Hydration for summer heat waves


Take away message from the Southwest US heatwave:

Being fit/young/health-conscious/experienced-hiker-biker will not protect you from the deadly effects of extreme heat.

So far this week 5 people, aged 19 to 33 have died in Arizona.  All were engaged in outdoor recreational activities despite the extreme heat.  I’m going to hazard a guess that they, and others who became ill but did not die, thought that being experienced and fit outdoor athletes gave them immunity to the effects of soaring temperatures and low humidity.  It does not.

Typically in heatwaves, we hear about the deadly effects of heat on the elderly, and this is true.  As we age, our ability to adjust to the dehydrating effects of extreme heat are diminished.  Thirst mechanisms don’t always kick in; sweat glands may not work so well; medications may exacerbate the situation.  Ironically free-living elderly may be most at risk for these effects.  Seniors living in assisted care may be at lower risk, because care-givers should be paying attention to fluid intake and any signs of heat stress.

There are two kinds of dehydration in a heat wave: water loss due to sweating combined with poor fluid intake, and salt/water loss, due to extreme sweating and failure to replace both water and sodium.  Unfortunately, the symptoms of these very different problems are similar, while the solutions are very different.  We’re very tuned in to the need to hydrate; we’re also badgered by health experts to cut back on salt, our primary source of sodium.  Certainly many people consume too many salty foods.  Many health conscious people with low or moderate sodium intakes are also tuned in to the anti-salt message.  Most of the time that’s not a problem.  But if those same health conscious low-salt people are subjected to extreme heat stress, with heavy sweating, they could get into trouble.  If they start to feel the effects of extreme heat stress, and they’re lacking fluid and salt, drinking plain water can make the situation worse.

Loss of 2% of your body weight from sweating is the definition of dehydration.  At that point you may start to experience some of the classic symptoms, such as dizziness, rapid pulse, fatigue and throbbing headache.   Muscle cramps can be a sign your sodium is getting low.  Of course, the best way to prevent dangerous heat stress is to avoid outdoor activities in heat waves.  If being outdoors and sweating is unavoidable, have a sodium-containing sports drink available, as well as water.  According to an article in Modern Hiker, you could lose 2 liters of fluid an hour hiking in extreme heat.  But your digestive system can only absorb about 1/2 liter an hour.  So drink up before heading out and carry enough water and/or sports drinks.  Some marathon runners and triathletes, who compete in high heat for hours, are known to drink shots of pickle juice or carry a bouillon cube to nibble for the salt, while also drinking water.

During extreme heat waves, hydration is important for everyone.  Plain water, herbal iced tea, seltzer and flavored or infused waters are all fine choices.  Watery foods, like watermelon, cucumbers, grapes, oranges, yogurt, plums and zucchini also contribute to your fluid intake.

Should you increase salt intake?  There’s really no good all-purpose answer to that question.  People with a variety of chronic medical conditions that impact sodium status — such as heart disease, kidney disease and hypertension — should discuss that with their physician.  Unless you’re engaging in intense outdoor physical activity that leads to heavy prolonged sweating, plain water should be sufficient.  Salt tablets are not advisable, and salt tablets alone do not solve a dehydration problem.  In extreme heat, water — whether you’re drinking it, swimming in it or pouring it over your head — is always the first line of defense.

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