INTRODUCTION

Chocolate and cocoa products are obtained from a long and complex work process to which cacao beans are subjected.

Nowadays, a new trend in the food market shows a steady increase in the consumption of cocoa products, because they are widely appreciated for their hedonic value and their multiple health benefits. Cocoa products have increasingly become objects of scientific research mainly because of their interesting phytochemical composition. The scientific com-munity wonders whether chocolate and other cocoa products can be considered as a super fruit or as biofunctional food products.

The aim of this study is to conduct a systematic review of the literature on cocoa and chocolate constituents and on their effects on human health and particularly on reproduction.

MACRONUTRIENTS AND FATTY ACIDS PROFILE OF COCOA AND CHOCOLATE: QUANTITY AND EFFECTS ON HUMAN HEALTH

According to Directive 2000/36 EC, chocolate is defined as a food obtained from cocoa and sugars, containing at least 35% total dry cocoa, composed of not less than 18% cocoa butter and not less than 14% degreased dry cocoa. In addition to the minimum percentages of cocoa butter and total dry cocoa, a maximum of 5% fats cocoa butter equivalents (CBE) by weight of the finished product is allowed. Therefore, chocolate is certainly composed of cocoa solids and cocoa butter; then other ingredients are usually added such as sugar to sweeten and lecithin to emulsify. However, chocolate now commercially available often contains several other foods such as cereals, dry nuts, and fruits. The three main categories of chocolate, white, milk, and dark, have different contents of cocoa solids, cocoa butter, and some components of milk. Dark chocolate does not contain milk solids, or at least should not, whereas they are contained in chocolate milk and white chocolate. The latter has only the fat part of cocoa (cocoa butter) to which, among other ingredients, is added a large quantity of sugar. Generally, milk chocolate contains a lesser amount of the nonfat part of cocoa than dark chocolate, which nonetheless contains variable proportions of the nonfat part of the cocoa bean. The content of nutrients in chocolate depends, in part, on the percentage of the nonfat portion of cocoa: the amount of carbohydrates decreases and the fats increase approximately linearly with the increasing percentage of cacao content. As a result, a higher percentage of cocoa means a higher amount of calories. However, the more cocoa content, the higher the minerals6 and polyphenols contents are. Dark chocolate, even that at higher cocoa content, does not maintain the proportions of macro-nutrients found in cocoa beans.In fact, the main component is not fats, as in the case of beans, but carbohydrates followed by total fats, and this is due to the choice of adding a larger proportion of sugar, which exceeds the amount of fats. The quantity of cocoa butter and minerals in chocolate also depends on the geographical origin of the cocoa beans, in particular on the growing conditions. Even fatty acids, which in cocoa butter are mainly organized as triacylglycerols, have a pattern that is influenced by geographical origin. As a result, it may happen that some chocolate types have a healthier fatty acid profile than others. Normally the fatty acids most represented are stearic acid (C18:0), oleic acid (C18:1), and palmitic acid (C16:0), which together constitute >90%.8,9 Saturated fatty acids (SFA), with C18:0 and C16:0 as the main fractions, are present in the highest proportions. Among the unsaturated fatty acids, monounsaturated fatty acids (MUFA) content is higher than polyunsaturated fatty acids (PUFA): C18:1, which represents about 30% of the fatty acids present in TAG, is quantitatively the most important unsaturated fatty acids, followed by linoleic acid (C18:2). Trans fatty acids were found to be present in chocolate11 but in variable amounts,12 and seem to be contained in low concentrations.

Differently from most of the SFA (C16:0 included) evidence shows that C18:0 has a neutral effect and does not increase blood total and low-density lipoprotein (LDL) cholesterol levels; it does not significantly influence blood coagulation, fibrinolysis, thrombotic tendency, and cardiovascular disease compared with C18:1 and C18:2. Some doubt remains, however, concerning the effects of stearic acid on thrombosis, inflammation, and blood pressure.

Also because of the high fat content, chocolate has a high caloric value. Nevertheless, no positive correlation has been shown between chocolate consumption and body mass index (BMI) and, contrariwise, chocolate intake appears to have an inverse impact on BMI in men and women.

