Caffeine is a widely consumed substance that can affect your body and brain. It is found naturally in coffee, tea, cocoa, and chocolate, and it is also added to some energy drinks, soft drinks, and medications.
Caffeine can improve your mood, alertness, and mental and physical performance. Still, it can also cause some unwanted side effects, especially if you consume too much or are sensitive to it.
This article discusses the common and uncommon side effects of caffeine.
Common Side Effects of Caffeine
The following are some common side effects of caffeine that may occur in low to moderate doses (up to 400 mg per day for healthy adults and up to 200 mg per day for pregnant and breastfeeding women).
1. Anxiety
Caffeine can stimulate your nervous system and increase your adrenaline levels, a hormone that prepares your body for action.
This can make you feel more alert and energetic and nervous, restless, jittery, or irritable. Caffeine can also worsen anxiety disorders and panic attacks and interfere with your sleep quality and quantity6.
2. Insomnia
Caffeine can make it harder to fall asleep, stay asleep, or get enough deep sleep.
This can affect your daytime functioning, mood, and health. The effects of caffeine on sleep depend on several factors, such as the amount and timing of caffeine intake, sensitivity and metabolism, and sleep habits and environment.
Caffeine can stay in your system for several hours, so avoiding consuming it at least six hours before bedtime is advisable. The American Academy of Sleep Medicine recommends limiting your caffeine intake to no more than 300 mg per day and avoiding it after 2 p.m1.
3. Digestive Distress
Caffeine can increase the production of stomach acid and stimulate the movement of your intestines. This can cause symptoms such as heartburn, acid reflux, nausea, vomiting, diarrhea, or abdominal pain.
These effects are more likely to occur if you consume caffeine on an empty stomach or if you have a gastrointestinal disorder, such as gastritis, ulcers, or irritable bowel syndrome.
To reduce the risk of digestive distress, limit caffeine intake, drink it with food, or choose decaffeinated or low-caffeine beverages2.
4. Headache
Caffeine can constrict the blood vessels in your brain, which can help relieve headaches caused by the dilation of these vessels, such as migraines. However, caffeine can also cause headaches in some people, especially if they consume too much or are not used to it.
Caffeine can also trigger withdrawal headaches if you suddenly stop or reduce your intake after regular or heavy use.
To prevent or treat caffeine-related headaches, moderate your caffeine intake, avoid abrupt changes in your consumption, and drink plenty of water to stay hydrated8.
Uncommon Side Effects of Caffeine
The following are some of the uncommon side effects of caffeine that may occur in high doses (more than 400 mg per day for healthy adults and more than 200 mg per day for pregnant and breastfeeding women) or in people who are very sensitive to it.
1. Rhabdomyolysis
This rare but serious condition involves the breakdown of muscle tissue and the release of a protein called myoglobin into the bloodstream. This can damage the kidneys and cause acute kidney failure.
Caffeine can increase the risk of rhabdomyolysis by increasing muscle activity and metabolism and interfering with calcium and potassium transport in muscle cells. Other factors, such as trauma, infection, drugs, or extreme exercise, can also cause rhabdomyolysis.
The symptoms of rhabdomyolysis include muscle pain, weakness, swelling, dark urine, and reduced urine output. If you suspect you have rhabdomyolysis, seek medical attention immediately3.
2. Addiction
Caffeine can cause physical and psychological dependence, meaning that you may feel the need to consume it regularly and experience withdrawal symptoms if you stop or reduce your intake.
Caffeine withdrawal symptoms can include headache, fatigue, irritability, difficulty concentrating, depressed mood, and flu-like symptoms. These symptoms can start within 12 to 24 hours of stopping caffeine and last for up to 9 days.
Caffeine addiction can also affect your behavior, such as causing you to spend a lot of time and money on obtaining and consuming caffeine or interfering with your social, occupational, or recreational activities.
To prevent or overcome caffeine addiction, you can gradually reduce your intake, substitute caffeine with other beverages, and seek professional help if needed9.
3. Hypertension
Caffeine can temporarily raise blood pressure by stimulating heart rate and constricting blood vessels. This effect is usually mild and short-lived and does not cause hypertension (chronic high blood pressure) in most healthy people.
