This article first appeared in The Magazine, issue 31, December 5, 2013, a subscriber-supported electronic periodical that publishes every two weeks. We’re crowdfunding a book from our first year of publication. Back the project to get a hardcover book or an ebook. Visit our Kickstarter page for details.

In the middle of Kelly Drive, a Philadelphia Marathon volunteer in an electric blue shirt stands with both arms stretched wide, shouting, “Caffeine! Caffeine!”

The second half of the marathon is a loop in which runners pass her outbound between miles 16 and 17 and returning between miles 22 and 23. On her left and right, racers grab at the packets of Mocha Clif Shot Energy Gel. She holds them loose in her hands so participants can easily snatch those 1.2-ounce packets, each of which contains 50 milligrams (mg) of caffeine.

It isn’t known precisely why two runners died on this course in 2011, one in the full marathon and one in the half marathon.1 The marathoner fell right before reaching the finish line; the half marathoner collapsed after passing beyond the line. This specific form of death has become common enough that it’s now reported in the same format: name, age, where they collapsed, and race experience.

Most studies about why these deaths occur have focused on the heart, and how it changes during strenuous activity. But the packets handed out by that race volunteer could be another factor as to why these deaths are so similar, and why heart attacks claim runners who’d had no prior cardiac problem and who’d previously completed multiple marathons without incident.

“Caffeine! Caffeine!” she calls, and runners in neon shirts and shorts and gloves and compression socks snatch them from her hands.

Caffeine: the drug

Caffeine is the most commonly used psychoactive drug in the world. Yes, it is a drug, and it can be addictive. Caffeine stimulates the central nervous system and increases heart rate. It also boosts dopamine levels in the same way as heroin, but at a much lower level.

If taken in moderate doses, caffeine typically isn’t dangerous. The FDA labels caffeine as GRAS — “generally recognized as safe” — for adults who don’t consume more than 400 mg a day. An 8-ounce cup of brewed coffee has anywhere from 95 to 200 mg of caffeine, according to the Mayo Clinic. (All coffees are different, but one cup to the FDA is not necessarily one cup to you and me: at most coffee shops, a small is 12 ounces and a medium is 16 ounces.)

Studies have shown that caffeine can also do a body good. It can increase brain function, lower the risk of cardiovascular disease and diabetes, and reduce the risk or onset of cancer and Parkinson’s disease. It’s also an antioxidant. I drink coffee every day, as do 63 percent of Americans.

Endurance athletes rely on caffeine for specific purposes. I’m going to get the obvious one out of the way: coffee has a laxative effect, which is important before heading out on a long run.

Beyond that, though, studies from the Journal of Strength and Conditioning, Journal of Sports Sciences, International Journal of Sports Medicine, Journal of Applied Physiology, and Journal of Science and Medicine in Sport have shown that taking in some caffeine before or during exercise can improve finish times in races.

A lot of runners use caffeine before and during races and handle it fine. I’m one of them. I have not run a marathon where I did not have a few ounces of coffee before the race, and then about 50 mg of caffeine delivered via Clif Shot Bloks during the marathon.

As headline-grabbing as these deaths are, they aren’t common. A New England Journal of Medicine study looked at marathon deaths from January 1, 2000, through May 31, 2010, and found the rate of cardiac death to be extremely low: one per every 259,000 runners who complete marathons and half marathons.

That seems like an awfully small number, subject to statistical chance and not a direct cause-and-effect relationship. But the basis for a direct connection has become increasingly sound, and people are consuming caffeine before and during races at a rate far above anything considered safe. And because it’s preventable and avoidable, each of these deaths could be seen as one too many.

Caffeine-delivery systems

Starting three years ago, the International Marathon Medical Directors Association (IMMDA) has warned runners to ingest no more than 200 mg of caffeine before and during a race, based on research that has shown that during exercise, caffeine affects the heart in ways that can send someone into cardiac arrest. “Every incident is disturbing,” says Dr. Lewis G. Maharam, chairman of the board of governors for the IMMDA and medical director of the Leukemia Lymphoma Society’s Team in Training. There was no single incident that led the group to put out the warning in 2010, but it stemmed from a “constant conversation on how to be safer.”

