It's 11 PM and Aaron has already had a full day of school, work, and after-school activities. He's tired and knows he could use some sleep. But he still hasn't finished his homework. So he reaches for his headphones — and some caffeine.

已经是晚上11点了，亚伦早已结束了一天的学习，工作和课外活动。他很累，知道自己可以休息一会儿了。但是他还没有做完作业，所以他拿起耳机——和咖啡。

What Is Caffeine?

Caffeine is a drug that is naturally produced in the leaves and seeds of many plants. It's also producedartificially and added to certain foods. Caffeine is defined as a drug because it stimulates the central nervous system, causing increased alertness. Caffeine gives most people a temporary energy boost and elevates mood.

什么是咖啡因？

咖啡因是一种天然存在于许多植物的叶子和种子中的药物，也可被人工生产，并添加到某些食物中。它之所以被定义为一种药物，是因为它会刺激中枢神经系统，让人神智更加清醒。咖啡因可使大多数人暂时精力充沛、心情良好。

Caffeine is in tea, coffee, chocolate, many soft drinks, and pain relievers and other over-the-counter medications. In its natural form, caffeine tastes very bitter. But most caffeinated drinks have gone through enough processing to camouflage the bitter taste.

咖啡因存在于茶、咖啡、巧克力、多数软饮料、止痛药和非处方药中。天然的咖啡因尝起来非常苦。但大多数含咖啡因的饮料已经经历了足够的处理苦味的工序。

Teens usually get most of their caffeine from soft drinks and energy drinks. (In addition to caffeine, these also can haveadded sugar and artificial flavors.) Caffeine is not stored in the body, but you may feel its effects for up to 6 hours.

通常，青少年从软饮料和能量饮料中获得咖啡因最多。（除了咖啡因，这些饮料也可以被添加糖以及人工香料。）咖啡因不会储存在体内，但你可以受到它长达六小时的影响。

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Got the Jitters?

Many people feel that caffeine increases their mental alertness. Higher doses of caffeine can cause anxiety, dizziness, headaches, and the jitters. Caffeine can also interfere with normal sleep.

紧张不安了吗？

许多人感觉咖啡因可以使他们的神智更加清楚。高剂量的咖啡可以引起焦虑、头晕、、头痛、紧张不安，亦会影响正常睡眠。

Caffeine sensitivity (the amount of caffeine that will produce an effect in someone) varies from person to person.file:///F:/%E6%88%91%E7%9A%84%E6%96%87%E6%A1%A3/My%20Knowledge/temp/9fd539d2-889c-427c-9355-43c8d32ed51f_128_files/label.png); background-position: 0% 0%; background-repeat: no-repeat no-repeat;">Ona verage, the smaller the person, the less caffeine needed to produce side effects. Caffeinesensitivity is most affected by the amount of caffeine a person has daily.file:///F:/%E6%88%91%E7%9A%84%E6%96%87%E6%A1%A3/My%20Knowledge/temp/9fd539d2-889c-427c-9355-43c8d32ed51f_128_files/label.png); background-position: 0% 0%; background-repeat: no-repeat no-repeat;">Peoplewho regularly take in a lot of caffeine soon develop less sensitivity to it. This means they may need more caffeine to achieve the same effects.file:///F:/%E6%88%91%E7%9A%84%E6%96%87%E6%A1%A3/My%20Knowledge/temp/9fd539d2-889c-427c-9355-43c8d32ed51f_128_files/label.png); background-position: 0% 0%; background-repeat: no-repeat no-repeat;">

咖啡因的敏感度（对人产生影响的咖啡因的量）因人而异。平均而言，体格越小巧的人，咖啡因所产生的副作用越少。咖啡因敏感度由人们的日常摄入量决定。定期摄入大量咖啡因的人很快便对其不再敏感，这可能就需要摄入更多的咖啡因来达到以前的效果。

Caffeine is a diuretic, meaning it causes a person to urinate (pee) more. It's not clear whether this causes dehydration or not. To be safe, it's probably a good idea to stay away from too much caffeine in hot weather, during long workouts, or in other situations where you might sweat a lot.file:///F:/%E6%88%91%E7%9A%84%E6%96%87%E6%A1%A3/My%20Knowledge/temp/9fd539d2-889c-427c-9355-43c8d32ed51f_128_files/label.png); background-position: 0% 0%; background-repeat: no-repeat no-repeat;">1

咖啡因是一种利尿剂，它会让人小便增多。目前尚不清楚它是否会导致缺水。安全起见，一个好建议是尽量不要在炎热天气、长时间训练或者其它可能会大量出汗的情况下摄入咖啡因。

Caffeine may also cause the body to lose calcium, and that can lead to bone loss over time. Drinking caffeine-containing soft drinks and coffee instead of milk can have an even greater impact on bone density and the risk of developing osteoporosis.

咖啡因也可能会导致钙的缺失，这就会引起骨质流失。引用含咖啡因的饮料和咖啡，而不是牛奶，会对骨质密度产生较大影响，并增加骨质疏松症的风险。

Caffeine can aggravate certain heart problems. It may also interact with some medications or supplements. If you are stressed or anxious, caffeine can make these feelings worse. Although caffeine is sometimes used to treat migraine headaches, it can make headaches worse for some people.