OTHER CONSTITUENTS OF COCOA AND CHOCOLATE: QUANTITY AND EFFECTS ON HUMAN HEALTH

Flavanols, a subgroup of dietary polyphenols present in many fruits and vegetables, may be associated with health benefits, particularly with reducing the risk of coronary diseases. Cocoa and chocolate products are rich in flavonoids, the most represented group of polyphenols, and flavanol monomers, procyanidin oligomers, and polymers are the most numerous flavonoids.

Even methylxanthines, which in cocoa are mainly theo-bromine (3,7-dimethylxanthine) and caffeine (1,3,7-trimethyl-xanthine),50 depend on the origin of cocoa beans: the theobromine/caffeine ratio and the amount of caffeine present in chocolate depend on the cocoa-growing geographical area.

The amount of methylxanthines is also different in the different types of chocolate. In fact, using food composition data from the U.S. Department of Agriculture (USDA) data-bases,6 it is possible to observe that the average caffeine content is 45 mg per 100 g of dark chocolate (45−59% cacao solids), 86 mg per 100 g of dark chocolate (60−69%), and 80 mg per 100 g of dark chocolate (70−85%). The average theobromine contents are 493, 632, and 802 mg, respectively.

Flavonoids and methylxanthines are the most recognizable active components of cacao. Although concerns regarding the bioavailability and the extent to which phenols are biologically active have not been completely clarified,51−57 numerous capa-bilities have been assigned to cocoa flavonoids. Several studies analyzing the biological properties of these molecules have provided considerable supportive evidence of flavonoid’s role in improving vascular functions, preventing related endothelial dysfunctions and diseases,58−66 reducing insulin-resistance indices (probably as a result of a decrease in insulin secretion67), increasing insulin-sensitivity,62,68 contributing to anti-inflammatory reactions,69−73 inhibiting platelet aggregation and activation,74−77 and decreasing blood pressure.60,68,78−81 However, a meta-analysis of randomized trials does not confirm the flavonoid effect on systolic blood pressure,67 whereas a second meta-analysis has found a small but statistically significant effect in lowering systolic and diastolic blood pressure in the short term. Multiple trials have emphasized that cocoa has the ability to change the lipid fraction not only by limiting its oxidation but also by directly altering the lipid profile of plasma, increasing high-density lipoprotein (HDL) and reducing LDL71,  and total cholesterol. Flavonoid effects on human total plasma antioxidant capacity, neurocognition, mood, and behavior remain controversial and limited. Some studies have shown how cocoa intake is correlated with a low prevalence of hypertension, atheroscle-rosis, dyslipidemia, and diabetes and cardiovascular disease as well as mortality and morbidity due to common causes. The protection of cardiovascular and endothelial tissue, as a consequence of chocolate consumption, may arise by the synergetic action of flavonoids, theobromine, and mag-nesium. Cocoa flavonoids also seem to improve intestinal flora. Even dark chocolate seems to change significantly gut microbial metabolism.

The effects of methylxanthines contained in cocoa and chocolate have been summarized in a recent review by Franco et al. Theobromine, the most abundant methylxanthine in cocoa and chocolate, can suppress cough and influence in a positive way cognitive performance and mood together with caffeine. In a study intended to probe the effects of theobromine on blood pressure, no change was observed on 24 h ambulatory or central systolic blood pressure after 3 weeks’ intake of a natural dose of theobromine cocoa (106 mg), whereas intake of theobromine-enriched cocoa (979 mg) resulted in increased 24 h ambulatory systolic blood pressure and lower central systolic blood pressure. According to the results of a study, the HDL cholesterol-raising effect of cocoa intake is mainly due to the theobromine content.

Enhancements in psychological functioning induced by con-suming chocolate with a high cocoa content are due, at least in part, to the combination of methylxanthines, biogenic amines, anandamide (N-arachidonoyl-ethanolamine), and N-acylethanolamines actions. The main monoamines contained in cocoa are phenylethylamine, tyramine, and tryptamine. Tyramine and phenylethylamine have the ability to act on different areas of the brain, which are responsible for mood control and the waking state. They are able to delay fatigue and induce the release of catecholamines (norepinephrine and dopamine) at the synaptic level, which consequently produces stimulation similar to that induced by amphetamine, including an attenuation of the sensation of hunger. Phenylethylamine, assisted by magnesium (found in abundance in chocolate) and small amounts of serotonin, acts on mood.

