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科学视角:给胆固醇正名~

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核心提示:本文就胆固醇的健康价值、人们为什么担心高胆固醇、什么导致了高LDL水平、你能做什么来降低你的胆固醇等给了大家一些健康贴士。


Cholesterol and Where It Lurks
Burgers. Bacon. Cheese fries. What do they have in common (besides being some people's idea of delicious)? They're all high in cholesterol.

Cholesterol, a waxy substance produced by the liver and found in certain foods, is needed to make vitamin D and some hormones, build cell walls, and create bile salts that help you digest fat. Actually, your liver produces about 1,000 milligrams of cholesterol a day, enough cholesterol so that if you never touched another cheese fry, you'd be OK. But it's hard to avoid cholesterol entirely because so many foods contain it.

Too much cholesterol in the body can lead to serious problems like heart disease. Many factors can contribute to high cholesterol, but the good news is there are things you can do to control them.

Lipids are fats that are found throughout the body. Cholesterol, a type of lipid, is found in foods from animal sources. This means that eggs, meats, and whole-fat dairy products (including milk, cheese, and ice cream) are loaded with cholesterol — and vegetables, fruits, and grains contain none.

The liver produces about 1,000 milligrams of cholesterol a day, and you probably consume about 150 to 250 milligrams in the foods you eat.

Because cholesterol can't travel alone through the bloodstream, it has to combine with certain proteins. These proteins act like trucks, picking up the cholesterol and transporting it to different parts of the body. When this happens, the cholesterol and protein form a lipoprotein together.

The two most important types of lipoproteins are high-density lipoproteins (or HDL) and low-density lipoproteins (or LDL). You've probably heard people call LDL cholesterol "bad cholesterol" and HDL cholesterol "good cholesterol" because of their very different effects on the body. Most cholesterol is LDL cholesterol, and this is the kind that's most likely to clog the blood vessels, keeping blood from flowing through the body the way it should.

On the other hand, HDL cholesterol removes cholesterol from the blood vessels and carries it back to the liver, where it can be processed and sent out of the body.

Why Do People Worry About High Cholesterol?
When you have too much cholesterol, it can be dangerous to your health. When LDL cholesterol levels are high, cholesterol is deposited on the walls of arteries and forms a hard substance called plaque. Over time, plaque causes the arteries to become narrower, decreasing blood flow and causing a condition called atherosclerosis (pronounced: ah-thuh-ro-skluh-ro-sis), or hardening of the arteries.

When atherosclerosis affects the coronary arteries (the blood vessels that supply the muscles of the heart), the condition is called coronary artery disease, which puts a person at risk for having a heart attack. When atherosclerosis affects the blood vessels that supply the brain, the condition is called cerebral vascular disease, which puts a person at risk of having a stroke.

Atherosclerosis may also block blood flow to other vital organs, including the kidneys and intestines. This is why it's so important to start paying attention to cholesterol levels as a teen — you can delay or prevent serious health problems in the future.

What Causes High LDL Cholesterol Levels?
Some of the factors that can lead to high cholesterol are:
●Overweight — Excess weight has been linked with high cholesterol levels.

●Heredity — If cholesterol problems or heart disease run in your family, you are at a higher risk for having problems.

●Diet — Remember the saying "you are what you eat"? Avoid foods that are high in cholesterol, saturated fat, and trans fat, all of which increase cholesterol levels and your risk of developing heart disease.

●Age — The risk of high cholesterol increases as you get older.

●Physical activity tends to increase HDL levels, which reduces your chance of developing heart disease.

What Can I Do to Lower My Cholesterol?
Some people who have high cholesterol levels need to be on medication as part of their treatment to lower it. Although most teens won't need to take medication to lower their cholesterol, it's still important to keep cholesterol in check because plaques can start to form during the teen years. To see if you have high cholesterol, talk to your doctor, who can test your cholesterol levels by drawing a sample of your blood.

You can't change your genes but there are things you can do now to decrease your risk for heart disease later.

The American Heart Association recommends that cholesterol intake should be less than 300 milligrams a day, total fat intake should be 30% or less of your total calories, saturated fat should be 10% or less of the total daily calories, and trans fats should be less than 1% of the total calories you consume.

