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    Microbes, Bones, and Heat

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    Do you know that the bacteria in your gut can enhance athletic performance? Or that the sports you play when you are a kid impact your bone health as an adult?  Or that your ability to row in the heat depends on how well you hydrate? In April, at the sports nutrition conference hosted by the sports-nutrition practice group of the Academy of Nutrition and Dietetics, the speakers offered updates on these topics of interest: 

    Performance-enhancing probiotics: A new frontier?

    Elite rowers have endurance, strength, strong minds, and the ability to recover from injuries. Could these positive traits be connected to the kinds of microbes in their guts (their microbiome)? Are the gut-brain and the gut-muscle connections in elite rowers comparable to those of non-rowers? Could specific gut microbes help non-elite rowers perform better?

    To discover the impact of the microbiome on exercise performance, FitBiomics, a biotechnology company, is studying the microbiome of top athletes, looking for performance-enhancing microbes. For example, marathon runners (compared to non-runners) have a higher amount of the bacteria Veillonella that efficiently eats lactic acid and reduces inflammation. Mice fed Veillonella improved 13 percent in endurance running. What if marathoners consumed Veillonella supplements? Would that help them run longer? Faster? More research is needed, but the information to date seems promising. Stay tuned.

    Parents: Bone up on bone health for your kids

    Given that up to 90 percent of peak bone mass is reached by age 18 in females and age 20 in males, parents should encourage their kids to participate in bone-building sports. This means weight-bearing sports–such as soccer–during early puberty. High-impact sports such as gymnastics and volleyball also contribute to bones by increasing bone mass by about 10 percent.

    Multi-directional sports (i.e., soccer) are better for bone health than one-directional sports (running). The jumping, cutting, and stopping that happen during soccer and basketball, for example, lead to stronger, more fracture-resistant bones. Track-and-field athletes who had participated in ball sports (such as soccer, volleyball, etc.) when they were younger had 50 percent fewer stress fractures than peers who hadn’t. Same goes for male runners who had played basketball; they had 82 percent fewer stress fractures. Military recruits who had played soccer and basketball when they were kids experienced fewer stress fractures during basic training. The moral: Parents should guide their kids carefully into sports that optimize bone health.

    Weight-conscious athletes such as rowers can impair their bone mass when they restrict calories to lose weight. A smart nutrition recommendation for dieting rowers is to consume foods naturally rich in calcium, i.e., drink more dairy milk or yogurt. Each cup of skim milk reduced risk for future stress fractures in by 62 percent when consumed by young female athletes. Athletes at risk of stress fractures should consume at least 1,500 milligrams of calcium per day plus 800 IUs of vitamin D. Female military recruits who took calcium and D supplements for eight weeks had 20 percent fewer stress fractures compared to un-supplemented peers. Adequate sleep also enhances bone health. How many high-school and college athletes do you know who actually get enough sleep?

    Exercising safely in hot weather   

    With global warming, rowers are more likely to be training and competing in unusually hot weather. To reduce the risk of exertional heat stroke (and death), rowers should allow 10 to 14 days to acclimatize to exercising in hot weather. During acclimatization, your body adapts to dissipate more heat, thereby enabling you to exercise better in hot conditions. Most physiological adaptations occur between days four and eight of heat exposure.

    During the first week of being exposed to heat, you should train only once per day; no double workouts. Ideally, you will have access during training to cool fluids, which are more likely to be consumed, and you will take small swigs of fluid frequently throughout a rowing session, as opposed to gulping fluid all at once. (Easier said than done for rowers.)

    When exercising in the heat, monitor your urine for color and quantity, and think WUT:

    Weight: Is my morning weight lower than the day before?

    Urine: Is my urine dark and concentrated? 

    Thirst: Am I thirsty upon awakening?

    Yes answers signal you are beginning the day under- hydrated.

    In terms of health risks, being adequately hydrated is more important than being heat-acclimatized (though being well-hydrated and heat-acclimatized is ideal for maximizing thermo-regulation). An adaptation to heat acclimatization is reduced sodium in sweat. Despite that adaptation, endurance athletes who do extended exercise in the heat often fail to replace adequate sodium. Salty sweaters (who have gritty sodium crystals on their skin) should purposefully consume sodium-rich foods and fluids.

    Some rowers salt-load for a day or two before an event, but researchers advise against that. The kidneys do a good job of excreting excess sodium via urine. The additional urine loss can be counterproductive, hurting, not enhancing, performance.

    Rowers should try to replace 70 percent to 80 percent of sodium and fluid lost during sweaty exercise. Knowing your sweat rate (by comparing pre- and post-exercise body weight) can reduce your risk of over- or under-hydrating. Drinking too much water is dangerous, because it dilutes the body’s sodium level and can lead to life-threatening hyponatremia (low sodium).

    Of all electrolytes, sodium is the biggest concern. Endurance rowers need to figure out how to replace sodium losses. Through trial and error, you can learn which salty foods taste good, settle well, and work for you. Pickle juice, bouillon cubes, mustard on soft pretzels, soy sauce on rice, and beef jerky are popular options that can be consumed both right before and/or after long rows.

    The bottom line

    Eating fiber-rich fruits, veggies, and whole grains will fuel your muscles, feed your microbiome, and impact your ability to perform at your best. Diary milk and yogurt, rich in natural calcium, will help keep bones strong. A sprinkling of salt can help retain water in your body. Fuel wisely, be responsible and bone up on good nutrition! 

    Sports nutritionist Nancy Clark, M.S., R.D., counsels both casual and competitive athletes in the Boston area (Newton: 617-795-1875). The sixth edition of her Sports Nutrition Guidebook offers abundant food tips on how to eat to win. For more information, visit

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