- 20+ Harmful Effects of Caffeine
- Top 25+ Caffeine Health Benefits
- 6 surprising benefits of caffeine
- Cognitive performance
- Burning fat
- Post-exercise recovery
- Atrial fibrillation
- Parkinson disease
- Alzheimer disease
- What is Caffeine?
- Caffeine Health Benefits
- 2) Attention and Alertness
- 3) Physical Performance
- 4) Parkinson’s Disease
- 5) Dementia and Alzheimer’s Disease
- 6) Liver Disease
- 7) Pain
- 8) Weight Loss
- 9) Memory
- 10) Asthma
- 11) Cancer Prevention
- 12) Type 2 Diabetes Prevention
- 13) Kidney Stones
- Insufficient Evidence:
- 14) Mood and Mental Health
- 15) Skin Protection
- 16) Erectile Dysfunction
- 17) Tinnitus
- 18) Gout
- Possibly Ineffective:
- Effects on Inflammation
- Limitations and Caveats
- Caffeine Side Effects
- Caffeine Drug and Substance Interactions
20+ Harmful Effects of Caffeine
The harmful effects of caffeine are sometimes harder to find information on than all of the reported positives.
Here are a few of the studies that concluded that caffeine could be potentially dangerous to one’s health.
Research Showing Harmful Effects of Caffeine
- More than 4 cups of coffee linked to early death. A Mayo Clinic partnered study found that men who drank more than four 8 fl.oz. cups of coffee had a 21% increase in all-cause mortality. However, those that reported that they consumed excessive amounts of caffeine were also likely to smoke and have poor fitness. Dr. Nancy Snyderman from NBC said there were a few discrepancies with the study, but stresses that moderation is still key. See Her Interview Here. Another study showed that those who consume 6+ coffees per day have a greater risk of developing heart disease.
- Caffeine consumption may raise blood pressure. Especially in those already suffering from hypertension and those who don’t normally consume caffeine. People with hypertension were given 250 mg of caffeine (about 2 coffees) and the data revealed that their blood pressure was elevated for about 2-3 hours after the caffeine. Src. A second study performed by The Mayo Clinic found similar results from a 160 mg dose. All participants experienced a marked rise in blood pressure and it was the most pronounced in those that didn’t normally consume caffeine. Src.
- Increased risk of heart attacks among young adults. A study conducted by Dr. Lucio Mos found that young adults who were diagnosed with mild hypertension had 4 times the risk of having a heart attack if they consumed the amount of caffeine equivalent to 4 cups of coffee. More moderate consumption showed 3 times the risk. Src.
- Caffeine linked to gout attacks. This study showed that people who binge on caffeinated beverages increase their risk for a gout flare-up. Src.
- Breast tissue cysts in women. One study showed that “Women who consumed 31–250 mg of caffeine/day had a 1.5-fold increase in the odds of developing fibrocystic breast disease and women who drank over 500 mg/day had a 2.3-fold increase in the odds of developing cysts. Src.
- Caffeine could cause incontinence. A study out of the University of Alabama showed that women who consume a lot of caffeine are 70% more likely to develop incontinence. Src.
- Caffeine may cause insomnia. Caffeine in a person’s system at bedtime can mimic the symptoms of insomnia. Src.
- Caffeine can cause indigestion. People who consume caffeinated beverages often report an upset stomach or indigestion. This mainly occurs when the beverages are consumed on an empty stomach. Src.
- Caffeine can cause headaches. While occasional doses of caffeine can relieve headache symptoms, the overuse of caffeine can cause headaches and lead to migraines. Src.
- Caffeine could reduce fertility in women. A study from The University of Nevada School of Medicine showed that caffeine can reduce a woman’s chances of becoming pregnant by about 27%. Src.
- Caffeine and miscarriage risk: In a recent study, both men and women who consumed at least two caffeinated beverages a day during the weeks prior to conception slightly increased the risks of a miscarriage. Src.
- Caffeine may not be healthy for type 2 diabetics. A study conducted by the American Diabetes Association showed that caffeine impaired glucose metabolism in those with type 2 diabetes. Src.
- Caffeine overdose. While overdose is rare, it can lead to many adverse symptoms including death, especially in those with underlying medical conditions. Some have a lower tolerance for caffeine than others. Src.
- Caffeine allergies. Some people have over-sensitivity to the caffeine molecule, which causes allergic-like reactions in the body such as hives and pain. Although not a true allergy, many report very negative symptoms after consuming even the smallest amounts. Src.
- Caffeine causes more forceful heart contractions. A recent study showed that immediately after energy drink consumption the heart produced more forceful contractions. It is unclear if this has any long-term health implications except for those with known health conditions. Src.
