“Caffeine produces the same behavioral effects as classical psychostimulants, such as cocaine and amphetamine.”
Your morning cup of coffee boosts your mood, increases focus and alertness. Coffee in moderation is beneficial and essential for our modern lifestyle. However, one-third of Americans drink too much caffeine, and like abuse of any substance, too much (>400 mg) causes negative side effects and behavior changes.
Signs of too much coffee/caffeine
Anxiety
Obsessive-compulsive disorder (OCD)
Headaches
Heartburn
Irritable bowel syndrome (IBS)
Back pain
Insomnia
Irritability
How much coffee is too much?
The United States Food and Drug Administration (FDA) states:
“For healthy adults, the FDA has cited 400 milligrams a day—that's about four or five cups of coffee—as an amount not generally associated with dangerous, negative effects.”
Keep in mind that cups of coffee vary dramatically in their caffeine content.
For example, a 20-oz cup of Starbucks coffee has 410-mg of caffeine, 2.5% higher than the FDA’s total daily caffeine recommendation.
Also, it should be noted that the majority of studies researching the effects of caffeine & coffee rarely exceed 300 milligrams, or 100 mg less than the FDA’s recommendation.
For caffeine-sensitive coffee drinkers, even 250-mg would be considered excessive. One 12-oz cup of Starbucks coffee has 260-mg, for example.
Caffeine Per 16-ounces of Coffee
Caffeine-Induced Anxiety
Caffeine-induced anxiety disorder is a medical condition where high amounts of caffeine cause severe anxiety. This has been known for at least 150 years but is largely unreported.
Studies have shown that caffeine intake of only 150 milligrams increases anxiety and can induce panic attacks in caffeine-sensitive people and 450mg in normal populations. Caffeine-induced anxiety can mimic disorders, such as bipolar, general anxiety, schizophrenia, and obsessive-compulsive disorder (OCD).
If you are a heavy coffee drinker and experience any form of general anxiety, reducing or eliminating caffeine is a good first step.
Coffee & Headaches
“Caffeine has been linked with migraine for many years, on the one hand as a trigger, and on the other as a cure.”
Regular consumption of coffee/caffeine leads to physical dependence, with at least 30% of Americans meeting DSM-IV criteria for caffeine addiction and caffeine-dependence syndrome. A caffeine-withdrawal headache is a cardinal symptom where you drink more coffee in order to avoid getting a headache or migraine.
Caffeine-induced headache has been recognized for more than a decade as the major cause of chronic daily or almost daily headaches in adults.
How does coffee cause headaches?
Caffeine induces urinary loss of magnesium. Magnesium affects neuromuscular conduction and nerve transmission and plays a beneficial role in chronic pain conditions and migraines
Excessive coffee consumption leads to acute diuretic effects and a “dehydration headache”
Caffeine withdrawal. Weekend headaches are common as you sleep in and delay your weekday caffeine intake schedule or drink less coffee during the day due to unforeseen coffee abstinence
Coffee & Heartburn
Gastroesophageal reflux (GERD) is synonymously known as acid reflux or heartburn. There are many cofactors to GERD, such as over-eating, obesity, greasy food, and lying down after eating, however, there is also a coffee connection.
Drinking too much coffee temporarily weakens (relaxes) the lower esophageal sphincter, which increases the risk of GERD. If you suffer from heartburn and consume copious amounts of coffee, you should consider reducing your intake.
A 2020 review paper, published in Critical Comments in Biomedicine (CCB) reviewed 85 studies and concluded:
“It was shown that to higher intakes of caffeinated drinks, fruit juice, milk, soft drinks and carbonated beverages are associated with aggravating symptoms in GERD, IBS and FD.”
The researchers also noted:
“Generally, coffee was identified as being the most frequently reported to cause symptoms in people with IBS and to manage these symptoms, the NICE (the National Institute for Health and Care Excellence) guideline proposes limiting the intake of high sources of caffeine such as coffee and tea, and subjects with IBS should not consume more than three cups of tea or coffee per day or 400 mg caffeine.”
