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How does caffeine keep us awake? - Hanan Qasim


30,114 Questions Answered

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Over 100,000 metric tons of caffeine are consumed around the world every year. That’s equivalent to the weight of 14 Eiffel Towers! Caffeine helps us feel alert, focused, and energetic, even if we haven’t had enough sleep — but it can also raise our blood pressure and make us feel anxious. So how does it keep us awake? Hanan Qasim shares the science behind the world’s most widely used drug.

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Caffeine (1,3,7 trimethylxanthine) belongs to methylxanthine class of chemicals, and it has some structural similarity to one of the DNA bases, adenine. It is found in the seeds, nuts, or leaves of numerous plants, where it functions to both protect them against predator insects and prevent germination of nearby seeds.

Even though caffeine is a psychoactive drug and is listed as “GENERALLY RECOGNIZED AS SAFE” by FDA, it is still not regulated. Pharmacologically, caffeine is considered as a central nervous system stimulant affecting both brain and spinal cord. Caffeine has several dose-dependent effects, as shown in this research paper.

Wondering how much caffeine will cause an effect? Two milligrams of caffeine/kg of body weight causes behavioral changes. These include: increased vigilance, higher performance and alertness. Slightly higher doses, 3-10mg of caffeine/ kg of body weight, increase motor activity, however, these doses also induce nervousness and jitteriness. In other words, caffeine isn’t for everyone and one dose doesn’t fit all. Read this article that presents different doses of caffeine in coffee and the acceptable doses based on age.

Now what makes caffeine effective? To understand that, let’s talk about some of the most important properties of a successful drug. Bioavailability is a measurement of the rate and extent to which a drug reaches at the site of action. A drug with high bioavailability is one in which most of the drug will be at the site of action, hence it will be more effective than a drug with low bioavailability. The highest bioavailability is 100% (seen with drugs administered intravenously). Caffeine has a bioavailability of 99%, so 99% of the dose will reach the brain and initiate its effect. The second property of a successful drug is half-life, or the time needed for a drug to reach half its initial concentration in the body. When we need the effect of a drug to be for only a moderate period of time, as in the case of caffeine, we look for drugs that have short half-lives. Caffeine has a half-life of 5 hours. Thus, most energy drinks and other caffeine containing beverages will act for up to 5 hours, after which the effect will be much less.

Caffeine has variable sources, but a surprising source for many people is decaffeinated beverages. As their name implies, caffeine has been removed from them, but decaffeinated doesn’t mean caffeine-free.or a beverage to be called a decaffeinated it should contain 1-2% of its initial caffeine, however, sometimes the concentration may reach as much as 20%. On the other hand, caffeine free means that the compound doesn’t have caffeine from the beginning in it. To understand the decaffeination process, watch this video.

It’s well known that caffeine awakens us and energizes the body, but also it can help in weight loss both directly and indirectly. Firstly, the direct effect of caffeine is an increased metabolic rate--with higher metabolic rate, the body burns more calories. Caffeine boosts in metabolic rate even in obese people, though the effect is more pronounced in non-obese people. Caffeine also boosts performance during exercise, indirectly causing more fat loss and weight loss. To understand how it works, watch this video.

Concerns about pregnant females consuming caffeine isn’t a new thing, as many studies on animals have shown that caffeine can cause birth defects, and increase the risk of other reproductive problems. However, there is a lack of conclusive studies in humans. The American Pregnancy Association recommends pregnant women limit caffeine intake to less than 200 mg per day.

Caffeine consumption in adolescents is increasing. Adolescence is a period when the final stages of brain development occur. Good nutrition and sleep are important for brain development. Adolescents often consume caffeine in sodas, energy drinks and flavored coffee. These beverages are also high in sugar, compromising nutrition, and caffeine can compromise sleep by causing alterations in sleep patterns. Minimal studies have been conducted on the effects of caffeine consumption in adolescence. Though  studies have shown that caffeine is relatively safe for adults, adolescets may experience different metabolic effects. For further info about this topic read this article.

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TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

Meet The Creators

  • Educator Hanan Qasim
  • Script Editor Eleanor Nelsen
  • Director Draško Ivezić
  • Producer Draško Ivezić
  • Animator Draško Ivezić, Ira Bulić
  • Storyboard Artist Draško Ivezić
  • Character Designer Draško Ivezić
  • Sound Designer Jure Buljević
  • Associate Producer Jessica Ruby
  • Content Producer Gerta Xhelo
  • Editorial Producer Alex Rosenthal
  • Narrator Addison Anderson

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