A good way to check your hydration level is through your urine.
Although Scott warned there are foods — such as beets and certain dietary supplement ingredients — that can alter the color of your urine, typically, your urine should be straw-colored (light) and clear when you’re well hydrated, said Eslinger.
“Darker and more concentrated urine suggests dehydration,” she said.
This is important, because “long-term consequences of dehydration can include urinary tract infections, kidney stones, even kidney failure, and on the extreme end of the spectrum, seizures, and ultimately death,” said Scott.
Having a battle buddy is important, he added.
“It's usually somebody else who notices something about you before you notice it yourself,” he said. “A buddy might point out you're dragging behind or seem clumsier, ask if you’re okay, and remind you to drink something.”
How much is good enough?
To be fully hydrated, drinking small amounts of fluids constantly throughout the day is best.
Eslinger highlighted that most people need several hours to drink enough fluids to replace what they have lost through sweat.
“The sooner you get started, the less strain you place on your body from dehydration, which is a primary contributor to heat exhaustion,” she said. “Drinking at shorter intervals is more effective than drinking large amounts infrequently.”
And while the ideal amount of fluids varies by individual due to body weight, activity, environment, and other factors, Scott suggests that a good rule of thumb is aiming “to consume half your body weight in pounds in fluid ounces daily” as a starting point.
According to his suggestion, an individual weighing 150 lbs. should consume about 75 oz. of liquids daily from food and beverages — that’s equal to almost 9.5 cups. But that’s under normal circumstances and activities. If you exert yourself more than usual, such as exercising or working in the heat, you should aim for more.
The Human Performance Resources by CHAMP (HPRC) at USU’s Consortium for Health and Military Performance (CHAMP), recommends aiming for 16-32 oz. of fluid every hour, but no more than 48 oz. per hour, during exercise or high-exertion activities. Likewise, hydrating with water during activity under one hour in duration is sufficient. However, for activity lasting longer than one hour, research supports consuming sports drinks that contain electrolytes and carbohydrates.
In addition, many fruits and vegetables are rich in water and minerals, including melons, berries, peaches, oranges, cucumbers, celery, and lettuce. Milk is also an effective rehydrating option, too, Scott said.
“Dairy milk, for those that tolerate dairy, is one of our best hydrating beverages,” he said. “It naturally contains both of those electrolytes (sodium and potassium), and it’s predominantly made up of water.”
What’s even better, chocolate milk is not only rehydrating, he said, but it also helps to replenish some of the carbohydrates that your body burns during prolonged exercise of 60 minutes or longer.
During those types of activities, “your body uses carbohydrates stored in the liver and muscle in the form of glycogen as its predominant fuel source,” said Scott.
“Chocolate milk has carbohydrates, which helps replenish some of those glycogen stores; protein, which we know is important for the repair process; calcium and vitamin D, which we know are crucial for bone health,” he said. “So, it really is a complete deal.”
What to Do During Deployed Operations?
In a deployed environment, options may be limited during operations. In that case, Scott said, “consuming foods and beverages that replace fluids and electrolytes (sodium and potassium) will typically work out better than just plain water alone, but it's important to incorporate those fluids throughout the entire day.”
To make it easier, Eslinger recommends hydrating before work, during work, and after work — especially for people working regularly in high-heat climates, like the desert.
In general, Scott recommends taking rest breaks from high-exertion activities, keeping track of work-to-rest ratios, and using hydration tables based on different heat categories.
Years of military operations in extreme climates has yielded lessons learned for optimal hydration, such as monitoring the Wet Bulb Globe Temperature. Similar to the heat index, this tool is useful in measuring the heat stress on the body and can help “reduce the number of heat stress injuries for participants and leadership,” concluded Eslinger.