So far this year, four cardiac-related causalities have fit the pattern: Alain Rettig, 45, in the TCS Amsterdam Marathon, 1 km from the finish line; Ricki Savage, 27, in the Dublin Marathon at the finish line; Jake Zeman, 35, in the Rock ’n’ Roll Savannah Marathon, feet from the finish line; and Kyle Chase Johnson, 23, in the Pittsburgh Half Marathon, less than a mile from the finish line.

Despite the IMMDA recommendation and the regular reporting on race deaths, caffeine remains a safe energy boost in the eyes of many runners. That volunteer stood on the Philadelphia Marathon Course and yelled “caffeine” over and over again, thinking she was helping those runners by handing out supplies from one of the race’s sponsors.

I found no evidence that the companies that make these caffeine-laden products are encouraging unsafe levels of consumption, but neither are all of these products labeled to indicate appropriate limits during endurance events. Nor is there much education by the companies, running magazines, races, or government about how to track one’s total intake of caffeine during extended exertion. Every individual is left to his or her own calculations.

Through a survey conducted through The Magazine, I found that runners are pounding Red Bulls, 5-Hour Energy drinks, and extra-large coffees before a run and then, while running, slurping down caffeinated supplements, eating caffeinated foods, and taking caffeine pills that bring them far past the 200 mg point. (The full details of the survey appear later in this article.)

“The wrong product with the wrong person can lead to what you’re describing: people dropping dead at these races,” says Dr. John P. Higgins, associate professor of medicine at the University of Texas Health Center in Houston and chief of cardiology at the Lyndon B. Johnson General Hospital. He is also a 10-time marathoner.

In March 2013, he and 17 other researchers wrote a letter to the FDA (PDF) about the increased reports of health complications, emergency department visits, and injuries and deaths related to what they called “highly caffeinated energy drinks,” which were projected to be a $19.7 billion industry in the U.S in 2013.

In May 2013, the FDA opened an investigation into caffeine-additive products, including not just energy drinks but also food products, citing gum, waffles, and even jellybeans.

According to an FDA spokesperson, the agency started looking into caffeine last fall by “taking a fresh look at the potential impact that the totality of new and easy sources of caffeine may have on health,” with a focus on children and young adults. The proliferation of added caffeine to food is a concern, the spokesperson adds. There is no timeline for when the investigation will be complete.

Though no brand name was called out by the FDA, Jelly Belly now makes a caffeinated product called Extreme Sports Beans, which it pitches to athletes for “when your workout needs a little more kick.” The owner of the Running Company of Haddonfield, where I buy all my running gear, says they’re flying off the shelves.

The finish-line heart attack death

Despite the benefits of running, marathoning can inflame heart tissue, even in healthy runners who have run multiple marathons or half marathons without incident. It can also trigger underlying heart disease in middle-aged runners, even if these runners previously had unexceptional heart exams and stress tests.

In a recent study, researchers at the Quebec Heart and Lung Institute at Laval University looked at marathoners between the ages of 18 and 60 who had run an average of eight marathons. They first examined the runners right after the Quebec City marathon and then again three months later. They found that strenuous exercise can temporarily harm heart tissue, especially in poorly trained athletes.

“The low-risk runner morphs into a high-risk runner in a race,” says Dr. Arthur J. Siegel, director of internal medicine at McLean Hospital and associate professor of medicine at Harvard Medical School. His studies on runners and cardiac arrest have appeared in the American Journal of Medicine and the World Journal of Cardiovascular Diseases.

These deaths can happen without caffeine, but caffeine makes any kind of underlying or temporary heart problem worse, Siegel says. That’s because caffeine affects myocardial blood flow, which is the rate at which blood moves through the heart’s muscles to infuse it with oxygen so it can push re-oxygenated blood out to the rest of the body.

In two separate studies from the University Hospital in Zurich, Switzerland, researchers measured the myocardial blood flow of men and women who took in 200 mg of caffeine an hour before riding a stationary bike for 50 minutes. That’s the same amount of caffeine in one 2-ounce bottle of 5-Hour Energy, two Chocolate Cherry Clif Shot Energy Gels, or four Double Latte Power Gels.

