Effects on the Body
You can feel the effects of caffeine in your system within a few minutes of ingesting it, and it stays in your system for many hours—its half-life can range from as little as two hours to as long as 12 hours due to individual differences in metabolism and absorption. Caffeine can affect the body in a variety of ways.
Hormones
Caffeine can alter the effects of several hormones.
Adenosine: Caffeine can inhibit the absorption of adenosine, which calms the body. This can make you feel alert in the short run, but cause sleep problems later. Adrenaline: Caffeine injects adrenaline into your system, giving you a temporary boost, but possibly making you fatigued and depressed later. If you take more caffeine to counteract these effects, you end up spending the day in an agitated state and might find yourself jumpy and edgy by night. Cortisol: Caffeine can increase the body’s levels of cortisol, the “stress hormone,” which can lead to other health consequences ranging from weight gain and moodiness to heart disease and diabetes. Dopamine: Caffeine increases dopamine levels in your system, acting in a way similar to amphetamines. This can make you feel good at first, but after it wears off you can feel low. It can also lead to physical dependence.
Sleep
Caffeine can affect your sleep by keeping you awake longer, thereby shortening the amount of sleep you get, and giving you less time in the restorative stages of sleep. This takes a toll on your level of alertness the next day and on overall health. Interestingly, though, caffeine doesn’t affect the stages of sleep the way other stimulants do, so it’s a better choice than speed or other uppers if you need to stay awake.
Weight
Many experts believe that increased levels of cortisol lead to stronger cravings for fat and carbohydrates, and cause the body to store fat in the abdomen. (Abdominal fat carries with it greater health risks than other types of fat.) Also, if increased cortisol levels lead to stronger cravings for caffeine-laden foods, the body goes into a cycle that leads only to worse health. Research also suggests that caffeine may impair the ability to taste sweet flavors and increase cravings for sugar-laden treats. The good news, though, is that caffeine can speed up metabolism. Also, it can help the body break down fat about 30% more efficiently if consumed prior to exercise. (You must be exercising to get this benefit, though.) Additionally, caffeine can keep blood sugar levels elevated, leaving you feeling less hungry.
Exercise
If caffeine elevates levels of cortisol and other hormones for a temporary boost after the caffeine wears off, the body can feel fatigued and feelings of mild to moderate depression can set in. This can make physical activity more difficult. On the positive side, caffeine has been found to enhance physical performance and endurance if it isn’t overused. This, combined with its effect of fat burning during exercise, can actually enhance workouts and enable you to get in better shape if you take it at the right time.
Caffeine and Stress
Caffeine and stress can both elevate cortisol levels. High amounts of caffeine can lead to the negative health effects associated with prolonged elevated levels of cortisol (as in chronic stress). However, small to moderate amounts of caffeine can lift your mood and give you a boost.
The Verdict on Caffeine
With potential negative and positive health consequences, caffeine can be your friend, as long as you consume it in controlled doses.
Don’t take too much: Because of the health risks associated with higher levels of caffeine, as well as the risk of physical dependence that can come with four cups of coffee or more each day, it’s wise to limit your caffeine intake. (Withdrawal symptoms can include cravings, headache, fatigue and muscle pain.) Avoid caffeine after 2 p.m.: Because sleep is important to proper physical functioning, and caffeine can stay in your system for eight hours or longer, limit your caffeine intake to the first part of the day to ensure that your sleep isn’t disrupted. Enjoy caffeine with physical activity: Caffeine is best ingested before exercise—that way your performance is enhanced and the stress-management benefits of exercise can keep you healthy and feeling less stressed throughout the day.
