Is Too Much Caffeine Bad For You?

While caffeine is considered a necessary part of most people's morning routine — and occasionally afternoon and evening, too — there are some health impacts to keep in mind before downing those daily espressos. Caffeine is a naturally occurring compound found in ingredients such as nuts, seeds, and other plants. It is one of the world's oldest natural stimulants, dating as far back as brewed teas in 2737 B.C. Some of the most common sources of the stimulant include coffee, tea, energy drinks, soft drinks, and yerba mate. 

According to one study published in the Journal of Food Science, an estimated 80% of the world's adult population consumes some form of caffeine every single day. In North America, that figure is even higher at 90 percent of adults. So, the question is: Do the vast majority of adults have reason to be concerned when it comes to their caffeine fix of choice?

According to Healthline, once consumed orally, caffeine is absorbed into the bloodstream from the gut, broken down into compounds by the liver, and transmitted to the brain where it gets to work stimulating the body.

Once in the brain, caffeine performs a number of functions, including blocking the effects of a neurotransmitter called adenosine, which is responsible for relaxing the brain and making the body feel tired. Without the effects of caffeine, adenosine levels build throughout the day, causing tiredness over time. Since caffeine blocks the effects of adenosine, the body feels more alert.

Caffeine has also been shown to increase blood adrenaline levels. The study published in the Journal of Food Science suggested that after consuming a certain amount of caffeine, participants had improved reaction times and short-term memory recall as well as overall alertness.

In addition to the stimulation most turn to caffeine for, other potential health benefits of caffeine include lowered risk of depression, increased metabolism and fat burning, and even lowered risk of brain diseases such as Alzheimer's and Parkinson's.

While caffeine is generally considered safe for human consumption, there are a few negative side effects that come with it. According to a study published on NCBI, excessive intake of caffeine, particularly via energy drinks, can bring on irregular heartbeat, trouble sleeping, tremors, anxiety, and restlessness. Another study, published by Neurology, notes that over-consumption of caffeine can also result in daily headaches, migraines, and high blood pressure in some adults.

While these side effects might be intimidating, the Dietary Guidelines Advisory Committee has determined that a daily intake of up to 400 milligrams of caffeine is perfectly safe for any healthy adult. That amount of caffeine equates to roughly four cups of brewed coffee, two energy drinks, or 10 cans of soda per day.

However, the USDA has warned against powder or liquid forms of caffeine, which can contain toxic levels of caffeine that could lead to health complications and even death (via Mayo Clinic). According to the American College of Obstetricians and Gynecologists, women who are pregnant or trying to become pregnant should limit their caffeine intake to 200 milligrams daily.

All in all, the average adult relying on their morning cups of joe can rest easy, knowing that the caffeine being put to work in their system is likely doing more good than harm.