Secret of Coffee
(CNN)Throughout the ages, coffee has
been called a virtue and a vice for our
health. The latest study comes
down in favor of virtue: It says that drinking coffee, whether regular or
decaf, could reduce the risk of death.
Researchers started with data from surveys of adults in the United States
that asked how much coffee they consumed, as well as other foods and drinks,
and then they looked at their rates of death and disease over the following two
decades.
The study was large, including more than 200,000 women and 50,000 men.
At first, researchers did not see an obvious relationship between coffee
consumption and death rates. Study participants who drank between less than a
cup of coffee and three cups a day had 5% to 9% lower risk of dying than those
who drank no coffee. Those who drank more than three cups a day did not see any
benefit. The finding was murky, like previous studies, some of which suggested
a benefit and some did not.
But when the researchers looked at coffee consumption only among people who
said they never smoked, the relationship became clearer: Those who drank
between less than a cup of coffee and three cups a day had 6% to 8% lower risk
of dying than noncoffee drinkers. Those who drank three to five cups and more
than five cups had 15% and 12% lower death rates.
"The lower risk of mortality is consistent with our hypothesis that
coffee consumption could be good for you (because) we have published papers
showing that coffee consumption is associated with lower risk of type 2
diabetes and (heart) disease," said Ming Ding, a doctoral student in the
Harvard School of Public Health department of nutrition. Ding is the lead
author of the study, which was published on Monday in the journal Circulation.
It might have been hard to see the link between coffee consumption and
lower death rates because coffee and smoking often go hand-in-hand, and any
benefits associated with the first could have been canceled out by the second.
Although the study participants were asked about smoking, there might have been
a tendency, especially among heavy smokers, to underestimate the average number
of cigarettes they smoked per day, Ding said.
What's behind the
lower death rate?
It's possible that people who drink a lot of java have healthier diets
overall and drink less soda, which has been linked to higher rates of death and
heart disease, or that they have healthier diets overall.
But that's probably not what links coffee to lower death rates -- researchers
took into account the health benefits of drinking less soda and eating well.
They also took into account the fact that coffee drinkers were more likely to
have vices such as drinking alcohol and eating red meat.
At least some of the health benefits associated with coffee consumption are
probably a direct result of the ingredients in coffee, Ding said. It contains
chemicals such as lignans and chlorogenic acid that could reduce inflammation
and help control blood sugar, both of which could help reduce the risk of heart
disease.
In keeping with this possibility, Ding and her colleagues found that coffee
drinkers were about 10% less likely to die of heart disease. They were also
between 9% and 37% less likely to die of neurological diseases such as Parkinson's
and dementia.
The researchers also found that study participants who drank at least a cup
of coffee a day had between 20% and 36% lower rates of suicide, although those
who drank less than a cup had 36% higher rates.
Several other studies have hinted at an association between coffee
consumption and lower suicide rates, but it was a bit unexpected to see, Ding
said. It is not clear whether chemicals in coffee have a direct effect on
mental health or whether people who drink a lot of coffee have higher rates of
employment or certain lifestyles that are associated with lower suicide rates,
she added.
Although previous studies have suggested that drinking coffee could protect
against cancers such as prostate and liver, the current study did not find lower
rates of cancer deaths among java drinkers.
However, there may not have been a large enough number of deaths because of
specific cancers, such as liver cancer, to be able to see a difference between
coffee drinkers and nondrinkers, Ding said.
