How Blood Doping Poses Dangers to Amateur Cyclists

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Professional cycling is no stranger to performance enhancing drugs and, it turns out, amateur cyclists are following the pro lead. The New York Times noted a rise in blood doping with erythropoietin (EPO) among amateur cyclists in 2012 after two racers tested positive at that year's Gran Fondo in New York, and there's evidence that the practice has not abated. Why? Testing for blood doping is expensive, and historically many amateur races, offering little or no prize money for the winner, have foregone it. But blood doping doesn't just ruin the race for everyone who is trying to have a little weekend competition; it's sincerely dangerous — and moreso for amateurs who are not surrounded by race doctors. Here's a look at what EPO can do to the body. 

1. It Can Stop the Heart in Your Sleep
EPO is a naturally occurring hormone that stimulates bone marrow to up your red blood cell count, according to the World Anti-Doping Agency. Simply put, more red blood cells means more oxygen traveling to muscles. Pro athletes may be able to dose themselves precisely, with small amounts every day, but if you take too much EPO you end up with too many red blood cells, which actually thicken the blood and slow it down in your veins, says Stefan E. Franz, a nephrologist at Klinik Am Eichert in Göppingen, Germany.

Highly trained athletes have lower resting heart rates than average, sometimes as low as 20 beats per minute, which decreases even more during sleep. Add EPO to the mix, and your heart may slow down enough to kill you. 

2. It Can Cause Blood Clots, Heart Attacks, and Strokes
The same blood-thickening effect also increases the risk for blood clots, stroke and heart attack. "The most dangerous side effect relates to an increased risk of a thromboembolic event (clot)," says Amit Momaya a surgeon at the University of Alabama at Birmingham. The cellular components of the blood, or "hematocrit," usually make up about 40 percent of blood volume when centrifuged. As red blood cells accrue, hematocrit goes up as well and along with it, the risk of blood clots and heart attacks. 

That risk increases even more during a race. "If you race and sweat a lot then the blood volume goes down, and relative hematocrit goes up," says Stefan Franz. It only takes a few weeks of dosing with larger amounts of EPO for these risks to emerge.

3. It Increases Blood Pressure
In 2014, researchers in The Netherlands noted that four recent trials of kidney transplant patients receiving high doses of EPO after surgery found an increased risk of blood clots. "EPO is known to induce hypertension, so if you are a more mature male you might already have hypertension and taking EPO could have long-term risks," says Franz.

4. It Halts the Body's Ability to Fight Cancer
As a growth hormone, EPO also has antiapoptotic effects, meaning that it slows down the body's natural system of killing and removing damaged cells. "It doesn't cause cancer, but it might prevent the body from killing cancer cells, or it might aggravate growth of cancer cells," says Franz.  Some long-term studies of kidney patients have found an increased incidence of cancer for those treated with EPO, and experts hypothesize that the hormone may stimulate tumor growth. 

5. It Often Isn't Even EPO
Some doctors in the U.S. advertise their sports-performance enhancing services, and these corrupt practitioners could supply cyclists with pharmaceutical-grade EPO. But more likely, amateurs are simply ordering the drugs online, and there's no guarantee of what will arrive in the package.

Sometimes the substances don't contain any active ingredients and are mostly water, other times there is an active drug but in wildly varying doses, and very often the products are contaminated with bacteria or chemical byproducts, posing myriad unknown health risks. "You can never be sure what you actually get, and you can also get anaphylactic shock from contamination," , says Franz.

6. It Comes with Massive Unknown Risks
Other than using anecdotal evidence from the spates of cyclists who have died under mysterious circumstances, it is actually quite difficult to study the potential consequences of a healthy athlete taking EPO. All the clinical studies have centered on people with kidney problems or other chronic conditions, for whom the drug is actually indicated, Franz says.

"As you can imagine all the bountiful clinical studies are not done long term in healthy subjects," he says. Many cyclists also take testosterone medications, and this in combination with EPO has never been studied, he says.