咖啡因会加重某些心脏问题。它也可能会与一些药物或补品相互作用。如果你感到压力或者焦虑，咖啡因会加剧这些感觉。尽管有时咖啡因被用来治疗偏头痛，但它也可以使一些人头痛加剧。

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Moderation Is the Key

Caffeine is usually thought to be safe in moderate amounts. Experts consider 200-300 mg of caffeine a day to be a moderate amount for adults. But consuming as little as 100 mg of caffeine a day can lead a person to become "dependent" on caffeine. This means that someone may develop withdrawal symptoms (like tiredness, irritability, and headaches) if he or she quits caffeine suddenly.

适度是关键

通常情况下，适度的咖啡因很安全。专家认为，对成年人来说，每天200-300毫克的咖啡因足矣。但是每日只摄入100毫克咖啡因可让人上瘾。这意味着，如果他或她突然戒掉咖啡，可能会出现戒断症状（如疲劳、烦躁和头痛）。

Teens should try to limit caffeine consumption to no more than 100 mg of caffeine daily, and kids should get even less. The following chart includes common caffeinated products and the amounts of caffeine they contain:

青少年应试着控制每日的咖啡因摄入量不超过100毫克，儿童则更少。下面的图表包括含咖啡因的产品和咖啡因含量。

Drink/Food/Supplement饮料/食品/补品

Amt. of Drink/Food饮料/食品数量

Amt. of Caffeine咖啡因数量

SoBe No Fear8 ounces8盎司83 mg毫克

Monster energy drink“怪物”能量饮料16 ounces16盎司160 mg160毫克

Rockstar energy drink摇滚能量饮料8 ounces8盎司80 mg80毫克

Red Bull energy drink红牛能量饮料8.3 ounces8.3盎司80 mg80毫克

Jolt colaJolt可乐12 ounces12盎司72 mg72毫克

Mountain Dew山露12 ounces12盎司55 mg55毫克

Coca-Cola可口可乐 ;12 ounces12盎司54 mg54毫克

Diet Coke健怡可乐12 ounces12盎司45 mg45毫克

Pepsi百事可乐12 ounces12盎司38 mg38毫克

7-Up七喜12 ounces12盎司0 mg0毫克

Brewed coffee (drip method)滴滤咖啡5 ounces5盎司115 mg*115毫克

Iced tea冰茶12 ounces12盎司70 mg*70毫克

Cocoa beverage可可饮料5 ounces5盎司4 mg*4毫克

Chocolate milk beverage巧克力牛奶饮料8 ounces8盎司5 mg*5毫克

Dark chocolate黑巧克力1 ounce1盎司20 mg*20毫克

Milk chocolate奶油巧克力1 ounce1盎司6 mg*6毫克

Jolt gum Jolt口香糖1 stick每条33 mg33毫克

Cold relief medication感冒药1 tablet每片30 mg*30毫克

Vivarin咖啡因片剂1 tablet每片200 mg200毫克

Excedrin extra strength额外能量锭2 tablets每两片130 mg130毫克

*denotes average amount of caffeine

*表示咖啡因均量

Source: U.S. Food and Drug Administration, National Soft Drink Association, Center for Science in the Public Interest.

资料来源：美国食品和药物管理局，国家软饮料协会，公众利益科学中心

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Cutting Back

If you're taking in too much caffeine, you may want to cut back. The best way is to cut back slowly. Otherwise you could get headaches and feel tired, irritable, or just plain lousy.

减量

如果你正在服用过量咖啡因，你可能想要减量。最好的方法就是慢慢来，否则你就会头疼、易累、易怒，或者只是感觉糟透了。

Try cutting your intake by replacing caffeinated sodas and coffee with non-caffeinated drinks. Options include water, decaffeinated coffee, caffeine-free sodas, and caffeine-free teas. Start by keeping track of how many caffeinated drinks you have each day, then substitute one of these daily drinks with a caffeine-free alternative. Continue this for a week. Then, if you are still drinking too much caffeine, substitute another of your daily drinks, again, keeping it up for a week. Do this for as many weeks as it takes to bring your daily caffeine intake below the 100-milligram mark. Taking a gradual approach like this can help you wean yourself from caffeine without unwanted side effects like headaches.

试着少饮用含咖啡因的苏打水和咖啡饮料。可选择喝水、无咖啡因咖啡、无咖啡因苏打水和无咖啡因茶。从记录自己每日喝多少含咖啡因饮料开始，然后用无咖啡因饮料代替你的一种日常饮料。坚持一周。如果一周后你还是会摄入大量咖啡因，那就换一种饮料代替你的日常饮料，再保持一周。然后继续坚持数周，直到你每日咖啡因摄入量低于100毫克。这种循序渐进的方法可以使你慢慢不再依赖咖啡因，并不产生任何像头痛这样的副作用。

As you cut back on the amount of caffeine you consume, you may find yourself feeling tired. Your best bet is to hit the sack, not the sodas: It's just your body's way of telling you it needs more rest. Your energy levels will return to normal in a few days.

当你酌减咖啡因摄入量时，你会感觉很累。此时最好的办法是击打麻布袋，而不是喝苏打饮料。这只是你的身体以自己的方式提醒你它需要休息了，你的精力几天后便会恢复正常。

Reviewed by:Mary L. Gavin, MD
Date reviewed: January 2008
Originally reviewed by:Jessica Donze Black, RD, CDE, MPH

审查：玛丽·L·嘉文医师

审查日期：2008年1月
最初审查：杰西卡·唐泽·黑，注册营养师，彩色多普勒医师，公共卫生学硕士