The Science of Energy Gels

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My supply of gels
Understanding some of the science behind energy gels can help in evaluating and choosing the right gel.

1 Carbohydrate Absorption

There are three main components to the ease of absorption of a carbohydrate; how much water needs to be used to dilute it, how fast it gets into the blood and the digestive path in the gut.

1.1 Required Dilution – Isotonic Drinks

Isotonic drinks have a similar concentration (osmolality) of carbohydrate and electrolytes to the human blood and are easier to absorb[1]. The concentration is based on the number of molecules rather than the weight, so an isotonic drink with bigger molecules has more carbohydrate by weight. Maltodextrin is a long molecule that is a chain of glucose, so you can have a lot of it in an isotonic solution. Maltodextrin is isotonic at 150g/500ml, where fructose, glucose and sucrose (table sugar) are isotonic at 26g/500ml. This means that you need to dilute the simple sugars with six times as much water as Maltodextrin.

1.2 Absorption Rate - Glycemic Index

Main article: Glycemic Index

Glycemic index reflects how high a carbohydrate raises the blood sugar level.

  • Glucose is the standard against which everything else is measured, so it has a Glycemic Index of 100. Glucose is used because it raises the blood sugar faster than almost anything else.
  • Maltodextrin actually has a glycemic index of over 100, with values between 105 and 136.
  • Fructose has a low glycemic index of 19, as it has to go via the liver to be converted to glucose.

1.3 Digestive Path

While fructose has a low isotonic concentration and a low glycemic index, it can be absorbed via a different path (GLUT5) to glucose and Maltodextrin (GLUT2). This means that if you have enough glucose or Maltodextrin to saturate that absorption path, adding fructose will improve the overall usage of the carbohydrate intake[2].

1.4 Optimal Carbohydrate Intake

Most studies have shown that glucose and Maltodextrin can be absorbed and metabolized at up to 1.0 grams/minute, while Fructose is absorbed and metabolized at up to 0.6 grams/minute[3]. Combining Fructose with glucose/Maltodextrin can result in the metabolism of up to 1.75 grams/minuteCite error: Closing </ref> missing for <ref> tag [4] [5] [6] [7] [8] [9] [2] [1] [10] [11] [3] [12] [13] [14] [15] [16] [17] [18]

</references>
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