However, some people may be more sensitive to the blood pressure-raising effect of caffeine, especially if they have a genetic variation that affects how they metabolize caffeine or if they have an existing cardiovascular condition, such as hypertension, heart disease, or arrhythmia.
If you have high blood pressure or a heart condition, consult your doctor before consuming caffeine and monitor your blood pressure regularly5.
4. Rapid heart rate
Caffeine can increase your heart rate by stimulating your nervous system and increasing your adrenaline levels. This can make you feel more energetic and alert, but it can also cause palpitations or a sensation of your heart beating too fast, too hard, or irregularly.
This effect is usually harmless and temporary and does not affect your heart health in most cases. However, some people may be more prone to caffeine-induced palpitations, especially if they have a low tolerance to caffeine or if they have an underlying heart condition, such as a congenital heart defect, a valve disorder, or an arrhythmia.
If you experience frequent or severe palpitations, seek medical attention, as they may indicate a more serious problem9.
5. Fatigue
Caffeine can help you overcome fatigue and drowsiness by blocking the action of adenosine, a brain chemical that makes you sleepy.
However, caffeine can also cause fatigue in some situations, such as when it wears off, when you consume too much, or when you disrupt your sleep cycle. When caffeine wears off, you may experience a crash or a rebound effect, where you feel more tired than before. This can lead to a cycle of caffeine dependence, where you need more caffeine to stay alert and avoid withdrawal symptoms.
When you consume too much caffeine, you may feel exhausted, as caffeine can overstimulate your nervous system and deplete your energy reserves. When you disrupt your sleep cycle, you may also feel fatigued, as caffeine can interfere with your sleep quality and quantity and affect your circadian rhythm, which is your natural 24-hour cycle of sleeping and waking.
To prevent or reduce caffeine-related fatigue, you can limit caffeine intake, avoid consuming it late in the day, and maintain good sleep hygiene3.
6. Urinary Changes
Caffeine can affect your urinary system in various ways, such as increasing your urine output, changing your urine color, or causing urinary incontinence. Caffeine can increase your urine output by acting as a diuretic, making your kidneys produce more urine.
This can help flush out toxins and excess fluids from your body, but it can also cause dehydration and electrolyte imbalance if you lose too much water and minerals. Caffeine can also change your urine color, making it darker or lighter, depending on how much water you drink and the caffeine you consume.
Caffeine can also cause urinary incontinence, which is the involuntary leakage of urine. This can happen because caffeine irritates your bladder and increases your bladder pressure, making it harder to hold your urine. This effect is more common in women, especially those who have a history of urinary incontinence or who are pregnant, menopausal, or elderly.
To avoid or minimize caffeine-related urinary changes, drink plenty of water, limit caffeine intake, and practice pelvic floor exercises2.
Sources
- AASM. (2013, November 15). Late afternoon and early evening caffeine can disrupt sleep at night. https://aasm.org/late-afternoon-and-early-evening-caffeine-can-disrupt-sleep-at-night/
- Healthdirect. (2019). Caffeine. https://www.healthdirect.gov.au/caffeine
- Healthline. (2019, August 7). Rhabdomyolysis: Symptoms, Causes, Diagnosis, and Treatment. https://www.healthline.com/health/rhabdomyolysis
- Healthline. (2019, December 16). How Caffeine Affects Your Body and Brain. https://www.healthline.com/health/caffeine-effects-on-body
- MedlinePlus. (2021, January 26). Caffeine. https://medlineplus.gov/caffeine.html
- Pietrangelo, A. (2019, December 5). How long does caffeine last in your system? Healthline. https://www.healthline.com/health/how-long-does-caffeine-last
- Sleep Foundation. (2020, September 17). How long does it take for caffeine to wear off? https://www.sleephealthfoundation.org.au/sleep-topics/caffeine-and-sleep
- WebMD. (2020, April 13). Caffeine and Headache. https://www.webmd.com/migraines-headaches/triggers-caffeine
- WebMD. (2020, July 1). Caffeine Myths and Facts. https://www.webmd.com/diet/caffeine-myths-and-facts