Effectiveness, Tolerance, and Headaches
Why do so many patients coming out of anesthesia after major surgery feel a headache? It's because, in most cases, they're not used to going so long without coffee. The good news? If they wait a few more days, they can start saving coffee again for when they really need it.
The effectiveness of caffeine varies significantly from person to person, due to genetics and other factors in play. The average half-life of caffeine—that is, how long it takes for half of an ingested dose to wear off—is about five to six hours in a human body. Women taking oral birth control require about twice as long to process caffeine. Women between the ovulation and beginning of menstruation see a similar, if less severe, extended half-life. For regular smokers, caffeine takes half as long to process—which, in some ways, explains why smokers often drink more coffee and feel more agitated and anxious, because they're unaware of how their bodies work without cigarettes.
As one starts to regularly take in caffeine, the body and mind build up a tolerance to it, so getting the same kind of boost as one's first-ever sip takes more caffeine—this, researchers can agree on. Exactly how that tolerance develops is not so clear. Many studies have suggested that, just as with any drug addiction, the brain strives to return to its normal function while under "attack" from caffeine by up-regulating, or creating more adenosine receptors. But regular caffeine use has also been shown to decrease receptors fornorepinephrine, a hormone akin to adrenaline, along with serotonin, a mood enhancer. At the same time, your body can see a 65 percent increase in receptors for GABA, a compound that does many things, including regulate muscle tone and neuron firing. Some studies have also seen changes in different adenosine receptors when caffeine becomes a regular thing.
Caffeine, it's been suggested, is probably not directly responsible for all these changes. By keeping your brain from using its normal "I'm tired" sensors, though, your caffeine may be causing the brain to change the way all of its generally excitable things are regulated. Your next venti double shot goes a little less far each time, in any case. Photo by zoghal.
A 1995 study suggests that humans become tolerant to their daily dose of caffeine—whether a single soda or a serious espresso habit—somewhere between a week and 12 days. And that tolerance is pretty strong. One test of regular caffeine pill use had some participants getting an astronomical 900 milligrams per day, others placebos—found that the two groups were nearly identical in mood, energy, and alertness after 18 days. The folks taking the equivalent of nine stiff coffee pours every day weren't really feeling it anymore. They would feel it, though, when they stopped.
You start to feel caffeine withdrawal very quickly, anywhere from 12 to 24 hours after your last use. That's a big part of why that first cup or can in the morning is so important—it's staving off the early effects of withdrawal. The reasons for the withdrawal are the same as with any substance dependency: your brain was used to operating one way with caffeine, and now it's suddenly working under completely different circumstances, but all those receptor changes are still in place. Headaches are the nearly universal effect of cutting off caffeine, but depression, fatigue, lethargy, irritability, nausea, and vomiting can be part of your cut-off, too, along with more specific issues, like eye muscle spasms. Generally, though, you'll be over it in around 10 days—again, depending on your own physiology and other factors.
Update: Commenter microinjectionist offers his own summary of more recent caffeine studies, which offers expanded reasons why caffeine users feel a "morning crash," as well as why your whole body, not just your brain, might feel so bad when you withdraw.
Effectiveness, Tolerance, and HeadachesWhy do so many patients coming out of anesthesia after major surgery feel a headache? It's because, in most cases, they're not used to going so long without coffee. The good news? If they wait a few more days, they can start saving coffee again for when they really need it.The effectiveness of caffeine varies significantly from person to person, due to genetics and other factors in play. The average half-life of caffeine—that is, how long it takes for half of an ingested dose to wear off—is about five to six hours in a human body. Women taking oral birth control require about twice as long to process caffeine. Women between the ovulation and beginning of menstruation see a similar, if less severe, extended half-life. For regular smokers, caffeine takes half as long to process—which, in some ways, explains why smokers often drink more coffee and feel more agitated and anxious, because they're unaware of how their bodies work without cigarettes. As one starts to regularly take in caffeine, the body and mind build up a tolerance to it, so getting the same kind of boost as one's first-ever sip takes more caffeine—this, researchers can agree on. Exactly how that tolerance develops is not so clear. Many studies have suggested that, just as with any drug addiction, the brain strives to return to its normal function while under "attack" from caffeine by up-regulating, or creating more adenosine receptors. But regular caffeine use has also been shown to decrease receptors fornorepinephrine, a hormone akin to adrenaline, along with serotonin, a mood enhancer. At the same time, your body can see a 65 percent increase in receptors for GABA, a compound that does many things, including regulate muscle tone and neuron firing. Some studies have also seen changes in different adenosine receptors when caffeine becomes a regular thing.Caffeine, it's been suggested, is probably not directly responsible for all these changes. By keeping your brain from using its normal "I'm tired" sensors, though, your caffeine may be causing the brain to change the way all of its generally excitable things are regulated. Your next venti double shot goes a little less far each time, in any case. Photo by zoghal.การศึกษา 1995 แนะนำว่า มนุษย์เป็นความอดทนของยาประจำวันของคาเฟอีน — โซดาเดียวหรือติดกาแฟอย่างจริงจังซึ่งอยู่ระหว่างวันที่ 12 และสัปดาห์ และยอมรับว่ามีความแข็งแรงสวย ทดสอบหนึ่งใช้ยาคาเฟอีนปกติมีบางคนที่รับเป็นดาราศาสตร์ milligrams 900 ต่อวัน อื่น ๆ placebos ซึ่งพบว่า กลุ่มที่สองได้เกือบเหมือนในอารมณ์ พลังงาน และเตรียมพร้อมหลังวันที่ 18 คนที่ใช้เทียบเท่ากับเก้า pours กาแฟแข็งทุกวันไม่ได้จริง ๆ รู้สึกมันอีกต่อไป พวกเขาจะรู้สึกว่ามัน แม้ว่า เมื่อพวกเขาหยุดการคุณเริ่มรู้สึกถอนคาเฟอีนอย่างรวดเร็ว ที่ใดก็ได้จาก 12 ถึง 24 ชั่วโมงหลังจากที่คุณใช้ล่าสุด นั่นคือส่วนใหญ่ของเหตุผลที่ถ้วยแรกหรือสามารถในตอนเช้าเป็นสิ่งสำคัญดังนั้น — มันเป็น staving ออกผลช่วงถอน สาเหตุของการถอนเท่ากันเช่นเดียวกับการอ้างอิงใด ๆ ของสาร: สมองของคุณใช้ในการปฏิบัติงานไป ด้วยคาเฟอีน และตอนนี้ มันก็ทำงานภายใต้สถานการณ์ที่แตกต่างอย่างสมบูรณ์ แต่เปลี่ยนแปลงตัวรับทั้งหมดจะยังคงอยู่ในตำแหน่ง อาการปวดหัวมีผลเกือบสากลของตัดคาเฟอีน แต่ภาวะซึมเศร้า อ่อนล้า ถูกกระตุ้น irritability คลื่นไส้ และอาเจียนให้ตัดของคุณ เกินไป กับปัญหาเฉพาะ เช่นตากล้ามเนื้อกระตุก ทั่วไป แม้ว่า คุณจะขึ้นในรอบ 10 วัน — อีก ขึ้นอยู่กับสรีรวิทยาของคุณเองและปัจจัยอื่น ๆ ด้วยUpdate: Commenter microinjectionist offers his own summary of more recent caffeine studies, which offers expanded reasons why caffeine users feel a "morning crash," as well as why your whole body, not just your brain, might feel so bad when you withdraw.
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