Cocoa is most commonly associated with chocolate and has a variety of nutritional benefits that can confirm positive health attributes. The cocoa bean is an accident source of dietary polyphenols, containing more finale antioxidants than most foods. It is well known that polyphenols are associated with beneficial health effects, therefore cocoa is rich in polyphenols, and dark chocolate, which contains a high percentage of cacao and high antioxidants compounds relative to other chocolate types, have assumed significant importance to health.
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The nutritional aspects of cocoa
Cocoa contains a significant quantity of fat, ~40 -50% contained in cocoa butter. This is comprised of 33% oleic acid, 25% palmitic acid, and 33% stearic acid. The polyphenol content constitutes approximately 10% of a whole bean dry weight. The polyphenols that cocoa contains include catechins (37%), anthocyanidins (4%), and proanthocyanins (58%). The proanthocyanins are the most prevalent phytonutrient in cocoa.
It is important to note that the bitterness of polyphenols is the reason that unprocessed cocoa beans are unpalatable; manufacturers have developed a processing technique to eliminate this bitterness. However, this process markedly decreases the polyphenol content. Polyphenol content can be lowered by up to tenfold.
Cocoa beans also contain nitrogenous compounds – these include both protein and methylxanthines, namely theobromine and caffeine. Cocoa is also rich in minerals, phosphorus, iron, potassium, copper, and magnesium.
The cardiovascular effects of cocoa consumption
cocoa is predominantly ingested in the form of chocolate; chocolate consumption has seen a recent increase globally, with dark chocolate becoming increasingly popular owing to its high concentrations of cocoa and associated beneficial health effects compared to normal or milk chocolate. In addition, come on chocolates with lower cocoa content such as milk chocolate are typically associated with adverse events due to high sugar and fat contents.
In terms of ingesting cocoa, dark chocolate is the predominant cocoa foodstuff associated with health-promoting effects; cocoa in its raw form is unpalatable.
There is a series of beneficial effects on the cardiovascular system that is associated with regular intake of cocoa-containing foods and beverages these encompass effects on blood pressure, vascular and platelet function, and insulin resistance.
Polyphenols, which are present in high concentrations in cocoa and dark chocolate, can activate endothelial nitrogen oxide synthase. This leads to the generation of nitrogen oxide, which lowers blood pressure by promoting vasodilation. Studies have shown improvements in pulse wave speed and sclerotic score index. Moreover, greater concentrations of plasma epicatechins aid in the release of endothelium-derived vasodilators and increase the concentration of plasma procyanidins. This leads to greater production of nitrogen oxide, and its bioavailability.
Once released, nitrogen oxide also activates the prostacyclin synthesis pathway, which also acts as a vasodilator and so also contributes to protection against thrombosis.
A systemic review has suggested that regular chocolate consumption, quantified as <100g/week, may be linked with a reduced risk of cardiovascular disease; the most appropriate dose of chocolate was 45g/week, as at higher levels of consumption, these health effects may be counteracted by elevated sugar consumption.
With regards to specific forms of cardiovascular disease, a Swedish prospective study has linked chocolate consumption with a reduced risk of myocardial infarction and ischemic heart disease. However, a lack of association between chocolate intake and risk of atrial fibrillation has been reported in a cohort of United States male physicians. Alongside this, a population-based study of 20,192 participants has failed to demonstrate an association between high chocolate intake (up to 100 g/day) and incident heart failure.
Cocoa has also been shown to play a role in treating cerebral conditions such as stroke; a large Japanese, population-based, prospective study rated an association between a lowered risk of stroke in women, but not men, with regards to chocolate consumption.
The effect of cocoa consumption on glucose homeostasis
Cocoa contains flavanols which improves glucose homeostasis. They can slow down carbohydrate digestion and absorption in the gut, which forms the mechanistic basis of their action. Cocoa extracts and procyanidins have been shown to dose-dependently inhibit pancreatic α-amylase, pancreatic lipase, and secreted phospholipase A2.
Cocoa and its flavanols also improved glucose insensitivity by regulating the transport of glucose and insulin signaling proteins in insulin-sensitive tissues such as the liver, adipose tissue, and skeletal muscle. This prevents oxidative and inflammatory damage associated with type 2 diabetes.
Results from the Physician Health Study have also reported an inverse relationship between cocoa consumption and the incidence of diabetes. In a cohort of multiethnic subjects, a lowered risk of developing type 2 diabetes has been found, with the highest intake of chocolate products and cocoa-derived flavonoids.
Moreover, a prospective study in Japanese pregnant women has also demonstrated a reduced risk of gestational diabetes among those women in the highest quartile of chocolate consumption.
Other studies which demonstrate the association of cocoa and glucose homeostasis have shown that cocoa extracts and procyanidins inhibit the production of enzymes for the digestion of carbohydrates and lipids, which suggests a putative role in the control of body weight in conjunction with a reduced-calorie diet.
Moreover, a single-blind, randomized placebo-controlled crossover human study has shown the metabolic benefits of consuming polyphenol-rich dark chocolate and the possibility of adverse effects occurring with polyphenol-poor chocolates.