- Worse menopause symptoms. A recent study published in The Journal of The North American Menopause Society showed that menopausal women who consumed caffeine had a greater degree of vasomotor symptoms. Src.
- Caffeine consumption can lead to increased anxiety, depression and the need for anxiety medication. Src and Src. See also our article as to why caffeine causes anxiety and panic attacks.
- Caffeine increases the number of sugary beverages consumed by people, which contributes to obesity and diabetes. Src.
- Caffeine inhibits collagen production in the skin. This effect is dose-dependent but really heavy caffeine consumers should be aware. The study.
- Caffeine interferes with ossification and could also lead to a greater risk of bone fractures. This is dose dependent, but heavy caffeine consumers should take note. Study 1 (pdf) Study 2.
- Caffeine does not help with prolonged sleep deprivation: This can lead to a false sense of security for those that have been sleep deprived for multiple days in a row and choose to get behind the wheel or do some other focus required task, thinking that as long as they have caffeine, they’ll be able to perform. Researchers from the American Academy of Sleep Medicine came to this conclusion after studying caffeine’s effects on their sleep-deprived test subjects. Here’s the study in detail.
- Caffeine may impair hearing loss recovery: For guinea pigs exposed to excessive levels of noise, caffeine was shown to delay the rate at which the guinea pigs recovered from noise-induced hearing loss. Here are the results of a recent study that investigated the problem. A correlation to humans is believed to exist but more research will be needed.
When not managed caffeine can quickly become an out of control problem.
If you are experiencing any tell-tale signs of the risks above, then it’s time to start cutting back. Otherwise, it’s just a matter of time.
If you want to reduce your caffeine intake (or quit entirely), here’s how:
1.Download our book Awake(it’s free).
2. Do the Overcoming Caffeine Withdrawal course at Udemy.
3. Use the Wean Caffeine supplement (something we helped get to market). It helps you avoid the painful withdrawal symptoms that often come when quitting caffeine abruptly.
Other Claims Against Caffeine
You may have heard or read about other negative health effects from caffeine consumption, but as of now, there just isn’t enough evidence to fully endorse those as legitimate health concerns.
Some of those negatives include:
- Adrenal fatigue
- Irregular heartbeat
- Accelerates bone loss. Src.
Caffeine is a drug and can affect people differently just like any other substance. It’s important that consumers understand how caffeine interacts with their bodies in regards to their personal health histories.
The food and beverage industry spends millions, if not billions, of dollars worldwide to fund studies and promote caffeinated products as safe or even healthy.
Fortunately, caffeine is one of the most researched substances on the planet and there does exist some unbiased data in which to glean some reliable information from.
While much of the research published does allude to the safety and even potential benefits of caffeine (in moderation), there are a handful of research studies that highlight the potentially harmful effects of caffeine.
The risks of suffering from any of the harmful effects of caffeine are diminished by being aware of how much is personally being consumed daily.
It is also important to be aware of any pre-existing medical conditions that may contribute to caffeine’s negative effects.
Written by Ted Kallmyer, last updated on December 6, 2019
Top 25+ Caffeine Health Benefits
Caffeine is the most widely used substance on the planet and it is also one of the most researched in regards how it affects the human body.
We’ve dug through many of those scientific studies and compiled a list of the possible caffeine health benefits people may experience from using caffeine.
27 Possible Caffeine Health Benefits
- In Japan, researchers have shown that caffeine increases memory. Also, a newer study out of Johns Hopkins University showed that a 200 mg caffeine pill helped boost memory consolidation.
- Caffeine mixed with carbs replenishes muscle glycogen concentrations faster after exercise.
- Caffeine detoxes the liver and cleanses the colon when taken as a caffeine enema.
- Caffeine helps keep you alert while driving during periods of sleep restriction. Here’s the research
- Caffeine can stimulate hair growth for balding men and women.
- Caffeine relieves post-workout muscle pain by up to 48%.
- Caffeine relieves pain associated with sleep loss better than analgesics. The study.
- Caffeine may protect against Parkinson’s disease. Research shows that those who consume coffee are at less risk of developing Parkison’s disease and it even reduces the risk of those genetically more likely to develop the condition. Here’s the study.
- Caffeine may help ward off Alzheimer’s.
- Caffeine increases stamina during exercise.
- Caffeine through coffee may protect against eyelid spasm.
- Caffeine may protect against Cataracts.
- Caffeine may prevent skin cancer. A new study out of Rutgers University found that caffeine prevented skin cancer in hairless mice. Another study showed that caffeinated coffee drinkers have less risk of developing melanoma.
