Reaching Down Deep

January 29, 2015
A growing field that helps people optimize their diets based on their unique DNA, nutrigenetics is making its way into athletics.
By Lauren Cahoon Roberts

Lauren Cahoon Roberts is a freelance writer based in Ithaca, N.Y., who has covered issues in health and wellness for a broad range of publications. She can be reached at: cahoon.lauren@gmail.com.


As a triathlete who routinely competes in Ironman competitions, Addison Huddy is always looking for an edge. For most endurance athletes, that edge comes from tried and true methods such as rigorous training, healthy eating, and sufficient, high-quality sleep. But to get the most out of those tactics, Huddy underwent a personalized analysis of his DNA to better understand his nutritional needs and optimize his diet accordingly.

Along with a small but growing number of athletes around the world, Huddy now knows which vitamins and nutrients will maximize his performance. Access to this information is being made possible by a relatively new and still developing scientific discipline called nutrigenetics, which is only just gaining visibility among athletic professionals.

Nutrigenetics examines how an individual's unique genetic code affects their response to different nutrients. With this information, an athlete can take a more personalized approach to nutrition and eating for performance. Instead of athletes trying to optimize their diets through trial and error, a quick cheek swab and corresponding lab test can yield more accurate information on the nutrients most likely to help them be at their best.

While the technology is available to anyone who can pay the fee, which ranges from $65 to $500, depending on the company and service, it's relatively untested. Nevertheless, for Huddy, having his genes tested was a no-brainer. "I'm a big believer that knowledge is power," he says. "I think it's pretty amazing where genetics is going to take us."

THE SCIENCE
At the center of nutrigenetics are nucleotides, which form the basic building blocks of DNA and play a key role in metabolism. Every human being has variations in their genes known as polymorphisms, which can comprise long sequences of DNA or just one nucleotide variation within a link of the DNA chain. While long-chain polymorphisms can affect a body's ability to process nutrients, single-nucleotide polymorphisms (SNPs) are by far the most common.

SNPs are variations in a person's DNA sequence that are passed down through one's parents. They originated at some point during human evolution when minor copying "errors" were made by nature as DNA was replicated during reproduction and growth. They occur about once every 1,500 nucleotides and the pattern of different SNPs is unique to each individual. Considering the huge number of nucleotides in the body, this means unrelated people are genetically distinct by approximately two to three million SNPs.

When it comes to nutrition, SNPs are important because they can change the production and function of proteins in the body. These proteins interact with nutrients such as vitamins in a variety of ways, and they play a vital role in how the body responds to different foods. For example, some proteins bind to vitamins and help them get absorbed by cells. Others convert them into useful biological building blocks. A third type of protein will degrade vitamins and cause them to be expelled from the body. Changes to any of these proteins can impact how well certain foods are metabolized. That means two individuals can respond differently to any number of foods, depending on their genetic makeup.

A number of SNPs have proven connections to certain nutrients. These SNPs have been identified as useful markers around which diet and supplement regimens can be designed.

CAFFEINE BREAKTHROUGH
Caffeine, most notably in the form of coffee, presents a clear example of how genes can dramatically affect a person's response to certain foods. "After decades of being perplexed about why there are extreme differences in how caffeine affects people, scientists looked at users' genotypes, and that helped solve the mystery," says Nanci Guest, MS, RD, CSCS, a dietitian and personal trainer who collaborates with the nutrigenetics company, Nutrigenomix.

A single gene known as CYP1A2 is most influential in the metabolization of coffee. CYP1A2 has two variations--one causes the body to metabolize caffeine quickly, while the other is responsible for slower metabolization. Knowing which variation they have can be vital to athletes who utilize caffeine as a performance enhancer.

For athletes who metabolize caffeine more slowly, consuming a large amount just prior to competition may not have the desired effect. In addition, since the stimulant remains in their system for a longer period of time, it may increase their risk of negative side effects such as high blood pressure and heart attack.

These athletes have to be cautious in their approach to caffeine supplementation. "We think slow metabolizers should take less caffeine, and they should do it well before their competition," says Stuart Kim, PhD, Professor of Developmental Biology and Genetics at Stanford University and founder of the Stanford Sports Genetics program, which provides nutrigenetic and other types of gene tests to athletes. "Since their enzymes access caffeine in the bloodstream in a delayed fashion, if they take it too close to their event, they could overshoot and the beneficial effects of the substance won't kick in until long after they're needed.

"On the other hand, those who metabolize caffeine faster should generally take it closer to the beginning of their event, as well as during the event if necessary," he continues. "Otherwise, they may lose its benefits before the competition's over."

After getting his DNA tested at the Stanford Sports Genetics lab and discovering he was a fast caffeine metabolizer, Huddy changed his intake approach. "Instead of only doing one big burst of caffeine, I spread it out over the course of the day to sustain the benefits," he says. "That was a big element they discussed with me in my genetic counseling at Stanford."

