Most athletes can metabolize sugar without problems. That’s because exercise enhances the transport of sugar from your blood into your muscles with far less insulin than needed by the body of an unfit person. The unfit body contributes to the rise in blood sugar that triggers the need for excess insulin and leads to the “crash.”
The most common reason for “sugar crashes” (hypoglycemia) among athletes relates to running out of fuel. The shakiness and sweats are because the athlete did not eat enough carbs to maintain normal blood glucose levels and the brain is now demanding sugar. One marathoner thought the 100-calorie gel he took at mile 16 caused him to “crash.” More likely, he needed 200 to 300 calories to meet his energy needs, not just 100 calories.
Regarding health, some sugars are better for you than others because they offer more nutrients. For example, the sugar in sport drinks provides “empty calories” with no nutritional value (unless they are fortified to give a healthier appearance). The sugar in orange juice is accompanied with vitamin C, folate, potassium, and many other vitamins, minerals, and plant compounds that contribute to good health.
While juice offers slightly less nutritional value than you’d get by eating the whole fruit, most anti-juice hype is targeted at overfat people. Liquid calories from juice, soda and sports drinks do not contribute to satiety (fullness). Hence, drinking sugary beverages with meals adds extra calories that can contribute to undesired weight gain. Yet, for active people who want to gain weight, juice can help a skinny athlete easily boost calorie intake while simultaneously adding carbs for fuel that enhances muscle-building workouts.
Even though refined sugar adds “junk calories” to a sports diet, you need not eat a sugar-free diet to have a good diet. A fit and healthy person’s menu can accommodate 10% of calories from refined sugar (World Health Organization’s guidelines). Yet, if you frequently consume sports drinks, gels, and sports candies—as well as other sweets—you can easily consume more than 250 to 350 calories (10% of calories) from refined sugar. Please don’t displace too many fruits, veggies and whole grains with empty calories from sugar…
For more information:
Nancy Clark’s Sports Nutrition Guidebook