- People who consume caffeine have a lower risk of suicide. Src.
- Caffeine may reduce fatty liver in those with non-alcohol related fatty liver disease. This study comes out of Duke University.
- Caffeine is shown to reduce liver fibrosis risk in patients with hepatitis C. As little as 100 mg per day is believed to have protective benefits. Src.
- Caffeine consuming men showed increased semen volume and significantly less sperm DNA fragmentation than non-caffeine consuming men. Src.
- Men who consume 250-375 mg of caffeine per day have a much lower risk of developing ED (erectile dysfunction). The reduced risk was even observed among men consuming as little as 85 mg of caffeine daily. This research was conducted by The University of Texas Medical School. Src.
- Caffeine may prevent ringing in the ears (tinnitus) in women: A study published in The American Journal of Medicine followed a group of 65,085 nurses since 1991. The women who consumed the most caffeine had the lowest incidences of tinnitus reported. Src.
- Caffeine Reduces Kidney Stone Risk. In a large 217,883 person study, those that consumed caffeine from any source had less kidney stone formation than those that did not consume caffeine. The researchers believe that this is because caffeine makes the urine more dilute. Src. Caffeine has also been shown to reduce the mortality rate in those with chronic kidney disease. Caffeine appears to have a protective effect on the progression of the disease. Here’s the study. Another study (2018) also confirmed that caffeine consumption reduces the mortality rate for those living with kidney disease. .
- Caffeine improves reaction time and logical reasoning during times when sleep isn’t possible or restricted. See the study here.
- Caffeine helps those with asthma. A study published in the U.S. National Library of Medicine concluded that caffeine seems to open airways and help asthmatics breathe easier similarly to theophylline a drug currently used and one that’s a close cousin to caffeine. The study.
- Reduces driver error: A recent study conducted by the Australian Department of Defence found that caffeine consumption improves driving performance and reduces driver error. Caffeinated gum was used in the study on soldiers that had been sleep-deprived for 50 hours.
- Caffeine may prevent weight gain: Research out of Germany showed that weight loss study participants who drank 2-4 cups of caffeinated coffee a day were more likely to be successful at keeping the weight off than those who did not consume caffeine. The study. Another study showed that caffeine stimulates brown fat cells causing them to burn more calories. This increases the overall metabolic rate. Another 2019 study conducted on rats showed that rats given a dose of caffeine equivalent to 4 cups of coffee a day gained 22% less body fat than rats given no caffeine but fed the same high fat, high sugar diet.
- Caffeine reduces chronic inflammation. Researchers from Stanford University found that caffeine blocks the expression of a gene responsible for low-grade chronic inflammation as we age. This inflammation eventually leads to high blood pressure, hardening of the arteries, and heart disease. Caffeine seems to help reduce this age-related inflammation in those that are regular consumers of the drug.
- Caffeine is good for the heart. A study out of Germany found that the amount of caffeine typically in 4 cups of coffee daily helps strengthen heart muscle cell function and prolongs the life of heart muscle cells. You can read the study’s abstract here.
- Caffeine helps premature infants: A few doses of caffeine given to premature babies drastically improves lung function and overall survival rate. Newer research found that this therapy produces no long-term side effects as the children age. Src.
There can be negative health consequences from consuming too much caffeine, so don’t go too crazy. Also, some of the benefits of caffeine have only been researched within the context of caffeinated coffee.
Here are some further health benefits when the caffeine is consumed via coffee. It is also interesting that some of these benefits didn’t carry over to those that drank decaffeinated coffee.
Caffeinated Coffee Health Benefits
- Caffeinated coffee cuts mouth and throat cancer risk by 50%.
- Coffee can reduce the risk of stroke as much as 22%.
- Shown to reduce the risk of several types of cancer.
- Heart rhythm disturbance hospitalizations decrease with coffee drinkers.
- Coffee decreases the risk of type 2 diabetes.
- People who drink at least 4 coffees or teas have lower blood pressure according to a new study out of Paris. Tea drinkers had the most blood pressure benefit, while coffee drinkers had just slightly less.
- Research out of Greece shows that Greek boiled coffee may increase longevity and heart health.
- Those who drink coffee after a heart attack are less likely to die from the incident. Research shows that heart attack victims who consume more than 2 cups of coffee daily have the least risk of mortality from the heart attack.
While this list might seem like a green light for caffeine consumption, it does come with a few caveats. In most cases, caffeine’s health benefits were realized by those who consumed moderate coffee/caffeine amounts. Also in some of the studies above, the caffeine was concentrated and applied directly to the body area being researched, i.e. cataracts and baldness, etc.. Therefore, dietary caffeine would not produce the same results.
