When your body gets overheated, it responds in several ways as it races to cool you back down and prevent serious health problems. Heat stress is when your internal body temperature rises above the normal range of 97 to 99 degrees Fahrenheit. This triggers physiological responses geared toward maintaining normal body temperature. Our internal body temperature is so tightly regulated that an increase of less than 1 degree activates functions such as sweating to cool our body and restore balance. Heat stress can put strain on many areas of the body, including the kidneys. The kidneys transport nutrients throughout and remove waste from your body.
A review published in Comprehensive Physiology evaluated how the cardiovascular system and kidneys respond to heat stress. When your body overheats, your heart pumps more blood, the blood vessels in your organs narrow, and the blood vessels in your skin widen to help decrease the excess heat. While this redistribution of blood to the skin is a positive response to help cool you down, it also decreases blood flow and volume to the kidneys by up to 30 percent. Restricted blood flow reduces the amount of oxygen and nutrients that is delivered to the kidneys. Prolonged exposure to heat stress and decreased blood flow to the kidneys can lead to kidney damage and even kidney failure.
Heat stress can be life-threatening to people who have medical problems that affect body temperature regulation or are otherwise vulnerable to overheating. Seniors, children, people who work outdoors (including military personnel and firefighters) and those who live in parts of the world where it is extremely hot may have an increased risk of heat stress. Some common signs of heat stress include muscle cramps and dehydration. People suffering from heat stress may also experience symptoms of heat exhaustion (pale skin, extreme fatigue, dizziness, heavy sweating, headache and blurred vision) and heat stroke (high body temperature, convulsions, confusion and even unconsciousness). It is important to recognize these signs and get medical help as soon as possible.
The next time you’re out in the hot weather, stay hydrated. Drink water often—even before you get thirsty. The Occupational Safety and Health Administration suggests that outdoor workers drink water every 15 minutes. Finally, limit your sun exposure by taking frequent rest breaks under the shade or inside an air-conditioned building in order to protect your kidneys.
Ijeoma Obi, MS, is a PhD candidate in the University of Alabama at Birmingham’s Department of Medicine, Nephrology Division, Section of Cardio-Renal Physiology and Medicine.