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Safe Levels of Daily Caffeine Intake

author image Erica Kannall
Erica Kannall is a registered dietitian and certified health/fitness specialist with the American College of Sports Medicine. She has worked in clinical nutrition, community health, fitness, health coaching, counseling and food service. She holds a Bachelor of Science in clinical dietetics and nutrition from the University of Pittsburgh.
Safe Levels of Daily Caffeine Intake
Limit caffeine intake to avoid feeling restless or anxious. Photo Credit Fuse/Fuse/Getty Images

Coffee, teas, sodas and energy drinks are widely consumed beverages found on the shelves of nearly every market. Their popularity comes from the caffeine content and ability to stimulate your central nervous system. While consuming some caffeine daily is generally regarded as safe, too much may cause adverse health effects. In addition, these beverages may contain added sugar and cream to enhance the flavor, but such ingredients may contribute to weight gain and tooth decay.

Action of Caffeine

Caffeine, a compound found naturally in certain foods such as coffee, tea and cocoa, acts as an adenosine receptor antagonist in the brain. Adenosine has sleep-promoting effects, so blocking the function of it reduces fatigue and sleepiness. Caffeine also causes the neurons in your brain to fire more quickly, exciting your central nervous system. According to an April 2010 article in the "Journal of Food Science," other benefits of caffeine include improved concentration and physical endurance. Consuming high doses of caffeine can have many adverse impacts on your health, however.

Upper Intakes for Adults

Caffeine is readily absorbed into your bloodstream, processed by your liver and has a half life of roughly five hours in your body. According to the "Journal of Food Science," consuming less than 400 milligrams of caffeine per day is generally regarded as safe, and some regulatory agencies have set an upper limit of caffeine intake per day at 450 milligrams. That equates to roughly 3 to 4 cups of drip coffee, 4 to 5 cups of black tea or two energy drinks, depending upon their caffeine content.

Pregnant Women and Children

If you are pregnant you should limit your caffeine intake further. Caffeine passes through the placenta to your baby freely. The fetus does not have the ability to metabolize caffeine the way an adult body can. According to an article published in November 2008 in the journal "BMJ," increased caffeine intake during pregnancy can lead to fetal growth restriction and possibly spontaneous abortion. To best minimize your risk, consume less than 100 milligrams of caffeine per day, or no more than 1 to 2 cups of coffee. Caffeine may also have adverse impacts in children, such as disturbing their sleep, and intake should be limited to 2.5 milligrams of caffeine per kilogram of their body weight per day.

Side-Effects of Caffeine

Consuming large doses of caffeine may produce a variety of unwanted side-effects. You may experience a rapid heart beat, anxiety, depression, insomnia, restlessness, frequent urination, headache or nausea, according to MedlinePlus. If you are currently drinking more caffeine than the recommended amounts, consider slowly reducing your intake in order to avoid withdrawal side-effects, such as headache, irritability, drowsiness and nausea. The "Journal of Food Science" notes that the dose at which caffeine becomes toxic to your body is difficult to establish, but may be near 10 grams per day, or roughly 100 cups of coffee.

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