"How much caffeine is too much?" might be a better question. Coffee is actually an incredibly healthful drink, offering a hefty dose of antioxidants and a bitterness that spurs digestion.
However, because it also contains caffeine, it is best to enjoy this warm treat in moderation. It is quite possible to drink too much coffee and exceed an appropriate daily caffeine intake level, and in fact, many Americans already do!
So for those who have ever wondered, "How much caffeine can I have in a day san negative side effects?" look no further.
What Is Caffeine and What Does It Do?
Caffeine is considered a natural stimulant and is most commonly found in coffee, tea, cacao, energy drinks, soda, and stimulant drugs. It works by stimulating the brain and central nervous system to stay alert and focused. In this way, it may also help stave off tiredness.
When consumed, the gut rapidly absorbs the caffeine from the gut into the bloodstream where it then travels to the liver. Once there, it is broken down into compounds that affect various organs differently. However, it exerts most of its effect on the brain.
Caffeine blocks the neurotransmitter adenosine, which generally promotes feelings of relaxation and tiredness. It blocks adenosine by attaching to its receptors without activating them. In addition, it can increase blood adrenaline levels and increase the activity of dopamine and norepinephrine, two other neurotransmitters with high reactivity in the brain. This effect creates further brain stimulation, generating a state of arousal, alertness, focus, and high energy.
Technically, caffeine is one of the only FDA-approved drugs legally added to foods and drinks. But which food and drinks have the most caffeine?
Amount of Caffeine in Different Foods and Drinks
Caffeine is naturally derived from the nuts, seeds, or leaves of certain plants that are then harvested and processed to produce caffeinated goods. The following goods contain about this much caffeine in one serving:
• Coffee 8 ounces (oz): 102-200 mg (milligrams)
• Venti Starbucks coffee: 410 mg
• Decaf coffee 8 oz: 3-12 mg
• Energy drinks: 75-300 mg
• 5 Hour Energy Extra Strength: 230 mg
• Tea 8 oz: 40-120 mg
• Soft drinks: 20-70 mg
• Yerba mate: 65-130 mg
• Caffeinated flavored waters: 30-100 mg
• Ben & Jerry's coffee-flavored ice creams: 65 mg
• Hershey's Special Dark Chocolate: 20 mg
• Hershey's milk chocolate: 9 mg
• Chobani Coffee and Cream Greek yogurt: 3 mg
• Clif shot energy gels: 100 mg
• Sport energy chews/beans: 20-50 mg
• Hydroxycut hardcore: 270 mg
• Excedrin migraine: 130 mg
• Midol complete: 120 mg
Potential Benefits of Caffeine
As mentioned, it is known to improve mood and brain function in terms of focus, concentration, and acuity. It does this by acting on the three neurotransmitters already discussed (adenosine, dopamine, and norepinephrine) and shifting their communication messaging.
In one study, participants who ingested 40-450 mg of caffeine demonstrated improved alertness, short-term memory recall, and reaction time. In other studies, caffeine helped lower the risk of depression and risk of suicide.
Caffeine is also associated with potentially boosting metabolism and fat burning capability due to the stimulation of the nervous system. Some research shows that the stimulant may help increase metabolism by 11 percent and fat burn by 13 percent, which would mean burning an extra 70-100 calories per day. Although this only equates to the amount of energy in a piece of fruit, it can be meaningful in the long term. Nonetheless, most studies show that these effects are short-term rather than long-lasting.
Caffeine may also help improve exercise performance by increasing the use of fat as fuel and preserving glucose in the muscles for longer periods of time. This allows one to exercise harder for longer and delay muscle exhaustion. It may also improve muscle contractions and reduce the perceived rate of exertion, making a workout feel easier. These effects are most potent when the caffeine is ingested within an hour of performance.
Finally, caffeine is associated with a lower risk of heart disease, despite it raising some people's blood pressure short term. Drinking two to four cups of coffee per day has also been correlated with a lower risk of stroke and is protective against diabetes.
Additionally, the stimulant is linked to several other health claims including liver protection, decreased risk of cancer, reduced risk of multiple sclerosis, gout prevention, gut health, longevity, and vitality.
However, just because caffeine offers some positive effects does not mean that more is better.
Negative Effects of Caffeine
Before beginning, caffeine consumption is generally considered safe for most people, especially healthy adults, albeit its habit-forming (addictive) qualities. Nonetheless, drinking too much can definitely elicit negative side effects.
The U.S. Department of Agriculture (USDA) considers a daily intake of 400 mg of caffeine or about the equivalent of 2-4 cups of coffee a day to be safe. Yet, consumption of 500 mg of caffeine in one dose has led to some fatal overdoses. Thus, it is recommended to limit caffeine/coffee consumption to closer to 200 mg per day.
