The Athlete's Kitchen: Sports Nutrition: Carbs in the News

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The Athlete's Kitchen: Sports Nutrition: Carbs in the News

Written by Nancy Clark, MS RD CSSD on 25 August 2019.


Too many of today's runners believe carbohydrates are "bad." If that's true, what does the latest sports nutrition research say? The following studies, presented at the American College of Sports Medicine's 66th Annual Meeting (Orlando FL, May 2019) indicate sports scientists agree that carbohydrates (grains, fruits, veggies; sugars, starches) can be health- and performance-enhancing sport foods. As you may (or may not) know, ACSM is a professional organization for sport science researchers, exercise physiologists, dietitians, doctors, and health-care providers for athletes (www.ACSM.org).  Here are some answers to questions posed by ACSM researchers.

 • Does sugar cause Type 2 diabetes? 

No. Type 2 diabetes is less about eating sugar, and more about lack of exercise. Most runners can enjoy a little sugar without fear of health issues. Muscles in fit bodies burn sugar for fuel. In unfit bodies, sugar accumulates in the blood. Fitness reduces the risk of developing Type 2 diabetes (T2 Db). 

     In a 6-week training study to boost fitness, 35 middle-aged men with over-weight or obesity who were at risk for developing T2 Db performed either endurance cycling, weight lifting, or high intensity interval training. Regardless of type of exercise, all types of training improved the bodies' ability to utilize glucose with less insulin. 

     These subjects had blood glucose levels within the normal range at the start of the study; their glucose levels improved with exercise. While we need more research to fine-tune the kinds of exercise that best manage blood glucose, rest assured that living an active lifestyle is a promising way to reduce your risk of Type 2 diabetes. 

 • Can natural foods replace ultra-processed commercial sport drinks and foods? 

Yes, standard (natural) foods can be fine alternatives to commercial sport fuels. Look no farther than bananas! In a study, athletes who enjoyed bananas (for carbs) plus water (for fluid) during a 46 mile (75 km) bike ride performed just as well as those who consumed a sport drink with an equivalent amount of carbs plus water. 

     Natural foods offer far more than just fuel; they contain abundant bioactive compounds that have a positive impact on health and performance.  For example, after the ride with bananas, the cyclists had lower levels of oxylipins (bioactive compounds that increase with excessive inflammation) compared to the sport drink ride. Athletes who believe commercial sports foods and fuel are better than standard foods overlook the benefits from the plethora of bioactive compounds found in real foods. While cyclists, as compared to runners, might have an easier time consuming bananas during exercise, enjoying a pre-run banana would get those bioactive compounds into your body.

 • Are potatoes—an easy-to-digest sports fuel—a viable alternative to commercial gels? 

Yes. In a study, athletes ate breakfast and soon thereafter competed in a 2-hour cycling challenge that was then followed by a time trial. For fuel, the subjects consumed either potato puree, gels, or water. The results suggest 1) both potato and gel empty similarly from the gut, and 2) potatoes are as good as gels for supporting endurance performance. 

     The subjects completed the time trial in about 33 minutes when they ate the potato or the gel. This is six minutes faster than with plain water. (Any fuel is better than no fuel!) For runners, gels might be more convenient, but snacking on a salted boiled potato during a long run could be a welcomed flavor-change from sugary carbs.

 • Is fruit juice a healthful choice for athletes? 

Yes, fruit juice can be an excellent source of carbohydrate to fuel muscles. Colorful juices (such as grape, cherry, blueberry, orange) also offer anti-inflammatory phytochemicals called polyphenols. In a study, subjects did muscle-damaging exercise and then consumed a post-exercise and a pre-bedtime protein recovery drink that included either pomegranate juice, tart cherry juice, or just sugar. The protein-polyphenol beverages boosted muscle recovery better than the sugar beverage. 

 • Does carbohydrate intake trigger intestinal distress for ultra-marathoners? 

