Caffeine is a stimulant, which means it can help you wake up in the morning or give you a burst of energy in the afternoon. For most people, a moderate amount of caffeine, which is equal to about 250 milligrams -- or around 2 cups -- a day, is perfectly safe, according to the University of Maryland Medical Center.

Many over-the-counter weight-loss supplements contain caffeine because of its potential effects on metabolism and weight. Whether or not caffeine can bring about a slight increase in weight loss, however, may depend at least in part on the source, and how long you've been consuming caffeine.

If you're looking for some quick energy before a workout or a pick-me-up in the late afternoon hours, both a cup of coffee and a caffeine pill can do the trick. Caffeine stimulates the central nervous system and so speeds up mental and physical processes.

According to "The Goodman and Gilman Manual of Pharmacology and Therapeutics," caffeine, which is a stimulant found in many foods, is the most widely-used psychoactive drug in the world. Although coffee has a high caffeine content, apples do not. Therefore, there is more caffeine in a cup of coffee than in an apple.

Most Lipton teas contain some caffeine. Decaffeinated teas contain very little, only 4 mg per serving. If you want to avoid caffeine completely, herbal teas are a good choice. They are not made from tea leaves, so they do not contain caffeine.

Caffeine is a chemical primarily found in coffee and tea, but which also appears in various sodas, sports drinks and foods. It is a stimulant, therefore causing changes in metabolism as well as increases in focus and energy. Caffeine is addictive and can cause withdrawal following cessation after frequent use.

Caffeine is a stimulant most people use to give them energy and to stay alert. A moderate amount of daily caffeine intake is 250 mg which equals approximately 3 cups of coffee. Although it offers no nutritional benefit it is not considered hazardous when consumed moderately.

Caffeine has gained a lot of attention over the last couple decades, leading to more informed consumers. The reasons for the attention stem from concerns about cancer, anxiety, headaches and jittery stomachs. The amount of caffeine varies significantly between beverages and brands.

Caffeine is a highly popular nervous-system stimulant commonly used to alleviate fatigue and increase alertness or wakefulness.

Caffeine affects the body in a variety of ways. It stimulates the central nervous system, improves mood and creates feelings of alertness, reduced fatigue, boosted endurance and mental activity. It speeds up the heart and constricts the blood vessels.

While caffeine can be used in a wide variety of foods and beverages, it is derived from a few main sources. Those sources include tea leaves, cocoa beans -- which are used to make chocolate -- kola nuts and coffee beans.

Whether you've decided to cut back on caffeine on your own, or your doctor recommended you reduce your caffeine intake, one strategy is to eliminate black and green tea, which both contain caffeine. Even black teas that are labeled "decaffeinated" contain trace amounts of caffeine.