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International Journal of
Environmental Research
and Public Health
Review
Chocolate, “Food of the Gods”: History, Science, and
Human Health
Maria Teresa Montagna 1 ,* , Giusy Diella 1, Francesco Triggiano 1, Giusy Rita Caponio 2,3,
Osvalda De Giglio 1, Giuseppina Caggiano 1, Agostino Di Ciaula 2and Piero Portincasa 2, *
1
Department of Biomedical Sciences and Human Oncology, Section of Hygiene, University of Bari Aldo Moro,
Medical School, Piazza G. Cesare 11, 70124 Bari, Italy; giusy.diella@uniba.it (G.D.);
francescotrigg@hotmail.it (F.T.); osvalda.degiglio@uniba.it (O.D.G.); giuseppina.caggiano@uniba.it (G.C.)
2Department of Biomedical Sciences and Human Oncology, Clinica Medica “A. Murri”, University of Bari
Aldo Moro, Medical School, Piazza G. Cesare 11, 70124 Bari, Italy; giusy.caponio@uniba.it (G.R.C.);
agostinodiciaula@tiscali.it (A.D.C.)
3Department of Soil, Plant and Food Science (DISSPA), University of Bari Aldo Moro, Via Amendola 165/a,
70126 Bari, Italy
*Correspondence: mariateresa.montagna@uniba.it (M.T.M.); piero.portincasa@uniba.it (P.P.);
Tel.: +39-080-547-8476 (M.T.M.); +39-080-547-8293 (P.P.)
Received: 27 November 2019; Accepted: 3 December 2019; Published: 6 December 2019
Abstract:
Chocolate is well known for its fine flavor, and its history began in ancient times, when
the Maya considered chocolate (a cocoa drink prepared with hot water) the “Food of the Gods”.
The food industry produces many different types of chocolate: in recent years, dark chocolate, in
particular, has gained great popularity. Interest in chocolate has grown, owing to its physiological
and potential health effects, such as regulation of blood pressure, insulin levels, vascular functions,
oxidation processes, prebiotic effects, glucose homeostasis, and lipid metabolism. However, further
translational and epidemiologic studies are needed to confirm available results and to evaluate other
possible effects related to the consumption of cocoa and chocolate, verifying in humans the effects
hitherto demonstrated only
in vitro
, and suggesting how best to consume (in terms of dose, mode,
and time) chocolate in the daily diet.
Keywords: chocolate; cocoa; Food of the Gods; Theobroma cacao; nitric oxide; cardiovascular effects
1. Background
The history of chocolate began with the Maya, who were probably the first people in South
America to cultivate the cocoa plant [
1
]. For the Maya, chocolate was a cocoa drink prepared with hot
water and often flavored with cinnamon and pepper. It was called the “Food of the Gods” and was
presented at the table of Emperor Moctezuma II by the Aztecs [1].
In 1502, Christopher Columbus was the first European to encounter cocoa. He captured a canoe
that contained cocoa beans, which were considered “mysterious-looking almonds” and identified as a
form of currency in Mesoamerica [2,3].
Cocoa appeared in Europe in 1528, when the Spanish conquistador Hern
á
n Cort
é
s brought
samples of cocoa to King Charles of Spain, spreading the great effects of the beverage prepared from
this “brown gold” [
3
,
4
]. It was in 1753 that the Swedish scientist Carl Linnaeus named the cocoa plant
Theobroma cacao, from the Latin name Theobroma [literally ‘food of the Gods’], and the Aztec word
xocolatl [i.e., xococ (bitter) and atl (water)] [5].
The characteristics of chocolate were long ignored in Europe owing to difficulties with an
environment unfavorable to its growth. The natural habitat of the cocoa tree is the lower level of an
evergreen rain forest. Cocoa plants respond well to relatively high temperatures (with a maximum
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Int. J. Environ. Res. Public Health 2019,16, 4960 2 of 21
annual average of 30–32
◦
C and minimum average of 18–21
◦
C) and generally high relative humidity:
often as much as 100% during the day, falling to 70–80% at night [
6
]. According to the latest published
data of the International Cocoa Organization (ICCO), the total world production of cocoa beans in
2016–17 was 4,739,000 tons, principally from Africa (3,622,000 tons) [7].
Demand for organic cocoa products is also expanding, as consumers are increasingly concerned
about food security and other environmental issues. However, the organic cocoa market still represents
a very small share of the total cocoa market, estimated at less than 0.5% of total production [8].
In this review, we will discuss the main evidence relating to cocoa and chocolate, exploring the
possible effects on human health related to their consumption.
2. Chocolate Varieties
Starting from cocoa beans, through various processes of transformation (Figure 1), the food
industry produces different types of chocolate with defined ingredients and characteristics [1,9–11].
(1) Dark chocolate contains cocoa bean solids (up to 80% of the total weight) and cocoa butter.
With the intense, persistent aroma of cocoa, it melts in the mouth, leaving a pleasant, bitter aftertaste.
Its quality depends on the percentage of cocoa. Most of the health benefits attributable to chocolate are
associated with consuming the dark type.
(2) Gianduja chocolate is a combination of hazelnuts, cocoa, and sugar; it is brown.
(3) Milk chocolate contains cocoa butter, sugar, milk powder, lecithin, and cocoa (the latter not
less than 20–25%). With a bright appearance, it has an intense, persistent aroma and sweet taste with a
slightly bitter accent of cocoa.
(4) White chocolate contains cocoa butter, milk, and sugar with no cocoa solids; it has a sweet,
pleasant taste.