The British Medical Journal published a study that reviewed 201 studies concerning coffee and caffeine. The researchers concluded that based on all evidence to date, the health benefits of consuming coffee outweigh any risk involved.
We can conclude that caffeine consumed via natural sources is probably the best since many of the health benefits of caffeine are probably largely due to the high antioxidant levels found in regular coffee and tea.
Written by Ted Kallmyer, last updated on December 20, 2019
6 surprising benefits of caffeine
Caffeine—the principal active ingredient in coffee, tea, and energy drinks—is found in more than 60 plants globally. Experts believe that these plants evolved over millions of years to produce caffeine as a natural pesticide against destructive insects.
The Canon of Medicine, written by the Persian physician-philosopher Avicenna in 1025 CE, was the first medical text to acknowledge coffee as a potential therapeutic agent. At that time, coffee was largely used to clean the skin and improve body odor. Today, most people use it and other caffeinated beverages to keep awake and alert—but caffeine has a slew of other health benefits.
Researchers have shown that caffeine can boost alertness and wakefulness in some consumers. In one study involving 9,003 British adults, caffeine was linked to dose-dependent improvements in visuospatial reasoning, simple reaction time, choice reaction time, and incidental verbal memory. These results were durable and more prevalent in older vs younger adults, which indicated that tolerance to caffeine’s cognitive benefits may be incomplete. Moreover, a muted response was observed in tea drinkers in which researchers observed improvement only in simple reaction time and visuospatial reasoning. Of note, caffeine can cause anxiety in some consumers.
- See Also: Does caffeine have an effect on your sex life?
Caffeine changes the body’s preferred metabolic substrate from glycogen to fat, thus increasing lipolysis; it stimulates hormone-sensitive lipase. At very high doses—as in those who binge on energy drinks—caffeine kicks protein kinase A into action, an enzyme key to lipid and glucose metabolism.
Intense exercise burns off loads of glycogen. Caffeine promotes glycogen resynthesis, which is needed for recovery. In well-trained athletes, when paired with carbohydrate intake, post-exercise caffeine consumption stimulates glycogen build-up.
Before we look at caffeine’s potential benefit in those with atrial fibrillation, let’s unpack more general effects of caffeine on the heart. Caffeine increases heart rate and contractility, inhibits the negative inotropic and chronotropic actions of adenosine, and acts as both a positive inotrope and chronotrope by inducing β1-receptor activation—thus setting off the sympathetic nervous system.
In high-power studies involving healthy adults, coffee intake was not linked to atrial arrhythmias. Other researchers have shown that caffeine does not increase the risk of atrial fibrillation. Drinking 9 cups of coffee a day, however, was linked to a two-fold increased risk of premature ventricular contractions. Moreover, drinking 10 cups of coffee a day has been linked to increased risk of sudden death in patients with coronary artery disease who previously experienced cardiac arrest. Of note, experts have shown that in habitual coffee drinkers, the adrenergic and proarrhythmic effects of caffeine are reduced.
So, the reason why caffeine could possibly help people with atrial fibrillation is that it has antifibrotic actions, and atrial fibrosis is important in the pathogenesis of atrial fibrillation.
- See Also: Can coffee save your life?
In observational studies, caffeine intake has been linked to a lower risk of Parkinson disease. According to the authors of an editorial published in Neurology discussing this association:
“The protective effect of caffeine (found not only in coffee, but also in tea, and some sodas) has been demonstrated in large prospectively followed populations of men, with a dramatic reduction in risk (up to fivefold for persons who drank more than 4 cups of coffee a day). Decaffeinated coffee afforded no protection, pointing to caffeine rather than other substances in coffee or tea as the underlying pharmacologic agent. No such linear relationship is found in women, in whom the protective effects are either nonexistent or U-shaped.”
Furthermore, although caffeine does not reduce excessive daytime somnolence in patients with Parkinson disease, some researchers have shown that it may improve motor function in this population.
In one study of the association between coffee and/or tea consumption at midlife and the risk of dementia or Alzheimer disease risk in late-life (mean follow-up period: 21 years), researchers found that compared with coffee abstainers, coffee drinkers had a decreased risk of dementia/Alzheimer disease. Interestingly, the lowest risk—65% decreased—occurred in those who drank 3-5 cups of java a day.
