Coffee’s ‘Sweet Spot’: Consumption and Cardiometabolic Risk

This transcript has been edited for clarity. 
Welcome to Impact Factor, your weekly dose of commentary on a new medical study. I’m Dr F. Perry Wilson of the Yale School of Medicine.
Each and every day, 1 billion people on this planet ingest a particular psychoactive substance. This chemical has fairly profound physiologic effects. It increases levels of nitric oxide in the blood, leads to vasodilation, and, of course, makes you feel more awake. The substance comes in many forms but almost always in a liquid medium. Do you have it yet? That’s right. The substance is caffeine, quite possibly the healthiest recreational drug that has ever been discovered.
This might be my New England upbringing speaking, but when it comes to lifestyle and health, one of the rules I’ve internalized is that things that are pleasurable are generally bad for you. I know, I know — some of you love to exercise. Some of you love doing crosswords. But you know what I mean. I’m talking French fries, smoked meats, drugs, smoking, alcohol, binge-watching Firefly. You’d be suspicious if a study came out suggesting that eating ice cream in bed reduces your risk for heart attack, and so would I. So I’m always on the lookout for those unicorns of lifestyle factors, those rare things that you want to do and are also good for you.
So far, the data are strong for three things: sleeping, (safe) sexual activity, and coffee. You’ll have to stay tuned for articles about the first two. Today, we’re brewing up some deeper insights about the power of java.
I was inspired to write this article because of a paper, “Habitual Coffee, Tea, and Caffeine Consumption, Circulating Metabolites, and the Risk of Cardiometabolic Multimorbidity,” appearing this week in the Journal of Clinical Endocrinology and Metabolism (JCEM). This study may be the most comprehensive study yet to go beyond the simple associations between caffeine intake and outcomes, to try to answer the question of how this miraculous substance does what it does.
This is not the first study to suggest that coffee intake may be beneficial. A 2013 meta-analysis summarized the results of 36 studies with more than a million participants and found a U-shaped relationship between coffee intake and cardiovascular risk. The sweet spot was at three to five cups a day; people drinking that much coffee had about a 15% reduced risk for cardiovascular disease compared with nondrinkers.
But here’s the thing. Coffee contains caffeine, but it is much more than that. It is a heady brew of various chemicals and compounds, phenols, and chlorogenic acids. And, of course, you can get caffeine from stuff that isn’t coffee — natural things like tea — and decidedly unnatural things like energy drinks. How do you figure out where the benefit really lies?
The JCEM study leveraged the impressive UK Biobank dataset to figure this out. The Biobank recruited more than half a million people from the UK between 2006 and 2010 and collected a wealth of data from each of them: surveys, blood samples, biometrics, medical imaging — the works. And then they followed what would happen to those people medically over time. It’s a pretty amazing resource.
But for the purposes of this study, what you need to know is that just under 200,000 of those participants met the key criteria for this study: being free from cardiovascular disease at baseline; having completed a detailed survey about their coffee, tea, and other caffeinated beverage intake; and having adequate follow-up. A subset of that number, just under 100,000, had metabolomic data — which is where this study really gets interesting.
We’ll dive into the metabolome in a moment, but first let’s just talk about the main finding, the relationship between coffee, tea, or caffeine and cardiovascular disease. But to do that, we need to acknowledge that people who drink a lot of coffee are different from people who don’t, and it might be those differences, not the coffee itself, that are beneficial.
What were those differences? People who drank more coffee tended to be a bit older, were less likely to be female, and were slightly more likely to engage in physical activity. They ate less processed meat but also fewer vegetables. Some of those factors, like being female, are generally protective against cardiovascular disease; but some, like age, are definitely not. The authors adjusted for these and multiple other factors, including alcohol intake, BMI, kidney function, and many others to try to disentangle the effect of being the type of person who drinks a lot of coffee from the drinking a lot of coffee itself.
These are the results of the fully adjusted model. Compared with nonconsumers, you can see that people in the higher range of coffee, tea, or just caffeine intake have almost a 40% reduction in cardiovascular disease in follow-up.
Looking at the benefit across the spectrum of intake, you again see that U-shaped curve, suggesting that a sweet spot for daily consumption can be found around 3 cups of coffee or tea (or 250 mg of caffeine). A standard energy drink contains about 120 mg of caffeine. 
But if this is true, it would be good to know why. To figure that out, the authors turned to the metabolome. The idea here is that your body is constantly breaking stuff down, taking all these proteins and chemicals and compounds that we ingest and turning them into metabolites. Using advanced measurement techniques, researchers can measure hundreds or even thousands of metabolites from a single blood sample. They provide information, obviously, about the food you eat and the drinks you drink, but what is really intriguing is that some metabolites are associated with better health and some with worse
In this study, researchers measured 168 individual metabolites. Eighty of them, nearly half, were significantly altered in people who drank more coffee. 
This figure summarizes the findings, and yes, this is way too complicated. 
But here’s how to interpret it. The inner ring shows you how certain metabolites are associated with cardiovascular disease. The outer rings show you how those metabolites are associated with coffee, tea, or caffeine. The interesting part is that the sections of the ring (outer rings and inner rings) are very different colors.
Like here.
What you see here is a fairly profound effect that coffee, tea, or caffeine intake has on metabolites of VLDL — bad cholesterol. The beverages lower it, and, of course, higher levels lead to cardiovascular disease. This means that this is a potential causal pathway from coffee intake to heart protection. 
And that’s not the only one.
You see a similar relationship for saturated fatty acids. Higher levels lead to cardiovascular disease, and coffee intake lowers levels. The reverse works too: Lower levels of histidine (an amino acid) increase cardiovascular risk, and coffee seems to raise those levels.
Is this all too good to be true? It’s hard to say. The data on coffee’s benefits have been remarkably consistent. Still, I wouldn’t be a good doctor if I didn’t mention that clearly there is a difference between a cup of black coffee and a venti caramel Frappuccino. 
Nevertheless, coffee remains firmly in my holy trinity of enjoyable things that are, for whatever reason, still good for you. So, when you’re having that second, or third, or maybe fourth cup of the day, you can take that to heart. 
F. Perry Wilson, MD, MSCE, is an associate professor of medicine and public health and director of Yale’s Clinical and Translational Research Accelerator. His science communication work can be found in the Huffington Post, on NPR, and here on Medscape. He tweets @fperrywilsonand his book, How Medicine Works and When It Doesn’t, is available now. 
 
Any views expressed above are the author’s own and do not necessarily reflect the views of WebMD or Medscape.