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Int. J. Environ. Res. Public Health 2019, 16, x; doi: www.mdpi.com/journal/ijerph
often as much as 100% during the day, falling to 70–80% at night [6]. According to the latest published
data of the International Cocoa Organization (ICCO), the total world production of cocoa beans in
2016–17 was 4,739,000 tons, principally from Africa (3,622,000 tons) [7].
Demand for organic cocoa products is also expanding, as consumers are increasingly concerned
about food security and other environmental issues. However, the organic cocoa market still
represents a very small share of the total cocoa market, estimated at less than 0.5% of total production
[8].
In this review, we will discuss the main evidence relating to cocoa and chocolate, exploring the
possible effects on human health related to their consumption.
2. Chocolate Varieties
Starting from cocoa beans, through various processes of transformation (Figure 1), the food
industry produces different types of chocolate with defined ingredients and characteristics [1,9–11].
(1) Dark chocolate contains cocoa bean solids (up to 80% of the total weight) and cocoa butter.
With the intense, persistent aroma of cocoa, it melts in the mouth, leaving a pleasant, bitter aftertaste.
Its quality depends on the percentage of cocoa. Most of the health benefits attributable to chocolate
are associated with consuming the dark type.
(2) Gianduja chocolate is a combination of hazelnuts, cocoa, and sugar; it is brown.
(3) Milk chocolate contains cocoa butter, sugar, milk powder, lecithin, and cocoa (the latter not
less than 20–25%). With a bright appearance, it has an intense, persistent aroma and sweet taste with
a slightly bitter accent of cocoa.
(4) White chocolate contains cocoa butter, milk, and sugar with no cocoa solids; it has a sweet,
pleasant taste.
Figure 1. The processing of chocolate from cocoa beans.
3. Nutritional Aspects
Cocoa, the basic ingredient in chocolate, contains a significant amount of fat (40–50% as cocoa
butter, with approximately 33% oleic acid, 25% palmitic acid, and 33% stearic acid). It also contains
polyphenols, which constitute about 10% of a whole bean’s dry weight [12]. Cocoa bean is one of the
best-known sources of dietary polyphenols, containing more phenolic antioxidants than most foods
[13]. Three groups of polyphenols can be identified in cocoa beans: catechins (37%), anthocyanidins
(4%), and proanthocyanidins (58%); these flavonoids are the most abundant phytonutrients in cocoa
Figure 1. The processing of chocolate from cocoa beans.
3. Nutritional Aspects
Cocoa, the basic ingredient in chocolate, contains a significant amount of fat (40–50% as cocoa
butter, with approximately 33% oleic acid, 25% palmitic acid, and 33% stearic acid). It also contains
polyphenols, which constitute about 10% of a whole bean’s dry weight [
12
]. Cocoa bean is one of the
best-known sources of dietary polyphenols, containing more phenolic antioxidants than most foods [
13
].
Three groups of polyphenols can be identified in cocoa beans: catechins (37%), anthocyanidins (4%), and
Int. J. Environ. Res. Public Health 2019,16, 4960 3 of 21
proanthocyanidins (58%); these flavonoids are the most abundant phytonutrients in cocoa beans [
14
–
16
].
However, the bitterness caused by polyphenols makes unprocessed cocoa beans rather unpalatable.
Manufacturers have, therefore, developed processing techniques for eliminating the bitterness. Such
processes decrease the polyphenol content by up to 10-fold: for consumers the product is markedly
different, mainly owing to the low-polyphenol content [
12
,
15
] and the other substances added during
the processing phase (e.g., sugar, emulsifiers such as soy lecithin). It is well known that polyphenols
are associated with beneficial effects, therefore cocoa (rich in polyphenols) and dark chocolate (with a
high percentage of cocoa and higher phenolic antioxidant compounds compared to the other chocolate
varieties [13]) have assumed significant importance [17].
The nitrogenous compounds of cocoa include both proteins and methylxanthines (theobromine
and caffeine) [
18
]. Cocoa is also rich in minerals: potassium, phosphorus, copper, iron, zinc, and
magnesium [
18
]. The nutritional values of cocoa and two types of chocolate appear in Table 1[
13
,
19
,
20
].
Table 1. Nutritional values per 100 g of cocoa and two types of chocolate.
Chemical Composition Cocoa Dark Chocolate Milk Chocolate
Water (g) 2.5 0.5 0.8
Protein (g) 20.4 6.6 7.3
Lipid (g) 25.6 33.6 36.3
Cholesterol (mg) 0 0 10
Carbohydrate (g) 11.5 49.7 50.5
Sugar (g) traces 49.7 50.5
Total fiber (g) - 8 3.2
Sodium (mg) - 11 120
Potassium (mg) - 300 420
Iron (mg) 14.3 5 3
Calcium (mg) 51 51 262
Phosphorus (mg) 685 186 207
Thiamin (mg) 0.08 0.07 0.09
Riboflavin (mg) 0.3 0.07 0.39
Niacin (mg) 1.7 0.6 0.6
Vitamin A (µg) 7 9 25
Phenolics (mg) 996–3781 579 160
Flavonids (mg) - 28 13
Theobromine (mg) - 802 125
Energy (kcal) 355 515 545
Energy (kJ) 1486 2155 2281
4. Lights and Shadows in Chocolate and Cocoa Consumption
Chocolate consumption has recently increased around the world; dark chocolate, in particular,
has become very popular for its high concentrations of cocoa and beneficial effects on human health
compared with normal or milk chocolate [
21
–
24
]. In addition, milk chocolate could be associated with
adverse effects due to its sugar content.
