新视野大学英语读写教程听力 第三册 te-unit02-a

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[00:00.00]，就把hxen.com复制到QQ个人资料中！Iron and the Effects of Exercise
[00:-1.00]1  sports medicine experts have observed for years that endurance athletes,
[00:-2.00]particularly females, frequently have iron deficiencies.
[00:-3.00]Now a new study by a team of Purdue University researchers
[00:-4.00]suggests that even moderate exercise may lead to reduced iron in the blood of women.
[00:-5.00]2  "We found that women who were normally inactive
[00:-6.00]and then started a program of moderate exercise showed evidence of iron loss,"
[00:-7.00]says Roseanne M.Lyle, associate professor at Purdue.
[00:-8.00]Her study of 62 formerly inactive women
[00:-9.00]who began exercising three times a week for six months
[00:10.00]was published in the journal Medicine & Science in Sports & Exercise.
[00:11.00]3  "Women who consumed additional meat
[00:12.00]or took iron supplements were able to bounce back," she notes.
[00:13.00]"But the new exercisers who followed their normal diet
[00:14.00]showed a decrease in iron levels."
[00:15.00]4  Iron deficiency is very common among women in general,
[00:16.00]affecting one in four female teenagers
[00:17.00]and one in five women aged 18 to 45, respectively.
[00:18.00]But the radio is even greater among active women,
[00:19.00]affecting up to 80 percent of female endurance athletes.
[00:20.00]This means, Lyle says,
[00:21.00]that "too many women ignore the amount of iron they take in".
[00:22.00]Women of child-bearing age are at greatest risk,
[00:23.00]since their monthly bleeding is a major source of iron loss.
[00:24.00]Plus, many health-conscious women increase their risk by rejecting red meat,
[00:25.00]which contains the most easily absorbed form of iron.
[00:26.00]And because women often restrict their diet in an effort to control weight,
[00:27.00]they may not consume enough iron-rich food,
[00:28.00]and are liable to experience a deficiency.
[00:29.00]5  "The average woman takes in only two thirds
[00:30.00]of the recommended daily allowance for iron,"
[00:31.00]notes another expert.
[00:32.00]"For a woman who already has a poor iron status,
[00:33.00]any additional iron loss from exercise
[00:34.00]may be enough to tip her over the edge into a more serious deficiency,"
[00:35.00]notes the expert.
[00:36.00]6  Exercise can result in iron loss through a variety of mechanisms.
[00:37.00]Some iron is lost in sweat, and, for unknown reasons,
[00:38.00]intense endurance exercise
[00:39.00]is sometimes associated with bleeding of the digestive system.
[00:40.00]Athletes in high-impact sports such as running
[00:41.00]may also lose iron through a phenomenon
[00:42.00]where small blood vessels in the feet leak blood.
[00:43.00]7  There are three stages of iron deficiency.
[00:44.00]The first and most common is having low iron reserves,
[00:45.00]a condition that typically has no symptoms.
[00:46.00]Fatigue and poor performance may begin to
[00:47.00]appear in the second stage of deficiency,
[00:48.00]when not enough iron is present to form the molecules of blood protein
[00:49.00]that transport oxygen to the working muscles.
[00:50.00]In the third and final stage, people often feel weak,tired,
[00:51.00]and out of breath--and exercise performance is severely compromised.
[00:52.00]8  "People think that if they\'re not at the third stage,nothing is wrong,
[00:53.00]but that\'s not true,"says John L.Beard, who helped design the Purdue study.
[00:54.00]"You\'re not stage 3 until your iron reserves go to zero,
[00:55.00]and if you wait until that point, you\'re in trouble."
[00:56.00]9  However,
[00:57.00]most people with low iron reserves don\'t know they have a deficiency,
[00:58.00]because traditional methods of calculating the amount
[00:59.00]of iron in blood(by checking levels of the blood protein that transports oxygen)
[-1:00.00]are not sufficient,Beard states,
[-1:-1.00]Instead, it\'s important to check levels of a different compound,
[-1:-2.00]which indicates the amount of storage of iron in the blood.

[-1:-3.00]While active, child-bearing age women
[-1:-4.00]are most likely to have low iron stores,he notes,
[-1:-5.00]"Men are not safe,
[-1:-6.00]especially if they don\'t eat meat and have a high level of physical activity."
[-1:-7.00](An estimated 15 percent of male long distance runners have low iron stores.)
[-1:-8.00]Beard and other experts say
[-1:-9.00]it\'s advisable for people in these groups
[-1:10.00]to have a yearly blood test to check blood iron reserves.
[-1:11.00]10  If iron levels are low,
[-1:12.00]talk with a physician to see if the deficiency should be corrected
[-1:13.00]by modifying your diet or by taking supplements.
[-1:14.00]In general, it\'s better to undo the problem
[-1:15.00]by adding more iron-rich foods to the diet,
[-1:16.00]because iron supplements can have serious shortcomings.
[-1:17.00]Supplements may produce a feeling of wanting to throw up,
[-1:18.00]and may be poisonous in some cases.
[-1:19.00]The best sources of iron,
[-1:20.00]and the only sources of the form of iron most readily absorbed by the body,
[-1:21.00]are meat, chicken, and fish.
[-1:22.00]Good sources of other forms of iron include dates,
[-1:23.00]beans, and some leafy green vegetables.
[-1:24.00]11  "Select breads and cereals with the words \'iron-added\' on the label,"
[-1:25.00]writes sports diet expert Nancy Clark.
[-1:26.00]"This added iron supplements the small amount that naturally occurs in grains.
[-1:27.00]Eat these foods with plentiful Vitamin C
[-1:28.00](for example, drink orange juice with cereal
[-1:29.00]or put a tomato on a sandwich) to enhance the amount of iron absorbed."
[-1:30.00]Clark also recommends cooking in iron pans,
[-1:31.00]as food can derive iron from the pan during the cooking process.
[-1:32.00]"The iron content of tomato sauce
[-1:33.00]cooked in an iron pot for three hours showed a striking increase,
[-1:34.00]the level going up nearly 30 times," she writes.
[-1:35.00]And people who are likely to have low iron
[-1:36.00]should avoid drinking coffee or tea with meals,she says,
[-1:37.00]since substances in these drinks
[-1:38.00]can interfere with iron being absorbed into the body.
[-1:39.00]12  "Active women need to be a lot more careful about their food choices,"
[-1:40.00]sums up Purdue\'s Lyle.
[-1:41.00]"If you pay attention to warning signs before iron reserves are gone,
[-1:42.00]you can remedy the deficiency before it really becomes a problem."
 

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