In a review article published in Current Neuropharmacology, researchers offered one potential explanation for the neuroprotective effects of caffeine:
“Recent experimental evidence suggests that the primary target of the neuroprotective effects of caffeine is either the activation or the inhibition of the A1 and A2A adenosine receptor subtypes. The use of adenosine receptor antagonists, such as caffeine, has shown its usefulness not only in the treatment, but also in the protection against . Experimental evidence supports the use of caffeine and other adenosine receptor antagonists, as well as adenosine receptor agonists, in the reduction of hyperalgesia, excitotoxicity, inflammatory response, dyskinesia, akinesia, sensory and motor deficits, and neuronal cell death related to the pathophysiology of the discussed neurodegenerative diseases.”
Caffeine is the world’s most widely consumed psychoactive drug. It boosts physical and mental performance and may decrease the risk of type 2 diabetes, Parkinson’s disease, Alzheimer’s, and more. However, there are major drawbacks to consider. Read on to learn the caffeine benefits, side effects, and interactions.
What is Caffeine?
Caffeine is a plant compound and stimulant (methylxanthine). It has a similar structure to other plant compounds like theobromine, xanthine, and theophylline .
For the average person, coffee or tea is the main source of caffeine. Coffea arabica and Coffea canephora (Robusta) are two types of plants that produce coffee beans. Meanwhile, the Camellia sinensis leaves are used for black, green, and white teas .
Although coffee and tea both contain caffeine, they can have different effects on our health. This may be due to their different amounts of caffeine, polyphenols, or other components .
Caffeine is consumed around the world for its beneficial effects on energy, physical and mental performance, alertness, and mood. Many people praise its ability to keep them awake and focused on their tasks. Still, its prolonged use comes with certain drawbacks worth attention .
- Boosts physical and mental performance
- Relieves pain and headaches
- Protects the liver
- Helps prevent Parkinson’s and Alzheimer’s
- Helps prevent diabetes and kidney stones
- May support weight loss
- Can cause tolerance and dependence
- Withdrawal can be extremely unpleasant
- May worsen anxiety and insomnia
- Increases blood pressure and heart rate
- May contribute to glaucoma at high doses
How Does it Work?
Since caffeine’s structure is similar to adenosine, it can block adenosine receptors (mainly A1 and A2A). It increases the activation of the sympathetic (fight-or-flight) nervous system, which results in stimulatory effects .
Consumers may feel more energized and awake due to caffeine blocking A1 receptors. This also causes heart-pounding effects .
Caffeine binds to phosphodiesterase receptors and blocks phosphodiesterase activity. As less phosphodiesterase receptor molecules become available, cAMP cannot bind to the receptors and it accumulates in the cells. This produces effects such as vasodilation (widening of blood vessels), and fat oxidation (breakdown) .
Caffeine Health Benefits
Caffeine is a part of different FDA-approved drugs for migraine headaches, along with acetaminophen, aspirin, sumatriptan, diclofenac, and others .
Based on its proven efficacy, caffeine is also FDA-approved for simple (tension) headaches and the prevention of postoperative headaches .
Ironically, headache is one of the most common symptoms of caffeine withdrawal, which can be a limitation for its long-term use .
2) Attention and Alertness
Multiple clinical reviews have confirmed the potential of caffeine to increase mental alertness in low-to-moderate doses (40-300 mg). The effects were even more pronounced in non-regular users and during sleep deprivation .
In a study of 36 participants, caffeine exhibited dose-dependent effects on alertness and attention. When people who usually do not drink caffeinated products consumed high doses of caffeine, they had a higher increase in brain function. Regular and tolerant users may still feel the same effects, but to a smaller extent .
A lack of sleep can cause delays in reaction times. In a study of 20 sleep-deprived participants, a total daily dose of 800 mg of caffeine helped improve reaction speed and accuracy .
In one study, twelve young adults either had sufficient sleep (9 hours) or a lack-of-sleep (4 hours). 100 mg of caffeine improved both groups’ coordination, judgment, memory, and reaction time during a driving task .
However, some reviews have underlined the tolerance to its stimulant effects, abuse potential, and a potential toxicity that comes with higher doses .
3) Physical Performance
A comprehensive clinical review summarized 21 meta-analyses on caffeine and physical performance. A large body of evidence suggests that “caffeine ingestion improves exercise performance in a broad range of exercise tasks.” It showed beneficial effects on :
- Muscle endurance
- Muscle strength
- Aerobic endurance
- Anaerobic power
Caffeine particularly helps anaerobic exercises like sprinting or jumping. This effect may arise from its anti-fatigue effects and by improving endurance, physical strength, and power output .
When caffeine delays fatigue, the body’s muscles can contract more forcefully. People may exercise longer and eventually increase their training volume or overall work. Aerobic exercise such as running, jogging, cardio workout, swimming, and biking can benefit the most from increased training volume .