According to Kim, the bottom line is that if an athlete knows their own particular caffeine metabolism, they can better time their intake to improve performance. "It could give you a leg up," he says.

OTHER GENETIC CLUES
Beyond caffeine, there are a number of performance-enhancing nutrients that are thought to affect individual athletes differently depending on their genes. In its testing program, the Stanford Sports Genetics Program looks at a span of 150 different polymorphisms. For example, results have shown that certain athletes have genetic predispositions to vitamin D, calcium, and iron deficiencies, among others.

"We've found a large number of genetic variations in people's vitamin and nutrient absorption," says Kim. "Athletes can use the test results to address deficiencies and make sure they're at their peak."

Vitamin C is a well-known antioxidant and another nutrient that can be spotlighted by genetic testing. According to Guest, because every athlete has a unique genetic makeup, vitamin C should not be supplemented in a one-size-fits-all manner. "If you take too much, it can inhibit your body's adaptation to training," she says. "But if you have too little, you can be at risk of impairing your body's ability to repair muscles and repair oxidative damage."

How much is enough again depends on an athlete's genetic code. Nutrigenomix has a test for the GSTT1 gene, which affects a person's efficiency in utilizing vitamin C. Similar genetic tests exist for other nutrients and these includes folate (MTHFR gene), which assists in red blood cell formation, tissue repair, and amino acid metabolism, and omega-3 fatty acids (NOS3 gene).

Additionally, Nutrigenomix has a test for the ACE genotype, which, according to the company, indicates if someone is at risk for salt-sensitive hypertension. Since sodium is an electrolyte, this test can be particularly important in preventing athletes with the ACE genotype from aggravating the condition by replacing their electrolytes after workouts via high-sodium foods.

Other genetic testing can examine an individual's susceptibility to certain health problems based on their diet. Tests for the APOA2 gene variant can tell if someone is more or less at risk for heart disease, type 2 diabetes, or obesity if they eat a diet high in saturated fats.

Another gene variant is TCF7L, which is linked to an individual's susceptibility to type 2 diabetes when exposed to a traditional Western diet high in red, processed meat, and low in fiber. This variation may explain the fact that some individuals are seemingly able to eat whatever they want and still maintain a low glycemic load, while others see a spike in their glycemic load in response to processed foods. According to Guest, athletes could be tested for the TCF7L variants to determine if they would benefit from a whole grain, low glycemic index diet.

SUCCESS STORIES
Along with providing athletes with a breakdown of their needs, nutrigenetics can serve as a motivator for many athletes who may not always adhere to healthy diet and exercise plans. "When I talk to the athletes, I find they aren't always complying with their regimens--sometimes skipping vitamins or certain weight-training exercises--so their efforts are often below the optimal level," says Kim. "A personal nutrigenetic report could dramatically change an athlete's attitude and compliance."

Stephen Bauer can confirm this. As an ex-triathlete, current sports performance coach for football, wrestling, and track and field, and an exercise physiologist for the Stanford program, he got his own DNA tested and found that he's susceptible to both vitamin D and iron deficiencies. This knowledge has changed his attitude towards these nutrients.

"Despite being at the level where you should be very cognizant of your nutrition, it's easy to lapse," says Bauer. "With this information, though, I'm more diligent in maintaining my nutrient levels."

According to Paul Chamberlain, founder of Beyond Nutrition, a sports and nutrition counseling firm based in the United Kingdom, his clients have also benefitted from the testing. One of these was a cyclist looking to lose weight in order to improve his speed. "He wanted to be sure that if we put him on a low-carb, protein-rich diet, it would work for him," says Chamberlain. "And the test bore out that if he did eat a lot of carbs, he would store them around his belly, which would make it difficult for him to lose the weight. That was my inclination already, but it was nice to have it confirmed by the test data."

PROCEED WITH CAUTION
While the fundamental science behind SNPs is sound and a growing number of athletes claim the testing has benefitted them, nutrigenetics has yet to receive widespread recognition as an effective tool for improving athletic performance. Shawn Arent, PhD, CSCS, FACSM, an Associate Professor in the Department of Exercise Science and Sport Studies at Rutgers University, is familiar with nutrigenetic testing, but cautious about acknowledging its role in improving athletic performance. "[Nutrigenetic testing is] in its infancy right now," he says. "I'd be hesitant to recommend it to athletes at this point."

Arent explains that, as it stands now, nutrigenetic testing is more proven in the arena of basic health maintenance and improvement. "In terms of health, it's easily the next frontier," he says. "In the areas of cardiovascular disease and obesity, I don't dispute that we now have more knowledge [from nutrigenetics] about these problems. How does that information translate to athletic performance? That's less clear."