Therefore, only dark chocolate, with high percentages of cocoa, flavonoids, and theobromine and
low content of sugar, differently from milk chocolate or other types of chocolate, would be associated
with health-promoting effects [
11
], including the prevention of cardiovascular disease. Similarly, cocoa
induces positive effects on blood pressure, insulin resistance, and vascular function. It increases
production of nitric oxide (NO) and has antioxidant effects, e.g., delayed oxidation of low-density
lipoprotein (LDL) cholesterol and inhibiting ultraviolet-induced DNA oxidation [25,26].
The advantages and disadvantages of chocolate and cocoa consumption are discussed in the
following sections, according to in vivo or in vitro studies.
Int. J. Environ. Res. Public Health 2019,16, 4960 4 of 21
4.1. Cardiovascular Effects
A series of beneficial effects on the cardiovascular system might occur following regular intake of
cocoa-containing foods and beverages. Benefits include effects on blood pressure, insulin resistance,
and vascular and platelet function [25].
Polyphenols, abundant in cocoa and dark chocolate, activate endothelial NO synthase; that leads
to generation of NO [
27
], which lowers blood pressure by promoting vasodilation [
28
–
33
]. Indeed,
following the consumption of dark chocolate, effects include improvement of the pulse wave speed
and of the atherosclerotic score index, with parietal relaxation of large arteries and dilation of small
and medium-sized peripheral arteries. Higher concentrations of plasma epicatechins help release
endothelium-derived vasodilators and increase the concentration of plasma procyanidins, which leads
to greater NO production and bioavailability [
32
]. Once released, NO also activates the prostacyclin
synthesis pathway, which acts as a vasodilator in synergy with NO, thereby contributing to thrombosis
protection [
17
]. Further, the anti-inflammatory and vasoprotective properties of prostacyclin are
enhanced by its ability to reduce plasma leukotrienes [17,34,35].
A meta-analysis of randomized trials report that both acute and chronic chocolate and cocoa
ingestion effectively increased flow-mediated vasodilatation, reduced systolic and diastolic blood
pressure, and reduced serum insulin levels [
36
]. In young and healthy adults, a daily ingestion of
20 g of higher cocoa chocolate (90%) for a 30-day period improved vascular function by reducing
central brachial artery pressures and promoting vascular relaxation [
37
]. A Swedish prospective study
linked chocolate consumption (
≥
3–4 servings/week) with lower risk of myocardial infarction and
ischemic heart disease [
38
]. On the other hand, a large prospective study exploring data from 83,310
postmenopausal women free of pre-existing major chronic diseases found no association between
chocolate consumption and risk of coronary heart disease, stroke, or both combined. Conversely,
an increased risk existed among women less than 65 years, in the highest quintile of chocolate
consumption [
39
]. A lack of association between chocolate intake and risk of atrial fibrillation was also
reported in a large cohort of United States male physicians [
40
]. Another population-based, prospective
study on 20,992 participants failed to demonstrate an association between high chocolate intake (up
to 100 g/day) and incident heart failure [
41
]. A systematic review suggested that regular chocolate
use (<100 g/week) may be linked with reduced cardiovascular risk, and that the most appropriate
dose of chocolate consumption was 45 g/week, since higher levels might counteract the health benefits
due to adverse effects linked with elevated sugar consumption [
42
]. These findings were similar to
results from a large cohort of Swedish men, which showed a J-shaped association between chocolate
consumption and incidence of heart failure, with protective effects absent in subjects consuming
≥
1
serving per day [43].
Cocoa plays also a role in treating cerebral conditions, such as stroke; in fact, cocoa intake is
associated with increased cerebral blood flow [
44
]. In the same way, daily chocolate consumption
may reduce the likelihood of a stroke attack [
18
,
45
]. However, a large Japanese population-based,
prospective cohort study reported an association between chocolate consumption and lower risk of
stroke in women but not in men [26].
Table 2shows the studies on cardiovascular effects related to cocoa or chocolate consumption.
4.2. Glucose Homeostasis
Cocoa components offer potential as antidiabetic agents, especially with type 2 diabetes mellitus
(T2D). This aspect is of particular relevance owing to the emerging worldwide epidemic of metabolic
syndrome, including obesity, T2D, and dyslipidemia [46].
Cocoa and flavonols improve glucose homeostasis by slowing carbohydrate digestion and
absorption in the gut [
47
,
48
]. Indeed, cocoa extracts and procyanidins dose-dependently inhibit
pancreatic
α
-amylase, pancreatic lipase, and secreted phospholipase A2 [
48
,
49
]. Cocoa and its
flavonols improve insulin sensitivity by regulating glucose transport and insulin signaling proteins in
insulin-sensitive tissues (liver, adipose tissue, and skeletal muscle) preventing in these tissues oxidative
Int. J. Environ. Res. Public Health 2019,16, 4960 5 of 21
and inflammatory damage associated with the disease [
47
]. In younger and normal body-weight men,
the results from the Physicians’ Health Study reported an inverse relation of chocolate consumption
with incident diabetes [
50
]. In a multiethnic United States cohort, authors found a lower risk
of developing T2D in subjects with the highest intake of chocolate products and cocoa-derived
flavonoids [
51
]. A dose-response meta-analysis, however, suggested a nonlinear association between
chocolate consumption and the risk of T2D, with a peak protective effect at 2 servings/week and no
benefit recorded when increasing consumption was above 6 servings/week [52].
A prospective study in a large number of Japanese pregnant women also showed a lower risk of
gestational diabetes in subjects in the highest quartile of chocolate consumption [53].
