You rely on your morning cup of coffee to wake you -- and the caffeine in your coffee can have many effects on your body that can do just that. From increasing how fast your heart beats to constricting your blood vessels, caffeine in coffee has a stimulant effect on your nervous system. Understanding how caffeine affects your body can also help you understand how to avoid consuming too much caffeine.
Cause
While the exact body pathways the caffeine triggers is unknown, one theory is that caffeine blocks a cascade of hormones that keeps your blood vessels widened, according to MayoClinic.com. Another theory related to your blood vessels is that caffeine stimulates the adrenal gland to release hormones such as epinephrine and norepinephrine. These hormones activate your body's flight-or-flight response, which in turn affects your blood vessels.
Effects
The added epinephrine and norepinephrine in your body that occurs as a result of caffeine, has several effects on your body. In terms of your blood vessels, norepinephrine especially stimulates vasoconstriction, which means your blood vessels become smaller. While your veins are constricted, the bronchioles in your lungs become larger, causing you to increase the amount of oxygen you take in. This makes you feel more alert and awake. When the effects of caffeine wear off, your blood vessels will widen and your breathing rate will slow, which can make you feel more tired.
Moderate Intake
The amount of caffeine you drink can affect the extent your blood vessels constrict. For example, moderate caffeine intake may not have a significant impact on your blood vessels. A moderate coffee intake includes three 8 oz. cups of coffee a day, which is about 250 mg of caffeine daily, according to Every Diet. Exceeding this amount may cause adverse effects, ranging from high blood pressure due to constricted blood vessels, headaches and nervousness.
Sensitivity
Even if you are drinking a moderate amount of coffee per day, it is possible to be more sensitive to the effects of caffeine than other people, according to MayoClinic.com. One method to tell if caffeine has a vein-constricting effect on your body is to take your blood pressure, then drink a cup of coffee or other coffee beverage. After 30 minutes, take your blood pressure again. If your blood pressure has increased five to 10 points, you may be more sensitive to coffee's effects.
References
- MayoClinic.com; Caffeine: How Does It Affect Blood Pressure?; Sheldon Sheps, M.D.; November 2009
- "Scientific American"; How Does Caffeine Affect the Body?; February 1999
- EveryDiet; Coffee (Caffeine) and Its Effects in the Human Body; August 2011
- Go Ask Alice!; Caffeine's Effects on Health; June 2008
- Colorado State University; Adrenal Medullary Hormones; R. Bowen; May 1998
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