You may love your daily cup of coffee for its flavor or the caffeine jolt it gives you. While you are sipping on your favorite drink, the caffeine in your body is affecting a number of your body functions, including your blood flow through your blood vessels. Knowing how your body responds to caffeine can help you to determine the right amount, if any, for you.
Caffeine and cAMP
Caffeine sets off a number of chemical reactions in the body that affect vasodilation, or the widening of your blood vessels. Caffeine first stops the action of a chemical called PDE, a messenger responsible for signaling the body to break down cAMP, a chemical that is in part responsible for vasodilation. When cAMP is not broken down as quickly, your body releases two hormones: epinephrine and norepinephrine. Known as the "fight or flight" hormones, these are the same hormones that cause your heart to race and you to breathe harder when you are in a dangerous situation.
Parasympathetic Response
The hormones released in response to caffeine affect the sympathetic nervous system, which is the part of your body that responds to emergencies. The sympathetic nervous system constricts some blood vessels and dilates others. For example, caffeine opens up the blood vessels that go to your body tissues, but tightens the blood vessels in the brain. It accomplishes this by stimulating your heart muscle to beat faster as it sends a message to your smooth muscles such as the muscle in your stomach to relax. As a result, you feel more alert and awake, temporarily reducing fatigue.
Withdrawals
Although caffeine takes some time to leave your body, it eventually does. This can lead to hyperdilation for the blood vessels in the brain, in which the vessels constrict significantly, leading to headache. You also may experience other side effects related to your blood vessels returning to their normal size, such as feeling muscle fatigue because blood flow had been increased to your muscles. When the blood vessels constrict to their normal size, you may feel more tired.
Considerations
Caffeine's effect on your blood vessels can be beneficial when you need a quick burst of energy or concentration. However, they can have ill effects if you have a complicating condition such as high blood pressure or a heart condition. Also, consuming excess amounts of caffeine -- 600 mg or four to seven cups of coffee a day -- can be harmful for anyone, according to the U.S. Food and Drug Administration. Symptoms you have consumed too much caffeine include feeliung jittery or shaky, have trouble falling or staying asleep, or feeling like your heart is beating unevenly.
References
- "Scientific American"; How Does Caffeine Affect the Body?; Neal Smatresk; February 1999
- MayoClinic; Caffeine: How Does It Affect Blood Pressure?; Dr. Sheldon Sheps; November 2009
- "Mail Online: Before You Take Another Sip of Your Coffee
- Evergreen State College: How Caffeine Is Processed By the Body
- U.S. Food & Drug Administration; Medicines in My Homes: Caffeine and Your Body; Fall 2007
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