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Sleep & Caffeine


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Caffeine is a natural substance that can be extracted from plants. Natural sources of caffeine include coffee beans, tea leaves and cocoa beans. It also can be produced synthetically.

Caffeine is a type of drug that promotes alertness. These drugs are called “stimulants.” Caffeine acts as an “adenosine receptor antagonist.” Adenosine is a substance in your body that promotes sleepiness. Caffeine blocks the adenosine receptor to keep you from feeling sleepy.

Caffeine begins to affect your body very quickly. It reaches a peak level in your blood within 30 to 60 minutes. It has a half-life of 3 to 5 hours. The half-life is the time it takes for your body to eliminate half of the drug. The remaining caffeine can stay in your body for a long time. Effects can last from 8 to 14 hours.

Coffee accounts for 54% of the caffeine consumption in the world. Tea accounts for another 43%. On any given day, about 85% of Americans use caffeine products. The average daily consumption of caffeine in the U.S. is about 200 mg per person. This is about three times higher than the world average. But it is still only half of the caffeine consumption in heavy tea-drinking countries such as England and Sweden.

Caffeine is a product that has both positive and negative effects. These effects depend on the amount of caffeine you consume and when you consume it:

Positive Effects

Caffeine is considered a moderately effective alerting agent. It can have a positive effect on your reaction times, mood and mental performance. A normal dose of caffeine is about 50 mg to 200 mg.

Caffeine works best when you take it on an intermittent, off-and-on basis. Higher doses can have much more potent effects. A dose of 500 mg or 600 mg of caffeine can affect you much like a low dose of an amphetamine. The effects of caffeine wear off quickly when you use it regularly. Your body builds up a tolerance to it.

Negative Effects

Caffeine can have a disruptive effect on your sleep. The most obvious effect is that it can make it hard for you to fall asleep. This will reduce your total sleep time. Caffeine also can reduce the amount of deep sleep that you enjoy.

The effects of caffeine can occur even when you consume it earlier in the afternoon or evening. These effects also can be stronger in older adults. It takes their bodies a longer time to process caffeine. Regularly consuming high doses of caffeine may cause complications during pregnancy.

At high doses, caffeine can produce these common side effects:

  • Diarrhea
  • Sweating
  • Nausea
  • Increased heart rate
  • Increased breathing rate
  • Muscle tremors

Withdrawal symptoms can occur when you stop taking caffeine after using it regularly for a long time. These symptoms include:

  • Headaches
  • Sleepiness
  • Low energy levels
  • Bad moods

Summary

Caffeine has both positive and negative attributes. It can be very effective for improving your concentration, alertness and energy. But these effects can be brief if you consume high doses of caffeine on a daily basis. Caffeine also can have a negative effect on your sleep. It can reduce the quantity and quality of your sleep. These effects can occur even when you are unaware of them.

Recommendations

Like most substances, you should use caffeine in moderation. These are some general guidelines for you to follow:

  • You should limit your caffeine consumption to no more than about 300 mg to 400 mg per day. This equals about three to four cups (8-oz) of coffee.
  • Women who are pregnant or nursing should consume even less caffeine or avoid it altogether.
  • Parents should limit the amount of caffeine that their children consume.
  • People with high blood pressure or other heart problems should avoid high levels of caffeine.
  • It is best if you avoid caffeine in the late afternoon and in the evening.

Caffeine Levels

Caffeine levels vary widely from one product to another. In particular, the caffeine content of coffee can be very unpredictable.

Scientists at the University of Florida bought a 16-oz cup of the same type of coffee from one coffee shop for six straight days. They analyzed each cup of coffee to determine how much caffeine it contained. They found a wide range of caffeine levels in the six cups of coffee. The lowest level was 259 mg of caffeine and the highest was 564 mg.

Coffee’s caffeine content depends on many factors. These include the type of bean that is used and how the coffee is prepared. In the same way, the size of a tea bag, number of tea leaves and brewing time can affect the caffeine level of a cup of tea.

Caffeine is added to many soft drinks. The U.S. Food and Drug Administration classifies caffeine as a substance that is “generally recognized as safe,” or GRAS. This means that caffeine is not regulated by the FDA as a food additive. It must appear as an added ingredient on a drink’s label. But the label does not need to show the amount of caffeine in the drink.

The following table will help you compare the caffeine levels found in a number of common products:


Product

Serving Size

Caffeine (mg)

Coffee

 

 

Coffee, brewed

1 cup (8 oz)

95

Espresso

1 oz

64

Coffee, instant

8 oz

62

Coffee, brewed, decaf

1 cup (8 oz)

2

 

 

 

Tea

 

 

Lipton Black Tea

1 cup

55

Lipton Original Iced Tea

16 oz

50

Tea, brewed

1 cup (8 oz)

47

Lipton 100% Green Tea

1 cup

45

Tea, instant, unsweetened

1 cup (8 oz)

26

Lipton Brisk Tea

12 oz

9

Tea, herbal

1 cup (8 oz)

0

 

 

 

Energy Drinks

 

 

No Fear

16 oz

166

Full Throttle

16 oz

144

Jolt

24 oz

142.4

 

 

 

Sodas

 

 

Pepsi One

12 oz

54

Mountain Dew

12 oz

54

Mello Yellow

12 oz

52.5

Diet Coke

12 oz

46.5

Pepsi

12 oz

37.5

Diet Pepsi

12 oz

36

Coca Cola Classic

12 oz

34.5

Caffeine free Coke, Pepsi

12 oz

0.0

Sprite, 7-Up

12 oz

0.0

 

 

 

Medications

 

 

NoDoz

1 tablet

200

Vivarin

1 tablet

200

Extra Strength Excedrin

2 tablets

130

Anacin

2 tablets

64

 

 

 

Other

 

 

Chocolate chips, semi-sweet

1 cup (6 oz bag)

104

Chocolate chips, milk chocolate

1 cup

34

Baking chocolate, unsweetened

1 square

23

Milk chocolate bar

1 bar (1.55 oz)

9

Chocolate pudding, ready-to-eat

Snack size (4 oz)

6

Frozen yogurt, chocolate

1 cup

5

Chocolate ice cream

1 cup

4

Hot cocoa

1 packet, 6 oz water

4

Chocolate syrup, fudge-type

2 tbsp

3

Chocolate-chip cookie, packaged

1 cookie

1

 

 

 

Note: The caffeine levels for most of the brand-name drinks are estimates. They were converted from the 8-oz serving size listed by the beverage companies. This change was made to reflect the standard can or bottle-sizes in which the drinks are sold.

Caffeine content for generic products was obtained from the USDA National Nutrient Database for Standard Reference. The content of brand-name products was obtained from the manufacturers' Web sites.

By Donald R. Townsend, PhD
Updated August 3, 2006



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