The New Rules of Hydration

Old: Protein exacerbates dehydration.
New: Protein enhances hydration.

The first generation of sports drinks contained no protein because it was believed to slow the absorption of fluid into the bloodstream from the stomach and intestine. But new evidence suggests that a small amount of protein actually enhances both fluid absorption and retention in athletes.

A recent study from the Universidad Catolica San Antonio in Spain found that a carb-protein sports drink actually entered the bloodstream significantly faster than a carb-only sports drink when used by cyclists pedaling at a moderately high intensity level.

More: How Much Water Should You Drink?

In another study from St. Cloud State University in Minnesota, athletes retained a carb-protein sports drink 15 percent better than a carb-only drink, meaning 15 percent less of it was wasted in the bladder. "A small amount of protein in a sports drink may enhance absorption and retention by increasing osmolality," says Robert Portman, Ph.D., and CEO of PacificHealth Labs, manufacturer of the protein-powered Accelerade sports drink.

"Small" is the operative word. Packing your water bottle with protein powder is not the secret to peak performance. Too much protein slows absorption and hampers hydration. Research shows that sports drinks containing only about five grams of protein per 12 oz. not only re-hydrate better, but also reduce muscle damage and increase endurance compared to drinks without protein. Recently, the International Society of Sports Nutrition recommended the use of protein-added sports drinks by both competitive athletes and daily exercisers.

More: Bottled water: Better than tap?

Old: Caffeine exacerbates dehydration.
New: Caffeine does not affect dehydration.

Caffeine is a known diuretic, which means it increases urine production and has a dehydrating effect. But research has also shown that during exercise, the body is able to circumvent the diuretic influence of caffeine, which can boost athletic performance by stimulating the nervous system and reducing perceived effort.

A new study conducted at the University of Birmingham in England found that caffeine increases the rate at which supplemental carbohydrates (those consumed during the workout as opposed to those already stored in the body) are burned during exercise. In the study, cyclists received either a 6 percent glucose solution or a six percent glucose solution plus caffeine during a two-hour indoor cycling test.

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Researchers found that the rate at which the supplemental carbs were burned was 26 percent higher in the cyclists receiving carbs with caffeine, concluding that the caffeine may have increased the rate of glucose absorption in the intestine. By providing fuel to working muscles at an accelerated rate, caffeine helps athletes work harder for longer periods of time.

But don't overuse it. Reserve caffeine consumption for races and occasional high-intensity workouts. "The best use of caffeine as an ergogenic aid [energy booster] is prior to competition," says Jose Antonio, Ph.D, author of Supplements for Endurance Athletes. "The beneficial effects of caffeine on athletic performance are reduced with habituation, so the more often you rely on it, the less it will do for you."

Although no major sports drink brand contains caffeine, some flavors of sports gels do, such as Gu Chocolate Outrage, Strawberry Clif Shot, and Chocolate Accel Gel.

More: What's in Your Water?

The Cardinal Rule

One principle of proper hydration hasn't changed: Practice makes perfect. Experiment with various hydration strategies to learn what works best for you. Try different sports drinks in varying amounts, and hydrate at different times during your workout to discover the optimal mix.

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