While this much caffeine has no effect on myocardial blood flow when a body is at rest, it has a significant effect when you work out. Healthy bike riders experienced a 14 to 22 percent drop in myocardial blood flow; those with coronary artery disease experienced an 18 to 25 percent drop.

This is very bad news, because, when exercising, your arteries increase blood flow from 300 to 400 percent, says Higgins. Your heart needs to work harder, and therefore needs more blood flow to the myocardial muscles of the heart so it can keep the pumping going. But if your myocardial blood flow drops, you get what Higgins calls a “supply-demand mismatch.”

“You’re working your system more, and at the same time, you’re impairing your system’s ability to increase its blood flow,” he says. That starves the heart muscles of oxygen, which can lead to outcomes like chest pain, myocardial ischemia, or even myocardial infarction — a heart attack.

That New England Journal of Medicine study mentioned earlier looked at marathons and half marathons from January 1, 2000, through May 31, 2010. Researchers identified 59 marathon and half marathon cardiac events that happened during the running of the race and in the finish line recovery area up to one hour after runners finished. Interviews with survivors and surveys of family members of the deceased did not include questions about caffeine. However, the authors concluded that “demand ischemia (i.e., ischemia due to an imbalance between oxygen supply and demand) may be operative in exercise-related acute coronary events during long-distance running races.”

In 2010, the IMMDA released guidelines to runners about how to prevent cardiac incidents. These recommendations included, for a 10K (10 km, or about 6 miles) or longer run, taking a baby aspirin before running, limiting caffeine consumption to no more than a total of 200 mg before and during the race, and not sprinting at the end.

The group put these recommendations out “based upon successful resuscitations where we spoke and interviewed these patients and found that they were drinking tons of caffeinated products before they did the race, like three Red Bulls or energy drinks,” says Maharam. The recommendation of taking a baby aspirin came from Siegel’s work.

There’s something else involved, too, in why these deaths happen close to the finish line. Maharam has seen so many of these cardiac incidents that he coined the term “the X Spot.” For races he oversees, it’s where he stations paramedics.

“The very spot where you can see the finish line first is where these people get sudden death. It’s unbelievable,” he says. “The added rush of adrenaline that you know you’re going to finish. That’s where their heart stops.”

Caffeine won’t hit every person the same way. Taking in 50 mg of caffeine before or during a race probably won’t affect someone, like me, who drinks a cup of coffee every morning as much as it will a person who doesn’t drink caffeine at all.

Then why would someone who doesn’t drink coffee suddenly start taking in caffeine during a race? Or start loading up on products that take them far beyond the 200 mg recommendation?

Simple: because races give these products a tacit stamp of approval by sponsoring them and by handing them out before, during, and after the event.

The business of caffeinating runners

Most runners need to eat during a race to replenish the water, electrolytes, and minerals (like sodium and potassium) that they’re sweating out and to feed themselves carbohydrates to have fuel to burn, especially if they’re running four to six hours.

Runners used to eat actual food, like orange slices, or they might carry sugar (or high-fructose corn syrup) in the form of jellybeans. Gu Energy Gel debuted in 1991. Clif made its first Shot Energy Gel in 1997. A lot of companies are in the endurance caffeine game: Jelly Belly, Power Bar, and Honey Stingers all make “fuel” packaged and ready to go, with or without caffeine. GNC sells dozens of caffeinated products.

Coffee and energy drinks market to runners, too. Dunkin’ Donuts is a sponsor of the Broad Street Run in Philadelphia, which is the largest 10-mile race and seventh largest overall race in the country. They also plant runners in coffee cup costumes in the actual race. At the end of the Run the Bridge 10K, which bounces from Camden to Philadelphia and back, runners were given free samples of Melitta coffee at the finish line.

In May 2014, Red Bull is sponsoring Wings for Life World Run, which will start at the same time in 40 countries. There isn’t a finish line; instead, athletes will try to outrun a “catcher car” that sets off 30 minutes after the start. Red Bull sent me a press release about the run series while I was working on this story.