The observed effects on glucose homeostasis seem to be strongly dependent on the amount of
polyphenols. In fact, a single-blind randomized placebo-controlled cross-over study showed, after
4 weeks, negative metabolic effects (i.e., raised fasting insulin, insulin resistance, and salivary cortisol)
in subjects consuming 20 g/day dark chocolate with negligible polyphenol content but not in those
consuming the same amount of polyphenol-rich (500 mg) chocolate [54].
Therefore, the daily consumption of small quantities of flavonols from cocoa or chocolate,
associated with a dietary intake of flavonoids, would constitute a natural and economic approach
to prevent or potentially contribute to the treatment of T2D with minimal toxicity and negative side
effects [
47
]. However, most commercially available soluble cocoa products or chocolates contain low
amount of flavonols and are rich in sugar and calories. Therefore, high consumption of chocolate will
induce paradoxical consequences, i.e., weight gain and impaired glucose homeostasis, especially in
T2D patients and obese individuals [48].
Table 3shows the studies on glucose homeostasis effects related to cocoa or chocolate use.
4.3. Cancer
Results regarding the effects of cocoa/chocolate consumption on cancer are rather controversial.
Early studies suggested that excess chocolate intake could be a predisposing factor to tumor
development (as colorectal and breast cancer) [55,56].
According to other
in vitro
studies, cocoa inhibits the growth of cancer cells; however, the exact
anticancer mechanisms are poorly understood [57,58].
Some authors demonstrated that cocoa liquor procyanidins significantly reduced the incidence
and multiplicity of lung carcinomas and decreased thyroid adenomas developed in male rats, and
inhibited mammary and pancreatic tumorigenesis in female rats [
59
,
60
]. Cocoa procyanidins also
reduced vascular endothelial growth factor activity and angiogenic activity associated with tumor,
determining down-regulation of tyrosine kinase ErbB2 [61].
In the last years, the treatment of different ovarian cancer cell lines with various concentrations of
cocoa procyanidin-rich extract, inducing cytotoxicity and chemosensitization, showed a significant
percentage of cells in sub-G1/G0 (hypodiploid) phase, which increased with increasing concentration,
and a significant accumulation of cells in the S phase was seen [
62
]. This effect is probably due to
an increase in intracellular levels of reactive oxygen species (ROS) [
63
]. In an animal study, a diet
containing dark chocolate reduced the total number of aberrant crypt foci in the colon. The effect was
associated with down-regulation in the transcription levels of both COX-2 and ReIA [
64
]. In addition,
cocoa significantly decreased the tumor incidence and size in mice with colitis-associated cancer [65].
At present, further translational and prospective studies need to explore the intrinsic mechanisms
of cocoa’s anticancer action to support its use as a co-adjuvant in preventing and treating cancer [18].
Table 4shows the studies on cancer related to cocoa or chocolate use.
4.4. Obesity and Lipid Metabolism
Recently, some studies have investigated the preventive or therapeutic effects of cocoa and cocoa
constituents against obesity and metabolic syndrome [
66
]. Administering cocoa to rats decreased
visceral adipose tissue [
67
]. DNA analysis conducted on the liver and mesenteric fat tissue provided
Int. J. Environ. Res. Public Health 2019,16, 4960 6 of 21
interesting clues. In that study, the authors observed decreased expression of various genes associated
with fatty acid transport and synthesis in the liver and mesenteric fat as well as increased expression of
genes associated with thermogenesis [18,67].
In a clinical study, smelling dark chocolate was assessed to evaluate an appetite response.
Chocolate produced a satiation response and reduced appetite; thus, it could be helpful in preventing
weight gain [
68
]. Further, flavonoids can produce metabolic events that induce reduction of lipogenesis,
induction of lipolysis, and increased adiponectin secretion; such events reduce lipid deposition and
insulin resistance, thus mitigating obesity [17].
A study reported a significantly greater and dose-dependent weight gain over time in subjects with
more frequent chocolate consumption. However, no information was provided about the consumer
profile of enrolled subjects and the type of chocolate consumed (in particular, the specific amount of
dark chocolate) [69].
A recent meta-analysis reported the lack of effects of cocoa or dark chocolate on weight, body
mass index (BMI), and waist circumference. However, a subgroup analysis showed reduced weight
and BMI following cocoa/dark chocolate supplementation
≥
30 g chocolate per day in trials between
4–8 weeks, pointing to the relevant role of the consumed dose and trial duration [70].
Dark chocolate might also operate in combination with other nutraceuticals, and have positive
effects on lipid profile. Our group has recently reported distinct effects of 24 g almond varieties on
organoleptic features and on gastrointestinal function (gallbladder and gastric emptying, orocecal
transit) in healthy subjects [
71
]. One 4-week crossover feeding trial among 31 overweight or obese
adults determined that daily consumption of almonds (42 g/day) alone or combined with dark chocolate
was beneficial for total cholesterol, low-density (LDL) lipoprotein cholesterol, and apolipoprotein B
concentrations. The authors concluded that incorporating almonds, dark chocolate, and cocoa into a
diet without exceeding energy needs could reduce the risk of coronary heart disease [72].
A meta-analysis showed that, in the short term (2–12 weeks), dark chocolate/cocoa consumption
can significantly lower total and LDL cholesterol levels, but has no effect on high-density lipoprotein
HDL and triglycerides [
73
]. Similar results derive from a placebo-controlled cross-over study, in
which daily consumption of cocoa flavonol-containing dark chocolate bars with added plant sterols
significantly reduced serum total and LDL cholesterol [74].
Normal weight obese syndrome consists of an excessive body fat associated with a normal BMI,
and a higher risk for cardiovascular morbidity and mortality. A group of normal weight obese women
consuming dark chocolate (100 g/day, 70% cocoa) for a short period (one week) displayed a rise in the
HDL cholesterol levels, and a decrease of the LDL/HDL cholesterol ratio and abdomen circumference.
