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Coffee is good for you, a new study says. Wait, no, coffee is actually not that good for you, a newer study says. It seems like research on coffee keeps contradicting itself: That cup o' joe is simultaneously the cause of and the cure to everything.
So what's the truth? We asked nutritionists to weigh in on the science of java.
There's so much conflicting evidence out there about coffee's health benefits because, first of all, nutrition science is a relatively young field, says registered dietitian Susan Mitchell. And coffee is a pretty complex beverage, so it's true that there are both positive and negative health effects to drinking it.
"It's interesting - so, if you look at how people think about it, it's as a vehicle of caffeine," says Rob van Dam, epidemiologist at Harvard University and the National University of Singapore. "So people would talk interchangeably about coffee and caffeine." But coffee also contains a lot of vitamins, minerals, antioxidants and flavonoids, he says. "Things we typically see in fruits and vegetables we see in coffee - which is not that surprising considering coffee (comes from) a plant," van Dam says.
The bad news
Unfiltered coffee is not great for you.
That means Turkish coffee or coffee made with a French press.
"We know that if you have unfiltered coffee, that there is a substance called cafestol that increases your cholesterol level," van Dam says. "So if you drink it throughout the day, it can increase your risk of heart disease." But if you use a filter, or drink instant coffee - or if you only drink French press coffee or Turkish coffee every once in a while - you're OK, he says. "But if you drink it every day in huge amounts, it may have an effect on your cholesterol levels."
The caffeine in coffee may be harmful during pregnancy.
"We have concerns that high caffeine intake may be detrimental to the fetus," van Dam says. "Because the fetus can't metabolize caffeine very well - they don't have the ability to make it dissolve from the blood stream." And that can mean the fetus is taking in less nutrition.
"So, for women who are pregnant, although the evidence is not conclusive, we do suggest limiting coffee consumption at this stage of life," van Dam says.
Lots of cream and sugar in your coffee is not doing your health any good.
"The coffee-shop kind of coffees are high in calories because they're large beverages and they have lots of cream and sugar. It seems obvious, but it's something to consider," van Dam says.
The good news
Coffee has been shown to lessen the risk of some of the country's most common illnesses. Moderate coffee consumption - one to three cups a day - have been associated with a lower risk for heart attacks, especially in women. Some studies have shown a lower risk for cancers like endometrial, prostate and some breast cancers. And coffee has also been linked to a lower risk of Parkinson's disease.
It's also been shown to lower your risk of diabetes.
"Most of our research has been on diabetes - there are 35 studies now on coffee and diabetes," van Dam says. "These have been quite consistent - people drinking more coffee have a lower risk of diabetes. It is remarkably consistent. It's hard to imagine another factor that coffee drinkers have that would be so effective."
And it may help reduce the risk for developing depression.
Women who drank two or three cups of coffee a day were 15 percent less likely to develop depression when compared to women who drank just one cup a day, one study found.
The answer is, as the answer often is: You be you. If you don't like coffee, the evidence of its benefits isn't strong enough for nutrition scientists to recommend that you start drinking it. If you do, the evidence of its harms isn't strong enough for them to recommend that you stop.
"If you like coffee and you don't have a specific health condition - you can just kind of enjoy your coffee, regularly, as you like it," van Dam says. "It's find to drink three, four, five cups of coffee a day, at least based on what we have found on the research available."