The effect of cocoa consumption on cancer
Effective cocoa consumption on cancer is controversial. Earlier studies initially suggested that chocolate intake could be a predisposing factor to the development of colorectal and breast cancer. However other studies have shown that cocoa can inhibit the growth of cancer cells in vitro; despite this, the mechanisms for this anti-cancer activity are not well understood.
With regards to the active component in cocoa which produces such anti-cancer effects, procyanidins specifically have been shown to reduce the incidence and multiplicity of lung cancers as well as decrease thyroid adenoma size in male rats. These compounds could also inhibit mammary and pancreatic tumorigenesis in female rats. Cocoa procyanidins also reduce activity associated with tumor-associated activities such as tumor vascular endothelial growth factor activity and angiogenic activity.
The treatment of different types of ovarian cancer cell lines with various concentrations of cocoa rich in procyanidin has been shown to induce cytotoxicity and chemosensitization. Notably, a significant percentage of cells in the G0/G1 phase of the cell cycle with increasing concentration. In addition to this, a significant proportion of cells were also arrested in the S phase. These effects are thought to be attributed to increased intracellular levels of reactive oxygen species.
Several studies have also demonstrated various effects of cocoa on the risk and spread of cancer. Cocoa polyphenols have been shown to produce antiproliferative effects because of interference with polyamine metabolism in in vitro human studies. In in vivo rat studies proanthocyanidins present in dark chocolate have been shown to inhibit the mutagenicity of pancreatic cancers at the initiation stage as well as exerting chemoprotective effects in the lung, decreasing the incidence and spread of carcinomas in a dose-dependent manner.
To determine the full effect of cocoa on the risk of reducing the risk or severity of cancer, further translation and prospective studies are necessary.
The effect of cocoa on the immune system
Studies on immune system effects related to cocoa or chocolate use have shown that a cocoa-enriched diet can modulate intestinal immune responses in young rats. In particular, theobromine and cocoa were demonstrated to be responsible for systemic intestinal antibody concentration as well as modifying the lymphocyte composition in young healthy rats.
In studies of humans, a randomized double-blind crossover study has shown that dark chocolate consumption improved leukocyte adhesion factors as well as vascular function in men that were overweight. Moreover, participants in a cross-sectional, observational, human study who moderately consumed cocoa were found to have a reduced frequency of chronic disease compared to lower consumers. In addition, the consumption of cocoa was inversely associated with allergies and physical activity.
The effect of cocoa on body weight
Counterintuitively, there is an association between the consumption of cocoa and its potential role as a therapeutic measure against obesity and metabolic syndrome. This comes from several in vitro mice and rat studies as well as randomized control trials, prospective human, and case-control studies in humans.
In mice and rats, obese rodents supplemented with cocoa lessened the incidence of obesity-related inflammation, fatty liver disease, and insulin resistance. Cocoa ingestion also decreased fatty acid synthesis and transport to the liver and adipose tissues.
In humans, the smell or ingestion of dark chocolate can alter hunger, suppressing appetite because of changes in ghrelin, the hormone responsible for feelings of hunger. Regular consumption of dark chocolate could favorably affect levels of high-density lipoprotein cholesterol (the ‘good’ cholesterol), the ratio of lipoproteins, and inflammation markers; similar effects were seen when the consumption of dark chocolate in combination with almonds, was shown to improve lipid profiles in the blood.
Overall, cocoa and its derived products can act as functional foods as they contain several compounds the produce health benefits. Its positive health benefit affects the immune, cardiovascular, and metabolic systems to name a few. In addition, studies have demonstrated the positive effects of cocoa consumption on the central nervous system.
There are some limitations with studies designed to investigate the effect of cocoa – namely, that they evaluate the health-promoting properties of cocoa and not of chocolate itself. This is notable as cocoa is predominantly eaten in the form of chocolate, whose nutritional profile is distinct from that of cocoa. As such, the role of chocolate on human health is not entirely comparable to that of cocoa.
Other limitations include the relative paucity of epidemiological studies examining the health effects of cocoa in different forms – namely dark chocolate which is increasing in popularity. Moreover, there are several confounding factors such as other diet components, environmental exposures, lifestyle, and volume of chocolate consumption, as well as its composition which limit the strength of the evidence presented by studies.
Further translational studies are necessary to determine the possible effects of consuming cocoa, and chocolate and to verify results demonstrated in in vitro tests on animals.
References:
- Montagna MT, Diella G, Triggiano F, et al. (2019) Chocolate, "Food of the Gods": History, Science, and Human Health. Int J Environ Res Public Health. doi:10.3390/ijerph16244960.
- Katz DL, Doughty K, Ali A. (2011) Cocoa and chocolate in human health and disease. Antioxid Redox Signal. doi10.1089/ars.2010.3697.
- Maraldi T, Vauzour D, Angeloni C. (2013) Dietary polyphenols and their effects on cell biochemistry and pathophysiology. Oxid Med Cell Longev. doi:10.1155/2014/576363.
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