Anandamide, an endogenous lipid belonging to the class of endocannabinoids, acts as a cannabinoid receptor agonist, mimicking the central and peripheral action of cannabinoids such as 9-tetrahydrocannabinol (the active ingredient of cannabis extracts). Although an interesting double-blind trial has recognized a marginal role of all psychoactive substances apart from xanthine, the biological activity of amines and anandamide may contribute to the feeling of reward derived from the act of consuming chocolate and the pleasant post-consumption euphoria. Studies carried out on the abuse of stimulants suggest a causal relationship to self-therapy for mood control resulting from cocoa intake.

COCOA AND CHOCOLATE CONSTITUENTS: EFFECTS ON HUMAN REPRODUCTION

Cocoa consumption affects reproduction not only by its effect upon sexual appetite but also by possibly interfering with the etiology of subfertility. Cocoa polyphenols have been shown to be potent antioxidants, and oxidative stress (an imbalance be-tween pro-oxidants and antioxidants due to decreased anti-oxidant defense mechanisms or an increase in reactive oxygen and/or reactive nitrogen species) is known to be involved with the causes of male and female infertility, reproductive diseases (including endometriosis, polycystic ovary syndrome, and unexplained infertility), and pregnancy complications (namely, pre-eclampsia and miscarriages).

Although attempts have been made to prevent reproductive disorders through antioxidant supplementation, the effectiveness of this strategy has not been demonstrated. For this reason, positive contributions of the phytochemical cocoa in preventing reproductive problems can only be speculated, but the possible correlation continues to fuel exploration through high-quality clinical trials. Moreover, the bioactive constituents of cocoa may contribute to reducing reproductive difficulties through actions directly exerted on the vascular endothelium and circulation.

In further regard of its effects on reproductive capacity, it must also be noted that even in low doses, cocoa contains caffeine, a molecule known to cross the placental barrier freely and which is slowly metabolized during pregnancy.

The fetus does not have sufficient enzymes to inactivate caffeine; thus, its metabolites accumulate in the fetal rain. Caffeine, if consumed in large amounts, may seemingly result in a reduced fecundability, although other prospective studies have demonstrated either little or no effect or even an increased fecundability. Caffeine has also been positively correlated with spontaneous abortion, congenital malformation, fetal death, fetal growth restriction, preterm delivery, and decreased birth weight. Again, some studies have yielded conflicting results, although caffeine has been conclusively demonstrated to decrease fetal weight and increase the risk of “small for gestational age” fetal development. In any case, caffeine seems to compromise normal reproduction function and to increase embryo−fetal risks.

Accordingly, the World Health Organization’s recommended threshold of caffeine consumption (200 mg/day in Nordic countries and 300 mg/day equivalent to 4.6 mg/kg of body weight/day in a 65 kg person in the United States) should be well adhered to. Chocolate’s added contribution to caffeine intake should be noted, particularly when other drinks rich in caffeine are already included in a diet.

COCOA AND CHOCOLATE CONSTITUENTS: EFFECTS ON HUMAN PREGNANCY

During pregnancy so many hemodynamic and metabolic changes occur that considerable attention to maternal and fetal nutrition is warranted. From Prochownich’s early 20th century publication about the relationship of diet to pregnancy attention to maternal−fetal nutrition has grown in terms of improving the end point of fetal health globally. During gestation, biomolecular metabolism and cellular redox activity undergo changes that shift the balance in favor of oxidizing agents and pro-oxidants, thereby reducing total plasma antioxidant capacity in advanced gestation.

The oxidation−reduction imbalance leads to oxidative stress-linked pathological conditions concerning both the mother and the fetus and, relatedly, the susceptibility of embryonic and syncytiotrophoblastic cells to oxidative damage. The alteration of the redox status is a constant of gestation, but its extent is significantly higher in cases leading to spontaneous abor-tion and in pregnancies with pre-eclampsia conditions or with hypertension alone. The oxidative imbalance in pregnancy and the need for an additional caloric intake from the 10th to the 13th week of gestation represent valid reasons to choose foods with antioxidant properties. The availability of foods with these characteristics and the inclusion of these foods in the diet of pregnant women are considered new strategies and lead to scrupulous food choices that combine a modest energetic intake (between 100 and 400 kcal, as a function of the index of prepregnancy body mass) with a high content of antioxidant molecules nutritional profiles. Available scientific evidence suggests that chocolate with a high cocoa content, consumed daily in modest quantities (30 g/day for 24 weeks), may fit properly into this nutritional strategy without entailing negative consequences in terms of weight during various trimesters. Anyway, it is recommended not to overdo with consumption of chocolate and cocoa products because most of these are high-calorie foods. As a result, they should be consumed in moderation, especially during pregnancy, and the amount of chocolate to be consumed should be calculated on the basis of the specific calories of the chocolate chosen, the caloric intake derived from other foods, the physical activity level, and the maternal BMI.

