HOfficials from Europe, Japan, America, Japan, and Europe have warned residents not to go out in the sun, as northern hemisphere temperatures are among the highest ever recorded. It’s not just to prevent heat-stroke, but to prevent the long-term consequences as well. Medical researchers have begun to discover links between prolonged heat exposure and chronic conditions such as diabetes, kidney stones, heart disease, and obesity, due to climate change driving summer temperatures higher than ever before. “While increased risk for heat stroke is an obvious manifestation of global warming, climate change is actually causing health problems today, in both direct and indirect ways,” says Richard J. Johnson, a medical professor and researcher at the University of Colorado Anschutz Medical Campus, and one of the world’s foremost experts on the intersection of heat stress and kidney disease.
Johnson says that hotter weather can increase the risk of becoming dehydrated. This could lead to cognitive dysfunction, hypertension, acute kidney injury, or high blood pressure. Chronically dehydrated individuals are more likely to retain toxins and have a lower ability to expel them. This can lead the body and kidneys to store higher levels of glucose and salts. These substances can increase the risk of diabetes and metabolic syndrome. This medical term refers to high blood sugar and high blood pressure as well as abdominal obesity, which is thought to affect nearly 25% of U.S. adults. According to him, the likelihood of developing metabolic disease and the risk of having a heart attack or stroke will rise as temperatures rise.
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Another possible result of rising temperatures is the increased formation of kidney stones. An article published in The, 2008 by a research team. Proceedings of the National Academy of Sciences, argues that one unanticipated result of global warming is the likely northward expansion of the present-day south-eastern U.S. kidney stone “belt,” where heat and humidity are higher, and cases are currently concentrated. Low fluid intake and excessive fluid loss can increase the risk of kidney stones. Both of these factors are caused by high heat. The paper’s authors found that, based on projections of climate change-induced temperature gains, the percentage of the U.S. population living in high-risk zones for kidney stones will grow from 40% in 2000 to 56% by 2050, and to 70% by 2095. Even if kidney stones don’t develop, consistent exposure to high heat and dehydration—in agricultural laborers, for example—has been shown in some cases to cause irreversible kidney damage, as described in a 2015 case study co-authored by Johnson and published in ScienceDirectSugarcane workers from El Salvador were involved. “The kidney is very sensitive to heat stress,” says Johnson. “It is a barometer for health and climate change.”
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Johnson, the author Nature Wants Us to Be Fat: The Surprising Science Behind Why We Gain Weight and How We Can Prevent—and Reverse—It, A new paper on the link between obesity and dehydration is due to be published by Johnson. This has obvious implications for people who live in warmer areas. “When an animal starts developing dehydration, this triggers fructose production from carbs,” says Johnson. Fructose can stimulate the release of vasopressin which is responsible for storing water. Vasopressin stimulates fat production. Camels, he points out, don’t store water in their humps, they store fat. The fat that is produced when it’s burned becomes water. “Fat is actually used by animals to survive when water is not available,” he says. Fat production is the body’s reaction to—and anticipation of—dehydration.
Johnson’s hypothesis is that “climate change is making it easier to get dehydrated and hot, and in so doing it will activate this chemical reaction so that when carbs are present, it will lead to more fructose and vasopressin being made,” he says. “You can actually create obesity in animals by making them slightly dehydrated, so there’s a very strong link between dehydration, heat stress, and obesity.”
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Of course, dehydration isn’t a natural consequence of the heat. It is easily staved off by drinking water—not sugary drinks—staying rested, and finding shade. If you work in high temperatures, it is essential to stop and drink water or electrolyte solution. This will replenish the potassium and sodium lost from sweating. “Wear a hat,” says Johnson. “Get out of the sun.” His advice sounds just like any other health official’s for a reason. Heat can kill. Sometimes quickly—heat waves kill more people annually in the U.S. than hurricanes, lightning, tornadoes, floods, and earthquakes combined—and sometimes slowly. “If you go to an ER with heat stress, it increases your risk for developing chronic kidney disease later on in life,” says Johnson.
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