4) Parkinson’s Disease
Caffeine is neuroprotective and may prevent nerve cell degeneration, which occurs in Parkinson’s .
Additionally, by inhibiting adenosine receptors, it improves mobility and motor functions in Parkinson’s patients .
In a study of 61 Parkinson’s patients, 100 mg of caffeine twice daily for 3 weeks reduced movement slowness (bradykinesia). However, it had no other effects on Parkinson’s symptoms .
In one study, out of 430 healthy subjects, those who consumed caffeinated coffee had a lower risk of developing Parkinson’s disease. It even reduced the risk in those genetically predisposed to develop the condition .
Additionally, in a study of 29,000 participants, both habitual coffee and tea drinkers had a lower risk for Parkinson’s .
5) Dementia and Alzheimer’s Disease
In a long-term study of 1,400 people, drinking 3 to 5 cups of coffee per day at midlife could decrease dementia or Alzheimer’s disease (AD) risk by about 65% during their elderly years .
In one review, coffee had a positive effect on brain function. Moderate caffeinated coffee consumption decreased the risk of dementia and AD later in life. However, caffeinated tea had no effects .
In mice, caffeine suppressed amyloid beta production. Amyloid beta contributes to brain inflammation and the onset of Alzheimer’s disease .
6) Liver Disease
Caffeine is associated with a lower risk of liver fibrosis (scar tissue in the liver). In a study of 306 patients with fatty liver disease, people who drank caffeinated coffee had less severe liver scarring than the ones who did not drink caffeinated coffee .
In a cross-sectional study of 910 veterans with chronic hepatitis C, a minimum of 100 mg of caffeine daily reduced the odds of liver tissue scarring .
Additionally, in a survey of 177 liver biopsy patients, caffeine consumption was associated with less severe liver tissue scarring. Two cups of coffee daily helped reduce the severity of tissue scarring .
A study of 274 cirrhosis cases and 458 healthy individuals found that caffeinated coffee prevented liver cirrhosis (chronic liver damage). However, intake from sources other than coffee (such as tea or energy drinks) did not show the same benefits .
According to a review of 20 studies with 7,238 participants, caffeine can slightly but significantly improve the effectiveness of acetaminophen, ibuprofen, and other painkillers .
8) Weight Loss
Many supplements are promoted to stimulate weight loss, but none of them has yet been supported by strong clinical evidence and approved by the health authorities. A healthy, calorie-controlled diet and increased physical activity remain the only proven strategies for weight control .
A combination of ephedrine and caffeine enhanced fat burning and weight loss and reduced blood lipids in five trials of over 500 participants .
That said, pure ephedrine and Ephedra-based products are banned by the FDA due to their high abuse potential and adverse effects on heart health .
Caffeine remained a popular ingredient in over-the-counter fat burning supplements. It may increase energy usage and improve metabolic rate, which helps prevent weight gain .
A meta-analysis published in 2019 included 13 clinical trials of 606 participants. The authors concluded that “caffeine intake might promote weight, BMI and body fat reduction” .
By breaking down stored fat, caffeine shows potential benefits in weight loss management. In a study of 2,100 participants, the ones who drank 2 to 4 cups of caffeinated coffee a day were more successful at shedding weight than those who did not .
In a study of 95 healthy young adults, moderate doses of caffeine (200 mg) increased memory performance. Although the results were not significant, high to moderate caffeine users had increased memory recall compared to low users .
In another study, 140 young adults participated in two experiments. The participants that consumed caffeinated coffee in the morning had significantly better performances on a memory recall test in the early morning, but not in the late afternoon .
One review concluded that caffeine was inconsistent in its effects on memory. It was the most beneficial in improving memory during simple tasks, but not complex ones .
According to a review of 7 clinical studies, caffeine can help open the airways and relieve bronchitis symptoms including wheezing, coughing, and breathlessness .
The effect is similar to theophylline, a common asthma drug. Theophylline and caffeine are very similar in structure, but caffeine’s effects are short-lived and last only up to 4 hours .
11) Cancer Prevention
Mouth and Throat Cancer
A 26-year observational study examined almost 1 million men and women to look at the association between caffeine and oral/pharyngeal (mouth and throat) cancer.
There was an association between high caffeinated coffee intake and reduced risk of oral cancer. Those who consumed 4 to 6 cups of caffeinated coffee daily had up to 2 times lower cancer rates .
In an observational trial of 489,706 men, there was an inverse association between caffeinated coffee and colon cancer rates .
On the other hand, there was no link between caffeine and rectal cancer risk in a study of 120,000 nurses .
