Coffee: What the Science Really Says

… with an image that keeps taking a hit. Millions of people around the world drink coffee every day, the most popular drink for centuries. When coffee first arrived in Europe, it was seen less as a food and more often as a medicine, just like tea. Everyone loves a cup of coffee, or two, or three, or … which makes this substance one of the essential (over)consumed staples of daily life.
Scientific studies show that coffee has numerous effects on the human body. At the same time, plenty of rumours and misconceptions about the negative health effects of coffee consumption are still doing the rounds, both among the public and in medical circles.The historical background
The history of coffee goes back well into the second-to-last millennium. It's wrapped in plenty of legends, such as the one about the goatherd Kaldi, who one night noticed that some of his animals — after eating the red berries of small shrubs — were bounding around cheerfully while the others slept. Kaldi then tried the berries himself and immediately felt a stimulating effect.
When a monk came across him, he noticed Kaldi's euphoric state, brewed a drink from the plant, and realised that his tiredness disappeared, letting him stay awake at night and get on with his prayers.
Kaffa, in Ethiopia, is thought to be the region of origin. The invigorating drink spread through the Arab world via slave traders and became the most widely traded "raw material" of its day. Coffee reached Europe by sea from Mocha in Yemen, also known as Mokka.
The first coffee houses appeared in the Orient and, in 1645, in Venice, the major trading city with the Far East. Oxford, London and Paris followed. The pastry to go with it was served in Vienna in the shape of a Turkish crescent — the first literary mention of the croissant, known locally as the "Gipfeli".
Arabica coffee has a 60 per cent share of the world market, and Robusta coffee around 30 per cent. Its economic importance in international trade is beyond doubt, with an annual global trade volume of USD 22 billion. Around 90 countries produce 8 million tonnes of coffee every year. Brazil is the biggest producer, with 28% of the world harvest. More than 50 per cent is bought and processed by the USA, Germany, France, Italy and Japan. Every Swiss person drinks an average of 9.1 kg of coffee a year, the third-highest consumption in the world after Finland and Norway.

Coffee and its effects
As early as the 16th century, British doctors described the health benefits of coffee in detail, ranging from "aids digestion, speeds up the mind, lightens the heart" to "relieves coughs, headaches and dropsy". Even so, coffee still has to fight its harmful reputation to this day, which, according to the proven results of numerous studies, is a
persistent misconception. For some illnesses, such as cirrhosis of the liver, diabetes or dementia, coffee even appears to have a clearly protective effect. Thanks to its stimulating effect and its taste, it sparked people's research interest early on. But it was only at the suggestion of Johann Wolfgang von Goethe that the German chemist Ferdinand Runge first isolated caffeine — probably the most important substance in coffee — in 1820.

Coffee and kidney function
Franz Kafka is said to have remarked, "If coffee really dehydrated the body, I would have turned to dust long ago." In very high amounts, coffee does stimulate the need to urinate, but without drawing water out of the body, as is commonly assumed. Coffee therefore doesn't have a dehydrating effect and makes a significant contribution to your daily fluid needs.

Coffee and the cardiovascular system
A very slight and short-lived rise in blood pressure has only been demonstrated in people with hypertension. In people without hypertension, drinking more than three cups of coffee a day shows no difference compared with just one cup a day. According to more recent studies, coffee is not a risk factor for atrial fibrillation, coronary heart disease or stroke.

Coffee and diabetes mellitus
A 2009 meta-analysis (a summary of various studies) using data from almost 500 000 participants impressively shows an inversely proportional dose-response relationship in coffee drinkers regarding the incidence of type 2 diabetes. For each cup of coffee consumed, the calculated risk of developing the disease drops by around seven per cent. The exact mechanism behind this effect is not yet known and remains the subject of further studies. A Dutch cohort study with 17 000 participants showed a halved diabetes risk in people drinking more than seven cups of coffee a day.

Coffee and the stomach, gut and bile
The muscles of the gut are stimulated by the acids and bitter compounds in roasted coffee, which have a laxative effect. A recent study at the surgical university clinic in Heidelberg found a bowel-stimulating effect from postoperative coffee consumption after colon surgery, compared with water. An increased risk of developing stomach or duodenal ulcers has not been demonstrated in various studies, even with high coffee consumption. A US study shows a significantly reduced risk of gallstone formation when drinking at least four cups of coffee a day (a risk reduction of 45% in men and 28% in women).

Coffee and cancer
A recently published meta-analysis of 40 prospective cohort studies concluded that coffee consumption has no harmful effect on health. If anything, it might even help protect against cancers of the bladder, breast, oral cavity, pharynx, uterus, oesophagus, liver (HCC), leukaemia, prostate and rectum/colon. We hope this information has brought coffee a little closer to you, made it easy to enjoy with a clear conscience, and cleared up a few misconceptions along the way.

Sources: Coach Magazine, Marcello Corazza and Sascha A. Müller, Surgical Clinic, Cantonal Hospital