Human beings love their caffeine. In fact, caffeine is the most commonly used drug in the world. For this reason caffeine, one of the most active ingredients in coffee, has been studied extensively to help us understand how it affects our bodies. Caffeine can be found in a variety of sources, such as tea, cocoa, and cola drinks.
For many individuals, coffee helps them stay awake and alert throughout the day. Caffeine is the stimulant in coffee that competes for the same protein spaces as the sleep-promoting chemical adenosine. Caffeine also stimulates the heart, smooth muscles, increases stomach secretions, and promotes urination.
Research suggests that moderate amounts of caffeine influence the following in adult humans:
- Caffeine increases alertness and reduces fatigue, which may be significant in low arousal situations (e.g. late night work shifts).
- Caffeine improves performance on attentiveness tasks and simple tasks that require a sustained response. Increased attentiveness is clearest with reduced alertness, although there is evidence that benefits may still occur when the person is unaffected. The effects on more challenging tasks are difficult to assess and most likely interactions between the caffeine and other variables that increase alertness (e.g. personality and time of day).
- Regular caffeine consumption appears to be beneficial, with higher users having better mental functioning.
- Caffeine use increases metabolic rate.
Too much caffeine can yield negative side effects including the following:
- Caffeine can increase blood pressure in people who do not drink caffeinated drinks regularly. High blood pressure is directly correlated with an increase in strokes and brain disease, which increase the risk of dementia.
- Caffeine may inhibit fine motor movement control (e.g. producing shaky hands).
- It can increase the secretion of the stress hormone, cortisol.
- Caffeine makes its users have difficulty falling or staying asleep.
- It may be addictive
- Postmenopausal women may suffer from accelerated bone loss with high caffeine consumption.
- Other short-term side effects include headache, nausea, and anxiety in many individuals.
Drinking up to 400 milligrams is generally safe depending on body weight and level of caffeine tolerance. Drinking more can result in a state of central nervous system over-stimulation called caffeine intoxication or "caffeine jitters".
In terms of children and adolescents, the American Academy of Pediatrics recommends that adolescents consume less than 100 milligrams of caffeine a day. Younger children should not drink any caffeinated beverages on a regular basis.
Here are examples of drinks that contain caffeine:
|Brewed coffee||8 oz. (237 mL)||95-200 mg|
|Brewed, decaffeinated||8 oz. (237 mL)||2-12 mg|
|Brewed, single-serve varieties||8 oz. (237 mL)||75-150 mg|
|Brewed, single-serve varieties, decaffeinated||8 oz. (237 mL)||2-4 mg|
|Espresso, restaurant-style||1 oz. (30 mL)||47-75 mg|
|Instant||8 oz. (237 mL)||27-173 mg|
|Black tea||8 oz. (237 mL)||14-70 mg|
|Black tea, decaffeinated||8 oz. (237 mL)||0-12 mg|
|Green tea||8 oz. (237 mL)||24-45 mg|
|Coca-Cola||12 oz. (355 mL)||23-35 mg|
|Diet Coke||12 oz. (355 mL)||23-47 mg|
|Diet Pepsi||12 oz. (355 mL)||27-37 mg|
|Dr. Pepper, regular and diet||12 oz. (355 mL)||36-42 mg|
|Pepsi||12 oz. (355 mL)||32-39 mg|
|Mountain Dew||12 oz. (355 mL)||54 mg|
|Diet Mountain Dew||12 oz. (355 mL)||54 mg|
Although caffeine can have some positive benefits, you should always consult your health care provider regarding further details specific to you.
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