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Coffee and tea are incredibly healthy beverages.
Most types contain caffeine, a substance that may boost your mood, metabolism and
mental and physical performance. Studies have also shown that it’s safe for
most people when consumed in low-to-moderate amounts.
However, high doses of caffeine may have unpleasant and even
dangerous side effects.
Research has shown that your genes have a major influence on
your tolerance to it. Some can consume much more caffeine than others without
experiencing negative effects (5Trusted Source, 6Trusted Source).
What’s more, individuals who aren’t used to caffeine may
experience symptoms after consuming what is typically considered a moderate
dose (4Trusted Source, 7Trusted Source).
Caffeine is known to
increase alertness.
It works by blocking the effects of adenosine, a brain chemical
that makes you feel tired. At the same time, it triggers the release of
adrenaline, the “fight-or-flight” hormone associated with increased energy (8Trusted Source).
However, at higher doses, these effects may become more
pronounced, leading to anxiety and nervousness.
In fact, caffeine-induced anxiety disorder is one of four
caffeine-related syndromes listed in the Diagnostic and Statistical Manual of
Mental Disorders (DSM), which is published by the American Psychiatric
Association.
Extremely high daily intakes of 1,000 mg or more per day have
been reported to cause nervousness, jitteriness and similar symptoms in most
people, whereas even a moderate intake may lead to similar effects in
caffeine-sensitive individuals (9, 10Trusted Source).
Additionally, modest doses have been shown to cause rapid
breathing and increase stress levels when consumed in one sitting (11Trusted Source, 12Trusted Source).
One study in 25 healthy men found that those who ingested
approximately 300 mg of caffeine experienced more than double the stress of
those who took a placebo.
Interestingly, stress levels were similar between regular and
less frequent caffeine consumers, suggesting the compound may have the same
effect on stress levels regardless of whether you drink it habitually (12Trusted Source).
Nevertheless, these results are preliminary.
Coffee’s caffeine content is highly variable. For reference, a
large (“grande”) coffee at Starbucks contains about 330 mg of caffeine.
If you notice that you often feel nervous or jittery, it might
be a good idea to look at your caffeine intake and cut it back.
Summary: Although
low-to-moderate doses of caffeine can increase alertness, larger amounts may
lead to anxiety or edginess. Monitor your own response in order to determine
how much you can tolerate.
