Caffeine, according to the U.S. National Library of Medicine, stimulates the central nervous system by blocking the activity of a chemical called adenosine.(1)
Most commonly known for being an active ingredient in caffeine, caffeine has a number of potential health benefits, but there are also some risks associated with excessive consumption.
Research with caffeine provides information about the benefits, risks, and healthy levels of consumption associated with this substance.
Benefits of Caffeine
The stimulant properties of caffeine come with some benefits for health.
By facilitating weight and fat loss, caffeine can also reduce diabetes risk.
In fact, a review of 13 studies, published in a 2014 edition of Diabetes Care, showed that coffee intake decreases the risk of diabetes, with caffeinated coffee having slightly stronger benefits when compared to decaffeinated versions.(3)
The physical benefits of caffeine consumption can also extend to sports performance.
A 2012 study in the Journal of Sports Sciences found that ingesting caffeine 90 minutes prior to completing an hour-long cycling session improved performance significantly.(4)
A caffeine dose of 3 mg per kg of body weight was found to be effective, which is equivalent to about 200 mg of caffeine for a person weighing 150 pounds.
In addition, scientists completing a review of the research for a 2010 publication of the Journal of Strength & Conditioning Research determined that several studies show that caffeine can enhance a person’s performance in team and power-based sports and improve resistance training performance, primarily by increasing the number of repetitions a person can complete of an exercise.(5)
While the physical benefits of caffeine seem to be well-established, it is also noted that caffeine can improve mental functioning.
In fact, a 2010 study in Human Psychopharmacology: Clinical & Experimental found that caffeine quickens reaction time.(6)
It can also improve alertness, especially following a late night.
For example, a 2000 study in Psychophysiology found that consuming 200 mg of caffeine from coffee after a night of sleep deprivation reduced feelings of sleepiness as well as driving incidents during an early-morning driving task.(7)
Risks Associated with Caffeine Use
While caffeine can contribute to alertness and provide physical health benefits, consuming large quantities of caffeine is not entirely risk-free.
As the authors of a 2008 report in Sleep Medicine Reviews have reported, the research shows that people can become dependent on caffeine even with seemingly low daily intake, and they can experience sleep difficulties with caffeine.(8)
Caffeine can increase alertness after a less-than-restful night of sleep, but ironically, it can also sometimes disrupt sleep, leading to worsened sleep quality.
Caffeine may also be problematic for individuals with high blood pressure.
In a study of older adults with hypertension, those who consumed three or more cups of coffee per day had significantly higher blood pressure over the course of the day when compared to those who consumed no coffee.
This study, which was included in a 2016 edition of Clinical Nutrition, suggests that those with high blood pressure should limit caffeine intake.(9)
It is also wise to limit caffeine consumption during pregnancy, as a review of 14 studies, published in 2016 in Public Health Nutrition, revealed that consuming 350 or more mg of caffeine per day during pregnancy increases the risk of pregnancy loss.(10)
Withdrawal is another risk associated with caffeine when use is discontinued suddenly.
A 2004 report in Psychopharmacology indicates that research with caffeine shows that withdrawal causes headaches in about 50 percent of people, with stronger withdrawal symptoms occurring among those who typically consume higher amounts of caffeine.(11)
Effects of Caffeine on the Body
Beyond the risks associated with caffeine, it is important to consider its physiological effects.
According to the University of Delaware, caffeine inhibits vasopressin, which causes increased urination.(12)
It also constricts the blood vessels and can increase heart conductivity. Furthermore, it raises adrenaline levels and can also increase gastric activity, causing an upset stomach or heartburn.
In the brain, caffeine works by halting the activity of adenosine and causing the release of brain chemicals called neurotransmitters.
For example, according to the authors of a 2016 report in Neuroscience & Biobehavioral Reviews, caffeine consumption facilitates the activity of the neurotransmitter dopamine, which has a stimulant effect.(13)
Recommended Daily Consumption
Caffeine consumption has clear effects on the brain and body, and with these effects comes both risks and benefits.
Despite some risks associated with caffeine use, moderate consumption is generally deemed safe. FDA states that 400 mg of caffeine per day, which is equal to what is found in four to five cups of coffee, is typically not dangerous.(14)
Those who consume coffee at this level may even experience benefits, such as enhanced mental processing, improved health, and better physical performance.
Then again, some people may encounter sleep problems with too much caffeine, and it may be necessary to limit consumption in the afternoon and evening.
People with certain health conditions, such as pregnant women and those with high blood pressure, may also need to limit caffeine consumption.
Anyone who has concerns about what level of caffeine intake is safe for them should have a discussion with their health-care provider.