If you use coffee or other caffeinated products regularly to increase wakefulness, you have a lot of company. Americans consume about 45 million lbs. of caffeine each year; even people who don't consume coffee get about 91 mg a day, according to the University of Washington. As a central nervous system stimulant, caffeine produces numerous neurological effects. Research has found caffeine use can be beneficial, especially for women, but the old adage "everything in moderation" applies when it comes to caffeine intake.
Common Caffeine Sources
The most common sources of caffeine are coffee, tea, soft drinks, chocolate, and energy drinks. According to the National Toxicology Program, an 8-oz. cup of regular drip brewed coffee contains 65 to 120 mg of caffeine. A single ounce of espresso -- a shot -- contains 30 to 50 mg of caffeine; while an 8-oz. cup of brewed tea averages around 40 mg, brewed tea ranges from 20 to 90 mg, caffeinated energy drinks typically carry 80 mg, caffeinated soft drinks average 24 mg, and an ounce of dark chocolate carries between 5 and 35 mg.
Neurological Benefits
Drinking black tea and other caffeinated beverages throughout the day helps you stay alert even after extended periods without sleep, according to MedlinePlus.
Women who drink about four cups of coffee a day lower their risk of stroke by about 43 percent, but only if they don't smoke, according to results from a 24-year study of coffee consumption and health published in "Circulation" in 2009. Women smokers who drank four cups of coffee a day reduced their stroke risk by 3 percent. Conducted by researchers in Spain and at the Harvard School of Public Health, the study included 83,000 women.
Caffeine appears to offer protection against cognitive decline in older women, but not older men. For a study published in 2007 in the journal "Neurology," researchers tracked the caffeine consumption of 7,000 men and women older than 65 for four years. After comparing measures of the volunteers' cognitive performance taken at the beginning and at the end of the study, the researchers found that women who consumed more than three cups of coffee a day showed less loss of memory and verbal abilities than women who consumed one cup or less.
Precautions
Some experts warn that pregnant women put their unborn child at risk if they consume more than 500 mg of caffeine a day. According to the March of Dimes, caffeine easily passes from the mother to her unborn child through the placenta. Because the unborn child's system cannot break down and eliminate chemicals, caffeine levels in the blood remain elevated for a longer period of time. The March of Dimes says studies have found that children born to mothers who were heavy coffee drinkers had faster heart rates and increased breathing rates, experienced tremors, and were awake longer in the days after birth than children whose mothers were not heavy coffee drinkers.
Caffeine in two or three cups of coffee can increase your blood pressure, even if you don't have a history of high blood pressure, according to MayoClinic.com. If you already have high blood pressure, it's wise to limit your caffeine consumption to 200 mg a day and avoid caffeine right before exercise or hard physical labor since these activities naturally increase your blood pressure.
Moderate vs. Heavy Caffeine Use
Moderate caffeine intake --- 200 to 300 mg, equal to about two to four cups of brewed coffee a day --- isn't harmful, but heavy use that exceeds 500 to 600 mg a day --- about four to seven cups --- can affect your health, according to the MayoClinic.com. Too much caffeine consumption can cause insomnia, irritability, nausea, other gastrointestinal problems, fast or irregular heartbeat, and headaches from withdrawal and depression.
References
- University of Washington: Effects of Caffeine on the Nervous System
- National Toxicology Program: Caffeine
- MedlinePlus: Black tea
- Circulation: Coffee Consumption and Risk of Stroke in Women
- Neurology: The Neuroprotective Effects of Caffeine; 2007
- MayoClinic.com: Caffeine: How Does it Affect Blood Pressure?
Member Comments