Caffeine is a considered a safe ingredient. It is a stimulant that excites the nerves cells of the brain. While some stimulants, such as nicotine, are considered addictive, you aren’t likely to become addicted to caffeine if you consume it in moderation. But if you have caffeine regularly, you might feel like you're dependent on it. Without it, you might get a headache or feel fatigue, difficulty concentrating, nausea, and muscle pain.

Between 200 mg and 300 mg of caffeine, the amount in two to three cups of coffee, is considered a moderate amount and is generally considered safe for most adults.

Some studies have shown that moderate consumption of caffeine may reduce your risk of diabetes, gallstones, Parkinson's disease, and liver disease. Despite these studies, though, doctors aren’t recommending caffeine consumption as a means to reduce your risks of disease.

There is conflicting research on caffeine and pregnancy, but experts say pregnant women would be wise to moderate their intake. Some studies have linked a high intake of caffeine to increased risk for miscarriage and decreased fetal growth, but a cause-and-effect relationship has not been established. The Academy of Nutrition and Dietetics recommends getting less than 300 mg per day, the equivalent of up to three cups of coffee, depending on the brew.

Babies can indeed get a dose of caffeine from their mothers' milk. However, according to the American Academy of Pediatrics, "A morning cup of coffee is not likely to harm your baby, but too much caffeine can cause problems, such as poor sleeping, nervousness, irritability, and poor feeding."

The caffeine content in coffee can vary depending on brewing method, the type of bean used, and the amount prepared. For example, different extents of grinding the beans can yield different amounts of caffeine. Researchers in Florida ordered the same beverage from the same coffee shop for six consecutive days and found that the caffeine content ranged from 259 mg to 564 mg.

Caffeine's effects last long after you finish that cup of java. It takes 5 to 6 hours for your body to eliminate just half the caffeine in a cup of coffee, which is why having a cup in the afternoon can affect your sleep. In people who are more sensitive to caffeine, the effects may last even longer.

Caffeine helps the body absorb headache drugs more quickly, bringing faster relief. Adding caffeine requires less medication for the same effect, reducing the risk for potential side effects and possible drug addiction.

Antiaging products containing caffeine have been shown to help make skin smoother and reduce the appearance of wrinkles.

A recent study found that men have a greater response to caffeine than women; however, another study suggested that this might not always be a good thing. Researchers found that caffeine tended to harm the performance of men in collaborative, stressful situations (such as an office environment), but it improved the performance of women.

Older adults can be more sensitive to caffeine because it takes their bodies longer to process it.

According to the National Institute of Mental Health, anyone suffering from anxiety disorders should avoid caffeine because it can aggravate symptoms, which include exaggerated worry and tension.

Contrary to popular belief, caffeine will not help anyone who is intoxicated become sober.

Caffeinated beverages do not generally contribute to dehydration. In the short term, caffeine may have a mild diuretic effect in people who do not normally consume caffeine, but this is not the case for those who habitually drink caffeinated beverages. All beverages, including those that contain caffeine, help maintain hydration.

Deaths from caffeine overdose are rare, but they can be caused by convulsions or an irregular heartbeat. The amount of caffeine considered to be an overdose varies by a person’s size, age and gender, but in general, doses of greater than 10 grams can be fatal in adults. A typical cup of coffee has about 115 mg of caffeine, so you’d need to drink more than 85 cups to consume 10 grams.

The FDA limits the caffeine content in soft drinks to 71 mg per 12 oz serving, but there is no limit on the amount of caffeine “energy drinks” can contain. Several energy drinks have more than 100 mg of caffeine per serving, and some have more than 200 mg.

Because high doses of caffeine can enhance physical performance -- studies have shown it can increase muscle endurance during brief, intense exercise -- NCAA athletes are not allowed to consume high doses of caffeine. The NCAA allows up to 15 micrograms of caffeine per milliliter of urine, high enough to allow for normal consumption of caffeinated beverages, but low enough to bar the use of high-dose caffeine supplements.