Applying nutrition and hydration principles is of great benefit to optimize an athlete’s training and performance. The athletes that understand the digestion and absorption of nutrients and fluids are more likely to develop optimal methods of maintaining 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:
Recent research has shed new light onto understanding hydration. Endurance athletes attempt to offset dehydration in fear of the old myth that dehydration poses the threat of less than optimal performance. Contrary to the marketing claims made by the leading sports drink industry in the early 70’s – the need for maximum hydration is not necessary. In fact, it is not possible to drink enough to fully offset dehydration without causing a negative consequence. .An attempt to offset dehydration during intense exercise is the surest way to induce GI distress since too much fluid may result in a delayed gastric emptying response.
Furthermore, overhydration could induce a more serious condition called Hyponatremia, or water intoxication (sodium concentration of body fluids fall too low).
To overcome both the risk of GI distress or hyponatremia: drink enough fluid to slow dehydration and not necessarily prevent it. Continuous sipping is recommended, or else hydrating with small volumes every 20 – 30 minutes, or better yet, drink according to thirst.
Concentration and type of carbohydrate 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. Sports drinks are scientifically formulated for optimal gastric emptying. Furthermore, sports drinks also aid in replenishing glycogen stores in working muscles, as well as electrolyte balancing and replenishment and are therefore valuable hydration options. The concentration and the type of carbohydrates in a sports drink however, require some consideration.
There appears to be no major difference between glucose, sucrose, maltodextrins, fructose and starch on athletic performance itself. Fructose, however, has a slower absorption rate, and in large quantities, is likely to cause GI distress than any of the other carbohydrate s. Fructose is sweeter than maltodextrins and is often used to make the drink appealing. Maltodextrins remove the unpalatable sweetness, and sucrose is absorbed more rapidly than fructose. Thus read labels carefully, look for a combination of these carbohydrates. 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.
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.
Ergogenic aids:
High doses of vitamins and minerals and some ergogenic aids, such as creatine, 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 supplies 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.
