If we don’t know caffeine by now, you may well ask, when will we? (And do we have time for a fix while we’re waiting?) Make it a venti and sit down. We’ll explain a few things. First, caffeine is a complex compound. And it’s made even more so by America’s preferred delivery method, coffee. For instance, caffeine raises blood pressure, but habitual coffee drinkers are half as likely to die of heart failure as those who don’t fill their mug daily. And while caffeine spikes blood sugar, a java habit may help you dodge diabetes. MORE: How Science Is Messing with Your Morning Coffee Confused? Then use this primer to learn how to consume caffeine to your advantage—at work, in the gym, and for overall health. The Basic Biology To understand how a double espresso can take you from dead tired to completely wired, you need to understand the compound adenosine. Right now, adenosine is coursing through your veins, and its job is to put the brakes on your central nervous system. You might call it nature’s chill pill. That’s because as your day progresses, adenosine builds up naturally in your bloodstream, causing you to slow down and become sleepier—a convenient way to let you know it’s time to turn off the laptop and go to bed. Adenosine accomplishes this total-body shutdown by plugging into adenosine receptors—like electrical cords into outlets. “These connections inhibit the release of neurotransmitters, which are chemical messengers that control both brain and muscle function,” says William Lovallo, a professor of psychiatry and behavioral sciences at the University of Oklahoma. “As a result, your mind and your body slow down.” But as it turns out, caffeine is an excellent adenosine impersonator. In fact, when the two rivals jockey for the same parking space, caffeine wins. “If caffeine is plugged into the adenosine receptors, adenosine can’t do its job,” says Lovallo. “And this causes your central nervous system to run at a faster rate.” Thus, you experience the classic and often sought-after caffeine jolt. Now, here’s how to make that work for just about every part of your body: Your BrainThe science: Soon after your first sip, caffeine begins to work its magic by triggering the release of dopamine. Dopamine is a brain chemical that stimulates the area of your gray matter responsible for alertness, problem solving, and pleasure. “You have that feeling of being activated, sharper, and on the ball,” says Lovallo. “And you can also experience a mild mood-elevating effect.” All of which goes a long way in explaining why there are a bazillion Starbucks around the globe. Be smarter instantly: Down a cup of joe just before your next meeting—it’ll boost your mind power for about 45 minutes, according to an Austrian study that directly measured the impact of 100 mg of caffeine on brain activity. Be smarter for life: Refill your cup 3 times daily. Harvard researchers determined that men who drink 4 cups of caffeinated coffee per day are half as likely to develop Parkinson’s disease as those who skip the java—presumably because caffeine keeps dopamine molecules active. What’s more, blocking adenosine may slow the buildup of amyloid-beta, a toxic brain plaque associated with Alzheimer’s. Your HeartThe science: Adenosine helps blood vessels relax. But once caffeine infiltrates the receptors that line vessel walls, your arteries constrict, causing blood pressure to rise. In fact, research has shown that blood pressure may increase by as much as 10 points in non-habitual drinkers. Yet when Harvard researchers tracked the coffee intake of more than 128,000 people, they determined that drinking more than 6 cups of coffee a day didn’t boost the chance of developing heart disease. And scientists at Brooklyn College found that men who drank 4 cups of caffeinated coffee daily had a 53% lower risk of dying of heart disease than those who never took a sip. “If you don’t have hypertension to begin with, the temporary blood-pressure increase from a cup of coffee isn’t a problem,” says Matthew Sorrentino, a cardiologist and professor of medicine at the University of Chicago. “Plus, the impact on blood pressure tends to be smaller in habitual caffeine drinkers because their bodies become somewhat tolerant to its effects.” Take your health history into account: If caffeine makes your heart race or skip beats, you’re probably genetically sensitive to the stimulant. “Although this may sound serious, symptoms such as palpitations are actually considered innocuous, unless you’ve had a recent heart attack,” says John Kassotis, a cardiac electrophysiologist at SUNY Downstate in Brooklyn. Still, Dr. Kassotis suggests playing it safe. His rule: If you think you’re caffeine-sensitive, consult your physician to determine if you should limit your intake. Stick with antioxidant-rich java: Scientists aren’t sure whether it’s the caffeine or the antioxidants in coffee – or a combination of the two – that provides the cardiovascular benefits. But unless you’re caffeine-sensitive, go with the leaded variety. Research shows that antioxidant levels are about 15% lower in decaf. Your MusclesThe science: Because caffeine revs up your central nervous system, it slightly increases your heart rate and breathing rate, both of which help prepare your body for exercise. Caffeine may also have a direct effect on your muscles. Here’s how: Calcium must be released within a muscle fiber in order for that fiber to contract, and caffeine may block the adenosine receptors attached to muscle fibers, triggering electrical activity that prompts bigger bursts of calcium. “The result is a stronger muscle contraction,” says Terry Graham, a professor of human health and nutritional sciences at the University of Guelph in Ontario. Jump-start your workout: Studies show that consuming 140 to 400 mg of caffeine 30 to 60 minutes prior to exercise can improve both speed and endurance and make the workout seem easier. But to achieve these effects, researchers have used either caffeine pills or caffeinated soda. The reason: “Many other chemical compounds in coffee appear to counteract caffeine’s ability to impact your exercise session,” Graham says. Now you know why energy drinks were created. Use caution: If you have heart problems or a family history of heart disease, avoid high-caffeine energy drinks for 4 hours before exercising. A study in the Journal of the American College of Cardiology determined that 200 mg of caffeine decreases blood flow to the heart by up to 39% during exercise because it constricts coronary arteries. Your LiverThe science: When your central nervous system is activated, so is your body’s fight-or-flight response. This causes the release of stress hormones such as cortisol and adrenaline. These in turn signal your liver to pump sugar into your bloodstream. After all, had you been in a truly stressful situation—say, face-to-face with a cranky barista—your body would need that sugar for quick energy. But in everyday life, extra blood sugar is the last thing you need, because it signals your body to store fat and increases your risk of diabetes. Keep your blood sugar in check: Forgo the sugar in your coffee and you’ll actually reduce your risk of developing diabetes, according to multiple studies. For example, Harvard researchers determined that drinking 5 cups of coffee per day cuts in half the risk of developing diabetes. Scientists aren’t sure why coffee may have a protective effect against diabetes, but credit its high level of disease-fighting antioxidants. While visiting Starbucks, order a Caffè Americano, which is coffee at its finest: strong and flavorful, but sugar-free.