In a study of 450,000 subjects, caffeinated coffee drinkers had a lower risk of developing melanoma (skin cancer) than those who did not drink caffeine .
A meta-analysis of studies with non-melanoma skin cancer also found the protective effects of caffeine and coffee. Their regular intakes were associated with 14% and 18% lower cancer rates, respectively .
A review of 9 observational studies found 43% lower rates of liver cancer associated with the consumption of 2 cups of caffeinated coffee daily .
It’s worth mentioning that the above results come from observational studies. Additionally, other beneficial coffee ingredients may have contributed to the results. Well-designed clinical trials are needed to evaluate the potential anticancer effects of caffeine.
12) Type 2 Diabetes Prevention
In an observational study of nearly 90,000 healthy women, moderate caffeinated coffee consumption lowered the risk of type 2 diabetes in younger and middle-aged women .
Another review of 8 trials also showed that drinking caffeinated coffee is associated with a reduced risk of type 2 diabetes .
13) Kidney Stones
In a 20-year study of 217,883 healthy participants, high caffeine intake was associated with reduced rates of kidney stones .
Caffeine increases urinary excretion of calcium, which may cause kidney stone formation. At the same time, the higher intake of caffeine diluted urine and reduced kidney stone risk .
No valid clinical evidence supports the use of caffeine for any of the conditions in this section. Below is a summary of up-to-date animal studies, cell-based research, or low-quality clinical trials which should spark further investigation. However, you shouldn’t interpret them as supportive of any health benefit.
14) Mood and Mental Health
In a large cohort study of 43,599 men and 164,825 women, people who consumed caffeinated coffee had a lower rate of suicide. This could be due to caffeine’s ability to increase dopamine .
However, higher amounts (600 mg) can increase tension and anxiety, which can negatively affect mood .
The effects of caffeine on depression are also conflicting: there are studies showing both increased and decreased rates associated with caffeine consumption .
The explanation for conflicting results may lie in caffeine’s abuse potential and tolerance to both adverse and beneficial effects. Further research is warranted .
15) Skin Protection
The protective effects against skin cancer likely stem from caffeine’s antioxidant properties that protect skin cells against UV radiation from sun exposure. Additionally, it is used in cosmetic products to prevent fat accumulation and cellulite formation .
In a study of 40 dermatitis patients, a topical cream containing 30% caffeine helped reduce redness, itchiness, scaling, and oozing .
More studies are needed to evaluate the skin-friendly effects of caffeine.
16) Erectile Dysfunction
An observational study of 3,700 men showed that those who drank 2 to 3 cups of caffeinated coffee daily had a lower risk of erectile dysfunction. While healthy, overweight, and men with high blood pressure experienced these benefits, caffeine did not help diabetic men .
In a prospective study of 6,500 women, those who consumed the most caffeine had the lowest reported incidence of tinnitus (ringing in the ears) .
In a prospective study of 89,000 women, caffeinated coffee (but not tea) was associated with a lower risk of gout .
Controlled clinical trials are needed to evaluate the above benefits of caffeine found in observational studies.
According to the available clinical evidence, caffeine supplementation may not help with:
- Atrial fibrillation (irregular heartbeat)
- ADHD in children
Effects on Inflammation
In a study of 47 habitual coffee drinkers, drinking caffeinated coffee is associated with a decrease in inflammation markers (IL-18) .
Additionally, in another study of 1,390 healthy women and women with type 2 diabetes, those who drank caffeinated coffee had lower inflammatory marker (E-selectin and CRP) levels .
However, in a study of blood cells from 8 healthy individuals, 165 mg of caffeine supplementation decreased inflammation markers (IL-6, IL-8, PGE2, PGA2, PGD2, etc.) in some blood samples while it increased them in others .
In a study of 33 athletes, caffeine supplementation caused higher levels of inflammatory cytokines (IL-6 and IL-10) after exercise. It enhanced the body’s inflammatory response to exercise .
Caffeine increases inflammation in response to mental stress. In a study of 85 healthy subjects, habitual caffeinated coffee, but not tea, consumption was associated with increased blood vessel inflammation .
Further clinical research should cast more light on the conflicting effects of caffeine on inflammation.
Limitations and Caveats
Although caffeine seems to have promising health benefits, most of the studies only showed associations between its consumption and health improvement (causal studies are lacking).
Additionally, since many studies used coffee as their source of caffeine, it is possible that other compounds contributed to its effects.
Caffeine Side Effects
When used in adequate amounts, caffeine is likely safe for healthy individuals. Still, in sensitive people, it may cause some unpleasant side effects such as :
- Increased urination
- Muscle twitching
- The rambling flow of thought and speech
However, most of caffeine’s side effects tend to decrease with prolonged consumption and tolerance.
