Bonn, Germany Some people sit in their office and drink 10 cups of coffee a day. Others feel their heart racing after one espresso.
Everyone has their own tolerance for caffeine. Some experts say that particularly sensitive people are probably reacting to the coffee's tannin. People who suffer adversely from coffee should pay close attention to their body and its signals.
'Caffeine affects the central nervous system ... the metabolism,' says Antje Gahl of the German Nutritional Association (DGE).
Depending on the amount ingested, it can excite the heart and circulation, but also the stomach, intestines and kidneys. That's because caffeine blocks receptors that are responsible for picking up adenosine, which is produced by the body and promotes relaxation.
Thus, coffee usually has a desired effect when people drink it in the mornings and afternoon. 'They wake up, become concentrated and can make decisions faster,' says Hans Biesalski, a professor at the Institute for Biology, Chemistry and Nutritional Science at the Hohenheim University in Stuttgart.
Some people get the shakes after drinking coffee. In such cases, some quick exercise can help. It lets the body work off the energy that comes from the coffee.
Different people filter caffeine out at different speeds, says Gisela Olias of the German Institute for Nutritional Research in Potsdam. 'For some people, it takes three to five hours. For others, it can take up to 12,' says Gahl.
Biesalski says this is the reason for the different tolerances. 'We're all individuals,' he says, adding that he himself can easily stomach coffee after his evening dinner and has no problem falling asleep, but becomes ill after drinking tea.
A 125-millilitre cup of green or black tea contains 20 to 50 milligrams of caffeine sometimes called theine in tea according to the DGE. The same size cup of coffee contains 80 mg, while a 50 ml cup of espresso only contains 50 mg. The amount of caffeine in a cup of coffee depend on the preparation and roasting of the beans.
Espresso contains less caffeine because the beans are roasted more strongly. Additionally, the tannin, which cause so many problems for some people, is destroyed in the process. Finally, the water used for espresso is under more pressure and pushed through the coffee powder faster. 'That means less dissolved tannin,' says Biesalski.
These factors can make regular coffee more palatable if it's prepared in an espresso machine, says Biesalski. 'Anyone who doesn't like coffee after dinner because it keeps them from sleeping is well- advised to try espresso.'
People with sensitive stomachs should also check out these miniature Italian coffees. 'Chlorogenic acid is the strongest acid in coffee. It's only broken down 30 per cent during normal roasting, but up to 70 per cent in stronger roasting processes,' says Olias.
That means extremely roasted espresso beans have smaller concentrations of this acid, which encourages hydrochloric acid production in the stomach. But Biesalski says the jury is still out on which role chlorogenic acid plays in causing problems with coffee.
Analysis is still pending on almost 100 different coffee elements. But any of these could be responsible for making coffee unpalatable to some. 'Even today, we still don't know why some people can't handle filtered machine-brewed coffee,' says Biesalski.
He advises sensitive coffee drinkers to only consume as much as 'feels and tastes good.' Anyone who notices themselves becoming agitated should cut consumption. On the other hand, the researcher notes, 'as far as I know, there are no studies that show coffee has negative effects on healthy people. That means you can drink as much coffee as you want.' Still, people with heart problems and blood pressure problems should be careful.
© 2006 dpa - Deutsche Presse-Agentur 
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