Coffee drinkers should raise a cup to studies that show their favourite brew is far from the unhealthy habit it is often labelled, writes Jane Brody.
In decades past, experts repeatedly warned that a coffee habit could harm health and shorten lives. Now this idea has been flipped on its head with the publication of several studies finding the exact opposite - coffee can be good for you.
Coffee drinkers were found to live longer than abstainers, a recent 14-year study involving more than 400,000 people found.
And in a finding to warm the hearts of caffeine lovers, it also showed that the more coffee consumed each day - up to a point, at least - the greater the benefit to longevity.
The research, which found coffee had this effect on lifespans even after smoking and many other factors known to influence health and longevity were taken into account, still cannot prove cause and effect, but the findings are consistent with other recent large studies.
The observed benefit of coffee drinking was not enormous - a death rate among coffee drinkers that was 10 to 15 per cent lower than among abstainers. But the findings are certainly reassuring and given how many people drink coffee, the numbers of lives affected may be quite large.
When the data was adjusted only for age, the study found the risk of death was greater among coffee drinkers. But when the researchers took into account other health-related characteristics among the participants, such as smoking, alcohol use, meat consumption, physical activity and body mass index, those who regularly drank coffee lived longer.
''Coffee drinkers shouldn't be worried,'' says Neal Freedman, an epidemiologist at the US National Cancer Institute who directed the study. ''Their risk is quite similar to that of non-drinkers.''
Coffee drinkers who were relatively healthy when the study began were less likely than non-drinkers to die of heart disease, respiratory disease, stroke, diabetes, infections, injuries and accidents.
The study, in The New England Journal of Medicine, examined data on 402,260 adults in the National Institutes of Health-AARP Diet and Health Study. They were aged 50 to 71 and free of heart disease, cancer and stroke when the study began in 1995. By 2008, 52,515 had died. Freedman and his co-authors examined why they died in relation to how much coffee they said they drank when the study began.
The risk of death gradually dropped as the number of cups the participants drank increased to four or five. At six cups or more each day, there was a slight rise in death risk, compared with that at four or five cups. But the chances of death remained lower than among people who drank no coffee.
Reflecting practices of the mid-1990s, the researchers considered a cup of coffee to be between 235 and 295 millilitres. The oversized cups now often served would count as more than one cup, Freedman said. Several extra-large cups can cause restlessness, irritability, sleeplessness and anxiety. Contrary to previous belief, at usual levels of consumption, coffee is no more of a diuretic than the equivalent amount of water. Up to six cups a day can be counted towards a person's recommended liquid intake.
But there can be wide variability in caffeine levels, even in similar beverages. As Jane Higdon and Balz Frei of Oregon State University reported in Critical Reviews in Food Science and Nutrition, when the same type of coffee was bought from the same store on six different days, the caffeine content varied from 130 milligrams to 282 milligrams in a regular cup.
Nor is caffeine the only compound in coffee important to health. In the new study, little or no difference was found in death rates among those who drank predominantly caffeinated or decaffeinated coffee. Other substances - such as antioxidants and polyphenols - probably also play a health-related role, the researchers noted.
Their findings should reassure people concerned about possible harm from substances long used to remove caffeine from coffee. Fear of these chemicals prompted many manufacturers to switch to the Swiss water method for removing caffeine.
But how coffee is brewed can make a health difference. Two prominent chemicals in coffee beans, cafestol and kahweol, are known to raise blood levels of cholesterol and especially artery-damaging LDL cholesterol. These substances are removed when coffee is prepared through a filter but remain in espresso, French press and boiled coffee. Single-serving coffee pods contain filters.
Even though coffee can cause a temporary rise in blood pressure, the new study, like those before it, found the risk of heart disease to be lower among otherwise healthy coffee drinkers. Other benefits suggested by recent studies include a reduced risk of Type 2 diabetes, liver disease and Parkinson's disease. Some research has found a reduced risk of depression, dementia and Alzheimer's disease among coffee drinkers.
People who engage in strenuous physical activities can also benefit, but only if their coffee has caffeine, which helps muscles use fatty acids for energy and blunts the effect of adenosine, extending the time before muscles fatigue. Post-exercise soreness is also reduced and recovery time shortened.
Whether coffee poses a risk to pregnant women remains controversial. A causal relationship between coffee consumption and miscarriage has not been demonstrated at caffeine intakes of less than 300 milligrams a day, but some studies have found increased risk of low birth weight associated with consuming more than 150 milligrams a day.
Keep in mind, too, that caffeine is a drug. Some medications interfere with the metabolism of caffeine and can increase its effects. In other cases, caffeine can enhance the effect of drugs such as aspirin.
The New York Times