Nine out of 10 Americans consume some type of caffeine regularly, making it the most popular behavior-altering drug. For most people, moderate doses of caffeine (about two to three cups of brewed coffee a day) are not harmful. However, heavy daily caffeine use (about four to seven cups of coffee) can cause restlessness, anxiety, irritability, muscle tremors, sleeplessness, headaches, nausea, diarrhea or other gastrointestinal problems and abnormal heart rhythms.

In order to prevent heavy caffeine use, you can adopt new caffeine habits. Try these tips: 

• Know how much caffeine is in the foods and beverages you consume
• Gradually reduce the amount of caffeine you consume; for example, drink one less can of soda or drink a smaller cup of coffee each day; this will help your body get used to the lower levels of caffeine and thereby lessen the withdrawal effects
• Replace caffeinated coffee, tea and soda with their decaffeinated counterparts; most decaffeinated beverages look and taste the same
• When preparing tea, brew for less time; this cuts down on its caffeine content; or choose herbal teas, which don’t contain this stimulant

The Truth About Energy Drinks
Energy drinks are often full of caffeine. When 10 different brands of energy drinks were tested, caffeine levels ranged from 0-141 mg/serving, according to a study in the Journal of Analytical Toxicology. In comparison, an average eight-ounce cup of brewed coffee contains 65 to 120 mg of caffeine, tea has 20 to 90 mg, and caffeinated soft drinks have 20 to 40 mg per serving.

The consumption of energy drinks on a daily basis can lead to the development of caffeine tolerance. For example, if you have an energy drink every morning before work, you might find yourself needing another at lunch to achieve the same effect. To avoid caffeine tolerance, dilute energy drinks with water.