Interestingly, some research shows that genes have a major influence on caffeine tolerance. Meaning, some people are able to surpass that 400 mg mark without complications while others can barely consume more than 50 mg without unpleasant side effects. Nonetheless, because of the associated risks, it is recommended that adolescents limit intake to no more than 100 mg per day and pregnant women no more than 200 mg per day.
Side Effects of Too Much Caffeine
1. Anxiety and/or anxious feelings: Caffeine triggers the release of adrenaline, which creates the flight-or-fight response. When this state persists, it causes the release of hormones that promote anxious, irritable feelings.
2. Nervousness/jitters: Even moderate doses of caffeine can lead to rapid breathing and increased stress levels that may feel like a panic attack. It does this by increasing muscle contractions and exerting effects on hormones.
3. Insomnia: Perhaps the most well-known side effect, caffeine can certainly prevent restful, quality sleep. Studies show that high caffeine intake can increase the amount of time it takes someone to fall asleep, decrease sleeping time and/or cause someone to wake up often throughout the night. Avoiding caffeine within 8-12 hours of bedtime is recommended.
4. Rhabdomyolysis: Also known as muscle breakdown, rhabdomyolysis is a condition where damaged muscle fibers enter the bloodstream and cause kidney failure among other problems. Although this side effect is quite rare, awareness is still important. More likely causes of muscle breakdown include trauma, infection, drug abuse/overdose, muscle strains, and poisonous bites from animals or insects.
5. Increased blood pressure: Although temporary, excessive caffeine can cause high blood pressure. Even though caffeine appears to be protective of heart disease and stroke, excessive doses raise pressure, which over time may increase the risk of heart disease and strokes. Just another reason why it is so important to sufficiently moderate consumption.
6. Digestive problems: It is no secret that many people drink coffee just to keep their bowels moving in the morning. The laxative effect of coffee is related to the release of gastrin, a stomach hormone that speeds colon activity (diarrhea). Caffeine may also increase peristalsis, wavelike contractions that propel food through the digestive tract. Because of these effects, though, coffee is also known to exacerbate symptoms of gastroesophageal reflux disease (GERD).
7. Racing heart: Once again, the stimulatory effects of caffeine are responsible for this side effect. Not only can the stimulant cause increased heart rate, but it can lead to an altered heartbeat rhythm called atrial fibrillation. However, the effects and severity of this system greatly vary from person to person.
8. Caffeine crashes: As physics states, what comes up must come down. Also known as rebound fatigue, caffeine can cause fatigue crashes after it is left the digestive system. Research suggests that although it temporarily improves mood and alertness, people are generally more tired than usual hours after drinking high amounts of caffeine. Moderating consumption and remaining under your individual threshold largely prevents this.
9. Frequent urination/dehydration: Caffeine does not directly cause dehydration, but because it over-stimulates the bladder causing more frequent urination, it is a potential consequence. In the long term, this can lead to urinary incontinence.
Caffeine overdoses can truly occur when too much is ingested in a short period of time. People who do not tolerate caffeine well are at the highest risk for this condition and symptoms include:
• Dizziness, confusion, and potential hallucinations
• Nausea and/or vomiting
• Breathing trouble
• Chest pain
• Uncontrollable muscle movements
• Convulsions at its worst.
Seeking medical treatment immediately if caffeine overdose is suspected is vital.
The Bottom Line
Coffee contains the stimulant drug known as caffeine. Touted as a morning energizer and afternoon pick-me-up, coffee is a beloved drink that also offers healthful benefits. Yet, too much of a good thing can quickly teeter towards bad, which is the case with coffee.
Under 400 mg of caffeine or 2-4 cups of coffee per day is generally considered safe, but some people are not able to tolerate that much and 200 mg of caffeine per day may be a more reasonable recommendation. Furthermore, consuming more than 400 mg per day greatly increases the risk of negative side effects such as anxiety, rapid heart rate, insomnia, and caffeine crashes.
The ultimate moral of the story is to simply drink responsibly! It can take some trial and error to determine a coffee/caffeine threshold, but the body will always tell you, so pay careful attention.
Caffeine Chart. Center for Science in the Public Interest. https://cspinet.org/eating-healthy/ingredients-of-concern/caffeine-chart.
Petre A. What Is Caffeine, and Is It Good or Bad for Health? Healthline. Published June 3, 2020. www.healthline.com/nutrition/what-is-caffeine#metabolism-fat-burning.
Rivers A. Caffeine Overdose: Symptoms, Side Effects, and Treatment. Healthline. Updated on December 6, 2018. www.healthline.com/health/caffeine-overdose#symptoms.
Spritzler F. 9 Side Effects of Too Much Caffeine. Healthline. Published August 14, 2017. www.healthline.com/nutrition/caffeine-side-effects.