Tea contains less caffeine than coffee. Of course, caffeine levels are affected by the blend, preparation method and brewing time. A typical 8-ounce cup of tea prepared from one tea bag brewed for 3 to 5 minutes contains 40 mg of caffeine, versus 100 mg in a cup of brewed coffee.
Extensive research has shown that moderate caffeine consumption is not a health risk, and that there is no scientific link between moderate caffeine consumption and the risk of cancer, cardiovascular disease or osteoporosis. For an adult, a moderate daily caffeine intake is generally understood to be about 300 mg a day, which is approximately 6 cups of brewed, hot tea or 3 cups of coffee a day.
No decaffeinated tea or coffee is completely caffeine free. Decaffeinated tea, like decaffeinated coffee, typically has about 4mg of caffeine per cup.