Chocolate supplementation during pregnancy, from the end of the first trimester to term, appears to reduce systolic and diastolic blood pressure during the weeks of gestation (Table 1). A second study, a pilot randomized controlled trial, found no association between chocolate intake (20 g/day for 12 weeks) and blood pressure levels and even between chocolate con-sumption and flow-mediated dilation (Table 1). We believe that the diverging results on blood pressure are due, in part, to the intervention of control: in the first study, women of the control group did not consume chocolate by protocol, whereas in the second study, women in the control group consumed chocolate as in the experimental group but it had a lesser amount of flavanols (400 mg of total flavanols vs <60 mg). It could be that the absence of differences is due to similar effects of the two kinds of chocolate, which had the same nutrients and bioactive components, except for flavanols. It is reasonable to assume that the observed effects of chocolate are not solely and directly due to polyphenols content, but it is possible to assume the existence of synergistic interactions between bioactive com-pounds. In this way, the amount of polyphenols would not be so important. We think that the main reason for diverging results on blood pressure in the two studies is that the two protocols consisted of interventions with very different timing: one of about 27 weeks (from the end of the first trimester to term) and one of 12 weeks (from about the 12th week of gestation). We hope other studies will be carried out on this topic in order to understand the real effect of choc-olate consumption on maternal blood pressure in pregnancy. We propose that a placebo chocolate free of any bioactive compound be used in future studies.

It has been suggested that chocolate consumption in pregnancy could be a reasonable strategy to prevent pre-eclampsia. Considering the characteristics and risk factors of pre-eclampsia, including maternal hypertension, placental disease, endothelial dysfunction, oxidative stress, and lack of nitric oxide, it is reasonable to think about the possibility of preventing pre-eclampsia by up-regulating nitric oxide (NO) availability due to antioxidant activity and the induction of NO-dependent vasodilatation by cocoa. In this regard, two recent studies, a cohort study and a control case one, have detected chocolate consumption’s contribution in reducing risks of pre-eclampsia and gestational hypertension. Anyway, a case-control study conducted on 2769 women found no associatio between chocolate consumption and reduced occurrence of pre-eclampsia.

Probably the systematic review already planned will provide more detailed answers about the possible connections between chocolate consumption and the risk of pre-eclampsia.

Although not all of cocoa’s potential health benefits to preg-nant women have been clearly confirmed, chocolate con-sumption during pregnancy has proven positive in some accounts and harmless in others. Overall, there is a natural female preference for chocolate that becomes markedly apparent during pregnancy, with an increasing trend following the progress of gestation. Chocolate in the balanced diet of a pregnant woman can instill psychological well-being to both the pregnant woman (typically during the time of high emotional lability) and the future child. The mother’s prenatal stress experience significantly predicted the infant’s fear responses, but in this relationship, maternal chocolate consumption during pregnancy appears to have the role of modulator. In fact, choc-olate consumption in pregnancy seems to reduce the negative effect of prenatal maternal stress on infant temperament. Furthermore, daily consumption of chocolate during pregnancy seems to determine in infants at 6 months a greater positive reactivity and activity.

CONCLUSIONS

Evidence shows that chocolate is able to produce beneficial effects for human health. However, some cocoa activities on humans should be investigated again. Currently it is possible to conclude that consuming chocolate in moderation is good for human health. Chocolate can also be used in the diet of pregnant women because no negative effect was found for either maternal or fetal health. Conversely, favorable effects were observed for mother, fetus, and future child. Future studies will reveal whether the cocoa products have also preventive effects of some complications of pregnancy.

Furthermore, because chocolate has many bioactive com-pounds, we hope that in the near future the labels of cocoa products will also report the kind and amount of bioactive substances. In this way everyone may consciously choose what to buy and consume; moreover, pregnant women could control the levels of intake of caffeine.