Energy gels are an easy-to-digest, fast-acting source of simple sugars that you can suck down on the go. They are designed to be a hybrid between sports drinks and energy bars to provide fuel and a limited amount of electrolytes during intense exercise. However, if your workout or race is under an hour, there is no need to replenish carbohydrates; your muscles can store enough glycogen to keep you going without supplements.
When choosing an energy gel, make sure to read the label. Some forms of sugars, such as fructose, can cause GI problems. Brown rice syrup and honey are more complex and therefore absorb more slowly than sucrose or glucose, this could be good or bad depending on how quickly you need the boost.
Gels typically contain 25g of carbohydrates and 100 calories and can be taken every 30-60 minutes of activity depending on intensity. Be aware that many gels also contain caffeine because caffeine can increase alertness and promote the use of fat for fuel. The amount of added caffeine ranges from 20mg to 100mg (coffee has about 85mg) which is unlikely to cause dehydration.
So what is the benefit? Experts have shown that using an energy source every 30-45 minutes during activity can help delay the onset of fatigue, increase blood sugar levels, and possibly enhance performance. However, that being said, there is no specific advantage of using a gel or chew over a regular sports drink or even sucking on packet of honey or a piece of candy. The end result is the same: sugar gets into your blood stream quickly to supply your muscles with glucose.
The bottom line: gels can be a convenient source of energy for triathlons, marathons or ultras but water works fine for anything under an hour. Always try out a new sports gel before you use it in a race, the quantity and timing is individual and some gels can cause GI distress by slowing the absorption of fluid. Also, remember to drink plenty of water. For exercise lasting over an hour, consuming 30-60 gram of carbohydrate every hour will stop you from feeling depleted. If you prefer to stick with a sports drink, look for one with about 14g of carbohydrate per 8oz of fluid and 100-200mg of sodium for electrolyte balance.
So is goo for you? You will have to try it for yourself; some runners hate the taste while others would not race without it. Either way, if you are not taking in some form of carbohydrate throughout your endurance activity, you are not maximizing your performance.