Caffeine: Its Sources and Effects
Caffeine occurs naturally in the leaves and seeds of many plants, including coffee beans, tea leaves and cocoa nuts. Recent studies have found that coffee is rich in antioxidants and contains pain-relieving and antibacterial compounds. What’s more, data show long-term consumption of caffeine is associated with a reduced risk of type 2 diabetes. It has flavor-enhancing qualities, which make it an obvious choice as an additive to almost every soft-drink beverage. And, not surprising, when you need to stay awake and focused, coffee can do the trick.
As with every type of food, caffeine-containing foods and beverages should be consumed in moderation. Caffeine is an addictive substance and is defined as a drug. Caffeine stimulates the central nervous system, causing increased heart rate and alertness. Caffeine also causes the brain’s blood vessels to constrict, increasing neuron activity in the brain and thereby telling the body to produce adrenaline. All of these events cause:
- your pupils to dilate,
- your breathing tubes to open up,
- your heart to beat faster,
- your blood vessels to slow blood flow to the surface (causing cold hands and feet) and to increase blood flow to the muscles (causing your muscles to tighten up),
- your blood pressure to rise,
- your blood flow to the stomach to slow down, and
- your liver to release sugar to the bloodstream for extra energy.
These increased stimuli can make a person irritable and jumpy. The stimuli also reduce a person’s natural ability to fall into a deep sleep, which over time can have a variety of negative consequences.
The half-life of caffeine in the body is about 6 hours. That means that if you consume a large cup of coffee containing about 200 milligrams (mg) of caffeine at three o’clock in the afternoon, by 9:00 pm you would still have about 100 mg of caffeine in your system. Although you may be able to fall asleep, your body may be unable to fall into a deep sleep, leaving you feeling tired the following day. Feeling tired may prompt you to start your morning off with a cup of coffee, and the cycle continues.
Those trying to reduce or eliminate their caffeine intake may find themselves tired, irritable, depressed, or even suffering from a severe headache as blood vessels in the brain dilate. These negative side effects discourage people from reducing or eliminating their caffeine intake.
So, how much caffeine should you consume daily? Moderate caffeine consumption is considered to be about 300 mg per day, which is equal to about three cups of coffee. However, most Americans consume far more than that. The following may offer some insight:
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|
Beverage (per 8 oz cup) |
Mg of caffeine |
|
Brewed coffee |
80 - 135 |
|
Instant coffee |
65 - 100 |
|
Brewed tea, imported |
60 |
|
Brewed tea, U.S. |
40 |
|
Soft-drink (12 oz can) |
50 |
An ounce of milk chocolate contains about 6 mg per ounce. Caffeine tablets, such as No-Doz, contain about 100 mg per tablet. Vivarin and Dexatrim contain about 200 mg per tablet.
If you want to monitor your intake of caffeine to ascertain that you remain within the recommended parameters for moderate consumption: keep in mind that coffee and tea, unless labeled as decaffeinated, contain caffeine. Also, any foods with chocolate listed in the ingredients, such as chocolate cakes, cookies (chocolate chip or Oreo), brownies, chocolate pudding, mocha ice cream, etc., all have caffeine. Soft drinks that contain caffeine will have caffeine listed in the ingredient list.
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