Hydration Replacement in the Heat and Humidity
Summer can be stressful for the aging person because of heat and humidity. The natural response to the Low Country’s heat is perspiration. This response is healthy, although unappealing. The esthetic problems of perspiration are not of medical significance, however. The important consideration is to ensure that the body receives adequate hydration. If water in the body is not replaced after sweating, the internal fluid volume gets low, which can result in medical problems including heat stress.
Who Is Susceptible to Heat Illness?
A person who spends time outdoors in heat greater than 85 degrees and in high humidity while performing vigorous exercise is susceptible to heat illness. Other factors that can make a person susceptible to heat illness include older age, heart disease, other chronic diseases, extreme exercise, sunburn, obesity, sleep deprivation, alcoholism and several drugs. Patients who take beta-blockers, tricyclic antidepressants, aspirin and diuretics are predisposed a person to heat disorders.
After playing tennis recently, I conversed about what should be done to replace fluid loss from playing in the heat and humidity. This conversation brought to light that this column has never actually researched this very important question. Hydration is important — especially for someone actually working or playing in the heat and humidity.
Quite a bit of science has delved into the best type of drink for preventing and treating heat and exercise induced volume depletion. Plain water works well and is the first choice if exercise and perspiration is not prolonged over several hours. However, many studies have shown that perspiration contains electrolytes, as well as water. These electrolytes are important for bodily function and contain sodium with an average concentration between 800 and 1,100 milligrams per litre.
Electrolytes also contain potassium, which is important to the heart and other organs. The potassium concentration in sweat averages 195 mg/litre. For the mathematicians reading this, you have already calculated that the loss of sodium is three to five times that of potassium. Another important element in sweat is calcium, but its loss is much lower than the other electrolytes, although it may contribute to muscle cramps.
Sports drinks argue that that we need to replace lost electrolytes, as well as some carbohydrates in the form of sugars to stay well hydrated and energized. The table below compares some of these drinks.
As we age, we need to prevent heat illnesses and avoid heat stress. Many of the precautions that we can take are common sense. The most important preventive measure is to stay hydrated with fluids that contain some carbohydrates and salt, such as sports drinks found at your local grocery store. To avoid too much salt intake, these sports drinks can be diluted. Avoid alcohol while in the heat because it is a vasodilator and diuretic, which could deplete blood volume. Coffee and tea are also diuretics. Although water is important, too much can dilute important electrolytes. My advice is stick to mainly water, and a mixture of water and sports drink powders. Note that orange juice is very high in potassium, sugar and calories, which could counteract any weight watching efforts.
Enjoy the heat and humidity but stay hydrated!
|TABLE COMPARING POSSIBLE FLUID REPLACEMENT|
|Ingredients per 8 oz.||Carb Content||Carbs||Protein||Calories||Sodium||Potassium||Caffeine||High Fructose|
|Gatorade® Endurance Formula||6%||14g||0g||50||200mg||90mg||0mg||Yes||No|
|Amino Vital RTD®||3%||8g||<1g*||35||10 mg||35mg||0mg||No||No|
|Propel Fitness Water®||1%||3g||0g||10||35mg||0mg||0mg||No||No|
• Accelerade is a registered trademark of Mott's LLP.• Amino Vital is a registered trademark of Ajinomoto.• Cytomax is a registered trademark of Cytosport, Inc.• Gatorade and Propel are registered trademarks of Stokely-Van Camp, Inc.• Powerade is a registered trademark of the Coca-Cola Company.• Propel is a registered trademark of PepsiCo.http://www.accelerade.com/products/ProductComparison.aspx, July 12, 2010
MUSCHealth.com Online Health Library Related Links:
Dehydration and Heat Stroke
Survival Tips for Seabrook Heat and Humidity
1. Drink plenty of fluids, carbohydrate-electrolyte (Gatorade or like)
2. Wear light colored clothing that wicks perspiration (cotton)
3. Do not do strenuous exercise during the hottest part of the day in full sun
4. Get acclimated - increase exercise gradually each day in the heat
5. Avoid sunburn
6. Enjoy the air conditioning – that’s why it was invented