IBS, GERD, & Coffee: Bottom Line
If you consume coffee and other caffeinated beverages and suffer from heartburn, IBS, or general gastrointestinal disorders, reducing caffeine intake below 400mg is recommended. For those that are caffeine sensitive, you might need to reduce caffeine consumption to under 250mg.
Caffeine & Back Pain
“Particularly interesting results of our studies concern the effect of excessive caffeine consumption on recurrent low back pain. Drinking of ≥6 cups of coffee a day increased the chance for the development of recurrent nonspecific low back pain by over 16 times versus respondents who did not consume excessive amounts of caffeine”
After headaches, nonspecific low back pain is the most common pain reported. Chronic low back pain is multi-factorial; sedentary lifestyle, prolonged sitting, obesity, postural stress, cigarette smoking, and excessive coffee consumption are all factors in back pain.
Caffeine’s Role In Back Pain
Excessive caffeine disrupts calcium flow by altering calcium ions from the sarcoplasmic reticulum. This causes slow-twitch muscles, like the postural muscles of your low back to fatigue more quickly. Additionally, caffeine increases the release of catecholamines, such as epinephrine, which sensitize muscle nerve endings, increasing the perception of pain.
Coffee Amount & Back Pain
Less than 400mg of daily caffeine can cause back pain. One large (venti) Starbucks coffee alone has 410mg, equal to 6, 6-oz cups of coffee.
Insomnia
“The most prominent effects of caffeine on sleep are prolonged sleep latency, shorter total sleep time, increases in light sleep, and decreases in deep sleep.”
Image Source: O'Callaghan, Frances et al. “Effects of caffeine on sleep quality and daytime functioning.” Risk management and healthcare policy vol. 11 263-271. 7 Dec. 2018.
Caffeine, particularly in the form of coffee, is an adenosine receptor antagonist. Caffeine promotes wakefulness by blocking the sleep-promoting effects of adenosine. Drinking coffee negatively affects sleep latency, sleep duration, and sleep efficiency, and the relative time spent in deep sleep.
Without caffeine, adenosine concentration levels naturally increase during the day, and once they reach a certain point, they become drowsy. Caffeine blocks adenosine receptors, which makes you feel alert, but prolongs the feeling of drowsiness and leads to restlessness.
Coffee & Sleep
Depending on your level of caffeine sensitivity, as little as 60mg, or less than 3-oz of Starbucks coffee, can cause you to lose sleep. A standard small cup of coffee has about 100mg of caffeine, with many large specialty roasts having over 400mg. If you have trouble falling asleep, eliminating that afternoon cup of Joe and reducing total caffeine intake is a good first step.
Studies show that 200mg of caffeine, the equivalent of two small cups of coffee, first thing in the morning, reduced sleep efficiency by 3% in moderate coffee drinkers. For those consuming 4 or more cups of coffee (>400mg caffeine) regularly, insomnia or reduced stage-4 sleep are typical. A few bad nights of sleep result in more coffee consumed, creating a loop of caffeine dependence.
Irritability
Caffeine intoxication is called caffeinism. Mood swings and irritability are classic side effects of excess coffee consumption or caffeinism. Drinking two 12-oz cups of drip coffee or 300mg is about the top-end of the safe zone. Four or more standard cups of coffee or one large Starbucks (>400mg) is enough to cause irritability and mood swings.
Just like with alcohol, coffee has an intoxication threshold, once you pass it, nervousness, mood swings, agitation, and irritability manifest for many.
Final Thoughts
Coffee and caffeine is a drug. Like any drug, the dose makes the poison. Coffee in moderation not only improves alertness, focus, and makes us happy, but is also healthy for us.
However, drinking cup after cup is unhealthy and causes a host of problems, including poor sleep, agitation, mood swings, heartburn, IBS, anxiety, and chronic back pain.
I recently quit coffee and all forms of caffeine for 75 days. My first cup of coffee after this break was a small cup of100% Coffea arabica, about 120mg of caffeine. The cup was magical but incredible potent.
Jesse is Director of Pedal Chile and lives in Valdivia, Chile. Jesse has a Master of Science in Health & Human Performance and a Bachelor of Science in Kinesiology. Hobbies: MTBing, snowboarding, reading, taster of craft beers, and researcher.
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