Not always. During a 37 mile (60-kilometer) ultra-marathon, 33 runners reported their food and fluid intake. They consumed between 150 to 360 calories (37-90 g carb) per hour, with an average of 240 calories (60 g) per hour. This meets the recommendation for carbohydrate intake during extended exercise (240-360 calories; 60-90 g carb/hour). The majority (73%) of runners reported some type of gut issues. Of those, 20% of the complaints were ranked serious. 

     Interestingly, the GI complaints were not linked to carbohydrate intake or to gut damage. In fact, a higher carbohydrate intake potentially reduced the risk of gut injury. (More research is needed to confirm this.) Unfortunately, runners cannot avoid all factors (such as jostling, dehydration, and nerves) that can trigger intestinal problems.

 • We know that consuming carb during extended exercise enhances performance, but does it matter if marathoners consume a slow-digesting or a fast-digesting carbohydrate prior to a long run?

Likely not, but this can depend on how long you are exercising, and how often you want to consume carbohydrate. Well-trained runners consumed 200 calories of carbohydrate in UCAN (slow-digesting) vs. Cytocarb (fast-digesting) prior to a 3-hour moderately-hard run during which they consumed just water. At the end of the run, they did an intense sprint to fatigue. The sprint times were similar, regardless of the type of pre-run fuel. 

   That said, the slow digesting carb provided a more stable and consistent fuel source that maintained blood glucose concentration during the long run. Hence, endurance athletes want to experiment with a variety of beverages to determine which ones settle best and help them feel good during long runs. A slow-digesting carb can help maintain stable blood glucose levels without consuming fuel during the run. Fast-digesting carbs need carbohydrate supplementation throughout the exercise to maintain normal blood glucose.

 Concluding comments: These studies indicate carbohydrate can help runners perform well. To be sure your muscles are fully fueled, include some starchy food (wholesome cereal, grain, bread, etc.) as the foundation of each meal. Consuming carbs from just fruit or veggies will likely leave you with inadequate muscle glycogen. Think twice before having just a chicken Caesar salad for a recovery meal.

 Nancy Clark, MS, RD counsels both casual and competitive athletes at her office in Newton, MA (617-795-1875). Her newly updated Sports Nutrition Guidebook is now available in a new sixth edition. For more information, visit www.NancyClarkRD.com. For her popular online workshop, visit NutritionSportsExerciseCEUs.com 

Keeping up with the latest science-based sports nutrition recommendations is a challenge. Runners are constantly bombarded with media messages touting the next miracle sports food or supplement that will enhance athletic performance, promote fat loss, build muscle, and help you be a super-athlete. At this year's Annual Meeting of the American College of Sports Medicine (www.acsm.org), a sports nutrition myth-busters session sponsored by Professionals In Nutrition for Exercise and Sport (www.PINESNutrition.org; a global network of sports dietitians) featured experts who addressed the myths that commonly confuse runners and all athletes.

 

MYTH: Protein supplements build bigger muscles.

 

Protein needs for a 150-pound (68 kg) runner average about 110 to 150 grams of protein per day. (More precisely, 0.7 to 1.0 g pro/lb. body weight/day; 1.6 to 2.2 g pro/kg./day) Hungry runners can easily consume this amount from standard meals. Yet, many runners believe they need extra protein. They consume protein shakes and bars in addition to protein-laden meals. They are unlikely to see any additional benefits from this higher-than-needed protein intake. Resistance exercise is a far more potent way to increase muscle size and strength than any protein supplement. Plus, your muscles need three times more carbohydrate than protein to be adequately fueled.

 

MYTH: Eating just before bedtime causes a runner to "get fat."

 

While it is true the body responds differently to the same meal eaten at 9:00 a.m., 5:00 pm, or 1:00 a.m., a runner will not "get fat" by eating at night. The main problem with nighttime eating relates to the ease of over-eating while lounging around and watching TV. When your brain is tired from having made endless decisions all day, you can easily decide to eat more food than required.

