CAFFEINE AND THE ATHLETE

Despite some of the known benefits of caffeine in endurance exercise, differences in metabolism, diet, and frequency of caffeine use are some of the factors that can determine how an individual will react to caffeine. Some athletes may actually experience a decrease in performance, usually due to side effects of caffeine.  Dehydration is a potential concern due to caffeine being a mild diuretic. Other side effects for performance may be abdominal cramps and diarrhea related to the large intestine contractions caused by caffeine.

Role of Caffeine in Endurance Sports - An Education

Glycogen is the principal fuel for muscles.  Exhaustion occurs when it is depleted.

A secondary fuel, which is much more abundant (how unnerving!), is fat. As long as there is still glycogen available, working muscles can utilize fat.

Caffeine mobilizes fat stores and encourages working muscles to use fat as a fuel. This delays the depletion of muscle glycogen and allows for a prolongation of exercise.

The critical time period in glycogen sparing appears to occur during the first 15 minutes of exercise, where caffeine has been shown to decrease glycogen utilization by as much as 50%. Glycogen saved at the beginning is thus available during the later stages of exercise. Although the exact method by which caffeine does this is still unclear, caffeine caused sparing in all of the human studies where muscle glycogen levels were measured. The effect on performance, which was observed in most experimental studies, was that subjects were able to exercise longer until exhaustion occurred.

Due to the high subjectivity of caffeine research for athletes, as every individual is different,  I believe the negative effects of consuming caffeine in the form of soft drinks for any endurance activity far outweighs any positive.  Because longer races have a greater baseline risk of dehydration, nausea and abdominal cramps, it is very important to consider the side effects of caffeine.

BE AWARE: Coffee or tea can interfere with the body’s absorption of many necessary nutrients.

Calcium

Caffeine causes calcium to be excreted in the urine and feces. For every 150 mg of caffeine ingested, about the amount in one cup of coffee, 5 mg of calcium is lost. This effect occurs even hours after the consumption of caffeine. One study of postmenopausal women found that those who consumed more than 300 mg of caffeine lost more bone in the spine than women who consumed less.

Caffeine also inhibits the amount of calcium that is absorbed through the intestinal tract and depletes the amount retained by the bones. Studies have shown that women with high caffeine intake suffer more hip fractures than those who avoid caffeine or drink in moderation (1 to 2 cups per day).

Vitamin D

Caffeine inhibits vitamin D receptors, which limit the amount that will be absorbed. Because vitamin D is important in the absorption and use of calcium in building bone, this could also decrease bone mineral density, resulting in an increased risk for osteoporosis.

Iron

Caffeine interferes with the body’s absorption of iron, which is necessary for red blood cell production. Drinking caffeine at the same time as an iron source can reduce absorption by up to 80%, according to the Nutrition Desk Reference. Any beverage containing caffeine should be separated from iron-containing foods or supplements by at least one hour.

B Vitamins

Caffeine has a mild diuretic effect, which increases urination. Water soluble vitamins, such as the B-vitamins, can be depleted as a result of the fluid loss. In addition, it interferes with the metabolism of some B-vitamins, such as thiamine (vitamin B1). The one exception to this rule appears to be vitamin B12. Caffeine stimulates the production of stomach acid, which actually helps the body absorb B12.  This is why you will see caffeine used in energy drinks that use B12 for energy.  BE AWARE OF THE AMOUNTS OF CAFFEINE USED FOR ENERGY DRINKS OR SUPPLEMENTS, it should not take more than the equivalent of ¼ - ½  cup of coffee to be effective.

Other Vitamins and Minerals

Caffeine may reduce the absorption of manganese, zinc and copper. It also increases the excretion of the minerals magnesium, potassium, sodium and phosphate. There is also evidence that caffeine interferes with the action of vitamin A.

Recommendations for athletes

If you choose to use caffeine, then here are a few tips that may help you maximize the benefits.

1. Ingest caffeine about 3 - 4 hours before the competition. Although blood levels of caffeine peak much sooner, the maximum caffeine effect on fat stores appears to occur several hours after peak blood levels.
2. Consider decreasing or abstaining from caffeine for 3 - 4 days prior to competition. This allows for tolerance to caffeine to decrease and helps ensure a maximum effect of caffeine. Be careful though, because some may experience caffeine withdrawal.
3. Make sure that you have used caffeine extensively under a variety of training conditions and are thoroughly familiar with how your body reacts to this stimulus. Never try anything new on race day.
4. Be prepared to accept the consequences if your urine test is above the current cutoff.