In addition, the findings of nutrigenetic testing aren't always revelatory, says Kendra Sticka, MS, MEd, RD, LD, an Assistant Professor of Dietetics and Nutrition at the University of Alaska Anchorage. She cites the MTHFR gene variant, which influences a person's folate requirements, as a prime example.

"There's a very clear SNP there," she says. "People with the MTHFR variant need a higher level of folic acid to have certain metabolic pathways function correctly. But it's common knowledge that if you take the recommended amount of folate, you should be fine. It's nice to know about your genetic predispositions, but do you need that much information to make a commonsense decision?

"Right now, the testing leads us back to what we already know," Sticka continues. "The results don't change our recommendations. If we discover that a person would be particularly responsive to exercise, that's good to know, but we're not telling anyone not to exercise."

Nutrigenetic testing also raises some ethical concerns for Arent. "Who's delivering the results?" he says. "If an athlete gets this genetic information, who's explaining it? Is it someone selling the promise of the science, but without the genetic background to explain it?"

Despite Arent's concern, most nutrigenetics testing facilities ensure that trained physicians, scientists, and dietitians are the only ones allowed to analyze a person's nutrigenetics test data. Some companies have tried to sell test results directly to consumers, but were stopped by the FDA.

Another area is how genetic test results are used and who sees them. This issue is a high concern for Kim, who would like to ensure that his services empower but not hinder athletes in professional sports organizations.

"By getting in on the ground floor in sport genetics, we can help make sure we empower athletes with a new edge and not hinder their careers," he says. "We don't want some quarterback being cut because something in his DNA was red-flagged."

Thus, Kim prefers to have individual athletes contact his program themselves and make their own choices around the test results. "We have a lawyer and two bioethicists working on this project because we don't want to cause discrimination," he says. "We're really setting policy on how this plays out."

IN THE FUTURE
Despite some setbacks, the field of nutrigenetics doesn't look like it will be going away any time soon. As companies continue to spring up and the testing is adopted by more users, the cost of the services is likely to go down. "In the next five years, every athlete is going to be genotyped to see what nutrients they need to perform optimally," says Guest. "It's a field that's just exploding."

Rikki Keen, MS, RD, CSSD, CSCS, a sports and clinical dietitian at Alaska Regional Hospital in Anchorage, believes it's important for sports dietitians, athletic trainers, and strength coaches to educate themselves on the benefits of nutrigenetics. "It's coming, and we need to be proactive about researching it so we can get on board when it arrives," she says.

However, Keen doesn't believe the testing will provide all the answers to athletes' dietary questions. "I don't think it will be the only tool that's used, but I do think it will be valuable when combined with other tests," she says. "For example, I'd like to compare the results to what I know from the metabolic testing and see how that's going to correlate."

Keen's employer has decided to incorporate nutrigenetic testing into its suite of patient services. The hospital is training physicians and other medical staffers to read the results of the tests Keen and her colleagues are preparing to conduct. The hospital also plans to compare the results to other information they typically gather from athletes.

"It's going to be interesting to link the patients' genetic profile to our results," says Keen. "The same goes for nutrition. I'm hoping the genetic testing can explain some of the differences we see between individuals."

Guest believes nutrigenetics will undoubtedly benefit elite athletes. "Athletes on professional, world, or Olympic teams want to have that competitive edge," she says. "As sports dietitians, we need as many tools in our toolbox as possible. If [nutrigenetic testing] can give an athlete a slight edge, that could be the difference between getting a gold medal or not."

With all that it promises in the future, athletes who have undergone the testing see it as a long-term investment. Huddy says he gets e-mails every couple of months from the Stanford researchers alerting him of newly identified genetic markers that may shed more light on his personal DNA. "Who knows what they'll find next," he says. "And the more knowledge I have about myself, the more confident I'm going to be as an athlete."


SIDEBAR:TEST TIME
In addition to the Stanford Sports Genetics program, Beyond Nutrition, and Nutrigenomix, there are a few other companies around the world that offer nutrigenetic testing, with a range of services and prices. These include Pathway Genomics in San Diego, Calif., and DNAlysis in Illovo, South Africa.

For those who want to pursue the testing, these companies offer a range of services and prices. The Stanford program asks for a $299 donation in exchange for a DNA genotype analysis that looks for variants associated with certain vitamin and mineral levels, caffeine metabolism, and iron levels. Nutrigenomix offers similar testing for $250, plus $100 for the requisite dietitian consult.

Beyond Nutrition offers a range of tests, including a vitamin D status test for about $65, a test to measure the efficiency of the stomach and small intestine for around $320, and a more comprehensive test which examines amino acids, vitamins, minerals, antioxidants, organic acids, and oxidative stress for roughly $500.

Pathway Genomics will analyze 75 genetic markers in your body known to impact metabolism, energy, and exercise, for about $300. For around $135, DNAlysis will test 20 genes involved in seven key biological processes related to the absorption of nutrients.
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