I recently moved from the East Coast to Los Angeles. One of the most common things I hear from people is that my blood will thin out as I adjust to the climate here. I'm told that the temperature difference will become acute and I'll find 60 degrees cold. Is it true that my blood will "thin" or is this an old wives' tale?
Like most old wives' tales, this one, though not true, has some logic behind it. The ability of the blood to coagulate, or clot, has nothing to do with how cold it is outside. "There are some genetic factors, and things like medications and smoking, that can affect the ability of the blood to clot. But it really has nothing to do with external factors like climate," says Dr. Sara Tariq, professor of internal medicine at the University of Arkansas for Medical Sciences.
To Southern California transplants from colder regions, it may seem as if their blood is thinning, and after a few seasons, 60 degrees here starts to feel like 40 degrees used to feel in, say, Chicago. But, says Dr. Robert Lavender, also a professor of internal medicine at the University of Arkansas, how cold a person feels is highly individual, and has nothing to do with blood coagulation.
"Some people are just more accustomed to the cold and better able to withstand it," he says.
Still, blood is part of the body's thermoregulation system. In cold weather, surface capillaries get smaller, pushing warm blood deeper into the body to help keep it toasty. In warm weather, more blood fills those capillaries so heat can escape through the skin. So if your vascular system gets used to year-round warmth, and then in January you board a plane to upper Minnesota, it'll take time for your blood delivery system to readjust. For a while, you'll feel like the cold you left behind is colder than you remember.
-- Susan Brink
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