Overcoming Athletic GI Distress

Applying accurate nutrition and hydration principles is of great benefit to an athlete's training and performance. The athlete that understands their individual digestion and absorption of nutrients and fluids is more likely to develop optimal methods of maintaining his or her blood volume (a critical issue for performance), without inducing nausea and vomiting (GI Distress).

For any fluid to be of benefit during exercise, it must first empty from the stomach and then be absorbed into the bloodstream from the intestines. A number of factors influence the gastric emptying rate, including hydration status, concentration of the liquid, volume, caloric density (concentration of the fluid), temperature of the liquid as well as external temperature, and exercise intensity.

The most common causes of GI distress are thus a spin off from these influences:

Hydration status : A delayed gastric emptying response results from dehydration, thus drinking when in a dehydrated state can cause gastrointestinal distress. Moreover, drinking at this point is unlikely to adequately hydrate the muscles. A common mistake made by many athletes is waiting to feel thirsty before hydrating. Furthermore, if lost fluids and electrolytes are not replenished, fatigue and heat illness can result.

Thirst is a sign that dehydration has already set in and performance is already being reduced. Thirst also tends to cause consumption of higher volumes of liquid at one time, and with the delayed gastric emptying, GI distress is almost guaranteed. Remember that dehydration is cumulative. To overcome this risk, do not wait until you feel thirsty; maintain fluid hydration regularly throughout training. Continuous sipping, if appropriate, is recommended, or else hydrating with small volumes every 20 – 30 minutes.

Concentration of the Fluid : The speed at which a beverage travels from the stomach in to the small intestine (the gastric emptying rate) depends on the energy content (calories) and volume of the beverage consumed. A small concentration of carbohydrate will encourage rapid absorption, but too much carbohydrate will slow gastric emptying and can result in GI distress. Research has consistently found that beverages with a carbohydrate concentration of 6 - 8%, empty from the stomach more slowly than either water or lower concentrations of carbohydrate. Carbohydrate/electrolyte drinks are thus often better than water for endurance training. Sports drink may also aid in replenishing glycogen stores in working muscles, as well as electrolyte balancing and replenishment.

Intensity of exercise: Stomach and intestinal distress tend to increase during high-intensity training. Stomach fullness is also directly related to gastrointestinal discomfort levels during intense sporting activity. Different intensities also result in different carbohydrate utilization. For instance, in endurance running and intermittent stop-and-go sports, there is a reduction in the rate of muscle glycogen depletion when carb drinks are consumed, but for strenuous cycling the rate of muscle glycogen depletion has not been shown to be affected.

Keeping in mind that gastric emptying is optimal at 6 - 8% carbohydrate sports drinks, consuming these fluids regardless of activity may help maintain athletic performance and prevent over volumizing with water.

Type of Carbohydrate: There appears to be no major difference between glucose, sucrose, maltodextrins, and starch on athletic performance itself, however sports drinks that contain mainly fructose may cause GI distress due to the fructose's slower absorption rate. Fructose is sweeter than maltodextrins and is often used to make the drink appealing. Read labels carefully; look for a combination of these carbohydrates. Maltodextrins remove the unpalatable sweetness, and sucrose is absorbed more rapidly than fructose. Carbohydrates regardless of whether solid or liquid will aid in athletic performance, but consider drinking them rather than eating them, since the fluid takes care of two very important performance issues: hydration and energy.

Ergogenic aids: High doses of vitamins and minerals and some ergogenic aids, such as creatine, or caffeine may cause GI distress. Creatine has recently become one of the most popular ergogenic aids marketed to athletes. Some studies have shown creatine supplementation may promote gains in strength, performance and fat-free mass which is either due to increased muscle mass or water retention. While not all studies report ergogenic benefits, most studies warn about the danger in incorrect dosing. There are also concerns about muscle cramping and increased muscle injuries and of course GI distress. Ingesting a carbohydrate drink at the same time creatine is consumed, has been shown to increase creatine accumulation in the muscle however it also increases water retention, as a result. The risk of developing GI distress is thus increased when combining sports drinks with ergogenic aids.

In Summary: GI distress may be an individual adversary. It is important to experiment to find out which sports products work best for you. Water is a good drink if exercising for less than one hour. Carbohydrate-electrolyte drinks, such as Gatorade are good for endurance and high intensity training as they are absorbed at optimal rates. Water provides no flavor or electrolytes, which cause athletes to want to drink. Beverages that cause athletes to want to drink help them stay well hydrated. Water has no energy while sports beverages contain carbohydrate. The carbohydrate helps athletes provide their muscles with the needed fuel to avoid early fatigue and poor performance. The sodium provided by sports beverages helps athletes maintain blood volume, a factor that is critical to maintaining sweat rates and performance. Sweat contains sodium that water alone does not replace. However, to prevent GI distress, these fluids should not be more than 6 – 8 % carbohydrate concentrated (approximately 14 grams of carbohydrate per 8 oz); they should have a mixture of sucrose, glucose and fructose; and they should provide a minimum of 100 mg sodium and 28 mg potassium per 8 oz servings.

Ilana Katz has a masters degree in dietetics with an emphasis in sports nutrition. She enjoys working with athletes from the elite to recreational. She specializes in body composition and weight management specific to individual goals and needs. Ilana, herself participates in many endurance and team events in order to relate personally to her clientele. Ilana is The Sport Factory's head nutritionist, has worked with many local celebrities, and is the founder of the nutrition program IndiFITualize. You may hear Ilana on the “Bert” radio show (Q100) as well as “Dave FM” in Atlanta.