Ask the Coach: Caffeine and Dehydration

By Coach John Hughes

RBR Reader Jack asks, “I love my coffee. When I stop at a convenience store with my buddies, I usually get a Coke or sometimes a Starbucks Frappuccino. They give me a hard time saying caffeine causes me to pee more and I get dehydrated. But I don’t go to the bathroom any more than they do after drinking Gatorade. Does caffeine dehydrate me?”

Jack, every morning I have a couple of shots of espresso before riding or cross-country skiing. On my bike depending on the season I’ll take a bottle of iced coffee or a thermos of hot coffee. Skiing I take a thermos of green tea mixed with powdered Gatorade. Gatorade isn’t any better than another sports drink. I just like the flavor.

Pros and Amateurs Use Caffeine

Before a hard climb or the end of a stage, a pro often has a Coke or a gel with caffeine. Caffeine is one of the few performance enhancing substances permitted by the World Anti-Doping Agency. US Anti-Doping Agency.

The NCAA limits caffeine intake. “A urinary caffeine concentration greater than 15 micrograms per milliliter constitutes a positive drug test, which results in a one-year suspension from competition, according to the NCAA’s drug testing manual.” An athlete would need to consume about 500 mg of caffeine two to three hours before an event to test positive. See the tables below of the amounts of caffeine in different drinks and foods.

Caffeine and Performance

PubMed published a study on Caffeine as an ergogenic aid, which concludes, “Caffeine has been studied for its potential use as an ergogenic aid. Several studies have demonstrated an improvement in exercise performance in submaximal endurance activities. Its potential ergogenic effect in acute, high-intensity exercise is less clear.”   

Caffeine and Dehydration

The National Library of Medicine published a study on Caffeine and diuresis during rest and exercise: A meta-analysis. Diuresis means increasing the urine production. The meta-analysis looked at 16 separate studies on caffeine ingestion and urine volume. The median caffeine dosage was 300 mg. The study concluded, “Caffeine exerted a minor diuretic effect which was negated by exercise. Concerns regarding unwanted fluid loss associated with caffeine consumption are unwarranted particularly when ingestion precedes exercise.”

Is caffeine a threat to hydration or rehydration? from Caffeine for Sports Performanceby Louise Burke, Ben Desbrow and Lawrence Spriet says, “Caffeine is a weak diuretic. It may influence the volume of urine production and loss by acting on some of the hormones involved in urine production, and it may also influence the loss of electrolytes in urine. However, tolerance to the diuretic effects of caffeine is acquired in as little as 4 or 5 days of regular caffeine intake.

Drinking enough during the day is important both for performance and for good health. Thirst is a factor in how much people drink. Habits, personal preferences, fluid availability and social activities also influence how much one drinks. Tea, coffee, cola drinks and energy drinks contribute a significant amount of voluntary fluid intake.

Caffeine Content Drinks, Foods and Supplements

Coffee and tea

Brewed coffee	250 ml cup (a little over one US cup)	40 – 110 mg of caffeine
Espresso	1 shot	25 – 215 mg
Starbucks Double Shot	192 ml can	130 mg
Starbucks Frappuccino	375 ml	90 mg
Black tea	250 ml cup	25 – 110 mg
Green tea	250 ml cup	30 – 50 mg
Iced tea	600 ml bottle	20 – 40 mg

Chocolate

Chocolate milk	60 g	5 – 15 mg of caffeine
Chocolate bar	60 g	58 mg

Soft drinks

Coca-Cola and Coke Zero	355 ml can	34 mg of caffeine
Diet Coke	355 ml can	46 mg
Pepsi	355 ml can	38 mg
Mountain Dew	355 ml can	36 mg
Dr. Pepper	355 ml can	40 mg

Energy drinks

Red Bull	250 ml can	80 mg of caffeine
Rock Star	500 ml can	160 mg
AMP	500 ml can	160 mg
Jolt	350 ml can	140 mg

Note the serving sizes differ. Red Bull, Rock Star and AMP each have 80 mg of caffeine per 250 ml. Jolt has 100 mg of caffeine per 250 ml.

Sports products

Most drinks, bars and gels have no caffeine. A few varieties of the following have caffeine. The labels say whether something has caffeine.
HEED	30 mg (1 heaping scoop)	25 mg of caffeine
Gatorade & Powerade	No caffeine
Clif Bloks (a few types)	1 blok	50 mg
Clif Bars (a few types)	1 bar	45 – 65 mg
GU (a few types)	1 gel	20 – 40 mg
PowerBar gel (a few types)	1 gel	25 mg
Hammer gel, Espresso	1 gel	50 mg

Other

V Pocket Rocket	60 g	160 mg of caffeine
Original 5-Hour Energy	60 g	215 mg
Excedrin Extra Strength	1 tablet	65 mg
NoDoz	1 tablet	200 mg

Daily consumption

The Food and Drug Administration recommends consuming not more than 400 mg of caffeine per day. Caffeine on a ride will have more of an effect if you consume less caffeine in your daily diet.

Experiment of one

Caffeine affects each of us differently. Caffeine may help you, make you jittery or have no apparent effect.

Eating & Drinking Like the Pros

I researched what several teams’ riders consume before, during and after a race and discussed the results with cycling nutrition experts. The answers may surprise you in terms of the variety and unusual nature of some of the food and drink. But the findings hold lessons and benefits for cyclists at all levels. We all require energy and replenishment of lost minerals and nutrients when we ride. Eating and drinking like the pros offers us the same nutritional benefits, which we can customize to our own needs – typically at a fraction of the cost of commercial sports food and drink, if we choose to make our own.

I worked with a professor of nutrition and an expert on hydration and electrolytes (both experts are cyclists) to create recipes for both sports drinks and food. They’re easy to make, with known, unprocessed ingredients, and can be tailored to your specific taste and needs.

The 15-page Eating & Drinking Like the Pros is just $4.99.

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Coach John Hughes earned coaching certifications from USA Cycling and the National Strength and Conditioning Association. John’s cycling career includes course records in the Boston-Montreal-Boston 1200-km randonnée and the Furnace Creek 508, a Race Across AMerica (RAAM) qualifier. He has ridden solo RAAM twice and is a 5-time finisher of the 1200-km Paris-Brest-Paris. He has written over 40 eBooks and eArticles on cycling training and nutrition, available in RBR’s eBookstore at Coach John Hughes. Click to read John’s full bio.