For many people, no day would be complete without the energy-jolting boost of a caffeinated beverage: Four out of every five Americans consume caffeine daily, according to Swedish Medical Center, making it the most commonly used drug in the world. Although coffee, colas, teas, energy drinks, chocolate and other caffeinated items can provide a convenient pick-me-up during moments of fatigue, caffeine produces a number of additional effects in the human body.
Blood Pressure
Caffeine can have temporary but dramatic effects on blood pressure. As MayoClinic.com explains, your systolic pressure can rise 3 to 14 millimeters of mercury, or mm Hg, and your diastolic pressure can rise 4 to 13 mm Hg after drinking two to three cups of coffee, or 300 to 450 mg of caffeine. This rapid rise may be particularly harmful if you already suffer from high blood pressure. Although the exact mechanism behind the blood pressure spike remains unknown, MayoClinic.com notes that caffeine may block an artery-widening hormone in the body or trigger a release of adrenaline--two events that raise blood pressure.
Dehydration
Consuming caffeine--particularly in non-liquid forms such as chocolate--can contribute to water loss and dehydration. Because caffeine is a diuretic, it increases urination and forces your body to excrete more water than normal, Brown University Health Education explains. Although caffeinated beverages like coffee and soft drinks replenish some of the water your body loses, dehydration can still occur if you are exercising, sweating excessively or consuming few additional liquids in your diet. For every cup of coffee you drink during the day, Brown University Health Education recommends consuming 8 oz. of water to replace lost fluids and prevent dehydration.
Osteoporosis
Although the link between caffeine and bone health remains ambiguous, large amounts of caffeine may reduce bone density and contribute to osteoporosis. As Health Services at Columbia University explains, caffeine's diuretic properties force you to excrete minerals along with water, and your body loses 5 mg of calcium in urine with every 150 mg of caffeine you consume--the approximate amount in one 8-oz. cup of coffee. If you eat a low-calcium diet, you may be at heightened risk for bone density loss and osteoporosis from caffeine.
Nervous System Stimulation
As a stimulant, caffeine can increase activity in the central nervous system. According to Global Health and Fitness, the most noticeable symptoms of this stimulation include dilated pupils, a rapid heart rate, muscle tension, increased alertness, insomnia and excitement--all of which occur shortly after you consume caffeine. Because the stimulating effects of caffeine wear off within several hours, some people become mildly dependent on it as a way to combat fatigue and maintain alertness.
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