Caffeine: Good When You Exercise, Bad When You Rest

Caffeine increases sugar absorption from the gut. Taking caffeine when you eat carbohydrate-containing foods can double your rise in blood sugar (Journal of Caffeine Research, April 16, 2011). Since more than 35 percent of North Americans will become diabetic and have high rises in blood sugar levels after meals, most people should not take caffeinated drinks with meals that contain carbohydrates: bread, spaghetti, or sugared foods and drinks. If you are already diabetic, your blood sugar levels rise even higher and you suffer cell damage. A high rise in blood sugar causes all the horrible side effects of diabetes: blindness, deafness, heart attacks, strokes and so forth. However, during exercise, caffeine can increase endurance (Medicine & Science in Sports & Exercise, July, 2010) by increasing the absorption of sugar from your intestines and by increasing the uptake of sugar by your exercising muscles by as much as 26 percent (Journal of Applied Physiology, June 2006). Caffeine is found in coffee, tea, chocolate, and cocoa.

Sugared drinks cause higher rises in blood sugar than sugared foods.
No solid food is allowed to pass into your intestines. After food enters your stomach, the pyloric sphincter closes. Food is kept in the stomach until it is turned into a liquid soup. Then the stomach muscles squeeze the soup through the pyloric sphincter into the intestines. An orange can be kept in your stomach for up to five hours before it passes into your intestines. Since fruit juice is a liquid, it passes into your intestines immediately. So orange juice causes an immediate high rise in blood sugar, while an orange does not. Studies show that fruits decrease diabetes risk, while fruit juices increase risk (Diabetes Care, July 2008).

Caffeine drives blood sugar levels even higher.
Adding caffeine to sugar in a drink causes blood sugar levels to rise even higher than drinks that have only sugar.

Fruit juice is as damaging as high fructose corn syrup or table sugar.
High Fructose Corn Syrup (HFCS) has been blamed for the ever-increasing rates of obesity and diabetes in North America over the last forty years. However, HFCS appears to be no more damaging than fruit juice or drinks sweetened with table sugar. Most soft drinks are sweetened with HFCS. Both HFCS and conventional sugar (sucrose) contain a mixture of two sugars, glucose and fructose, in nearly the same concentrations: HFCS has 55 percent fructose/42 percent glucose, while sucrose is a 50/50 mixture. These numbers are so close that most researchers feel that the slight increase in the concentration of fructose is not important enough to cause disease in itself. The fructose in orange juice, table sugar and HFCS are equally damaging to your health.

How fructose harms:
Fructose is far more damaging to the liver than glucose and is thought by many physicians to be the main cause of the fatty liver that causes insulin insensitivity and type II diabetes. When your blood sugar rises too high, the pancreas releases large amounts of insulin. Insulin converts sugar to triglycerides. Since high levels of blood triglycerides increase risk for clots, your good HDL cholesterol carries the triglycerides from your blood to your liver to fill up the liver with fat to cause a fatty liver. Fructose causes far higher blood and liver levels of triglycerides than glucose does, so fructose is a more potent cause of a fatty liver. Having a fatty liver prevents the body from responding to insulin and blood sugar levels rise to increase diabetes risk.

During exercise, muscles protect you.
Resting muscles are inactive. They need insulin to remove sugar from your bloodstream. On the other hand, contracting muscles can remove sugar from your bloodstream without even needing insulin (American Journal of Clinical Nutrition, July 2008). The maximum effect is during exercise and continues maximally for up to one hour afterward and disappears at around 17 hours (Journal of Applied Physiology, February 2010).

How caffeine and sugar help you during exercise:
Caffeine increases endurance by helping the body use more sugar from drinks that you take during exercise (Journal of Applied Physiology, June, 2005). The limiting factor to how fast you can move over distance is the time it takes to get oxygen into muscles. Since sugar requires less oxygen than fat or protein do, muscles move faster with more power when they burn sugar. Those who took sugared drinks with caffeine were able to absorb and use 26 percent more of the ingested sugar than those who took the same drinks without caffeine. Caffeine-laced drinks help improve endurance even more in hot weather (International Journal of Sport Nutrition and Exercise Metabolism, February 2011).

Caution!
You should take caffeinated sugared drinks only when you exercise and for up to an hour after you finish. Taking sugared drinks, with or without caffeine, when you are not exercising causes higher rises in blood sugars that increase risk for diabetes and cell damage.