It's been more than 1,400&nbsp;years since coffee emerged in Africa and more than 4,700 since a Chinese emperor discovered the delights of brewed tea. Today a dose of caffeine is as close as the kitchen or the corner coffee shop. 
And Americans do love their caffeine. According to the <a href="http://www.netreturns.biz/healthinfo/bouncelink.aspx?shortcut=ific" target="_blank">International Food Information Council Foundation</a>, about 85% of U.S. adults consume it every day in some form, such as a fancy mocha in the morning or a candy bar munched as an afternoon snack.
Caffeine acts as a mild stimulant for the central nervous system and the heart. It temporarily changes how the body and brain work, giving them a jolt of energy. The energy boost happens quickly&mdash;it's strongest about an hour after taking in caffeine. After about four to six hours, your body has metabolized about half of the caffeine you've consumed, according to the&nbsp;<a href="http://www.netreturns.biz/healthinfo/bouncelink.aspx?shortcut=fda" target="_blank">U.S. Food and Drug Administration</a>.
How much is too much? 
Used in moderation, caffeine is generally recognized as safe. The amount considered safe for most healthy adults is around 400 milligrams, or about four cups of brewed coffee. 

Everyone has a different sensitivity to caffeine, but it can have side effects. Caffeine may:
<ul>
 <li>Make your heart pump faster. </li>
 <li>Make you jittery and shaky. </li>
 <li>Temporarily raise your blood pressure. </li>
 <li>Cause headaches, dizziness or nervousness. </li>
 <li>Affect heart rhythm. </li>
 <li>Affect sleep. </li>
 <li>Increase stomach acids.</li>
</ul>
People with anxiety problems or panic attacks may find that caffeine makes these conditions worse. 
Pregnant women and breastfeeding women should consult their doctor about their caffeine intake. Caffeine can cross the placenta and affect an unborn child, and it can get into breast milk. But moderate amounts are considered safe, according to the <a href="http://www.netreturns.biz/healthinfo/bouncelink.aspx?shortcut=acog" target="_blank">American College of Obstetricians and Gynecologists</a> and other health organizations. 
The <a href="http://www.netreturns.biz/healthinfo/bouncelink.aspx?shortcut=modimes" target="_blank">March of Dimes</a> recommends that pregnant or breastfeeding women consume no more than 200&nbsp;milligrams of caffeine a day. 
Sources of caffeine
Caffeine is found in some unexpected places. It's used in both prescription and over-the-counter medicines that treat migraines, colds, tiredness and pain. It's also found in: 
Coffee. An 8-ounce cup of drip coffee can have 75 to 165 milligrams of caffeine. 
Tea. An 8-ounce cup of black tea has 14 to 70&nbsp;milligrams. 
Chocolate. Dark chocolate has 5 to 35&nbsp;milligrams per ounce, and milk chocolate has 1 to 15&nbsp;milligrams per ounce. 
Soft drinks. Some have 30 to 60&nbsp;milligrams of caffeine in 12&nbsp;ounces. 
Energy drinks.&nbsp;Most are similar to coffee, with about 100 milligrams per 8 ounces. Energy shots, though, can contain up to 200 milligrams.
Herbal products. Yerba mate, green tea extract, kola nut and other herbal products may have as much or more caffeine than coffee. 
Caffeine isn't a nutrient, so you won't find it on food nutrition panels. But when it's added to food, caffeine must be included in that food's ingredients list.
Cutting back
If you want to consume less caffeine&mdash;for health reasons or to save some money at the coffee shop&mdash;reduce your intake gradually. This will help avoid some of the withdrawal symptoms, such as headaches, fatigue and irritability. 
To cut back on caffeine, consider: 
<ul>
 <li>Mixing decaffeinated coffee with regular coffee.</li>
 <li>Brewing tea for less time. </li>
 <li>Choosing caffeine-free sodas.</li>
</ul>
Although it seems counterintuitive, consider replacing regular cups of coffee with lattes or other espresso drinks as you unplug your coffee cravings. A single, 1-ounce shot of espresso has just 45 to 75 milligrams of caffeine, compared to the 75 to 165&nbsp;milligrams found in a cup of drip joe.
Reviewed 5/17/2023

Caffeine: Is it safe?

Coffee and tea are major sources of caffeine, but it's also found in less expected places&mdash;medicine, for example.