I asked Red Bull if its product is safe for marathoners. Its spokesperson declined to speak by phone, but wrote via email: “Ever since Red Bull was introduced 25 years ago, it has been widely used by recreational and competitive athletes. The ongoing partnership between athletes and Red Bull is testimony to the claim that Red Bull actually works. Red Bull vitalizes body and mind.”

After pointing out that Red Bull has been approved for use in sport by NSF International, she continued, “Red Bull can be enjoyed by all kinds of people — truck drivers, businessmen, athletes, and college students. Red Bull Energy Drink is available in 165 countries because health authorities across the world have concluded that it is safe to consume.” She also pointed out that the caffeine content — 80 mg in an 8.4-ounce can of Red Bull Energy Drink — is labeled clearly on the cans.

That’s not a direct answer. And the NSF label claim is off base. NSF is a non-profit formerly known as the National Sanitation Foundation. According to the NSF Certified for Sport Web site, their company “certifies that what is on the label is in the bottle and that the product does not contain undeclared ingredients or unsafe levels of contaminants.”

The NSF label means that what’s in the can is in the can; the label is not a stamp of approval that those labeled ingredients are safe during exercise. Red Bull was also just sued for $85 million for wrongful death by the family of a 33-year-old man. The suit maintains that the man died after drinking the product and then playing basketball.

Clif is a frequent sponsor of races. At the Philadelphia Marathon expo, I could taste samples of their gels, some of which have no caffeine, while others have up to 100 mg of caffeine per package; and Clif Shot Bloks, which have from no caffeine up to 50 mg per serving. The expo displayed photos of runners leading pace groups in the race as part of the Clif Bar Pace Team.

“All of Clif’s flavors with added caffeine clearly state caffeine on the front and back of the package, and have a visual comparison to coffee to help the consumer,” wrote a Clif spokesperson in an email. Their caffeinated products also instruct athletes to take in one 15 minutes before activity, and then one during activity.

On Gu Energy Gels, the amount of caffeine, which ranges from none to 40 mg, is written on the front of the packets, right where you tear them open. Jelly Belly’s Extreme Sport Beans have a medallion on the front that shows it has 50 mg of caffeine per packet, which is one serving. (Their regular Sports Beans are not caffeinated.)

Jelly Belly tells athletes to take in one packet 30 minutes before exercise, then to use as needed. Gu tells runners to have one 15 minutes before activity and then one every 45 minutes. Power Gel recommends taking one every 20 to 45 minutes.

In 2012, the median male marathoner finished in 4 hours, 17 seconds. The median female marathoner finished in 4 hours, 42 minutes. Runners following some of these recommendations could be swallowing the contents of five or more packets per marathon.

A median female marathoner following Power Gel’s recommendations of taking one gel per 20 minutes would take in 14 packets during the race. If she takes in orange dream, vanilla, or kona punch, her total caffeine intake will be zero. But if she chooses double latte or tangerine, which have 50 mg each, she’ll hit 700 mg before she crosses the finish line.

A survey of consumption

I conducted an informal Internet-based survey using Google Forms through The Magazine, and 213 runners responded. This was absolutely a self-selected group, and we told them we would be asking questions about their caffeine consumption. I wasn’t attempting to get a statistically valid sample. Rather, I wanted to know how a sufficient number of runners motivated enough to respond interacted with caffeine in racing. (We promised anonymity, but noted we would quote aggregate data and responses in this article.)

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Of respondents, 70 percent said they ingest caffeinated items during a marathon. Seventy-three percent of those runners said they did not look up a manufacturer’s recommended dosage before trying them, and 68 percent said that they weren’t concerned about caffeine’s effects on them during a race.

The ways some people use caffeine are alarming: 26 respondents said they take in five or more caffeinated items during a marathon; two of them take in eight. Four responders wrote that they use caffeine pills: one carries a 200 mg caffeine pill to chew late in the marathon if needed, another has one 100 mg pill before the race and one at the halfway mark, and a third wrote in that he or she takes two 100 mg Vivarin pills at 16 miles.

Many respondents explained that they’re not sure if their fuel is caffeinated. “Fifty percent of the time, it’ll have caffeine, depending on the flavor I grabbed when packing for that race,” wrote one.

