On Hydration

There has been a long-standing argument about how to properly maintain adequate hydration. There are proponents of everything from pure water up through full-strength sports drinks with various additives. While the Æther echos with the debate and sports drink companies rake in the gold, research has continued since my last article on hydration 10 years ago, perhaps shedding more light on this arcane topic.

In order for the body to operate at peak efficiency, it needs to do four things: 1) maintain body temperature 2) maintain hydration 3) maintain energy levels, and 4) maintain electrolytes (salts, especially sodium).

Peak exercise efficiency occurs at a body temperature slightly above normal (thus the recommendation to warm up prior to exercise). To keep from overheating, the body produces sweat which cools by evaporation. The sweat contains water and salt, however the concentration of salt in sweat is much less than in the blood. Therefore, when you sweat, you lose more water than salt causing your blood to have increasing concentrations of salt. As you become more used to the heat, the sweat becomes even more dilute and you lose even more water in proportion to the salt loss. This means it is much more important to replace water than salt, at least in the short run. Most SCA combat activities don’t last long enough to require additional energy or salt supplements (such as carbohydrates [sugars]) during that activity. Energy can be replenished by having a small snack between bouts in a list. During extended melees or wars there may be some benefit to rehydrating with a carbohydrate-containing drink.

What is the best way to replenish what the body needs? At a minimum, you should be drinking water. Contrary to some older recommendations, research has shown that drinking when you are thirsty is actually a pretty good method of staying hydrated. In fact, one study that carefully looked at thirst and the concentration of salts in the blood concluded that people will become thirsty and drink before any decrease in body water was detected. The old mantra of "if you're thirsty, you're already dehydrated" may not hold water (so to speak). Other studies show that you may be about 2% low before thirst kicks in, but that level of mild dehydration won't affect physical performance.  

Daily water requirements range from 2 L (a bit over 2 quarts) in normal climates with low exercise to 15 L (4 gallons) with heavy exercise in the desert. Urine color is a good indicator of your hydration status. Urine that is no darker than weak lemonade indicates good hydration (note that certain foods, vitamins, and medications can color the urine making hydration hard to assess).

The salt losses are more than adequately replaced by eating a normal diet. The goal is to replace water loss minute-by-minute and salt losses day-by-day.

By now almost everyone is familiar with the problem of drinking too much water (hyponatremia or water intoxication). This is actually very rare and is only seen in endurance races such as ultramarathons where the participant drinks excessive amounts of water over several hours of participation. It typically takes at least 5 hours of prolonged exercise with excessive drinking to get to the point of hyponatremia with most cases occurring with activity of more than 8 hours.  Dehydration is much more common to see in SCA activities. Don’t hold off drinking water for fear of this rare condition.

The ideas about effects of the carbohydrate (sugar) content of sports drinks has changed over the years. Some studies from the 1960s showed that carbohydrates in drinks slowed the rate that they are absorbed from the stomach. This is the reasoning behind the recommendation to dilute sports drinks in half. More recent studies have shown this not to be true. However, drinks with more than about 10% carbohydrate content can cause cramps, nausea, and diarrhea. Not something you want to have in the finals of Crown Tourney, or, as one author put it, “You'll be running, but not necessarily on the field!" Products that are under 8% carbohydrate do not need to be diluted. Gatorade® at its recommended strength is 6% carbohydrate, and therefore does not need to be diluted. Diluting the drinks can make the mixes go farther and can make limited money and/or supplies last longer.

A misconception commonly encountered is that drinking cold drinks causes stomach cramps and delays stomach emptying. This has not been borne out in experimental trials. In fact, cold liquids stimulate the emptying of the stomach. Cool drinks are probably still better tolerated than ice cold (ever get a ‘brain freeze’?)

If you use carbohydrate-containing drinks, be careful that the containers are protected from insects. Bees and other stinging insects especially like sweet drinks. Rapidly swigging down a drink that contains a bee quenching his thirst can be very surprising for both the bee and the drinker, with disastrous results for both. Sports-top bottles are great for keeping the insects out and are easy to squirt through most helms. Soda cans are terrible as you can’t see what you’re drinking – be it hornet or cigarette butt! Make sure sweet liquids are properly stored and reusable containers are thoroughly cleaned as bacteria grow most heartily in sweet liquids.

Conventional wisdom has always been to avoid drinks with caffeine because it increases urine output. The studies that this conclusion is based on took people who had abstained from caffeine for a period of time. When they were subsequently given caffeine, they did have an increase in urine production. However, when a person has been imbibing caffeine for approximately four days, the effect on urine production goes away. Drinks that should be avoided are those that contain alcohol, carbonation, and fruit juices. Alcohol does cause increased urine production. Carbonated drinks can cause you to feel more full due to the bubbles in the stomach reducing the amount of fluid you’ll drink and possibly causing cramping and discomfort during exercise. Soft drinks are both carbonated and have high carbohydrate concentrations. Fruit juices are typically well above the recommended 10% carbohydrate level. Salt tablets should not be used as they irritate the stomach and can potentially send a person’s salt levels too high, which can also be life-threatening. The American average diet contains adequate salt to replace losses and salting food to taste has been shown to adequately replace electrolytes.

Energy drinks are overall bad news with lots of marketing hype and no proven performance enhancement. Some additives can be dangerous, if not deadly. Ephedra was removed from the US market several years ago due to its association with numerous deaths, some due to heat stroke. Other additives for improved energy (usually caffeine or its “natural” cousin guarana) may be high enough to stimulate urine production or cause heart problems. Creatine has been commonly used as a muscle-building and recovery aid. Unfortunately, it really doesn't increase the amount of muscle but pulls water into the muscle cells and out of the circulation. The muscles look bigger, but aren't any stronger. It has been associated with at least one dehydration death. Protein supplements put a load on the kidneys. Most people who eat meat will plenty of protein from their diet, even body builders.

Many of the recommendations for increased fluid intake during exercise has been driven by sports drink companies quest for your hard-earned money rather than good science. Don’t let the hype get in the way of taking proper care of yourself or your SCA brethren. Even a drink that has the proper balance of nutrients does no good if no one will drink it. Pick a non-alcoholic, non-carbonated, low-sugar drink that your local group likes and will drink plenty of and make sure it's easily available. Don't take the advice of "The Most Interesting Man in the World" - Don't "Stay thirsty, my friends".


----. The Textbooks of Military Medicine: Medical Aspects of Harsh Environments, Vol. 1. The Borden Institute. 2002.
            Chapter 5. Pathophysiology of Heatstroke
            Chapter 6. Prevention of Heat Illness

Armstrong, Lawrence E. Performing in Extreme Environments. Human Kinetics. 2000.

Bookspan, Jolie. Health & Fitness in Plain English, 3nd Edition. Healthy Learning. 2008.

Montain, Scott J, and Matthew Ely. Water Requirements and Soldier Hydration: Chapter 7 of Military Quantitative Physiolgy: Problems and Concepts in Operational Medicine. Borden Institute. 2012.

Tucker, Ross, and Jonathan Dugas. Fluid Intake, Dehydration, and Exercise. Accessed on 28 Aug 2015.

Copyright © 2015 Galen of Ockham, MC, OP (MKA Keith E. Brandt, M.D., M.P.H.)  May be used in SCA publications as long as content is not modified and proper credit given. For all other uses, please contact the author at galen@chirurgeon.org .

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