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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
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膽固醇及其所在
漢堡、培根和芝士薯條。它們除了被一些人當作美味之外，還有什么共同點？那就是它們都含有大量膽固醇。
膽固醇是一種由肝臟分泌的蠟狀物質，也可從某些食物中獲得。它的作用是合成維生素D和某些激素，形成細胞膜，以及產生用于消化脂肪的膽鹽。實際上，你的肝臟每天大約產生1000毫克的膽固醇，即使你不從其他來源攝取，這些膽固醇也已經足夠。但是，完全避開膽固醇非常困難，因為它存在于很多種食物中。
體內過多的膽固醇會造成嚴重的問題，比如心臟病。許多因素可以導致高膽固醇，但好消息是你可以采取措施去控制它們。
油脂就是遍布全身的脂肪。膽固醇也是一種油脂，存在于動物來源的食物中。這意味著雞蛋、肉類和全脂奶制品（包括牛奶、奶酪和冰激凌）都含有膽固醇——而蔬菜、水果和谷物中沒有。
肝臟每天產生約1000毫克膽固醇，而你會從食物中攝入約150到250毫克。
膽固醇因為不能單獨在血液中移動，所以必須和特定的蛋白質結合。這些蛋白質就像卡車一樣，將膽固醇裝載然后運到身體的不同部位。當這種結合發生時，膽固醇和蛋白質共同形成了脂蛋白。
最重要的兩種脂蛋白分別是高密度脂蛋白（HDL）和低密度脂蛋白（LDL）。你可能聽過人們把LDL稱作有害膽固醇，而把HDL稱作有益膽固醇，因為它們對身體有著非常不同的效果。大部分膽固醇是LDL，這類膽固醇最有可能阻塞血管，從而阻礙血液以其應有的方式在身體中流動。
反過來，HDL把膽固醇從血管中帶走，并將其運回肝臟。肝臟可以處理這些膽固醇并將它們排出體外。
人們為什么擔心高膽固醇？
當你的膽固醇水平過高時，你的健康可能面臨威脅。如果LDL水平很高，膽固醇會沉積在動脈壁上，并形成一種被稱為血栓的堅硬物質。一段時間后，血栓會使動脈變狹窄，血流減緩，還會造成動脈硬化。
當動脈硬化影響到冠狀動脈（供應心肌的血管）時，就形成了冠心病，帶來心臟病突發的風險。而當動脈硬化影響到供應大腦的血管時，就形成了腦血管病，使人面臨中風的風險。
動脈硬化也可能阻礙流向其他重要器官的血液，這些器官包括腎臟和腸道。這就是為什么從青少年時期開始關注膽固醇水平如此重要——你能在未來延遲甚至阻止嚴重的健康問題。
什么導致了高LDL水平？
一些可能導致高膽固醇的因素是：
●超重——過高的體重和高膽固醇水平是關聯的。
●遺傳——如果你的家族中有膽固醇問題或心臟病的例子，那么你有這些問題的幾率比別人更高。
●飲食——記得那句俗語“吃什么補什么”嗎？盡量避免含有大量膽固醇、飽和脂肪和反式脂肪的食物，因為它們都會提高膽固醇水平和你患心臟病的概率。
●年齡——隨著你年齡的增長，高膽固醇的可能性也在增加。
●體育鍛煉有利于提高HDL水平，幫助減少你患心臟病的可能性。
我能做什么來降低我的膽固醇？
一些膽固醇水平高的人需要包括藥物治療在內的療法來降低它。雖然大部分青少年不需要使用藥物治療來降低他們的膽固醇水平，但控制膽固醇仍然很重要，因為血栓可能在青少年時期就開始形成。如果你想知道自己的膽固醇水平是否過高，可以去找你的醫生，通過采血樣來測試你的膽固醇水平。
現在，你不能改變自己的基因，但還有些事情是你能做到的，而那可以減少你未來患心臟病的風險。
美國心臟協會建議：每天的膽固醇攝入量應少于300毫克；總脂肪攝入量應等于或少于你總熱量的30%；飽和脂肪應等于或少于每日總熱量的10%；反式脂肪應少于你所攝入總熱量的1%。
另外，保持一個健康的體重并堅持運動。定期的有氧運動——例如騎車、步行和游泳——能夠增強你的心臟，降低膽固醇并幫助你減掉多余體重。對于吸煙的人，戒煙也能幫助降低患心臟病的風險。
健康小貼士
以下是一些你可以嘗試的方法：
●食譜中多使用低膽固醇食物：水果、蔬菜、全麥食物（例如面包和麥片）、豆類和魚類；降低食譜中的飽和脂肪和反式脂肪的含量；用不飽和脂肪代替飽和脂肪和反式脂肪；用液體植物油或不含反式脂肪的人造黃油來代替黃油、起酥油和硬黃油；不要使用含有氫化植物油的產品。
●如果要食用肉類，盡量使用瘦肉和去皮的禽肉。要確保所有可見的脂肪在烹飪前都被切掉并把加熱過程中溢出的油脂都濾去。
●不要使用煎炸的方式，盡量用煮、烤、焙、烘、燉、蒸或炒的烹飪方法。
●相對于全脂牛奶，低脂或無脂牛奶更好，因為它們包含所有的營養而不含脂肪。其他的奶制品也要選擇低脂或無脂的，例如酸奶、奶酪和村舍式干酪（由脫脂凝乳制成）。在需要奶油芝士或酸奶油的菜譜中，你也可以使用低脂的白脫牛奶或酸奶作為替代。
●使用無反式脂肪的人造黃油。
●除了肉類，還有很多不同的蛋白質來源：魚類、豆類、堅果、豆腐或其他豆制品。
●相對于雞蛋，盡量僅使用蛋白或者采用不含膽固醇的雞蛋替代品。
●不要購買烘烤的產品，因為它們常常是由氫化油或反式脂肪制成的。
●在尋找脂肪和膽固醇含量低的零食？水果、天然蔬菜和低脂蘸醬、低脂全麥薄餅、無鹽爆米花或脆餅、明膠或低脂酸奶都可以嘗試。
如果你很關注膽固醇問題和心臟病，可以去和你的醫生討論。訪問美國心臟協會的網站，那里有很多的信息，也有你可以在家嘗試的低膽固醇的簡單菜譜。雖然不是所有導致心臟病和高膽固醇的因素都能被控制，但它們中的很多是可以的�，F在開始關心你身體吧，它會在未來回報你的。
審閱人：醫學博士Mary L. Gavin
審閱日期：2009年12月
相關閱讀：正確認識雞蛋跟膽固醇之“是非恩怨”