Our survey also found that more than half drink some kind of coffee before the race, with a small coffee being the most popular response (a quarter of respondents). Four participants drank 5-Hour Energy before a marathon; three drank a can of energy drink. (“Rockstar drink before every race, regardless of distance. I only due [sic] this on race day and not before any of my other training runs regardless of intensity of distance. It’s simply a little boost at 6 am.”)

Over half believe that caffeine helps them during a marathon. Two-thirds said they were not concerned about taking in too much caffeine during a marathon.

I can’t really blame them for not being concerned. Many said that the coffee they have during a race is part of their daily non-running routine (and, yes, some version of “going to the bathroom” was cited often). Others have completed multiple training runs and races with no problems, and many reported taking in only two or three 20 mg doses. When I asked how they came up with their caffeine dosing strategies, 59 percent said they made it up as they went along.

When Clif Shots and Gu’s are being handed out by the races, or 5-Hour Energy is giving out free samples during the pre-race expo, or Red Bull is sponsoring worldwide run events, a lot of runners see these products as being okay. If a race gives them to you — like they give you water and sports drink — they can’t be bad, right?

Ninety-two percent of respondents said they’d been offered free fuel items along the course in races, including New York City, Marine Corps, Chicago, Boston, Disney, New Jersey, Flying Pig, Lehigh Valley, Las Vegas, Wineglass, Shamrock, Atlantic City, Providence, Seattle, Twin Cities, Phoenix, Hartford, Fox Valley, Pittsburgh, Tacoma, Baltimore, Vermont City, and Delaware.

And Philadelphia.

Connecting caffeine to heart attack deaths

So why hasn’t this link been made clear? Why aren’t all races following the IMMDA guidelines?

Unless a medical examiner specifically orders a blood test for caffeine toxicity, there’s no way to tell how much of the stuff was in the runner’s system when they died. And, says Maharam of the IMMDA, caffeine won’t usually show up as a cause of death. Things like plaque rupture with coronary thrombosis, hypertrophic cardiomyopathy, and atherosclerotic coronary disease will.

Friends and family can try to piece together whether or not a runner had an energy drink or an extra-large coffee before a race or how many caffeine products they took throughout, but unless someone knew their specific fuel plan, down to the flavors of that fuel, there’s no way to know how much caffeine was in their system at the time of their deaths. And that’s not factoring in any additional free products the runners took in along the racecourse.

There has also been no big survey of how runners use caffeine. As illuminating and alarming as The Magazine’s unscientific survey was, we put out a request for responses only because no similar formal or informal work has been done.

Carrying out such work would most likely mean repeating the kind of study that the New England Journal of Medicine published about cardiac incident rates and including questions about caffeine, or working with races to distribute questionnaires. The latter seems less likely when races are sponsored by caffeine-product manufacturers.

“What we have a problem with in America is that there are coffee sponsors at the start lines, and they’re not going to give them non-caffeinated coffee because this is the coffee sponsor,” said Maharam. “That’s a lot of bucks to the marathon, so they’re not willing to put that recommendation in. In the expo, those 5-Hour Energy drinks and Rockstar and Red Bull take exhibit booths and are handing them out. So this is money. It’s very hard to get [marathons] to push the other way.”

Maharam is fervent on this point, and I contacted race directors at a dozen major events and event companies, including Rock ’n’ Roll, which manages dozens of races. A few declined, didn’t reply, or were unable to provide a response before publication.

But those who did respond are aware of the issue, and some take specific measures to ensure that they aren’t contributing to additional or unusual caffeine intake by providing unfamiliar products or uncontrolled quantities to runners.

Joe Gigas, race director of the New Jersey Marathon and Long Branch Half Marathon, wrote via email, “Some of the energy drink vendors which Dr. Maharam mentioned have been at our expo, and in general their products contain anywhere from 80 mg to 360 mg of caffeine per container. None of these drinks are available for sale at the start line or along the race courses.”

Gigas noted, “We always stress to our athletes not to do/wear/consume anything new/different on race day than they have thoroughly tested during their training program.” He wrote that the race offers coffee for sale at the starting line, but it’s largely consumed by staff and well-wishers.

