in chocolate that may promote alertness and may affect stress levels by prompting serotonin production, which is a calming neurotransmitter. The number of publications concerning cocoa and chocolate is increasing steadily. Of such publications, an increasing proportion concerns the effects of polyphenols and, in particular, flavonoids on human biology and health. Studies that link chocolate consumption with health outcomes (instead of intermediate outcomes like blood pressure) are less common. There appears to be some scientific evidence to justify eating a moderate amount of dark chocolate daily. A Special Session at the 24th Annual Meeting of the Society of Environmental Toxicology and Chemistry (SETAC) Europe in Basel in 2014, entitled Sustainability of Swiss Chocolate Production, considered sustainable chocolate production and human health issues associated with societal costs and benefits (Figure 1). Chocolate consumption is often described as a “guilty pleasure” by the many media that deal with healthy food: eating chocolate gives pleasure and comfort, although at the same time it makes one feel guilty because chocolate is mainly fat (and sugar) without much beneficial nutrition. Over the past decade this image problem of chocolate has shifted positively: claims that chocolate consumption has health benefits have been substantiated by scientific articles, and in the media chocolate has been given the status of “super food” or “brain food.” In a review article on chocolate and cocoa and human health, Latif (2013) reported potential beneficial health effects: prevention of cardiovascular diseases (reduction of oxidative stress, lowering of blood pressure, increased vasodilatation, increased platelet activity, antidiabetic effects, and antistress effects); effects on neurons; possible antitumor effects; anti-inflammatory effects; anti-obesity effects; and, better exercise recovery. Compounds held responsible for these benefits are antioxidants such as flavanoids that provide defense against free radicals. Chocolate also contains theobromine and caffeine, which are central nervous system stimulants, diuretics and smooth muscle relaxants, and valeric acid, which is a stress reducer. Health risks from chocolate include contribution to weight gain, heartburn, and allergies. Dark chocolate contains 513 kcal (2152 kJ)/100 g, which needs at least 1.5 hours cycling or walking to burn the energy (for comparison, avocado, another “super” food, contains 188 kcal [790 kJ]/100 g). The potential beneficial effects of chocolate are supported by epidemiological and human intervention studies. The latter are mostly randomized, blind, and placebo-controlled studies in which the effects of a daily consumption of a certain amount of chocolate or ingredients of chocolate are being studied. The first epidemiological “evidence” for beneficial health effects of chocolate were found in the Kuna Indian population of the islands of Panama. This population is characterized by a low prevalence of atherosclerosis, type 2 diabetes, and hypertension. The “secret” behind this is the daily intake of a homemade cocoa drink by the indigenous Kuna Indians. These traits disappear after migration to urban areas on mainland Panama and subsequent changes in diet (Latif 2013). The European Food Safety Authority (EFSA) is an authority in deciding whether commercially used health claims for food items are substantiated by scientific evidence. The health claim “cocoa flavonols help maintain endothelium-dependent vasodilatation, which contributes to normal blood flow” was supported by 6 studies with randomized controlled trials pertinent to the claim and approximately 10 additional studies. EFSA (2012) concluded that: normal blood flow is a beneficial physiological effect; there is a dose–effect relationship between flavonols and blood flow; 200 mg of cocoa flavonols should be consumed daily; and, the target population is the general population. A typical example of an epidemiological study is one on the influence of flavonoids from chocolate, wine, and tea on cognitive performance. Elderly Norwegian participants were asked to perform cognitive tests and to fill in a questionnaire on habitual food intake. A dose–dependent association was found between intake of chocolate, wine, and tea and cognition, with maximum effects at 10 g/day for chocolate, 100 mL/day for wine, and a linear effect for tea (Nurk et al. 2009). In reviewing beneficial chocolate health effects, Latif (2013) warns that the majority of the studies claiming benefits of chocolate are small-scale, and sponsored or carried out by chocolate manufacturers whose interests cannot be ignored. The worth of the global chocolate market is growing and estimated at 98.3 billion US$ by 2016 (Markets and Markets 2014). On the other hand, high costs are associated with the diseases that might be reduced by chocolate consumption. For instance, it is estimated that cardiovascular diseases cause an economic cost of 169 billion euro per year in Europe (Leal et al. 2006). Based on presumed health benefit effects, annual sales of food supplements containing resveratrol, a compound also present in chocolate and thought to be responsible for the “French health paradox” (the apparently paradoxical epidemiological observation that French people have a relatively low incidence of coronary heart disease, while having a diet relatively rich in saturated fats), amount up to 30 million US$ in the United States alone. However, a recently published and much talked about, large, long-term epidemiological study showed that resveratrol in red wine, chocolate, and grapes was not associated with improved health in elderly Italians (Semba et al. 2014). Latif (2013) also mentions that most products used in studies contain more polyphenols than commercially available products. Furthermore, milk and white chocolate contain more sugar and (far) less beneficial compounds. In the studies mentioned in this article, different daily dark chocolate doses are mentioned that might lead to health benefits. EFSA (2012) mentions 10 g high-flavanol dark chocolate, the study with elderly Norwegians states 10 g, and Latif (2013) reports approximately 60 g. There is scientific evidence for both physical and mental health positive effects of (dark) chocolate, although there remains much uncertainty. Dose–effect relationships are needed, as well as more focus on the negative health effects of chocolate consumption. The results of chocolate health studies may have considerable economic implications, for both chocolate manufacturers and for general health care. There seems some consensus about a beneficial dosage of 10 g dark chocolate per day (>70% cocoa).