The authors concluded that the regular consumption of dark chocolate would help in maintaining
a good atherogenic profile, due to the favorable effects on HDL cholesterol, lipoprotein ratios, and
possibly on inflammation markers [75].
Table 5shows the studies on obesity and lipid metabolism related to cocoa or chocolate use.
4.5. Intestinal Microbiota
In recent years, there is a growing interest in the study of intestinal microbiota and its changes
as result of a particular diet. The human gut harvests the intestinal microbiota, a huge collection of
microbes with a key role in energy storage and metabolic disorders [
76
]. Whereas flavonol monomers
and dimers are absorbed in the small intestine, procyanidins undergo metabolization by colonic
microbiota, with production of phenolic acids, subsequently absorbed, metabolized in the liver, and
eliminated in the urine or in feces [
77
–
80
]. Thus, gut microbiota is responsible for the metabolization of
polyphenols in other bio-active compounds (i.e., valerolactones [
81
], and various phenolic acids [
82
])
with potential anti-inflammatory properties [17].
Int. J. Environ. Res. Public Health 2019,16, 4960 7 of 21
A study conducted on rats fed with cocoa diet for 6 weeks highlighted a significant reduction of
percent of Bacteroides,Clostridium, and Staphylococcus, changes of tool-like reception expression, and a
reduction of immunoglobulin A intestinal secretion, significantly correlated with the decrease in the
proportion of the Clostridium and Streptococcus [78].
In pigs, cocoa consumption, in addition to determining changes in metabolites in biofluids and
tissues, as the increase in O-methyl-epicatechin glucuronide conjugates in serum, urine, and visceral
adipose tissue, induced a significant increase of the abundance of Lactobacillus species from the casei
group in feces and Bifidobacterium species in proximal colon contents [83].
Tzounis et al. [
79
] conducted the first human-intervention study designed to investigate the
influence of high cocoa flavanol intake on the growth of the human fecal microbiota. In particular,
these authors assessed that the intake of 494 mg of cocoa flavonoids/day for 4 weeks had a significant
effect on intestinal microbiota growth.
Table 6shows the studies on intestinal microbiota related to cocoa or chocolate use.
4.6. Immune System
In vivo
and
in vitro
studies showed that cocoa has regulatory properties on the immune cells
implicated in both innate and acquired immunity. In animals, these effects are present at systemic and
intestinal level [
84
,
85
]. In Lewis rats a 10% cocoa diet or a 0.25% theobromine diet were both able, after
one week, to lower serum concentrations of IgG, IgM, IgA, and intestinal IgA, as compared with control
diet. Both cocoa and theobromine modified the thymocyte composition increasing CD4-CD8- and
CD4+CD8- proportions, and changed the composition of mesenteric lymph node (reduced percentage
of T-helper) and spleen (increased proportion of T-helper). Taken together, the data suggest that
theobromine is the agent mediating the major immunoregulatory effects of cocoa [
86
]. Dark chocolate
consumption was found having anti-inflammatory effects in a 4-week randomized clinical trial, which
was especially visible in the reduced post-challenge responses of cytokines, vascular markers, white
blood cells, and leukocyte-activation markers [87,88].
Regular cocoa consumption could be related to preventing or improving health imbalance induced
by allergic processes [
89
]. The positive effects of cocoa flavonoids on the immune system (related
to several allergic mechanisms) are known, such as reducing the release of mediators, restoring
the balance of T-helper 1 and T-helper 2 cells [
90
], and down-regulation of IgE production [
89
,
91
].
By contrast, chocolate is one of the main potentially allergenic foods that is also capable of causing
hypersensitivity reactions, manifesting different clinical symptoms (e.g., fatigue, irritability, insomnia,
headache, asthma, and diarrhea) which appear in a few hours or days after food intake [92].
Table 7shows the studies on the immune system related to cocoa or chocolate use.
4.7. Central Nervous System
There is evidences of some beneficial effects on the central nervous system, but larger, prospective
studies are missing, so far.
In healthy volunteers, the ingestion of 100 g dark chocolate (72% cocoa) increased [
18
F]
fluorodeoxyglucose (
18
F-FDG) uptake in the visual cortex, in somatosensory, motor, and
pre-frontal cortices, as shown by combined positron emission tomography-computed tomography
(PET-CT) [
22
]. These findings point to dark chocolate-dependent acute effects on cerebral function [
22
].
The polyphenols in dark chocolate could act on the central nervous system (CNS) and neurological
functions through the production of NO [
11
,
17
]. Vasodilation and increased cerebral blood flow
provide oxygen and glucose to neurons, leading to increased formation of blood vessels in the
hippocampus [
11
,
93
]. The polyphenol-dependent antioxidant potential could contribute to amelioration
of some neurodegenerative disorders [
11
,
93
,
94
]. This inference is based on the fact that age-related
cognitive impairment and disorders, such as Alzheimer’s and Parkinson’s diseases, are related to the
accumulation of reactive oxygen species in the brain [11,94,95].
Int. J. Environ. Res. Public Health 2019,16, 4960 8 of 21
The effect of cocoa bioactives on signaling pathways in neurocytes may provide another support
for linking dark chocolate with regulation of brain function [
11
]. Cocoa flavonols and methylxanthines
can activate the cascade pathways of such molecules as rapamycin that play a crucial role in
synaptic function, neuronal growth, memory mechanisms, and the pathogenesis of neurodegenerative
disorders [96].
