Nutritional Intake and GI Problems...
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Nutritional Intake and Gastrointestinal Problems during Competitive Endurance Events
Medicine & Science in Sports & Exercise:
February 2012 - Volume 44 - Issue 2 - p 344–351
Highlights from Jeukendrop's study in February's blue journal. I thought this article was worth summarizing, as it provides some pretty good insight into IM nutrition.
A total of 221 endurance athletes (male and female, professional and amateur) were recruited from two Ironman triathlons (IM Hawaii and IM GER), a half-Ironman (IM 70.3), a MARATHON, a 100/150-km CYCLE race. A standardized postrace questionnaire quantified nutrient intake and assessed 12 GI symptoms on a scale from 0 (no problem) to 9 (worst it has ever been) in each competition.
Conclusions: The present study demonstrates that CHO intake rates vary greatly between events and individual athletes (6–136 g·h-1). High CHO intake during exercise was related not only to increased scores for nausea and flatulence but also to better performance during IM races.
Highlights:
-Fatigue during endurance events is generally not caused by a single factor but is the result of a multifaceted phenomenon that often coincides with dehydration, hyperthermia, CHO depletion, central fatigue, and hypoglycemia. (I thought that was well said.)
-the American College of Sports Medicine (ACSM) and the American Dietetics Association (ADA) advises athletes to consume CHO at rates of 0.7 g·kg-1 body weight per hour (30–60 g·h-1). (1 or 2 gels an hour.)
-An alternative contemporary recommendation (from Powerbar) suggests higher CHO intake rates of up to 90 g·h-1 for athletes competing in intense (ultra)endurance events longer than 2 h. (You know yo want to go faster! Try 3 gels an hour.)
-"the incidence of GI problems increases with exercise time"
-Mean CHO intake rates were not significantly different between IM Hawaii, IM GER, and IM 70.3 (62 ± 26, 71 ± 25, and 65 ± 25 g·h-1, respectively (The triathletes took in 62 to 71 grams of CHO per hour.)
- In contrast to the triathlons, the average CHO intake rate during CYCLE was significantly lower (53 ± 22 g·h-1.The lowest mean CHO intake rates were reported during MARATHON (35 ± 26 g·h-1)... (Runners think all they need to do is double knot their shoes.)
-Regardless of the event, individual CHO intakes among athletes varied greatly (range = 6–136 g·h-1). (that's grams per hour)
-Mean scores for upper and lower abdominal problems were not correlated with CHO intake rates in any of the triathlon events.
-When triathletes were divided into subjects experiencing serious GI problems and subjects with mild or without GI problems, CHO intake rates were not significantly different between both groups (65 ± 25 and 69 ± 27 g·h-1, respectively, P = 0.49).
-Previously recommended high CHO intake rates (up to 90 g·h-1) (21) were achieved by ~50% of the triathletes, 30% of the cyclists, and 15% of the marathon runners.
High CHO intake rates were significantly correlated with faster finishing times, and although they were not associated with higher average scores for upper or lower GI symptoms, they did seem to be a risk factor for nausea and flatulence. (Better work this compromise out in training.)
-73% of marathon runners failed to meet the comparatively low ACSM recommendations. (Surprise!)
-The lowest average CHO concentration (8.8% during IM Hawaii) still exceeds the general recommendations for the composition of sports drinks of 4%–8%. (Hypertonic solutons over 6% weren't necesarily an issue.)
-in this study and in previous studies, CHO intake rates have been correlated to faster finishing times, indicating that a higher CHO intake potentially improved endurance performance.
-In the present study, a high prevalence for serious GI distress (~30%) was reported during the IM races. Significantly lower frequencies of serious complaints were reported during IM 70.3 (14%), MARATHON (4%), and CYCLE (4%). (Wow, in IM almost 1/3 have serious GI problems and we are not talking a little nausea, but they would have us believe it is not the rate of caloric intake that is the problem.)
-the most important factor that influenced GI problems within our study was an individual predisposition and history of GI distress among athletes
-it has to be kept in mind that the incidence of GI problems increases with exercise time and might be increased under more extreme weather and race conditions. In the present study, we detected no clear relationship between CHO intake rates and GI distress. Mean upper and lower abdominal symptoms were not associated with CHO intake rates. Furthermore, mean CHO intake rates were not different between athletes with and without serious GI symptoms.
- Altogether, these data suggest that CHO intake can indeed be a risk factor for nausea and flatulence during exercise. However, those more minor symptoms are less likely to impair performance compared with symptoms such as diarrhea or stomach cramps, and it should be kept in mind that high CHO ingestion rates were correlated with faster finishing times.
-Altogether, the findings of the present study suggest a need for more individualized nutritional advice for endurance athletes, where each athlete finds his/her unique balance between the ergogenic effects of optimal CHO and fluid intake and the potential ergolytic effects of substantial CHO intakes causing GI distress.
-and lastly, This study was supported by a grant of Nestec (Powerbar) Ltd., Vevey, Switzerland. (Jeukendrop works for Powerbar. Thought I would point that out.))
-Summary: What I take home from this is that if you don't have a sensitive stomach it might be worth trying to get in more calories. Just be ready for nausea, gas and maybe worse. Thanks!
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Comments
Brian: Your take-home is right on target. In training, play with your nutrition. You can go up 5 - 10 grams of carbs/hour and see how your GI tract responds. Research is starting to show that up to 90 g carbs/hour is not unreasonable for some people.
Anytime I run mid-day or later, I get horrible stomach pains and nausea anytime past an hour or so of running. It only happens during running. If I run first thing in the morning, on an empty stomach, I usually don't have any issues. However, today I ran 13 miles at 11AM and thought I was going to lose it. I also had to find a bathroom quickly afterward. Sorry for the TMI but how do you fix a problem without describing it?
I didn't eat anything weird. My usual breakfast/coffee and then an apple with PB about an hour and a half before I ran. It's without fail that I get queasy now during long, moderate effort training runs. I never had this problem before. In 20+ marathons, stomach issues were never a concern. Not sure why this developed in the past 6-7 months.
Any advice/experience with this is welcome!
For me, with my last IM training in 2010, I was having horrible bloating, gas, etc. I was exhausted. Went to the doc and she did some tests that showed "yup- I'm exhausted" (high cortisol- but that was likely due to the stress of training)
After the race was completed, I tried several different elimination diets without relief.
When my husband suggested gluten elimination I was sure he was wrong, but I was desperate (and so was he- I was not fun to be around). Long story short- in 24 hours I had a significant reduction of symptoms. Once I educated myself about gluten and learned the foods with "hidden" gluten, I became symptom free and I have more energy. I went to my doc, but you have to be eating gluten for the test to be useful, and I refused to resume eating gluten.
I consider myself intolerant of gluten, not allergic.
My point is that I am over 40 and this happened. Our bodies change and what worked once, may not work now.