Caffeine is a psychostimulant drug. Since its effects vary among individuals, people alter their needs according to their level of tolerance. For example, if you always drink a cup of coffee in the morning, going a day or two without that usual fix is tough both for the mind and body .
Caffeine withdrawal can be a serious reaction of the body to the lack of this stimulant, with symptoms such as :
- Lack of focus
- Digestive issues
Those who take caffeine habitually, in any form, may build up a tolerance to different health effects, both adverse and beneficial .
The side effects of excessive caffeine intake include increased heart rate (tachycardia), restlessness, and anxiety. If you feel nervous and stressed, you should avoid it as well as sugar and other stimulants .
In a large cohort study of secondary school children, there was a positive correlation between caffeine and anxiety. A high intake of caffeine worsened anxiety, stress, and depression symptoms .
It is a well-known fact that caffeine can help with wakefulness. While this is a benefit for some people, it’s a problem for others who have sleep-related problems. Caffeine might disrupt the body’s natural hormone levels and wake-and-sleep cycles that promote restful sleep .
If you are suffering from insomnia, you should only have caffeinated drinks before noon or eliminate them altogether.
4) Reduced Insulin Sensitivity
In a study of 12 male participants, high doses of caffeine reduced their insulin responses .
In another study, high caffeinated coffee consumption temporarily decreased insulin sensitivity. A greater release of neurotransmitters (catecholamines) and free fatty acids, high insulin secretion, or less insulin clearance in the liver could have caused this decrease in sensitivity .
However, for most healthy people, caffeine should not have any significant effect on blood sugar levels .
5) Increased Blood Pressure
This effect depends on two factors: whether the user normally drinks caffeine and if they have a family history of hypertension (high blood pressure).
A meta-analysis of 16 studies showed that 410 mg of caffeine daily raised the risk for high blood pressure, even in healthy people. However, the ingestion of caffeine through coffee only had a small effect on blood pressure .
New users may experience higher spikes in blood pressure, but the effects subside soon after (about 4 days). Still, people with hypertension or those at risk should consume it with caution .
6) Increased Cholesterol
In a study of 30 adults, caffeine was associated with a significant increase in total blood cholesterol and LDL (bad) cholesterol .
Long-term consumption of caffeinated coffee may alter fat distribution in the body and contribute to atherosclerosis in some cases .
Caffeine raises the blood level of adrenaline. This hormone can increase blood pressure, contractility of the heart, and heart rate (tachycardia). The effect is more pronounced in those who do not frequently consume it or in those who take high doses .
8) Blood Clotting
Caffeine blocks adenosine A2a receptors and causes blood vessels to constrict .
In a study of 33 healthy subjects, a high dosage of caffeine increased blood platelet count and clotting, while exercise increased this effect even more. Fortunately, this response may be desensitized after prolonged usage .
In mice, when it binds to A2a receptors, caffeine may induce blood clotting .
9) Glaucoma (At High Doses)
In a cohort study of more than 120,000 healthy patients, the participants whose total caffeine consumption was more than 500 mg daily had higher glaucoma rates (elevated pressure in the eye) than those who consumed less than 125 mg daily .
In a different cohort study of 3,600 patients, habitual caffeinated coffee drinking was associated with higher eye pressure and glaucoma .
Caffeine Drug and Substance Interactions
In a study of 7 participants, fluvoxamine, an SSRI used to treat OCD and depression, inhibited CYP1A2, which is the main enzyme that breaks down caffeine. Taking Fluvoxamine and caffeine together may impair caffeine elimination, possibly causing adverse effects .
Propranolol is a beta-blocker that can help treat heart disease, high blood pressure, and chest pain (angina). Anti-anxiety effects of beta-blockers can be reduced by a high dosage of caffeine, as caffeine increases anxiety. Caffeine may interact with propranolol, increasing blood pressure .
Athletes normally use creatine to increase their exercise performance, including strength and endurance. However, caffeine consumption can reduce creatine’s effectiveness. In various studies, concurrent use of caffeine and creatine caused gut problems and dehydration .
Combining caffeine and alcohol is very common in the nightlife since many people add energy drinks to their alcoholic beverages.
Both caffeine and alcohol block adenosine receptors. The receptors help mediate both their negative effects, such as sleepiness, lack of muscle coordination, and anxiety. So when you mix them, they block the A1 receptors and may prevent you from noticing the side effects .
Additionally, when caffeine blocks A2A receptors, it can contribute to the addictive effects of alcohol .
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