HERE鈥橲 some bad news for people who can鈥檛 get out of bed without a cup of
coffee鈥攊t can raise levels of an amino acid linked to heart disease. The
discovery has fanned the flames of the debate over coffee鈥檚 safety.
So far, epidemiologists have found no clear link between coffee and heart
disease. However, there are hints that it could cause heart problems. One study
showed that unfiltered coffee could raise levels of 鈥渂ad鈥� cholesterol because it
contains chemicals called diterpenes that would normally stick to a paper filter
(快猫短视频, 29 January, p 28).
Filtering coffee seemed like a sensible precaution. But last week,
researchers revealed that even filtered coffee could be a problem.
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Marina Grubben of the Agricultural University in Wageningen, the Netherlands,
was investigating a link between coffee and levels of homocysteine, a chemical
linked to heart disease and strokes. Many studies have shown that high levels
are linked to heart attack risk; some doctors think high levels of homocysteine
are as dangerous as high cholesterol. And a few epidemiologists have noticed
that people with high homocysteine levels are more likely to be coffee
drinkers.
Grubben鈥檚 team asked 30 adults to drink a litre of unfiltered coffee every
day for two weeks. Thirty-four other people drank only water, tea, broth, milk
or chocolate drinks. The groups later switched beverages.
The results, in this month鈥檚 American Journal of Clinical Nutrition
(vol 71, p 480), showed that unfiltered coffee raised homocysteine levels by
around 10 per cent. Petra Verhoef of the Wageningen Centre for Food Sciences
heard about this finding and wondered if the increase was caused by the same
chemicals that raise cholesterol levels. So she and her colleagues carried out a
similar study of 26 volunteers who drank either no coffee or a litre of strong
filtered coffee every day for four weeks.
Homocysteine levels rose by 18 per cent in the people drinking filtered
coffee. 鈥淲e were surprised,鈥� she says. Her team had not expected to see an
effect without the diterpenes found in unfiltered coffee.
Verhoef is now studying other compounds in coffee that might be responsible
for raising homocysteine levels. 鈥淐affeine is one of the possible candidates,鈥�
she says.