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** Amino acids may help performance, but the evidence is unclear at the levels provided in most gels.
* [[Caffeine]] is great for improving performance and speeding the absorption of carbohydrate, but too much can upset the stomach.
* Flavor is important, as you won't want to take an unpalatable gel. Experiment with different flavors, as different people have different tastes.
This table is ordered by ease of digestion, which is a combination of the science of nutrition, personal experience and the experience of many runners I've talked to.
!'''Name'''!!'''Calories'''!!'''Carbs'''!!'''Sugar<sup>4'''</sup>!![[Maltodextrin]]<sup>1</sup>!!Glucose<sup>1</sup>!![[Fructose]]<sup>1</sup>!!Other Carbs<sup>1</sup>!!'''[[Protein| Protein]]'''!!'''Fat'''!!'''Sodium'''!!'''Potassium'''!!'''[[Caffeine]]'''!!'''Water to <br>be Isotonic<sup>5'''</sup>!!'''Weight<sup>6</sup> '''!!'''Carbs/g'''!!'''Cal/g'''!!'''Ease of digestion<br/> (higher is better)'''!!'''Recommended for'''
|[http://go.fellrnr.com/?id=35454X937677&xs=1&xcust=hammer&url=http%3A%2F%2Fwww.amazon.com%2FHammer-Single-Serve-Packets-Raspberry%2Fdp%2FB000RI2T4A Hammer Gel]
|Those looking for every advantage
|A less sweet Gu
|A Gu Alternative
|Those needing extra electrolytes
|Improved Recovery and Ultradistances
|Not Generally Recommended
* <sup>3</sup>The unusual nature of the ingredients in 2<sup>nd</sup> surge makes it harder to estimate the types of carbohydrates included.
* <sup>4</sup>The sugar value includes sucrose, fructose, glucose and other 'sugars'.
* <sup>5</sup>This is an approximation based on the amount of sugar, Maltodextrin, sodium and potassium, ignoring other ingredients. The water included in the gel is assumed to be the overall weight less the weight of the carbs, fat and protein. See [[The Science of Energy Gels]] for details on the isotonic calculations.
* <sup>6</sup>This is the net weight of the gel; generally the packaging added 2-3g to the gels according to my scales.
* <sup>7</sup>The chocolate flavor has 1.5g
* <sup>8</sup>The chocolate flavor has 2g
[[File:Gels.jpg|none|thumb|500px|Here is a visual comparison of the sizes of the various gels.]]
''<br/>Ingredients (Vanilla): Maltodextrin, Filtered Water, Energy Smart (Grape juice and Rice dextrins), Potassium Sorbate (as a preservative), Vanilla Extract, Citric Acid, Potassium Chloride, Salt, Amino Acids (L-Leucine, L-Alanine, L-Valine, L-Isoleucine).''
For marathon distance racing, I prefer [http://go.fellrnr.com/?id=35454X937677&xs=1&xcust=gu&url=http%3A%2F%2Fwww.amazon.com%2FEnergy-Gel-Chocolate-Outrage-24-Count%2Fdp%2FB000CSCRHY Gu] over all other gels I've tried. It contains 5g of [[Fructose]], with the rest of the calories coming from the easily digested [[Maltodextrin]]. I find that Gu can be consumed without any extra water as long as it is taken a bit at a time and [[How to eat a Gel| mixed with saliva]]. Some of the flavors can be a little strong, but the 'plain' Gu has a light cola flavor.
''<br/>Ingredients (Vanilla): Maltodextrin, water, fructose, Gu Amino acids (leucine, valine, histidine, isoleucine), potassium and sodium citrate, antioxidants (vitamin E and C),citric acid, calcium carbonate, vanilla, sea salt, preservatives (sodium benzoate, potassium sorbate), fumaric acid, herbal blend (chamomile, kola nut, ginger), pectin.''
=Gu (Peanut Butter)=
The peanut butter flavored [http://go.fellrnr.com/?id=35454X937677&xs=1&xcust=gu&url=http%3A%2F%2Fwww.amazon.com%2FEnergy-Gel-Chocolate-Outrage-24-Count%2Fdp%2FB000CSCRHY Gu] is different enough to justify its own section. The peanut butter flavor is far less sweet than the regular Gu
flavors, but if you like peanut butter it can be a lot more palatable. It also substitutes a little bit of fat and protein for the carbohydrate, as well as having a tiny bit more sodium and potassium. I find this flavor digests particularly well and I'd recommend trying get if you're a fan of peanut butter. Obviously, if you hate peanut butter or you have a peanut allergy this is not going to work for you.