A prospective study on elderly subjects (age
≥
65 years) with normal mini-mental state examination
at entry showed that chocolate intake was linked with a decreased risk of cognitive decline during a
median follow up of 48 months [
97
]. Results from a cross-sectional analysis in subjects aged 23–98 years
showed a better cognitive performance in those consuming chocolate more frequently. However,
following a prospective observation, a relationship between cognitive function and chocolate intake
was not confirmed when measured up to 18 years later [98].
4.8. Psychological Aspects
The social and psychological context of everyday life affects metabolic health, emotions, and
moods; it can play a role in determining dietary choices [
99
,
100
]. In some cases, chocolate consumption
can be indirectly associated with a form of depression: hysteroid dysphoria. This condition involves
frequent episodes of depression in response to feeling inadequate or socially rejected, which culminates
in true bulimic attacks for confectionery and chocolate. A true chocolate addiction (being chocoholic)
is akin to alcoholism and nicotine dependence; it affects 40% of the female and 15% of the male
population in Western countries [
101
]. The symptoms involve being responsive to drugs that enhance
serotonin transmission; this suggests that central serotonin pathways may be involved in chocolate
consumption. The presence of serotonin could explain why sugar and confectionery are strongly
desired during chocolate bulimic crises. The ingestion of carbohydrates (e.g., bread and chocolate)
increases the relationship between plasma tryptophan and other neutral amino acids; consequently,
the transport of tryptophan through the blood–brain barrier is activated, with an increase in cerebral
serotonin synthesis, which produces a feeling of energy and pleasure [102].
4.9. Sexual Aspects
Chocolate exerts several effects on human sexuality, mainly acting as an aphrodisiac [
103
].
Cocoa powder and chocolate contain three unsaturated N-acylethanolamines, which, acting as
cannabinoid mimics, could activate cannabinoid receptors or increase anandamide concentrations [
103
,
104
]. The latter, in conjunction with other components of chocolate (such as caffeine and theobromine),
produces a transient feeling of well-being. Anandamide enhances sexual performance in male
rats [
103
,
105
]. Moreover, serotonin has been found in several regions of the female genital tract
in humans and other animals, where it acts on vasoconstriction and vasodilatation. The principal
component of sexual arousal is peripheral vasocongestion of genital tissues; thus, serotonin could be
involved in the process of sexual stimulation [103].
Table 8shows the studies on the nervous system, and psychological and sexual aspects related to
cocoa or chocolate use.
Int. J. Environ. Res. Public Health 2019,16, 4960 9 of 21
Table 2. Studies on cardiovascular effects related to cocoa or chocolate consumption, included in this review.
Study Study Design Food Type Main Outcomes
Dong J-Y. et al. 2017 [26] Prospective human cohort study Chocolate
Inverse association between chocolate consumption and risk of
developing stroke in women
Engler M.B. et al. 2004 [29] Randomized controlled trial in human Chocolate Dark chocolate improved endothelial function and increased
concentration of plasmatic epicatechins in healthy adults
Fisher N.D. & Hollenberg N.K. 2006 [30] Randomized controlled trial in human Cocoa Cocoa enhanced several measures of endothelial function
(nitric oxide-dependent) to a greater degree among older, in
whom endothelial function is more disturbed, than younger
healthy subjects
Fisher N.D. et al. 2003 [31] Randomized controlled trial in human Cocoa Cocoa induced vasodilation via activation of the nitric oxide
system, providing a plausible mechanism for the protection
that flavanol-rich foods induce against coronary events
Murphy K.J. et al. 2003 [33] Randomized, double-blind,
placebo-controlled study
Cocoa
Cocoa flavanol and procyanidin supplementation significantly
increased plasma epicatechin and catechin concentrations and
significantly decreased platelet function
Schramm D.D. et al. 2003 [34] Randomized controlled trial in human Cocoa Valuating the food effects on the absorption and
pharmacokinetics of cocoa flavanols, carbohydrates increased
oral flavanol absorption
Schwab U.S. et al. 1996 [35] Randomized crossover trial in human Cocoa Palmitic acid-enriched diet (using palm oil) increased serum
lipids, lipoproteins and plasma cholesteryl ester transfer
protein activity compared with the stearic acid-enriched diet
(using cocoa butter)
Pereira T. et al. 2019 [37]
Randomized double-blind trial in human
Chocolate Cocoa-rich chocolate improved vascular function by reducing
central brachial artery pressures and promoting vascular
relaxation in young, healthy adults
Int. J. Environ. Res. Public Health 2019,16, 4960 10 of 21
Table 2. Cont.
Study Study Design Food Type Main Outcomes
Larsson S.C. et al. 2016 [38] Prospective human study Chocolate Chocolate consumption was associated with lower risk of
myocardial infarction and ischemic heart disease
Greenberg J.A. et al. 2018 [39] Prospective human study Chocolate No association between chocolate intake and risk of coronary
heart disease, stroke, or both combined was observed
Khawaja O. et al. 2015 [40] Randomized double-blind controlled
human study
Chocolate
No support to association between chocolate consumption and
risk of atrial fibrillation among male physicians
Kwok C.S. et al. 2016 [41] Prospective human study Chocolate Habitual chocolate consumption was not associated with the
risk of incident heart failure among healthy men and women
Steinhaus D.A. et al. 2017 [43] Prospective cohort human study Chocolate J-shaped relationship between chocolate consumption and
heart failure incidence
Francis S.T. et al. 2006 [44] Randomized controlled trial in human Cocoa Measurements of arterial spin labeling cerebral blood flow
demonstrated an increase in blood flow after ingestion of
flavanol-rich cocoa, suggesting its potential use for treatment of
vascular impairment
Walters M.R. et al. 2013 [45] Randomized controlled trial in human Chocolate Chocolate consumption is associated with an acute change in
cerebral vasomotor reactivity, independent of metabolic and
hemodynamic parameters.