 

     That said, bedtime carbohydrates to refuel depleted muscles and bedtime protein to build and repair muscles can optimize recovery after a day of hard training or competing. For runners who want to optimize muscle growth, eating about 40 grams of protein before bed provides an extended flow of amino acids needed to build muscle. (This bedtime snack has not been linked with fat gain). Cottage cheese, anyone?

 

MYTH: A gluten-free diet cures runners' gut problems.

 

If you have celiac disease (as verified by blood tests), your gut will indeed feel better if you avoid wheat and other gluten-containing foods. However, very few gut issues for non-celiac runners are related to gluten. FODMAPs (Fermentable Oligo-, Di-, Mono-saccharides and Polyols) are often the culprit. These are types of hard-for-some-people-to-digest carbohydrates found in commonly eaten foods such as wheat, apples, onion, garlic, and milk. For example, the di-saccharide lactose (a kind of sugar found in milk) causes gut turmoil in people who are lactose intolerant. The poorly digested and absorbed lactose creates gas, bloat and diarrhea.

     For runners who live in fear of undesired pit stops, a low FODMAP diet two or three days before a competition or long training session can help curb intestinal distress. Your sports dietitian can help you learn more about a short-term FODMAP reduction diet.

MYTH: Runners should avoid caffeine because of its diuretic effect

With caffeinated beverages, the diuretic effect might be 1.2 ml. excess fluids lost per mg. of caffeine. That means, if you were to drink a small mug (7 oz./200 ml.) of coffee that contains 125 milligrams of caffeine, you might lose about 150 ml. water through excess urine loss. But you'd still have 50 ml. fluids to hydrate your body—and likely more if you drink coffee regularly. Runners who regularly consume caffeine habituate and experience less of a diuretic effect. In general, most caffeinated beverages contribute to a positive fluid balance; avoiding them on the basis of their caffeine content is not justified.

MYTH: Athletes should be wary of creatine because it is bad for kidneys.

Creatine is sometimes used by athletes who want to bulk up. It allows muscles to recover faster from, let's say, lifting weights, so the athlete can do more reps and gain strength. A review of 21 studies that assessed kidney function with creatine doses ranging from 2 to 30 grams a day for up to five and a half years indicates creatine is safe for young healthy athletes as well as for elderly people. Even the most recent studies using sophisticated methods to assess renal function support creatine supplements as being well tolerated and not related to kidney dysfunction.

 

MYTH: The vegan diet fails to support optimal performance in athletes.

 

Without a doubt, vegan athletes can —and do—excel in sport. Just Google vegan athletes; you'll find an impressive list that includes Olympians and professional athletes from many sports (including not only running but also football, basketball, tennis, rowing, snowboarding, soccer, plus more.)

   

The key to consuming an effective vegan sports diet is to include adequate leucine, the essential amino acid that triggers muscles to grow. The richest sources of leucine are found in animal foods, such as eggs, dairy, fish, and meats. If you swap animal proteins for plant proteins, you reduce your leucine intake by about 50%. For runners, consuming 2.5 grams of leucine every 3 to 4 hours during the day optimizes muscular development. This means vegan runners need to eat adequate nuts, soy foods, lentils, beans and other plant proteins regularly at every meal and snack.

 

Most runners can consume adequate leucine, but some don't because they skip meals and fail to plan a balanced vegan menu. Vegan runners who are restricting food intake to lose undesired body fat need to be particularly vigilant to consume an effective sports diet. Plan ahead!

 

Nancy Clark, MS, RD counsels both casual and competitive athletes at her office in Newton, MA (617-795-1875). The newest 6th edition of her best selling Sports Nutrition Guidebook is being released in July 2019. For information about readymade handouts and PowerPoint presentations, visit www.NancyClarkRD.com.For her popular online workshop, see www.NutritionSportsExerciseCEUs.com.

Read more of Nancy Clark’s articles on  www.runohio.com 

 

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