When I was a kid, my parents refused to let me drink coffee because they believed it would "stunt my growth," but turns out that's of course a myth. Studies have failed shown again and again that coffee or caffeine consumption are related to reduced bone mass or how tall people are. But that's just the tip of the iceberg! Break out your super-size cup of joe, because coffee is the topic of this week's Healthcare Triage. 

When I set out to look at what research there was on coffee and health for a recent Upshot column. I assumed that I'd find a little research, but I thought I'd be associated with some good outcomes and some bad ones. That didn't turn out to be the case. There are SOOO MANY studies. To the research! Let's start with the heart. Just last year, a systematic review and meta-analysis of studies looking at long-term consumption of coffee and the risk of cardiovascular disease as published. Researchers found thirty-six studies involving more than 1,270,000 participants. The combined data showed that those who consumed a moderate amount of coffee, about 3-5 eight oz cups a day, were at the lowest risk for problems. Those who consumed five or more cups a day had no higher risk than those who consumed none. Just years earlier, a meta-analysis had been published looking at how coffee consumption might been associated with stroke. Eleven studies were found, including about 480,000 participates. As with the prior studies, consumption of 2-6 cups of coffee a day were associated with a lower risk of disease compared to those who drank none. Another meta-analysis published a year later confirmed those findings. Rounding out concerns about the effects of coffee on your heart, another meta-analysis examined how drinking coffee might be associated with heart failure. Again, moderate consumption was associated with a lower risk, with the lowest risk among those who consumed four servings a day. Consumption had to get up to about ten cups a day before any bad outcomes were seen.

Now you can find some studies linking caffeine to high blood pressure, but those usually aren't looking at coffee. You can also find studies linking unfiltered coffee to increases in serum cholesterol and triglycerides. Butt coffee that's been through a paper filter seems to have had the cholesterol raising agent, known as cafestol, removed. But those are processed measures, not outcomes. High blood pressure and high cholesterol are of concern because they can lead to poor cardiovascular outcomes or death. But drinking moderate amounts of coffee is linked to lower rates of pretty much all cardiovascular disease. Even consumers on the very high end of the spectrum appear to have very minimal, if any, ill effects.

But let's not cherry-pick. There are outcomes outside of heart health that matter. Many believe that coffee might be associated with an increased risk of cancer. Certainly individual studies have found that to be the case, and these are sometimes highlighted by the media. But in the aggregate, most of those negative outcomes disappear. A meta-analysis published in 2007 found that an increase coffee consumption by two cups a day was associated with a lower relative risk of liver cancer by more than 40 percent. Two more recent studies confirmed these studies. Results from meta-analyses looking at prostate cancer found that in the higher quality studies, coffee consumption was not associated with negative outcomes. The same holds true for breast cancer, where associations were also not statistically significant. It's true that the data on lung cancer show an increased risk for more coffee consumed, but that's only among people who smoke. Drinking coffee may be protective in those who don't. Regardless, the authors of that study hedge that their results should be interpreted with caution, because of the confounding and likely overwhelming effects of smoking on lung cancer. A study looking at all cancers suggested that coffee drinking might be associated with reduced overall cancer incidents, and that the more you drank, the more protection was seen. 

Drinking coffee is associated with better laboratory values in those at risk for liver disease. In patients who already have liver disease, it's associated with a decreased progression to cirrhosis. In those who already have cirrhosis, it's associated with a lower risk of death and a lower risk of developing liver cancer. It's associated with better responses to anti-viral therapy in patients with Hepatitis C, and better outcomes in patients with non-alcoholic fatty liver disease. The authors of that systematic review argue that daily coffee consumption should be encouraged in patients with chronic liver disease.

The most recent meta-analyses on neurologic disorders found that coffee intake has been associated with lower risks of Parkinson's Disease, lower cognitive decline, and a potential protective effect against Alzheimer's disease, but certainly no harm.

Another systematic review published in 2005 found that regular coffee consumption was associated with a significantly reduced risk of developing type 2 diabetes, the lowest relative risks (about a third reduction) in those who drank at least six or seven cups a day. The latest study, published in 2014, used updated data and included 28 studies and more than 1.1 million participants. Again, the more coffee you drank, the less likely you were to have diabetes. This included both caffeinated and decaffeinated coffee. 

But what about all cause mortality? There have been two meta-analyses published within the last year or so. The first reviewed 20 studies including about a million people, and the second included 17 studies containing more than a million people. And both found that drinking coffee was associated with a significantly reduced chance of death...period. 

Okay, let's take a breather. I grant you that pretty much none of the research I cited before contains randomized controlled trials. But here's the thing, it's important to remember that we usually conduct those trials to see if what we are seeing in epidemiologic studies holds true. But most of us aren't drinking coffee because we think it will protect us; we're worrying that it might be hurting us. There's almost no evidence for that at all. The epidemiologic evidence points in the other direction. It may be that RCTs would fail to show that coffee's saving us, but that's not what most people are worried about.

If any other risk factor had these kinds of positive associations across the board, the media would be all over it. We'd be pushing it on everyone. Whole interventions would be built up around it. For far too long though, coffee's been considered a vice, not something that might be healthy. That may change soon. The newest scientific report from the USDA nutritional guidelines, which I've discussed before, said that coffee's not only okay, it agrees that it might be good for you. This was the first time that the dietary guideline advisory committee reviewed the effects of coffee on health...ever. 

And look we should acknowledge that there's always a danger of going too far in the other direction. I'm not suggesting that we start serving coffee to little kids. Caffeine still has a number of effects parents might want to avoid for their children. Guidelines also suggest that pregnant women not drink more than 2 cups a day. I'm also not suggesting that people start drinking coffee by the gallon. Too much of anything can be bad. And finally, while the coffee itself may be healthy, that's not necessarily true of the added sugar and fat that many of us put into coffee based beverages.

But it's way past time that we stop viewing coffee itself as something we all need to cut back on. It's a completely reasonable addition to a healthy diet, with more potential health benefits seen in research than almost any other beverage we're consuming. It's time we started treating it as such.

Healthcare Triage is brought to you in part by views like you through Patreon.com, a service that allows you to support the show through a monthly donation. We especially want to thank our honorary research associates, Cameron Alexander and Qadeem Salehmohamed. Thanks Cameron and Qadeem. If you'd like to support the show, more information can be found at patreon.com/healthcaretriage.