Coffee is made from the roasted seeds of the coffee plant which grows in Africa, Asia, Brazil and many other places around the world. The leaves, fruit and other parts of the plant contain caffeine but only the ripe berries are usually harvested. There are two main species grown: arabica (Coffea arabica) which is indigenous to Ethiopia and is the dominant commercial crop around the world; and robusta (Coffea canephora) which is grown mostly in Vietnam and Brazil.

The berries are harvested by hand, while some coffee is collected from the dung of the Asian palm civet which eats the berries and excretes the valuable seeds after its digestive system imparts additional aromatic qualities. Hand-picked seeds are either dried in the sun for several weeks or soaked and allowed to ferment for a few days to remove any pulp from the fruit. Green coffee contains protein, fats, carbohydrate, caffeine, vitamins and antioxidants including chlorogenic acid, and is one of the most traded commodities in the world.

Roasting the dried seeds (beans) before grinding them to make coffee improves the flavour by caramelising starches, creating new aromatic compounds and reducing bitterness; however, some of the beneficial antioxidant phytonutrients are lost in this process. Coffee can also be de-caffeinated by soaking the seeds in water,  or steaming the seeds and then using a solvent to extract the caffeine before roasting.

Caffeine is a substance produced by the plant as an insecticide. It is toxic to many insects and herbivores, as well as dogs, but has found many uses in the food and beverage industry. This valuable substance is extracted when making de-caffeinated coffee and sold to the pharmaceutical industry.

Caffeine is rapidly absorbed, travelling to all tissues including the brain and placenta and has a half-life of 5-6 hours. It is metabolised by the liver into theobromine and theophylline, substances also present in chocolate, which is why chocolate keeps you awake. The liver then breaks these substances down to urates for excretion. Children should not consume caffeine products because they metabolise them much more slowly than adults.

Coffee is a useful medicine with stimulant anti-emetic, anti-narcotic and diuretic properties, but it is not usually use in this way. Unfortunately it can be abused when drunk regularly in large amounts with tolerance soon developing, and the characteristic nauseas headache and irritability becoming apparent when a routine morning coffee is skipped.[1]

Coffee stimulates the activity of the whole body by antagonising adenosine receptors which leads to an increased release of dopamine, noradrenalin, and glutamate, hence the improvement in mood. Apart from addiction,  coffee abuse can also lead to adrenal exhaustion called ‘burn out’. This condition usually results from a lack of rest combined with a reliance on stimulants and refined sugar to survive long periods of stress, without the proper dietary means to build sustainable, steady energy. In moderate amounts we use it as students to keep us studying for long hours over our books, and it is still a valuable aid to ward of sleepiness when driving long hours.

Coffee  also raises the heart rate and blood pressure, and in excess causes arrhythmia, palpitations, restlessness, anxiety and seriously compromises concentration an effect enhanced by guarana. Fortunately there are no apparent adverse effects on the risk of stroke or coronary heart disease.[2]

The effect of raising the metabolic rate also makes it a useful for dieting and green coffee bean extract is a common ingredient in weight-loss formulas. Apart from raising the metabolic rate, caffeine also increases thermogenesis, and shifts the production of energy from that favouring the oxidation of stored glycogen, to stored lipids, thus helping to burn fat stores.[3]

Coffee can produce excess stomach acid because it is a bitter, that is it stimulates the bitter-taste receptors on the back of the tongue. [4] This innervates the vagus nerve, which leads to the whole digestive system, causing an increased secretion of saliva, acid and enzymes. As a result, when drunk unsweetened in moderate amounts before a meal, coffee has a tonic effect on the digestive system, helping to compensate for an age-related decline in function. In large amounts, however, it causes excess stomach acid which promotes reflux and ulcers, has an acidifying effect on the whole body, and loads the liver and other organs of elimination with wastes.

