As triathalon season approaches each year, my patient roster becomes peppered with endurance athletes emerging from the winter hiatus. As they look ahead to triathlons, half-marathons, marathons and other highly-competitive events, questions arise about the beverages, bars and energy shots they should use to fuel these athletic endeavors.

[See Performance Foods: What and When to Eat Before Your Next Workout.]

I've reported previously about a category of poorly-absorbed carbohydrates called FODMAPs, which range from fructose and lactose to sugar alcohols (or polyols) and bean-derived galacto-oligosaccharides (GOS). In susceptible people--and particularly in larger doses--these carbs can trigger symptoms like gas, bloating and diarrhea. As it turns out, sports nutrition products are generally loaded with high-FODMAP ingredients.

As a result, sports nutrition products are terribly difficult to navigate for endurance athletes with Irritable Bowel Syndrome (IBS) or other food sensitivities. To complicate matters, many of these products are sold as dietary supplements rather than as food; their labels, therefore, may not disclose all the details one needs to decipher what's actually in them and at what levels. What's a sensitive-bellied Ironman to do?

[See Crazy for Exercise: Are We Overdoing It?]

-- Learn the lingo: High-FODMAP ingredients hide behind other terms on ingredient labels, particularly in sports nutrition products. Lactose isn't likely to be listed on a label, but you'll be getting plenty of it in a product with whey, whey protein concentrate, milk protein concentrate or (powdered) milk at the top of the ingredient list.

Fructose is easily recognizable as a stand-alone ingredient or within high-fructose corn syrup--but lurks undercover in ingredients like invert sugar; inulin/chicory root extract; fruit juice concentrates from apple, orange, pear or grape; agave nectar; and fructo-oligosaccharides (FOS). "Low carb" and "reduced sugar" are code words for "sweetened artificially," so be on the lookout for sugar alcohols like xylitol, sorbitol, erythritol or maltitol--these can create bloating and diarrhea. Sucralose, while not technically a FODMAP, can also cause gastrointestinal upset in some, particularly at doses in the 5- to 10-gram range.

-- Take stock of your food sensitivities: If you rely heavily on sports nutrition products but find many don't agree with your stomach, it may be worth getting tested for lactose intolerance, fructose intolerance and/or celiac disease to help pinpoint specific ingredients you may need to avoid.

[See Food Intolerance: Fact and Fiction.]

If you're not fructose intolerant, there's no need to avoid the fructose-containing FODMAPs. If you are fructose intolerant, you'll want to avoid both fructose and sugar alcohols. The more data you have, the easier it will be to zero in on products you're able to tolerate. A qualified registered dietitian can help you assess symptoms as they relate to the foods you eat to narrow down which food intolerances may be worth testing for.

Read more:
Sports Nutrition for Food-Sensitive Athletes