Are women really "cold-blooded?"


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My teenage brother recently let me in on a prank that he and his guy friends devised--on the day of the first snowfall, they're going to walk into school wearing nothing but Speedos.

"You're crazy!" I told him. "I could never do that."
"That's 'cause girls are 'cold-blooded.'"

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Like any big sister, my initial reaction was to prove him wrong. But, after giving it some thought, there may be some truth behind Mat's response. Given my past experiences, it does always seem like women are often colder than men. Does is just appear this way because women complain more, or are we naturally "cold blooded?" More specifically, is there actually a biological mechanism that makes us have colder blood than men? Michael Tipton, a professor of human and applied physiology at the University of Portsmouth, and Nigel Taylor, a professor of health sciences at the University of Wollongong, both support the latter hypothesis.

Before I explain why, I'll give you a little background. The skin of both men and women is usually held at a comfortable temperature by the blood pumping through minuscule, branch-like blood vessels called capillaries. Both sexes experience temperature changes when the tiny thermo-receptor cells just below the skin's surface detect cold and cause vasoconstriction to occur. In this process, the capillaries shut down and the blood that they would typically be using is redirected to more important places like the heart, the lungs. Taylor explains it quite simply: "If we reduce the blood flow to the skin, we're going to get more messages from the cold sensors in the skin that we are chilly."

Now what happens when we compare women to men? In a controlled, randomized, 219 person study published in a 1998 edition of the Lancet, researchers detected a statistically significant 2.8 degree Fahrenheit decrease in the skin temperature of women as compared to men. In his interpretation of the study, Tipton concludes that "if you lower people's temperatures by placing them in cold air, vasoconstriction happens more quickly in women... The blood flow to skin is shut down sooner and more intensely than in men, and afterwards it takes longer to warm up." This does not mean that the internal (blood) temperature of women is lower than men, just that their external (skin) temperature is lower. Taylor even states that "when a woman says she is cold, she really means her skin is cold."

This was a well-conducted study with extensive and professional physiological research to back it up. That being said, I do believe that there is a biological mechanism that causes women to feel colder than men, but I wouldn't go so far as to say to say that my brother is right in calling us "cold-blooded." Technically speaking, we're "cold-skinned"--take that Mathew!

Want to know why us ladies are "cold-skinned?" Check out my next blog.

2 Comments

I like how you connected your brother's prank to a scientific experiment. I think also men have more body fat and muscle than women, which could be why they feel more warm in the cold, especially when wearing speedos. I just read an article saying that men usually prefer colder temperatures, and that could lead to an interesting experiment. If you want to read more here is the article:

http://io9.com/why-do-womens-bodies-run-colder-than-mens-836827770

Hi Jesse! I agree with you when you say that men have more muscle than women, but I think that women have more fat than men (in general). This idea may account for why men are generally warmer. In his analysis of his well-conducted experiment, professor Muthu Periasamh (http://www.osuchildrensmusclegroup.org/periasamy.shtml) from Ohio State University says that "Our findings demonstrate for the first time that muscle...can generate [long-term] heat (http://www.newscientist.com/article/dn22250-muscles-that-do-nothing-can-keep-you-warm-and-thin.html#.Ump4MlCsiSo). Though fat may keep us insulated, it also blocks warmth from our cores from reaching our skin. I know I definitely don't have enough of either substance to be warm while wearing a Speedo in the snow!

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