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What Should I Eat?

BY NANCY CLARK
PHOTO BY ED MORAN

Wouldn’t it be nice if rowers could get a genetic test that tells them precisely what they should eat to enhance their performance? Of course, the answer is yes. Personalized (or precision) nutrition currently is a growing area of interest to all athletes. Yet the field is in its infancy. To date, precision nutrition is not precise enough to tell rowers what they could eat to  perform better. Plus, many factors impact performance and health, including sleep and dietary patterns. Regardless, athletes are buying expensive genetic-testing kits.

Speaking at the Academy of Nutrition and Dietetics annual conference in October, exercise physiologist David Nieman, director of the Human Performance Laboratory of Appalachian State University, said we can’t advise what to eat based on genetic testing because the results are too variable. More research is needed before athletes can get valid personalized nutrition recommendations.

Without question, exercise scientists are getting better at analyzing genetics and the metabolites (the end products of exercise metabolism) of individual athletes. This has the potential to improve our understanding of how genes, diet, and exercise interact. But the variety of response among athletes leaves big gaps in our current knowledge.

Case in point: genes related to caffeine metabolism. Consuming three to 13 milligrams of caffeine per kilogram of body weight reportedly improves athletic performance. But why do only some rowers perform better with caffeine? Is the difference due to genetics? Genetic tests can identify which rowers can metabolize caffeine quickly or slowly, but the data show no patterns that reliably link caffeine-metabolizing genes to enhanced athletic performance, Nieman said.

Genetics and inflammation 

Here are some examples of how personalized nutrition could help athletes, including rowers. We know that inflammation creates recovery problems for athletes. What if rowers with high inflammation could get a genetic test to determine if their exercise-induced inflammation or soreness was related to their genes? Could they then be advised to participate in, let’s say, gentle sculling instead of intense rowing? (And would they even do that?)

At the Western States 100-Mile Endurance Run, Nieman measured inflammation in 154 ultra-runners. The amount of inflammation varied widely. Some runners had very high levels of cytokines and others very little. Was this due to genetics?  Genetic testing couldn’t explain the differences.

We do know that exercising “on empty” creates inflammation. Nieman reported that athletes who exercise first thing in the morning before eating experience an immediate spike in inflammatory cytokines. Regardless of their genetics, rowers can reduce this inflammatory response by about 40 percent just by consuming carbs before and during extended exercise. 

Does the kind of carbohydrate eaten make a difference? Would consuming a banana or blueberries be less inflammatory than chugging a sugary sport drink? Here’s what research tells us about the impact of carbohydrates before and during exercise:

  • Cells function best when they are fed. Both sugar from a sport drink and sugar from a banana or blueberries can help cells function optimally and curb a negative stress response.
  • Polyphenol-rich fruit/fruit juice (such as blueberries, blueberry juice) curb the inflammatory response more than fruit low in polyphenols, such as a banana. 
  • The best dose of polyphenols from fruit is yet unknown.

Nieman’s initial research looked at the polyphenol quercetin (found in apples). He learned that very high doses of quercetin were not helpful. After testing polyphenols in amounts that athletes could consume easily, he saw better results. 

For example, when athletes ate one cup of blueberries a day for two weeks before a 75-mile hard-cycling test, the inflammatory response was much lower overall. That said, the response varied as much as 14-fold among the blueberry eaters. Eight cyclists experienced high inflammation, 13 had a moderate amount, and 10 had much less inflammation. Could genetic testing help identify the athletes who responded with high inflammation? If yes, could sport dietitians encourage those athletes to eat extra blueberries to get a stronger anti-inflammatory response? We don’t know yet. 

  • Similarly, among runners in the Western States 100-Mile Endurance Run, those who experienced a lot of muscle damage had a gene that limited their bodies’ use of choline, a nutrient that helps repair cell membranes. Could genetic testing help identify those runners so they could eat more choline-rich foods, such as eggs and liver? Would that help them decrease their post-exercise muscle damage, soreness, and inflammation? Stay tuned.

A multi-factorial view

We don’t yet know if inflammation is related primarily to genetics, diet, or some other factor, like the microbiome. (Microbiome refers to the billions of bugs that live in your gut and have a strong influence on your immune system.)  Neiman suspects that athletes with a robust, microbiome generate less inflammation when exercising compared to athletes with a weaker microbiome. How much does genetics influence the microbiome? 

We do know that rowers who eat a polyphenol-rich diet (fruits, veggies) do a good job of feeding their gut microbes. They tend to have a more vibrant microbiome than those who eat a diet filled with ultra-processed foods. Does diet reduce inflammation more than genes? We have so much to learn.

The bottom line: 
Rowers vary widely in their metabolic responses to hard exercise and to the ways that food influences that response. While we do not yet know what triggers the variance (genetics? diet? the microbiome?), we do know that diet can reduce inflammation, soreness, and muscle damage. By regularly consuming colorful fruits (berries, cherries, apples, etc.) and veggies (spinach, carrots, tomatoes, etc.), you’ll get more bang for your buck than spending that money on a genetic-testing kit that likely produces questionable nutrition recommendations. Be patient. The future of sports nutrition is just around the corner.

Sports nutritionist Nancy Clark, M.S., R.D., counsels both casual and competitive athletes in Newton. Mass. Her best-selling Sports Nutrition Guidebook is a popular resource, as is her online workshop. For more information, visit www.NancyClarkRD.com or call 617-795-1875.

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