首页
登录
职称英语
When scientists at the Australian Institute of Sport recently decided to che
When scientists at the Australian Institute of Sport recently decided to che
游客
2023-12-15
22
管理
问题
When scientists at the Australian Institute of Sport recently decided to check the Vitamin D status of some of that country’s elite female gymnasts, their findings were fairly alarming. Of the 18 gymnasts tested, 15 had levels that were "below current recommended guidelines for optimal bone health," the study’s authors report. Six of these had Vitamin D levels that would qualify as medically deficient. Unlike other nutrients, Vitamin D can be obtained by exposure to ultraviolet radiation from sunlight, as well as through foods or supplements. Of course, female gymnasts are a unique and specialized bunch, not known for the quality or quantity of their diets, or for getting outside much.
But in another study presented at a conference earlier this year, researchers found that many of a group of distance runners also had poor Vitamin D status. Forty percent of the runners, who trained outdoors in sunny Baton Rouge, Louisiana, had insufficient Vitamin D. "It was something of a surprise," says D. Enette Larson-Meyer, an assistant professor in the Department of Family and Consumer Sciences at the University of Wyoming and one of the authors of the study.
Vitamin D is an often overlooked element in athletic achievement, a "sleeper nutrient," says John Anderson, a professor emeritus of nutrition at the University of North Carolina and one of the authors of a review article published online in May about Vitamin D and athletic performance. Vitamin D once was thought to be primarily involved in bone development. But a growing body of research suggests that it’s vital in multiple different bodily functions, including allowing body cells to utilize calcium (which is essential for cell metabolism), muscle fibers to develop and grow normally, and the immune system to function properly. "Almost every cell in the body has receptors" for Vitamin D, Anderson says. "It can up-regulate and down-regulate hundreds, maybe even thousands of genes," Larson-Meyer says. "We’re only at the start of understanding how important it is."
But many of us, it seems, no matter how active and scrupulous we are about health, don’t get enough Vitamin D. Nowadays, "many people aren’t going outside very much," Johnson says, and most of us assiduously apply sunscreen and take other precautions when we do. The Baton Rouge runners, for instance, most likely "ran early in the morning or late in the day," Larson-Meyer says, reducing their chances of heat stroke or sunburn, but also reducing their exposure to sunlight.
Meanwhile, dietary sources of Vitamin D are meager. Cod-liver oil provides a whopping dose. But a glass of fortified milk provides a fraction of what scientists now think we need per day. (A major study published online in the journal Pediatrics last month concluded that more than 60 percent of American children, or almost 51 million kids, have "insufficient" levels of Vitamin D and another 9 percent, or 7.6 million children, are clinically "deficient," a serious condition. Cases of childhood rickets, a bone disease caused by lack of Vitamin D, have been rising in the U.S. in recent years.)
Although few studies have looked closely at the issue of Vitamin D and athletic performance, those that have are suggestive. A series of strange but evocative studies undertaken decades ago in Russia and Germany, for instance, hint that the Eastern Bloc nations may have depended in part on sunlamps and Vitamin D to produce their preternaturally well-muscled and world-beating athletes. In one of the studies, four Russian sprinters were doused with artificial, ultraviolet light. Another group wasn’t. Both trained identically for the 100-meter dash. The control group lowered their sprint times by 1.7 percent. The radiated runners, in comparison, improved by an impressive 7.4 percent.
More recently, when researchers tested the vertical jumping ability of a small group of adolescent athletes, Larson-Meyer says, "they found that those who had the lowest levels of Vitamin D tended not to jump as high," intimating that too little of the nutrient may impair muscle power. Low levels might also contribute to sports injuries, in part because Vitamin D is so important for bone and muscle health. In a Creighton University study of female naval recruits, stress fractures were reduced significantly after the women started taking supplements of Vitamin D and calcium.
A number of recent studies also have shown that, among athletes who train outside year-round, maximal oxygen intake tends to be highest in late summer, Johnson says. The athletes, in other words, are fittest in August, when ultraviolet radiation from the sun is near its zenith. They often then experience an abrupt drop in maximal oxygen intake, beginning as early as September, even though they continue to train just as hard. This decline coincides with the autumnal lengthening of the angle of sunlight. Less ultraviolet radiation reaches the earth and, apparently, sports performance suffers. [br] People can get vitamin D from the following EXCEPT_____.
选项
A、Sunlight.
B、Cod-liver oil.
C、Medium exercise.
D、Supplements of Vitamin D.
答案
C
解析
此题是事实题。由第一段可知,维生素D可通过晒太阳、饮食和补充剂来获取。
转载请注明原文地址:https://tihaiku.com/zcyy/3275105.html
相关试题推荐
Environmentalscientistsobservethatitisofgreatsignificancetoprotect
Environmentalscientistsobservethatitisofgreatsignificancetoprotect
Environmentalscientistsobservethatitisofgreatsignificancetoprotect
Environmentalscientistsobservethatitisofgreatsignificancetoprotect
Environmentalscientistsobservethatitisofgreatsignificancetoprotect
Environmentalscientistsobservethatitisofgreatsignificancetoprotect
Thebizarreanticsofsleepwalkershavepuzzledpolice,perplexedscientists,
Thebizarreanticsofsleepwalkershavepuzzledpolice,perplexedscientists,
Recently,apossiblealternativewayofproducingpaperhasbeensuggestedby
Recently,apossiblealternativewayofproducingpaperhasbeensuggestedby
随机试题
Thecostofstagingtheyear2000OlympicsinSydneyisestimatedtobeast
患者足底被铁钉扎伤,5天后出现牙关紧闭、颈项强直和角弓反张,遇声、光刺激后痉挛加
根据《建筑工程建筑面积计算规范》(GB/T50353-2013)规定,建筑物内
以下哪项是五苓散的君药A.白术 B.桂枝 C.茯苓 D.泽泻 E
患者,女性,25岁。左侧头部着地摔伤,曾出现意识丧失。无头痛、呕吐。查体:血压1
胡兰和唐君毅二人在知己和论敌之间,见解多有抵触,______视对方为长友,并未因
各种运输方式内外部的各个方面的构成和联系,就是( )。 A.运输系统
(2013年真题)北京2008年奥运火炬长72cm,重585g,燃料为气态丙烷
根据《建筑施工场界环境噪声排放标准》,建筑施工场界环境夜间噪声的“夜间"是指(
共用题干 男性,20岁,平素健康,受凉后,突发寒战、高热、头痛,第3天出现右侧
最新回复
(
0
)