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Warm up with iron.

Warm up with iron

Most women consume less iron than the recommended daily allowance of 18 milligrams. And that may help explain why many women shiver in environments where men are comfortable, according to two new studies.

John L. Beard at Pennsylvania State University in University Park measured responses in normal and anemic women to being submerged to the neck for 100 minutes in a 82[deg.]F pool. He tested each woman up to six time during the first phase of her menstrual cycle. Compared with the 10 who had normal levels of iron, the eight anemic women experienced almost twice as large a drop in body temperature (1.3[deg.]F), generated 13 percent less heat and had a lower metabolic rate. Moreover, blood glucose measurements indicate the anemic women warmed themselves less efficently -- relying more on glucose than on fats for the energy. After 12 weeks on iron supplements, the formerly anemic women responded normally.

But you don't have to be anemic to respond in this way. In a similar experiment, physiologist Henry C. Lukaski at the Agriculture Department's Human Nutrition Research Center in Grand Forks, N.D., measured the responses of 12 healthy bathing-suit-clad women to a 64[deg.]F draft. Prior to the first test, each had dieted on specially prepared low-iron repasts for 80 days. Until the next test, 100 days later, each consumed a revised diet offering them 16 mg of iron daily -- more than three times the previous level. While the low-iron diet seriously depleted body reserves of iron (measured as ferritin), Lukaski says the women never actually became anemic.

Tested after the low-iron diet, the women began shivering -- the body's attempt to warm itself -- after 84 minutes. Measurements showed their body temperatures had dropped almost 1.1[deg.]F. After the iron-repleting diet, the women went 8 minutes longer before shivering, experienced only half the drop in core body temperature observed in the first test, and produced only one-half to one-third as much norepinephrine -- a hormone that signals the body to generate more heat.
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Title Annotation:effect of iron deficiency on body temperature
Publication:Science News
Date:May 7, 1988
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