Int. J. Environ. Res. Public Health 2019,16, 4960 11 of 21
Table 3. Studies on glucose homeostasis effects related to cocoa or chocolate use, included in this review.
Study Study Design Food Type Main Outcomes
Gu Y. et al. 2011 [49] In vitro porcine study Cocoa Cocoa extracts and cocoa procyanidins inhibited
enzymes for digestion of carbohydrates and lipids,
suggesting a role in body weight management in
conjunction with a low calorie diet
Matsumoto C. et al. 2015 [50] Randomized human study Chocolate Inverse relation of chocolate intake with incident
diabetes mellitus in younger and normal–body weight
men
Maskarinec G. et al. 2019 [51] Cohort human study Chocolate products Participants with higher chocolate consumption and
higher flavanol intake from cocoa products experienced
a lower risk of developing type-2 diabetes
Yuan S. et al. 2017 [52] Prospective human study Chocolate Chocolate consumption was associated with decreased
risks of coronary heart disease, stroke, and diabetes
Dong J-Y et al. 2019 [53] Prospective cohort human study Chocolate Chocolate consumption was associated with a lower
risk of gestational diabetes mellitus
Almoosawi S. et al. 2012 [54] Single-blind randomized
placebo-controlled cross-over human
study
Chocolate Metabolic benefits of consuming polyphenol-rich dark
chocolate and possibility of adverse effects occurring
with polyphenol-poor chocolate
Int. J. Environ. Res. Public Health 2019,16, 4960 12 of 21
Table 4. Studies on cancer related to cocoa or chocolate use, included in this review.
Study Study Design Food Type Main Outcomes
Boutron-Ruault M.C. et al. 1999 [55] Randomized controlled trial in human Chocolate Chocolate intake resulted a risk factor to colorectal tumor
development
Carnesecchi S. et al. 2002 [57] In vitro human study Cocoa Cocoa polyphenols interfered with polyamine metabolism,
showing an important anti-proliferative effects
Yamagishi M. et al. 2002 [59] In vitro and in vivo rat study Cocoa Cocoa liquor proanthocyanidins inhibited mutagenicity of
2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and
rat pancreatic carcinogenesis in the initiation stage, but not
mammary carcinogenesis induced by PhIP
Yamagishi M. et al. 2003 [60] In vivo rat study Cocoa Cocoa liquor proanthocyanidins exerted chemopreventive
effects in the lung, decreasing the incidence and multiplicity of
carcinomas, and the quantitative values of adenomas in a
dose-dependent manner in the thyroid
Kenny T. et al. 2004 [61] In vitro human study Cocoa Down-regulation of tyrosine kinase ErbB2 and inhibition of
human aortic endothelial cell growth by cocoa procyanidins
Taparia S. & Khanna A. 2016 [62] In vitro human study Cocoa Treatment of ovarian cancer cell lines with cocoa
procyanidin-rich extract showed a significant percentage of
cells in sub-G1/G0 phase and a significant accumulation of cells
in the S phase
Taparia S.S. & Khanna A. 2016 [63] In vitro human study Cocoa Procyanidin-rich extract of natural cocoa powder caused
ROS-mediated caspase-3 dependent apoptosis and reduction of
pro-MMP-2 in epithelial ovarian carcinoma cell lines
Hong M.Y. et al. 2013 [64] In vitro rat study Chocolate
Chocolate diet-fed animals downregulated transcription levels
of COX-2 and RelA and lowered the proliferation index
Saadatdoust Z. et al. 2015 [65] In vitro mice study Cocoa Cocoa diet suppresses colitis-associated cancer tumorigenesis
Int. J. Environ. Res. Public Health 2019,16, 4960 13 of 21
Table 5. Studies on obesity and lipid metabolism related to cocoa or chocolate use, included in this review.
Study Study Design Food Type Main Outcomes
Gu Y. et al. 2014 [66] In vitro mice study Cocoa Dietary supplementation with cocoa in obese mice
ameliorates obesity-related inflammation, insulin
resistance, and fatty liver disease
Matsui N. et al. 2005 [67] In vivo rat study Cocoa Cocoa ingestion decreased fatty acid synthesis and
transport in liver and white adipose tissues,
determining a body weight, mesenteric white adipose
tissue weight and serum triacylglycerol concentrations
lower in rats fed the cocoa diet than in those fed the
mimetic cocoa diet
Massolt E.T. et al. 2010 [68] Randomized controlled trial in human Chocolate Smell or ingestion of dark chocolate determined
suppression of appetite because of the changes in
ghrelin.
Greenberg J.A. et al. 2013 [69] Prospective human cohort study Chocolate Habitual chocolate consumption was associated with
long-term weight gain, in a dose-response manner
Lee Y. et al. 2017 [72] Randomized controlled trial in human Chocolate and cocoa
Consumption of almonds alone or combined with dark
chocolate under controlled-feeding conditions
improved lipid profiles
Allen R.R. et al. 2008 [74] Double-blind placebo-controlled
cross-over human study
Chocolate
Regular consumption of chocolate bars containing plant
sterols and cocoa flavanols as part of a low-fat diet
supported cardiovascular health by lowering
cholesterol and improving blood pressure
Di Renzo L. et al. 2013 [75] Case-control human study Chocolate Regular consumption of dark chocolate determined
favourable effects on HDL cholesterol, lipoprotein ratios
and inflammation markers in normal weight obese
women
Int. J. Environ. Res. Public Health 2019,16, 4960 14 of 21
Table 6. Studies on intestinal microbiota related to cocoa or chocolate use, included in this review.
