When an master federal panel concluded earlier this year that drinking five cups of coffee a day can be part of a “healthy lifestyle,” even hinting that coffee is good for you, the announcement prompted a glut of headlines compliment the national habit.
This burst of coffee prompting was set off by the conclusions of the federal advisory committee that helps write the government’s Dietary Guidelines for Americans.
Strong and consistent proof shows that consumption of coffee within the moderate range (3 to 5 cups per day…) is not associated with increased risk of major chronic illness,” the panel’s report said. Moderate coffee use can be incorporated into a healthy lifestyle.
Yet at least for some scientists, it’s far from clear that coffee is harmful. In fact, emerging find from genetics suggest a very different take on America’s favorite drink: while coffee might possibly be beneficial for some people, it very well may be harmful for others.
In study not cited by the advisory committee, scientists have identified at least one special location in the genome – a single nucleotide out of roughly three billion – that short out whether a person processes caffeine quickly or slowly. And in those with the gene variant for handling caffeine slowly – roughly 50 percent of people – much coffee has been linked in separate studies to a higher risk of hypertension and heart attacks. Unfortunately, because genetic testing is expensive and rarely done, most people have little idea which gene variant they carry.
Regardless, the genetics study leads some experts to question whether a general rule about the impact of coffee – good or ill – is possible. In fact, the coffee argument reflects a deeper uncertainty about the nutrition advice routinely dispensed to the general public: How useful are dietary rules that apply to everyone.
There are spectacular metabolic differences in people and to expect that coffee will have the same health impact on everyone is absurd, said Sander Greenland, an emeritus epidemiology professor at UCLA, an master in study methodology who has studied coffee. They want to come out with the generalized recommendations.
The find out of the federal advisory panel is supported by dozens of studies showing that, on average, people who drink coffee are no worse off than those who don’t. In fact, several suggest that coffee drinkers may be more resistant to heart illness and other health troubles. Those studies, however, do not examine whether the test subjects process caffeine differently, or how genetics affects how people handle the stimulant.
Asked about those issues, some members of the federal advisory panel cast doubt on the science supporting the idea that genetics dramatically affects coffee’s impact on humans.
The debate over coffee may be mainly important for public health. According to survey data from an industry association, on any given day more people report drinking coffee than even tap water, bottled water, or soft drinks. In a survey of 2,000 adults, nearly 60 percent said they’d had coffee the day before.
The ubiquity of coffee has inspired dozens of studies of its health impact and collectively, at least, these Endeavour show little cause for worry.
One of the most notable was a study, conducted by National Institutes of Health scientists and release in the New England Journal of Medicine in 2012. The results suggested that coffee has far-reaching benefits – almost a miracle drug.
The study examined the health and coffee habits of much than 400,000 people over 13 years. They found that the people drinking larger amounts of coffee seemed to be healthier, though study said the benefits appeared to plateau after about three cups. Those who drank coffee were less likely to die of almost anything – heart illness, stroke, diabetes, even accidents – than non-drinkers. For example, people who had six cups of coffee a day were 10 percent less likely to die from any cause and 12 percent less likely to die of heart illness.
What they found is that, when it comes to coffee, moderate consumption is associated with better health: people who drank some coffee – about 1 to 4 cups – had a lower risk of heart illness. Those who had no coffee, or had lots of coffee – 5 cups per day or more, showed neither elevated nor reduce risks of heart illness. The study speculated that coffee, which is a complex chemical stew, may have both good and bad impact, and that in moderate amounts, the good impact outweigh the bad ones.
Another concern about the proof favoring coffee is that the studies don’t always agree with one another. For example, two years ago, a group of study from various universities looked at records for 43,000 people over more than 30 years and came to different conclusions: Among people less than 55 years old, people who drank more than 4 cups per day had a 50 percent higher risk of death.
The identical twins, who match each other genetically, developed caffeine very accordingly- if one identical twin was a “slow metabolizer,” so was the other. By contrast, the fraternal twins, who are less alike genetically, were much lower likely to process caffeine in the same way. In fact, the rates of caffeine metabolism in identical twins were twice as correlated as those between fraternal twins.
The idea that coffee’s effects may depend on genetics matches the widespread idea that coffee has different effects on people. Some people can sleep after a cup of coffee; others are up all night long.
The only hint may come from symptoms after drinking coffee, Palatini said. There are people who feel nervous, suffer insomnia and even have tremor after one cup, attesting to a direct effect of caffeine on the brain.