Also, maintain a healthy weight and get moving. Regular aerobic exercise — stuff like biking, walking, and swimming — strengthens your heart, lowers cholesterol, and helps you to lose excess weight. For people who smoke, quitting can help decrease the risk of heart disease.

Healthy Tips
Here are some helpful tips you can try:
●Eat a diet that contains many low-cholesterol foods: fruits, veggies, whole grains (like breads and cereals), legumes (beans), and fish.

●Eat a diet that is low in saturated and trans fat. Replace saturated and trans fats with unsaturated fats. Use liquid vegetable oil or trans fat-free margarine instead of butter, shortening, or stick margarine. Stay away from products that contain hydrogenated vegetable oils.

●If you eat meat, try using lean meats and skinless poultry. Make sure you trim off all noticeable fat before cooking and drain the fat from the pan after browning meats.

●Instead of frying, try boiling, broiling, baking, roasting, poaching, steaming, or sautéing.

●Instead of whole milk, use low-fat or nonfat milk, which contains all the nutrients without all the fat. Choose other low-fat or nonfat dairy products including yogurt, cheese, and cottage cheese. You can also substitute low-fat buttermilk or yogurt in recipes that call for cream cheese or sour cream.

●Use trans-fat-free margarine.

●Instead of meat, use different sources of protein including fish, beans, peas, nuts, and tofu or other soy products.

●Instead of eggs, try just egg whites or cholesterol-free commercial egg substitutes.

●Pass on commercially prepared baked goods, which are often made with hydrogenated oils or trans fats.

●Looking for snacks that are low in fat and cholesterol? Try fruits, raw veggies and low-fat dips, low-fat whole-grain crackers, plain unsalted popcorn or pretzels, gelatin, or low-fat yogurt.

If you are concerned about cholesterol and heart disease, talk to your doctor. Visit the American Heart Association's website, which contains lots of information as well as easy low-cholesterol recipes for you to try at home. Although not all the factors contributing to heart disease and high cholesterol can be controlled, many can. Start taking care of your body now and it will thank you in the future.

Reviewed by: Mary L. Gavin, MD
Date reviewed: December 2009

参考译文:
胆固醇及其所在
汉堡、培根和芝士薯条。它们除了被一些人当作美味之外,还有什么共同点?那就是它们都含有大量胆固醇。

胆固醇是一种由肝脏分泌的蜡状物质,也可从某些食物中获得。它的作用是合成维生素D和某些激素,形成细胞膜,以及产生用于消化脂肪的胆盐。实际上,你的肝脏每天大约产生1000毫克的胆固醇,即使你不从其他来源摄取,这些胆固醇也已经足够。但是,完全避开胆固醇非常困难,因为它存在于很多种食物中。

体内过多的胆固醇会造成严重的问题,比如心脏病。许多因素可以导致高胆固醇,但好消息是你可以采取措施去控制它们。

油脂就是遍布全身的脂肪。胆固醇也是一种油脂,存在于动物来源的食物中。这意味着鸡蛋、肉类和全脂奶制品(包括牛奶、奶酪和冰激凌)都含有胆固醇——而蔬菜、水果和谷物中没有。

肝脏每天产生约1000毫克胆固醇,而你会从食物中摄入约150到250毫克。

胆固醇因为不能单独在血液中移动,所以必须和特定的蛋白质结合。这些蛋白质就像卡车一样,将胆固醇装载然后运到身体的不同部位。当这种结合发生时,胆固醇和蛋白质共同形成了脂蛋白。

最重要的两种脂蛋白分别是高密度脂蛋白(HDL)和低密度脂蛋白(LDL)。你可能听过人们把LDL称作有害胆固醇,而把HDL称作有益胆固醇,因为它们对身体有着非常不同的效果。大部分胆固醇是LDL,这类胆固醇最有可能阻塞血管,从而阻碍血液以其应有的方式在身体中流动。

反过来,HDL把胆固醇从血管中带走,并将其运回肝脏。肝脏可以处理这些胆固醇并将它们排出体外。

人们为什么担心高胆固醇?
当你的胆固醇水平过高时,你的健康可能面临威胁。如果LDL水平很高,胆固醇会沉积在动脉壁上,并形成一种被称为血栓的坚硬物质。一段时间后,血栓会使动脉变狭窄,血流减缓,还会造成动脉硬化。

