How Much Caffeine Is Too Much?

Clinical Dietitian
Monday, May 6, 2019 - 3:34pm

Are you someone who relies on caffeine in the morning to start your day, or to power through the afternoon slump? If so, you aren’t alone. Caffeine is recognized as one of the most commonly consumed stimulants in the world and is used daily by millions of people to increase wakefulness, alleviate fatigue and improve concentration and focus.

Caffeine is a plant product commonly found in coffee beans, tea, soft drinks, cocoa and chocolate. Caffeine can also be found in some prescription and non-prescription drugs, including cold, allergy and pain relievers.

How Does Caffeine Affect the Body?

Caffeine works by stimulating the central nervous system. The effects of caffeine on the body may begin as fast as 15 minutes after ingestion and last up to six hours. Caffeine can raise blood pressure and body temperature, and increase stomach acid secretion, production of urine and blood flow to the skin and extremities.

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How Much Caffeine is Too Much?

According to the U.S. Food and Drug Administration (FDA), up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults, which is equivalent to about four or five cups of coffee. The caffeine content of certain foods and beverages can vary depending on factors such as how and where the coffee beans and tea leaves were grown and processed, and how the beverage product is prepared. In general, these products contain the following amount of caffeine:

  • Soft drink (12 oz), 30-40 mg caffeine
  • Green or black tea (8 oz), 30-50 mg caffeine
  • Coffee (8 oz), 80-100 mg caffeine 
  • Energy drink (8 oz), 40-250 mg caffeine

Certain symptoms can indicate that you may need to cut down your caffeine intake, including:

  • Migraine headache
  • Insomnia
  • Nervousness
  • Irritability
  • Restlessness
  • Frequent urination or inability to control urination
  • Upset stomach
  • Fast heartbeat
  • Muscle tremors

How Do I Cut Back on Caffeine?

It’s best to cut back on caffeine gradually. Stopping abruptly can cause withdrawal symptoms such as headaches, anxiety and nervousness. Unlike opioid or alcohol withdrawal, caffeine withdrawal is not considered dangerous, but it can be unpleasant. You may want to talk to your health care provider about how to cut back.

What About Decaf?

If a coffee or tea says “decaffeinated” does that mean it contains no caffeine? No. Decaf coffees and teas have less caffeine but still contain some caffeine. Decaf coffee typically has 2-15 mg in an 8-ounce cup.

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