The director of the Marine Corps Marathon, Rick Nealis, says he turned down Red Bull when the company first asked about handing out samples on the course, and limits Clif Shots (a version containing 25 mg) to a single station. He stresses moderation in all things, noting that a female runner died in his race in 2002 due to hyponatremia — drinking so much water and diluting plasma so thinly that the body can’t function.

Just say no

“Caffeine! Caffeine!”

The ground around the volunteer, and around the half dozen others handing out Clif Shots, wound up a mess, as at any race: spilled water, spilled Gatorade, and spent energy packets. About a third of the runners passing by grabbed something, some calling out for a specific flavor, or for caffeine or caffeine free.

Clif or Gu or Power Bar or Jelly Belly are not attempting to harm runners; there hasn’t to date been a concerted effort to connect all the dots between caffeine and adverse heart events, nor has the IMMDA recommendation been followed up by a large-scale educational effort or outreach to sponsors.

And running is a big business now. Marathons had about 500,000 finishers last year; half marathons had 1.85 million. A good business plan for any of these companies would have their product appealing to these runners, especially when some studies show that caffeine can make you faster.

But that research has been extrapolated too far, in both how these products are marketed and how we, the runners, take them in.

I’m tired of hearing about dead runners. We should start treating caffeine for what it is: a drug that, during exercise, could affect your heart.

“Caffeine! Caffeine!” that volunteer calls. I hope that next time, fewer runners answer.

Listen to a podcast with the author about this article.

Bibliography and sources

For more academic reading on the subject, these are the principal research papers upon which I relied in preparing this article.

Caffeine, the drug

“Caffeine Induces Dopamine and Glutamate Release in the Shell of the Nucleus Accumbens,” The Journal of Neuroscience, August 2002 (download as PDF)

Perks of caffeine, non-exercise studies

“Caffeine prevents age-associated recognition memory decline and changes brain-derived neurotrophic factor and tirosine kinase receptor (TrkB) content in mice,” Neuroscience, June 2008 (download as PDF)

“Coffee may help perk up your blood vessels,”American Heart Association Meeting Report, November 2013

“Coffee Consumption and Risk for Type 2 Diabetes Mellitus,” Annals of Internal Medicine, January 2004 (download as PDF)

“Coffee Reduces Risk for Hepatocellular Carcinoma: An Updated Meta-analysis,” Clinical Gastroenterology and Hepatology, November 2013 (download as PDF)

“Coffee consumption and breast cancer risk among BRCA1 and BRCA2 mutation carriers,” International Journal of Cancer, January 2006

“Association of Coffee and Caffeine Intake With the Risk of Parkinson Disease,” Journal of the American Medical Association, May 2000

Perks of caffeine, exercise studies

“Efficacy of acute caffeine ingestion for short-term high-intensity exercise performance: a systematic review,” Journal of Strength and Conditioning, January 2010

“Caffeine lowers perceptual response and increases power output during high-intensity cycling,” Journal of Sports Sciences, February 2007

“Effect of Caffeine on LT, VT and HRVT,” International Journal of Sports Medicine, July 2012

“Caffeine intake improves intense intermittent exercise performance and reduces muscle interstitial potassium accumulation,” Journal of Applied Physiology, November 2011

“Caffeine has a small effect on 5-km running performance of well-trained and recreational runners,” Journal of Science and Medicine in Sport, April 2008

Caffeine and the heart in exercise

“Cardiac Arrest during Long-Distance Running Races,” New England Journal of Medicine, January 2012 download as PDF

“Transient Myocardial Tissue and Function Changes During a Marathon in Less Fit Marathon Runners,” Canadian Journal of Cardiology, October 2013

“Caffeine decreases exercise-induced myocardial flow reserve,” Journal of the American College of Cardiology, January 2006

“Caffeine Impairs Myocardial Blood Flow Response to Physical Exercise in Patients with Coronary Artery Disease as well as in Age-Matched Controls,” PLoS One, May 2009

“The rationale for pre-race aspirin to protect susceptible runners from sudden cardiac death during marathons: Deconstructing the Pheidippides conundrum,” World Journal of Cardiovascular Diseases, August 2013

“Pheidippides redux: reducing risk for acute cardiac events during marathon running,” American Journal of Medicine, July 2012