By Safi Madain BS, CSCS | Contributing Author | Based on Safi’s article “Is it Goo for you?”

The Goo. Does this stuff really work while running? Some brands claim to give boosts of energy, while other brands claim to replenish energy sources. But is this supplement replenishing the right energy sources and can it accomplish such a feat in a feasible amount of time?

Let’s take a look at some facts about carbohydrate digestion and energy storage. Carbohydrate digestion begins in the mouth by an enzyme called amylase. The enzyme gets mixed around in the mouth while we are chewing. When the carbohydrate bolus (the ball of stuff formed from chewing) is swallowed, it sits in the stomach for about 30 minutes to two hours before it is passed on into the duodenum (the first part of the small intestine). The amount of time depends on if it is a complex or a simple carbohydrate, if it is a liquid or solid, and what else it is consumed with. Carbohydrates are not digested in the stomach because the enzymes required to digest carbohydrates are not active in the low pH environment of the stomach. It takes about another 30 minutes to an hour to digest carbohydrates in the small intestine and convert the sugars into glucose, and about another 30 minutes to an hour to absorb the glucose and store it for energy (liquid digestion and absorption is done at about half the time). We are looking at a minimum of 1 hour of digestion, absorption into the blood, and absorption into muscle tissue before energy is made available. The Goo will probably sit in the stomach for about 45 minutes to an hour before it is passed on to the small intestine because it is not a complete solid and it is not exclusively carbohydrate.

So the food consumed will not give instantaneous energy. By the time a runner actually has access to the energy the Goo may give, the race may very well be over. Two other factors that must be taken into consideration when consuming food during a run are, the reallocation of blood flow and blood glucose removal. First, blood shunted to the gut from the extremities during digestion may be a cause of more rapid fatigue because blood is taken away from working muscle. Blood flow to working muscle removes waste, delivers nutrients, and helps to maintain an optimal temperature for activity. A buildup of waste products, lack of nutrient delivery, and inefficient temperature regulation will reduce performance capabilities. Second, eating while exercising will stimulate two glucose transporters in skeletal muscle tissue to remove glucose from the blood, one transporter is insulin sensitive and the other is exercise sensitive. Thus, blood glucose may have the potential to be removed at twice the rate. The last thing a runner needs is to crash from rapidly lowered blood sugar levels.

Studies have shown that during long distance runs, glucose is required to aid in fat metabolism by supplying a specific substrate used in beta-oxidation. Beta-oxidation is the name of the process of burning fat for energy. This is where the saying “fats burn in a carbohydrate flame” comes from. Since we have a much smaller store of glycogen than fat, glycogen depletion may be a limiting factor in long distance running, but glycogen depletion does not occur rapidly; especially in those who carbohydrate load the week before the race. According to the National Strength and Conditioning Association, for a 2-hour maximum run, 99% of our expended energy comes from fat and that the rate of glycogen depletion is related to exercise intensity. Marathon running is considered a low to moderate intensity activity, so glycogen stores do not run out rapidly (the average human stores 300 to 400 grams of glycogen in muscle tissue). Glycogen and free-floating ATP predominate the first minute of running, and then our bodies start to shift to fat for energy. The reason? We do not need explosive movements for marathon running. Fat gives us 9 kcals per gram, compared to 4 kcals for carbs, thus it is much more efficient for long, slow running.

Many may also mistake fatigue from dehydration as low sugar levels. At two percent dehydration, our bodies can no longer function and we rapidly fatigue. This is why while running, a cup of water should be consumed every mile. Water is absorbed 4 to 5 times as fast as carbohydrate.

Let’s add everything up and see if the Goo can really work. It will take a bare minimum of 1 and a half hours to make energy from the Goo readily available for energy, we store 300 to 400 grams of glycogen in muscle tissue, and during long, maximal runs 99% of our energy comes from fat stores. The energy that we get from the Goo will not even have a chance to be used. So does the Goo really work? It probably does after the race. Carbohydrate loading and drinking plenty of water are adequate enough to keep you going during the marathon.

-Safi Madain BS, CSCS

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