Study Study Design Food Type Main Outcomes
Wiese S. et al. 2015 [77] Randomized, double-blind, cross-over
human study
Cocoa Comparative biokinetics and metabolism of pure monomeric,
dimeric, and polymeric flavan-3-ols
Massot-Cladera M. et al. 2012 [78] In vivo rat study Cocoa Cocoa intake affected the growth of certain species of gut
microbiota in rats and changes in the toll-like receptor pattern and
in the intestinal immune system
Tzounis X. et al. 2011 [79] Randomized controlled double-blind
crossover trial in human
Cocoa Consumption of the high–cocoa flavanol drink modified the gut
microflora, reducing the plasmatic triacylglycerol and C-reactive
protein concentrations.
Urpi-Sarda M. et al. 2007 [82] In vivo human and rat study Cocoa
Sensitivity and recovery of epicatechin, procyanidins, and phenolic
microbial metabolites after cocoa intake in human and rat urine
Jang S. et al. 2016 [83] In vivo and in vitro pig study Cocoa Consumption of cocoa powder enhanced the abundance of
Lactobacillus and Bifidobacterium species and induced a reduction of
tumor necrosis factor-αand toll-like receptor gene expression in
intestinal tissues
Table 7. Studies on immune system effects related to cocoa or chocolate use, included in this review.
Study Study Design Food Type Main Outcomes
Ramiro-Puig E. et al. 2008 [85] In vivo and in vitro rat study Cocoa Cocoa-enriched diet modulated intestinal immune responses in
young rats
Camps-Bossacoma M. et al. 2018 [86] In vivo and in vitro rat study Cocoa Theobromine in cocoa was responsible for systemic and intestinal
antibody concentrations and for modifying lymphocyte
composition in young healthy rats
Esser D. et al. 2014 [87] Randomized double blind crossover
human study
Chocolate
Dark chocolate consumption improved leukocyte adhesion factors
and vascular function in overweight men
Rodríguez-Lagunas M.J. et al. 2019 [89] Cross-sectional observational human
study
Cocoa Consumption of cocoa was inversely correlated with physical
activity and allergies. Moderate cocoa consumers had less
frequency of chronic disease than the low consumers
Abril-Gil M. et al. 2012 [91] In vivo rat study Cocoa Cocoa-enriched diet produced an immunomodulatory effect that
prevented anti-allergen IgE synthesis
Int. J. Environ. Res. Public Health 2019,16, 4960 15 of 21
Table 8. Studies on the nervous system, and psychological and sexual aspects related to cocoa or chocolate use, included in this review.
Study Study Design Food Type Main Outcomes
Fox M. et al. 2019 [22] Randomized controlled trial human
study
Chocolate
Dark chocolate with a high cocoa content has effects on colonic and
cerebral function in healthy volunteers
Madhavadas S. et al. 2016 [94] In vivo and in vitro rat study Chocolate Dark chocolate enhanced cognitive function and cholinergic
activity in the hippocampus and corrected metabolic disturbances
of rats
Moreira A. et al. 2016 [97] Prospective cohort human study Chocolate Chocolate intake was associated with a lower risk of cognitive
decline
Chrichton G.E. et al. 2016 [98] Longitudinal human study Chocolate Chocolate intake was associated with better cognitive function
Martin F.I. et al. 2012 [100] Randomized controlled trial in human Chocolate
Snacks differing in sensory properties and presentation differently
influenced postprandial anxiety, energy and emotional states
Salonia A. et al. 2006 [103] Observational human study Chocolate Positive association between daily chocolate intake and sexual
function.
Int. J. Environ. Res. Public Health 2019,16, 4960 16 of 21
5. Conclusions
Cocoa and chocolate act as functional foods, since both carry a number of substances contributing
to beneficial health effects. Chocolate combines some organoleptic characteristics with aphrodisiac and
antidepressant properties, extending its effects beyond the cardiovascular system, metabolic diseases,
CNS diseases, and psychological profiles.
We should stress that several studies evaluated the health-promoting properties of cocoa and not
of chocolate itself.
Moreover, because in chocolate processing, cocoa loses some of the polyphenol compounds (the
main constituents responsible for the beneficial effects on health), we think that the role of chocolate on
human health cannot be completely compared to that of cocoa. Despite the availability of a number
of
in vitro
and experimental reports, epidemiological studies assessing possible beneficial effects
of chocolate (in particular dark chocolate) are still scarce. One should keep in mind the presence
of a number of confounders (i.e., other diet components, lifestyle, environmental exposures, exact
consumption of chocolate, chocolate composition, duration of observation, and other risk factors).
Such conditions strongly limit the strength of evidences.
In conclusion, further translational studies need to evaluate all possible effects related to consuming
chocolate and to verify in humans the effects hitherto demonstrated only
in vitro
and on animals.
This approach could suggest how best to consume (in terms of dose, mode, and time) chocolate in the
daily diet, considering eating habits and lifestyle.
Author Contributions:
M.T.M., G.C., and P.P. conceived the study and reviewed the manuscript; G.D., F.T.,
O.D.G., and G.R.C. analyzed the scientific literature and wrote the manuscript; A.D.C. reviewed the manuscript.
All authors read and approved the final manuscript.
Funding: This study received no external funding.
Acknowledgments:
We thank the Edanz Group (www.edanzediting.com/ac) for editing a draft of this manuscript.
Conflicts of Interest: The authors declare no conflict of interest.
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