Scientists rarely get straight to the point. An ode to the unexpected discoveries. Today: how biochemist Martijn Katan discovered the cholesterol-raising factor in coffee.
Dieuke Kingma 6 July 2023, 16:13
‘How does drinking coffee affect the cholesterol level in your blood?
‘In 1976 I became a nutrition researcher in Wageningen. I studied the link between nutrition and cardiovascular disease and that is how I ended up in the coffee world. It struck me that in Scandinavian countries a connection was seen between drinking coffee, cholesterol and heart attacks, while in other countries it was not. I went there to take a look.
‘They had just discovered that the effect of coffee on cholesterol had to do with the way coffee was brewed. Scandinavian coffee increased cholesterol while filter coffee did nothing. In Scandinavian countries they make ‘boiling coffee’, where they let a large amount of coarsely ground coffee simmer in a pot on the fire. Then they let the coffee stand for a while so that the goo could sink to the bottom, and then pour it. There was no paper filter involved in preparing that coffee.
‘A colleague and I decided to make filter coffee and boiling coffee and spin them in a centrifuge. A centrifuge speeds up the process of gravity, so that the coffee grounds sink to the bottom faster. We wanted to examine that coffee grounds.
‘At one point my colleague stormed into my room in Wageningen. He was all excited, when normally he was a very cool and calm boy. I walked with him and saw: there was a layer of oil on top of the boiling coffee. That oil had been invisibly small droplets in the coffee and had been pushed up by the centrifuge.
‘I remember thinking: ‘There’s a substance in it that raises cholesterol and I’m going to find out what that is.’ I was trained to pick apart living things and see which molecule does exactly what. That was exactly what had to be done here.
‘First of all I had to have enough coffee oil and Nestlé could make that for us. I also had to have laboratory animals on which we could test substances from coffee oil. With a test animal you know exactly what it eats and for a rat you need much less of such a substance than for a human. We gave raw coffee oil to all sorts of animals: rats, hamsters, Mongolian rhinoceroses, rabbits and even monkeys. But coffee oil did not raise cholesterol in any animal. Then I thought: we need to test on humans.
‘I was thought to be crazy, but soon after Nestlé gave us coffee oil, we suspected that cafestol might be the substance we were looking for. I asked Nestlé to make enough pure cafestol for three people: Nestlé’s head of coffee research, a professor of gastrointestinal and liver diseases in Nijmegen, and myself. I didn’t want to do that experiment with students, as was customary. That was too much for me in this case.
‘And indeed, our cholesterol went through the roof from a tiny bit of cafestol. Thus, cafestol was key to the effect of coffee on cholesterol and myocardial infarction. It is the strongest cholesterol-raising substance that exists and you will only find it in coffee that is brewed without a filter. Once it was known that boiling coffee contained a substance that increased cholesterol, it was consumed a lot less in Scandinavia.
‘The human body is very mysterious, but you can still understand the world in terms of molecules, as in this research. That to me is the essence of science.’
Martijn Katan is emeritus professor of nutrition at VU University Amsterdam and a columnist for NRC.
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2023-07-06 14:13:53
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