当动脉硬化影响到冠状动脉(供应心肌的血管)时,就形成了冠心病,带来心脏病突发的风险。而当动脉硬化影响到供应大脑的血管时,就形成了脑血管病,使人面临中风的风险。

动脉硬化也可能阻碍流向其他重要器官的血液,这些器官包括肾脏和肠道。这就是为什么从青少年时期开始关注胆固醇水平如此重要——你能在未来延迟甚至阻止严重的健康问题。

什么导致了高LDL水平?
一些可能导致高胆固醇的因素是:
●超重——过高的体重和高胆固醇水平是关联的。

●遗传——如果你的家族中有胆固醇问题或心脏病的例子,那么你有这些问题的几率比别人更高。

●饮食——记得那句俗语“吃什么补什么”吗?尽量避免含有大量胆固醇、饱和脂肪和反式脂肪的食物,因为它们都会提高胆固醇水平和你患心脏病的概率。

●年龄——随着你年龄的增长,高胆固醇的可能性也在增加。

●体育锻炼有利于提高HDL水平,帮助减少你患心脏病的可能性。

我能做什么来降低我的胆固醇?
一些胆固醇水平高的人需要包括药物治疗在内的疗法来降低它。虽然大部分青少年不需要使用药物治疗来降低他们的胆固醇水平,但控制胆固醇仍然很重要,因为血栓可能在青少年时期就开始形成。如果你想知道自己的胆固醇水平是否过高,可以去找你的医生,通过采血样来测试你的胆固醇水平。

现在,你不能改变自己的基因,但还有些事情是你能做到的,而那可以减少你未来患心脏病的风险。

美国心脏协会建议:每天的胆固醇摄入量应少于300毫克;总脂肪摄入量应等于或少于你总热量的30%;饱和脂肪应等于或少于每日总热量的10%;反式脂肪应少于你所摄入总热量的1%。

另外,保持一个健康的体重并坚持运动。定期的有氧运动——例如骑车、步行和游泳——能够增强你的心脏,降低胆固醇并帮助你减掉多余体重。对于吸烟的人,戒烟也能帮助降低患心脏病的风险。

健康小贴士
以下是一些你可以尝试的方法:
●食谱中多使用低胆固醇食物:水果、蔬菜、全麦食物(例如面包和麦片)、豆类和鱼类;降低食谱中的饱和脂肪和反式脂肪的含量;用不饱和脂肪代替饱和脂肪和反式脂肪;用液体植物油或不含反式脂肪的人造黄油来代替黄油、起酥油和硬黄油;不要使用含有氢化植物油的产品。

●如果要食用肉类,尽量使用瘦肉和去皮的禽肉。要确保所有可见的脂肪在烹饪前都被切掉并把加热过程中溢出的油脂都滤去。

●不要使用煎炸的方式,尽量用煮、烤、焙、烘、炖、蒸或炒的烹饪方法。

●相对于全脂牛奶,低脂或无脂牛奶更好,因为它们包含所有的营养而不含脂肪。其他的奶制品也要选择低脂或无脂的,例如酸奶、奶酪和村舍式干酪(由脱脂凝乳制成)。在需要奶油芝士或酸奶油的菜谱中,你也可以使用低脂的白脱牛奶或酸奶作为替代。

●使用无反式脂肪的人造黄油。

●除了肉类,还有很多不同的蛋白质来源:鱼类、豆类、坚果、豆腐或其他豆制品。

●相对于鸡蛋,尽量仅使用蛋白或者采用不含胆固醇的鸡蛋替代品。

●不要购买烘烤的产品,因为它们常常是由氢化油或反式脂肪制成的。

●在寻找脂肪和胆固醇含量低的零食?水果、天然蔬菜和低脂蘸酱、低脂全麦薄饼、无盐爆米花或脆饼、明胶或低脂酸奶都可以尝试。

如果你很关注胆固醇问题和心脏病,可以去和你的医生讨论。访问美国心脏协会的网站,那里有很多的信息,也有你可以在家尝试的低胆固醇的简单菜谱。虽然不是所有导致心脏病和高胆固醇的因素都能被控制,但它们中的很多是可以的。现在开始关心你身体吧,它会在未来回报你的。

审阅人:医学博士Mary L. Gavin
审阅日期:2009年12月


相关阅读:正确认识鸡蛋跟胆固醇之“是非恩怨”

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