“CHOCOLATE, WHY IS IT SO IRRESISTIBLE? THE CHEMISTRY BEHIND PLEASURE AND ADDICTION”

Carmen Piras

Chocolate is one of the most cheap and popular antidepressants available in the market. What is in chocolate and why is it so good and irresistible? After you will read this articleyou will realise it is all about chemistry! All the properties of chocolate, in fact, depend on different molecules that are predominantly present in cocoa, one of the main components of chocolate.

HISTORY

Cocoa comes from the seeds of a plant with very ancient origins. The ancient civilisations of Olmecs, Mayas and Aztecs used to 1cultivate it as a food and as currency trading. The last led to the first name of the plant “Amygdalae Pecuniariae” (“Money Almond”), later replaced by the Swedish botanist Carl Von Linne with “Theobroma Cacao” (“Food of Gods”), which referred to the religious cults of these populations.

The consumption of cocoa was reserved mainly to upper classes (nobles, warriors and priests) that used to drink it for its energising and aphrodisiac properties with the addition of chilli, hot spices, anise, cinnamon and vanilla to mitigate the bitter taste. In 1528 it was imported to Europe, when the Spanish Conquistador Cortez offered it as a gift to the Spanish Royal Family. From Spain, the recipe of chocolate spread throughout Europe: Italy first, then France, England, Austria, Switzerland, Germany and then Scandinavia.

THE PLANT

Cocoa plant (Theobroma Cacao L.) is an evergreen tree that can reach up to 20 meters height. It can be cultivated only in certain areas, as it requires hot humid climates and mild temp2eratures ideally between 20 and 30°C. The main producing countries are, for this reason, situated in Africa (Ghana, Cameroon, Nigeria, Ivory Coast, Madagascar), Asia (Indonesia, Malaysia, Sri Lanka), Oceania (New Guinea, Papua) and Central and South America (Mexico, Brazil, Colombia, Ecuador, Venezuela).

3The fruits are collected a couple of times a year and the beans are extracted after natural fermentation. The fermentation takes place outdoors, in a 2 to 12 days period of time depending on weather conditions and quality of the beans. This process regards the sugars contained in the mucilage (glucose and fructose) and it is vital for the chemical composition and the biochemical characteristics. Once extracted, the seeds are then dried in order to stop the fermentation and decrease the moisture content to avoid the formation of mould. The drying process takes from 7 to 15 days when the seeds are exposed to the sun. The dry beans can be then processed to produce a variety of derivatives (e.g. chocolate, cocoa powder, pralines, snacks).

CHEMICAL COMPOSITION OF COCOA

The chemical composition of cocoa, thus the percentages of main components, varies depending on the geographical origin. The main components are:

  • water (5-7%)
  • lipids (45-53% – especially fatty acids such as palmitic acid, arachidic acid, linoleic acid, linolenic acid, stearic acid and sterols)
  • proteins (10-15% – g. albumin, prolamin, glutelin, globulin and enzymes)
  • starch and carbohydrates (2-4% – i.e. fructose, sucrose, lactose, cellulose, lignin)
  • tannin (6%)
  • gums (2-3%)
  • polyphenols (g. catechins, anthocyanins, proantocyanins)
  • organic acids
  • vitamins (vitamin A, B1, B2, B6, biotin, folic acid, nicotinamide)
  • minerals (e. sodium, potassium, magnesium, iron, chlorine, fluorine, iodine, chromium, nickel, zinc)
  • natural bioactive molecules.

The last are responsible not only for the aroma of cocoa, but also for the effects it induces. The characteristic aroma of cocoa can be attributed to different fermentation products (firstly vicilin, but also pyrazines, esters, aldehydes, ketones, alcohols, hydrocarbons, furans and phenols), whereas other natural components cause the effects that are normally associated with cocoa consumption. These include:

  • Theobromine and caffeine (methylxantines)

4These two molecules are present in different percentage (2-2.7% theobromine and 0.6-0.8% caffeine) and they induce:

  • increased concentration and attention
  • improved waking state
  • improved skeletal muscle contractility
  • vasodilatation
  • diuresis.

Theobromine has a lower stimulant effect compared to caffeine, which however is present at a lower concentration. Both molecules act as antagonists of adenosine purinergic P1 receptors. Adenosine has normally an inhibitory effect on central nervous system; consequently the antagonist action is responsible for the psychostimulant effects of these substances, but also for the side effects related to abuse, such as insomnia, tachycardia and agitation.

  • Biogenic amines (tyramine, tryptamine, histamine, 2-phenylethylamine)

5These are vasoactive molecules that, at a high concentration or in combination with MAO inhibitors (drugs with an antidepressant effect), may cause the so-called “cheese reaction”, which is characterised by redness, headache, pressure changes and even circulatory shock.

Among these molecules, 2-phenylethylamine is considered responsible for chocolate desire. Its structure is very similar to amphetamine, therefore it interacts with the same receptors, inducing various stimulant effects such as:

  • improved waking state
  • psychostimulation
  • reduction of fatigue
  • reduced sense of hunger.
  • Anandamide

6

This molecule interacts with the cannabinoid CB1 receptors inducing:

  • behavioural effects
  • effects on cognitive functions
  • improved mood
  • improved sensory perceptions
  • euphoria
  • sense of accomplishment and satisfaction.
  • Salsolin and salsolinol

78

These are alkaloids dopamine-derivatives, which are also present in the brain as endogenous molecules. They are responsible for the antidepressant effect of chocolate and the psychological dependence due to two actions on central nervous system:

  • inhibition of MAO enzymes and tyrosine hydroxylase, which results in increased serotonin levels with consequent improvement of mood
  • inhibition of catecholamines re-uptake (e. norepinephrine and dopamine), with consequent antidepressant effect and psychological dependence.
  • Clavamide, which has a considerable antioxidant activity.9
  • Tetratetrahydro-b-carboline, which act as neuromodulators on MAO enzymes, thus contributing to the antidepressant action.10

EFFECTS OF CHOCOLATE

 All these molecules together with others are responsible for the different effects of chocolate.

  1. Antidepressant effect12

Serotonin, associated with methylxanthines and 2-phenylethylamine, is responsible for the induction of endorphins production, opioids that are naturally synthesized by the brain and that have an exhilarating effect.

  1. Feeling of pleasure and addiction

13The feeling of pleasure induced by chocolate can be correlated to various substances, including theobromine, caffeine and anandamide, which act on the brain reward circuit. This is modulated by the neurotransmitter dopamine, whose release is induced by natural rewarding stimuli (e.g. food, and water), or drugs. It acts by facilitating the establishment of a positive memory related to cocoa assumption, with consequent sensation of pleasure after chocolate consumption and desire of more chocolate.

  1. Antioxidant effect

This is related to the presence of flavonoids, a class of polyphenols present at a higher concentration than in other commonly consumed foods. The antioxidant activity is important to fight free radicals, which are formed as a result of oxidative stress and are responsible for damage to cells and cellular components.

  1. Protective action on cardiovascular system

Due to the fact that dark chocolate promotes increased levels of HDL cholesterol, the “good cholesterol”. This improves the functioning of blood vessels (by increasing the ability of the endothelium to dilate) and prevents heart diseases.

Although chocolate has many positive effects, it is not for everyone! Are indeed excluded diabetics, people with allergies, gastroesophageal reflux (as chocolate consumption causes an increased gastric acidity), hyperuricemia, headache (due the presence of tyramine, that could trigger crises), obesity or liver diseases (due to the high lipid content).

Anyway, after reading this article, next time you will be in a bad mood, try to have some chocolate and it might act as a magic medicine!

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