DNA and blood testing can say a lot about athletic performance. But are they worth the effort? Credit: Illustrations by Graham Hutchings

For years, pro athletes have had an advantage most amateurs could only dream of: highly personalized diet plans and training regimens based on blood work, genetic analysis, and other high-tech diagnostics. What would it be like if the rest of us had easy access to the same kind of data?

Now you don't have to wonder. More than 40 companies now offer blood and performance testing geared specifically to us mortals. With performance-minded names like FitnessGenes, InsideTracker, and Precision Food Works, these outfits offer the latest iteration of the body-monitoring movement — think of it as a FitBit for your insides. Now serious gym rats, or the merely self-obsessed, can join the ranks of the New England Patriots, Pittsburgh Steelers, and New York Giants, who have tapped such tools to improve health and fitness.

"We use it to dial in diet, watch for overtraining, and get a better understanding of hereditary issues like high cholesterol," says Giants athletic trainer Ronnie Barnes. For the past three years, the team has used Quest Diagnostics' Blueprint for Athletes blood test and, he says, "I've definitely seen this make a difference in individuals' performance."

While a blood test from a routine physical contains much of the same information, there is an important difference between what you get from a doctor and what you get here: Physicians generally use data to look for problems; these services search for opportunities, putting test results into a context of peak performance and nutrition. Christopher Malenab, a semipro soccer coach and marathon runner in Sacramento, says information from a blood test led to dietary changes that helped him shave five minutes from his marathon time. "Blood doesn't lie," says Malenab. "It gives you hard data rather than just 'I feel better.' "

Here's how these tests work: For DNA versions such as FitnessGenes or PathwayFit, customers mail in about a thimbleful of saliva; several weeks later, an online report arrives. Genetic research has shown that among all humans, certain genes are linked to certain athletic and dietary traits. A personalized report tells you which of these genes you possess, and the service uses that information to provide a custom diet and exercise plan. You might learn, for example, that you're genetically predisposed to excel in endurance sports versus powerlifting, or that you have the gene for lactose intolerance and should avoid dairy.

Blood testing is what you would expect: Go to a lab, get blood drawn, and wait a few weeks for your results. But rather than give you a list of numbers for your doctor to decipher, your report will explain what those figures mean for your health and athletic performance. You'll get readings for a number of blood biomarkers — that is, any cell, hormone, nutrient, or other measurable substance. A high white blood cell reading, according to some companies, is a marker of inflammation and may indicate that you're not giving muscles enough time to recover from workouts. Or you might learn that certain foods — bananas, peanut butter, and shellfish, for example — are irritants to your gut that could be the source of your regular fatigue, and you'll be advised to change your diet.

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This kind of information can be a great motivator for change, says Shawn Arent, director of the Rutgers Human Performance Laboratory and a beta tester of Quest Diagnostics' Blueprint for Athletes, which recently became available for consumers. Last fall, Arent had the school's women's soccer team undergo blood tests every month. Over the course of the season, the tests showed when players became iron-deficient and required supplements to remain competitive. After two back-to-back losses, Arent saw an uptick in the players' levels of the stress hormone cortisol. That led him to suggest a rest day rather than up the intensity at practice. But the biggest benefit of testing, he says, was that the players finally began to heed the health advice he'd been doling out for years — sleep more, eat vegetables, take your vitamins. "Put the numbers in front of them, and all of a sudden they changed," Arent says. It's no coincidence, he adds, that the Rutgers team made the Final Four last season, without a single injured player.


Connor Barwin, outside linebacker for the Philadelphia Eagles and a 2014 Pro Bowler, also got a wake-up call when he took an InsideTracker blood test at the end of the 2014 season. His results came back in the healthy ranges — except for low testosterone. The test suggested he eat more red meat and nuts and get more sleep, changes that Barwin had intended to make but kept putting off. He switched habits, and two follow-up tests showed that his hormone levels were in the normal ranges. "It's another tool in the toolbox," Barwin says. "And in this league, small changes can make a big difference."

I consider myself fairly fit, and I exercise regularly. But I am no pro-football player. Could such testing, I wondered, make a difference for me?

First, I took a DNA test from FitnessGenes. I sent them my saliva sample and received an online report three weeks later. It listed 18 genetic markers linked to various athletic and dietary traits. Before digging in, I read a quick genetics primer on the company's website. I learned that FitnessGenes measures alleles, or forms of genes. Humans have two alleles for every genetic marker, one from each parent. Depending on the combination of those two alleles, you're more likely to possess certain genetic traits. It turned out that I had the combo of alleles that FitnessGenes associates with speed and the same gene found in elite sprinters. The report suggested interval training to make the most of that genetic predisposition. This struck me as weird — I'd never considered myself fast.

Reading on, I learned that I have just one copy of the allele linked to muscle growth from power training, or low reps of heavy weights. In other words, I need more reps to see the same gains as someone with two copies of that allele. To compensate, the site recommended I train with a high-rep scheme — 15 reps per set — at moderate weights. A few years ago, I had been doing just that, training with the P90X program and making steady gains, but then moved on to other methods. I suddenly remembered how quickly I progressed when I was doing P90X and made a note to start doing similarly intense, high-rep sets again.

Next, I sampled Quest's Blueprint for Athletes. My report detailed the levels of more than 40 blood biomarkers: cholesterol and white blood cell count; levels of nutrients such as vitamin D and iron; and, key for athletes, markers for metabolic waste and inflammation, which indicate whether one spends too much time training and not enough recovering. The report compared my numbers with the range found in the general healthy population, and it explained how diet, exercise, and stress may have contributed to my results.

While the test would have been useful, even crucial, if my muscles had been chronically inflamed or I had an unknown allergy, my results were fairly boring. The report confirmed that my levels of nutrients and blood cells were normal and that I had no sign of high inflammation. But my test did tell me that I was highly deficient in vitamin D — not uncommon for a guy living in the Northeast in the winter. But that vitamin is essential for muscle synthesis, and according to Quest's report, I needed more of it to build strength. Seeing this result in writing immediately made me want to buy supplements to correct my numbers.

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Such testing is not without controversy. Last fall, a group of geneticists advised consumers to be skeptical of DNA tests. "Genetic tests have no role to play in talent identification or the individualized prescription of training to maximize performance," they wrote in the British Journal of  Sports Medicine.

"There is a lot of hype but no substance," Claude Bouchard, a geneticist at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, and one of the report's authors, stated in an email. The problem: Some correlations between genes and specific traits have been observed consistently over the course of many trials, while other findings are preliminary and tenuous. The gene tied to lactose tolerance, for example, is not perfectly predictive. Plenty of people who have the gene can't stomach milk, and vice versa. Similarly, many blood markers have only recently been used to track athleticism rather than the presence of disease. Scientists know, for instance, that athletes need inflammation for muscle growth, but they don't know how much is optimal.

Daniel Reardon, CEO of FitnessGenes, readily agrees that we're in the early days of genetic research, which limits the ability to deliver highly individualized prescriptions. But, he adds, the tests can provide a compelling portrait of a subject's general health. "We're giving people big-picture information about how often they should train and eat based on peer-reviewed evidence," he says.

What's more, when it comes to technology, things have a way of moving a lot faster than expected. Ten years ago, no one imagined that millions of Americans would now go through life with activity monitors strapped to their wrists, or with apps tracking REM sleep cycles. It's not hard to envision that in maybe five years, training and eating according to the information contained in our genes and blood will be just as common.