Coffee isn't bad for you - but is it really good?

Coffee makers from global giants to smaller upstarts are putting their brews on ice. Photo / Getty Images

Conventional wisdom on coffee has flip-flopped. Once considered an indulgence with potentially harmful health effects, coffee is now being talked about as a magical elixir that could potentially save your life.

"Could this be true?" you've probably wondered. Could your coffee addiction actually be good for you?

The most recent round of breathless reports came this week, after the publication of a study in the journal Heart that reported that people who drank three to five cups of coffee a day - considered a "moderate" amount - had cleaner arteries than those who did not drink coffee. The study, which looked at 25,000 young to middle-aged men and women in Korea, did contain a lot of good news about coffee but there's been a lot of confusion, misinterpretation and wishful thinking about its conclusions.

The reality is that there's a growing body of research that supports the idea that coffee, in reasonable amounts, may not be as bad for you as people once thought. Brewed coffee, for instance, has been found to contain a tremendous amount of good-for-you antioxidants. In fact, the nation's top nutrition panel earlier this year weighed in on coffee for the first time in its history, saying that "strong evidence" shows it is "not associated with increased long-term health risks among healthy individuals." The key words here are "healthy individuals." Due to its high caffeine content, brewed coffee may always be a source of insomnia, irritability, acid reflux and other negative side effects for others, especially those with underlying conditions, such as anxiety disorder or heart disease. More importantly, there's still a lot of work that needs to be done to make the leap between coffee not being bad for you and coffee being the cause of better health.

Here's a look at the Heart study and other recent studies about coffee and what they do - and do not - say:

Heart disease

Researchers found an association between drinking three to five cups of coffee and the amount of coronary artery calcium, an early warning sign of heart disease. We don't have information to conclude there's a causal link. Since it was an observational study the scientists weren't really able to control for other things, such as diet, exercise and environmental factors that could have affected the outcome.

Also those in the study didn't have any signs of cardiovascular disease, so it's unclear how coffee consumption might affect those who already have heart disease. But as the study got passed around this week on blogs and social media outlets, many began to think that the findings were even more amazing - that the scientists had discovered that drinking coffee was better for your heart than, say, eating a plateful of broccoli. One story about coffee promised that "five a day keeps heart disease away." Others declared that the study found that coffee "prevents clogged arteries" or "prevents heart attacks" even though the study did not go there.

Long life

A study published in the

New England Journal of Medicine

in 2012 found that older adults who drank caffeinated or decaffeinated coffee had a lower risk of death than those who did not drink coffee. But the study, which was conducted by the National Cancer Institute and the AARP, adjusted out factors, such as alcohol consumption and smoking. They also found that the coffee drinkers were less likely to die from heart disease, respiratory issues and infections, but not for cancer. The researchers cautioned themselves that "whether this was a causal or associational finding cannot be determined from our data."

Depression

Researchers at the Harvard School of Public Health who tracked 50,000 women found that those who drank four or more cups of coffee with caffeine were 20 per cent less likely to develop depression, but the researchers said that they need to do more research before they can recommend that women should drink more coffee.

Type 2 diabetes

A study published in 2006 in

Diabetes Care

that looked at 88,259 American women ages 26-46 years without a history of diabetes at the beginning found that the women's relative risk for diabetes was lower if they drank two to three cups a day and even lower if they drank four or more cups a day. The results were similar for both caffeinated and non-caffeinated coffee. But the researchers were confounded as to what might explain that effect other than saying that an ingredient of coffee other than caffeine seemed to be at play.

Parkinson's disease

A study published in the

Journal of the American Medical Association

in 2000 analyzed health data from 8,004 Japanese-American men (aged 45-68 years) who were enrolled in a Honolulu study. The researchers found that higher caffeine intake seems to be associated with a significantly lower incidence of Parkinson's and that that's independent of smoking. In this study researchers said their work suggests the effect may be due to caffeine rather than another nutrient in coffee.