Why is sodium citrate better that sodium chloride?
Sodium chloride, found in regular table salt, is fine for consumption outside of exercise conditions. Exercise stress causes blood to be shunted away from digestion and toward working muscles. Blood is also shunted to the surface of the skin to aid in body cooling. Often, a second layer of stress is added by exercising in hot and/or humid environmental conditions. These stresses change fluid regulation in the body.
Key to any hydration process is fast absorption of water and electrolytes at the intestinal cells. In a resting condition, chloride is a key ion in this absorption process. But what happens during exercise is that immune and inflammation reactions occur due to the reduced blood flow to the gut. These reactions change the membrane potential of the cells and stimulate the release of chloride ions. The release of chloride ions sets off a series of reactions, ultimately leading to gut cramping and diarrhea.
We use sodium citrate because the citrate ion can be used as part of the Krebs cycle of energy production, also known as the citric acid cycle. Because citrate is metabolized differently than chloride during exercise, gastrointestinal (G.I.) problems are eliminated.
You say, "Hydration in the bottle, food in the pocket." Why are you opposed to using a liquid nutrition program for racing?
The body has different digestion and absorption rates for fluids, semi-solids and solids. A fluid solution of sucrose, glucose and sodium mixed at a 3.5- to 4-percent carbohydrate concentration has been shown to maximize fluid absorption. This percentage keeps osmolality low which allows for faster emptying out of the gut and greater fluid absorption.
Many currently available drink mixes have a 6- to 8-percent carbohydrate solution that includes fructose and maltodextrin components. One problem with this higher concentration is that it slows absorption. Additionally, fructose and maltodextrin (independently) have shown to produce 5-percent more heat production for their oxidation than glucose or sucrose. When athletes are racing in hot conditions, they certainly don't want digestion to add to the heat load.
Athletes that use "liquid calories" change the osmotic pressure in the gut which stimulates the body to shift fluid out of the plasma and other internal spaces to dilute the semi-solid solution in order for it to be absorbed. If you're pulling fluid from the body for digestion, you're effectively dehydrating yourself. Additionally, residual carbohydrate in the gut contributes to changing the membrane potential of intestinal cells. This allows them to become "leaky", contributing to G.I. distress, including diarrhea.
Doesn't eating real foods or energy bars slow absorption? How is this different than using liquid calories?
If an athlete is chewing solid food, the digestion process begins in the mouth and the calorie load to the gut is reduced because each bite of solid food has fewer calories than a big gulp of semi-solid, concentrated liquid.
You are not a big fan of gels, why not?
Most gels are made of maltodextrin, fructose and many have protein as well. These sugars increase internal heat production and unless the athlete can drink 8 to 10 ounces of water per gel, they end up with the effective dehydration problem again.