''<br/>Ingredients: Maltodextrin, water, fructose, Peanut butter (peanuts, salt), Gu Amino acids (leucine, valine, histidine, isoleucine), potassium and sodium citrate, antioxidants (vitamin E and C), preservatives (sodium benzoate, potassium sorbate), calcium carbonate, sea salt, fumaric acid, calcium chloride, pectin, citric acid, malic acid, herbal blend (chamomile, ginger).''
[http://go.fellrnr.com/?id=35454X937677&xs=1&xcust=gur&url=http%3A%2F%2Fwww.amazon.com%2FRoctane-Energy-Gel--Pack-Pomegranate%2Fdp%2FB002Y1XKW8 Roctane] is a more expensive variant on Gu, though the price has reduced significantly since its introduction. The main difference is the addition of 1.7g of amino acids, which may help slightly. I've not noticed any difference when using it, but if you like Gu and are looking for even a slight advantage, it may be worthwhile. If you are paying hundreds of dollars for a race entry and travel, then the extra cost is minor. If you take 8 gels in a 4-hour marathon, Roctane only adds $4-5 to the cost of the race. Of course, you'll need to practice with Roctane in your training, so you'll have to factor that cost in as well.
''<br/>Ingredients (Blueberry flavor): Maltodextrin, water, fructose, Roctane Amino acids (Histidine, Leucine, Valine, Isoleucine), Ornithine Alpha-ketoglutarate (OKG), sodium citrate, malic acid, citric acid, potassium citrate, natural pomegranate flavor, natural berry flavor, calcium carbonate, sea salt, caffeine, sodium benzoate, potassium sorbate.''
''<br/>Ingredients (Vanilla): Organic Maltodextrin, Organic Sugar, Water, Natural Flavor, Sea Salt, Potassium Citrate.''
[http://go.fellrnr.com/?id=35454X937677&xs=1&xcust=PBeg&url=http%3A%2F%2Fwww.amazon.com%2FPowerBar-Caffeinated-Strawberry-1-44-Ounce-Packets%2Fdp%2FB000A2BCIW PowerBar Gel] is noteworthy because of its higher sodium content that may help alleviate [[Hyponatremia]] and [[Cramps]]. I found the flavor stronger than Hammer, Gu or Cliff, but still quite pleasant. The level of fructose is higher than I'd like to see for digestibility. You may need to drink some water near the time you take PowerBar Gel due to the extra electrolytes.
''<br/>Ingredients (vanilla): Carbohydrate blend (Maltodextrin, fructose), water, electrolytes (sodium chloride, sodium citrate, potassium chloride), natural flavor, citric acid, sodium benzoate and potassium sorbate.''
''<br/>Ingredients (Gold flavor): Honey, Water, Potassium Citrate, Salt, Natural Flavors, Vitamins & Minerals, Niacinamide (Vit B3), Calcium Pantothenate (Vit B5), Pyridoxine, Hydrochloride (Vit B6), Riboflavin (Vit B2), Thiamine Mononitrate (Vit B1), Cyanocobalamin (Vit B12)''
The only ingredients in this [http://go.fellrnr.com/?id=35454X937677&xs=1&xcust=ch9&url=http%3A%2F%2Fwww.rei.com%2Fproduct%2F815338%2Fchocolate-9-energy-gel #9] are Agave and Cocoa, and Agave is predominantly fructose (55% fructose to 20% glucose). This amount of [[Fructose]] is slow to be absorbed and can be difficult to digest, making it a poor choice for most runners. The Agave makes this gel intensely sweet, which I did not like and the '[http://en.wikipedia.org/wiki/Dutch_process_chocolate processed with alkali]' means that most of the antioxidants are destroyed. This gel may be suitable for runners that suffer from a blood sugar drop after taking more conventional gels prior to exercise (see [[The Science of Energy Gels| The Science of Energy Gels]] for more details).
''<br/>Ingredients: organic agave nectar, cocoa processed with alkali''