You can also become dehydrated through enhanced diuresis, which is why the Greek coffee comes with a large glass of water. The mechanism of increased diuresis is caused by retention of salt in the kidney, and while coffee is only mildly diuretic, it becomes a potentially important issue during endurance sport where it is drunk to increase performance. Sports drinks all contain caffeine or its derivatives which increase diuresis acutely; however, over several days it is found that the sympathetic activation via the adrenal glands caused by the exercise inhibits the diuretic effect, so there is no significant impact on overall hydration.[5] It appears that the diuretic effect is only important for sedentary people consuming large amounts of caffeine such as office workers, café regulars and students. Caffeine also is thought to improve post-exercise glycogen stacking thereby improving the recovery period for athletes.[6]

Coffee contains protective polyphenol compounds which are antioxidant in activity, especially if it is organic coffee. One of particular interest is chlorogenic acid which has been found to help regulate blood sugar and therefore control insulin resistance. Coffee also contains diterpenes (cafestol, kahweol) which favourably influence liver detoxification enzymes and thereby help protect the liver from damage.

Constituents like these are also thought to help protect the body against malignancy. In fact coffee tends to have a greater effect when more is consumed, and in some countries like Finland and Norway it actually provides half of the daily intake of antioxidants; however, coffee consumption is usually allied to confectionary and other ultra-processed convenience foods which will certainly detract from any benefit. Coffee also contains acrylamide, a carcinogenic compound produced as a result of roasting the bean, indicating that you should certainly vary your sources of antioxidants in order to meet your RDA and not use coffee as a focussed source. Nevertheless, drinking coffee reduces the risk of colorectal, breast and liver cancer, as well as the total incidence of cancer, but the results for bladder and prostate cancer are inconsistent.[7]

The apparent positive effect of caffeine on cognitive ability has been attributed to improved alertness and memory in some studies, while in others, merely to a sense of relief arising from escaping caffeine withdrawal symptoms. Caffeine also reduces cerebral blood flow, hindering cognitive performance to some extent; however, on the positive side, long-term coffee consumption has been found protective against developing neurodegenerative diseases. For instance, in Alzheimer disease, there is evidence that caffeine both hinders β-amyloid production and helps restore memory deficits, while in Parkinson disease it can improve motor symptoms and help prevent the loss of dopaminergic neurons.[8]

The key is of course moderate coffee consumption with plenty of clean water. All other forms of carbonated, caffeinated drinks that contain synthetic additives and high fructose corn syrup should be avoided because they contribute to general degenerative disease processes such as inflammation and oxidative stress which, at the least, accelerate ageing. You should enjoy your coffee breaks as part of a lifestyle which provides plenty of fresh air and exercise, one which is sustained by a diet of nutritious wholefoods as was the case in traditional societies of the Middle East, Africa and the Mediterranean.

[1] Bartram, T 1998, Bartram’s Encyclopedia of Herbal Medicine, Marlowe & Company.

[2] Cappelletti et al. Caffeine: Cognitive and Physical Performance Enhancer or Psychoactive Drug? Current Neuropharmacology, 2015, 13, 71-88.

[3] Greenberg et al. Coffee, diabetes, and weight control. Am J Clin Nutr 2006; 84:682–93.

[4] McMullen et al. Bitters: Time for a New Paradigm. Evidence-Based Complementary and Alternative Medicine Volume 2015, Article ID 670504, 8 pages.

[5] Zhang et al. Caffeine and diuresis during rest and exercise: A meta-analysis. J Sci Med Sport. 2015 September; 18(5): 569–574.

[6] Cappelletti et al. Caffeine: Cognitive and Physical Performance Enhancer or Psychoactive Drug? Current Neuropharmacology, 2015, 13, 71-88.

[7] Wierzejska, R. Coffee consumption vs cancer risk—a review of scientific data. Rocz Panstw Zakl Hig 2015; 66(4): 293-298.

[8] Cappelletti et al. Caffeine: Cognitive and Physical Performance Enhancer or Psychoactive Drug? Current Neuropharmacology, 2015, 13, 71-88.