What is it?

Caffeine is a natural stimulant most commonly found in coffee, tea, cocoa, and various other foods and beverages. It is widely used for its ability to enhance alertness, improve concentration, and boost energy levels.

How does it work for medicinal purposes?

Caffeine works by blocking adenosine receptors in the brain, which prevents the onset of drowsiness. It also stimulates the central nervous system, increases the release of neurotransmitters like dopamine and norepinephrine, and enhances mental and physical performance.

What are the active ingredients that are important for its medicinal properties?

The primary active ingredient in caffeine is the caffeine molecule itself, known for its stimulating effects. It also contains trace amounts of other compounds that can contribute to its overall effects, such as:

• Theobromine: Found in cocoa, contributes to the stimulating effects.
• Theophylline: Found in tea, aids in respiratory benefits.

What forms does it come in?

• Coffee
• Tea
• Energy drinks
• Soft drinks
• Chocolate
• Caffeine tablets and pills
• Caffeine powders

What if I have an imbalance or deficiency?

There is no specific deficiency associated with caffeine itself, as it is not an essential nutrient. However, insufficient caffeine intake in habitual users can lead to withdrawal symptoms such as headaches, fatigue, and irritability.

When was it first used for medicinal purposes?

Caffeine has been used for centuries, with the earliest known use dating back to ancient Ethiopia where coffee was consumed. It has been widely recognized for its stimulating effects and has been used medicinally since at least the 16th century.

What does Caffeine help with?

Caffeine is a mild stimulant found in coffee, tea, cocoa and many soft drinks. People have used it in nearly every culture for hundreds of years. It is also added to pills, gels and sports drinks.

Caffeine is one of the most studied substances on earth. For alertness and sport, the human trial evidence is strong and consistent. For mood and long-term brain health, the evidence comes from population studies, not trials.

• Staying sharp and awake when you need to focus
  Strong evidence — many randomised human trials, in both tired and well-rested people. Trials found faster reaction times and steadier attention. People also reported less mental fatigue within 30 to 60 minutes of taking it. The effect was largest in tired or sleep-deprived people, but rested people gained too.
  Evidence grade A · Traditional tier T0
• Lasting longer in running, cycling or swimming
  Strong evidence — many randomised trials in endurance athletes. Trials found longer time to exhaustion and faster time trials. Most of this research used 3 to 6 mg per kg of body weight. That dose was taken 30 to 60 minutes before exercise.
  Evidence grade A · Traditional tier T0
• Getting more out of a workout or a game
  Strong evidence — randomised trials across endurance, strength and team sports. The International Olympic Committee lists caffeine as a performance aid. Trials found gains in endurance, strength and team sport tasks. In these studies the effort felt easier, fatigue came later, and the body drew more on fat for fuel.
  Evidence grade A · Traditional tier T0
• Low energy, shift work and short nights
  Strong evidence — consistent human trials, including studies in sleep restriction and shift work. People in trials felt more energy within 20 to 45 minutes. Lab studies show caffeine blocks adenosine, the brain chemical that signals tiredness. Gains were clearest during short sleep, shift work and heavy mental or physical loads.
  Evidence grade A · Traditional tier T0
• Headaches and migraine attacks
  Good evidence — randomised trials of caffeine combined with common pain relievers. Adding caffeine to aspirin or acetaminophen improved migraine relief in trials. That is why it sits in many over-the-counter headache pills. Caffeine is known to narrow blood vessels in the head and to help the body take up these pain relievers. Small amounts also ease a caffeine withdrawal headache almost at once.
  Evidence grade B · Traditional tier T0
• Burning a few more calories and managing weight
  Early evidence — many small human studies, with modest and fading effects. Studies found a small rise in calories burned and more fat used during exercise. The effect was mild, and it shrank as people got used to caffeine. Nothing on file shows useful weight loss when diet and exercise stay the same.
  Evidence grade C · Traditional tier T0
• Feeling flat, low mood, mild depression
  Early evidence — large population studies only, with no randomised trials on file. Large population studies linked regular caffeine use with better mood. The same studies found lower rates of depression and of suicide. These studies watch people over time, so they cannot show cause. In lab studies caffeine nudges dopamine activity, a pathway many antidepressants also use, but far more gently.
  Evidence grade C · Traditional tier T0
• Worry about memory loss later in life
  Early evidence — large observational studies of habitual coffee and caffeine drinkers. Long-term coffee and caffeine drinkers had lower rates of Alzheimer's and Parkinson's disease. This comes from watching groups of people, not from trials. The pattern is consistent and makes biological sense, but it does not show that caffeine caused it.
  Evidence grade C · Traditional tier T0

What Caffeine has not been shown to do

• Caffeine has not been shown to prevent Alzheimer's or Parkinson's disease, since the link rests on observational data only.
• It has not been shown to produce real weight loss on its own, without changes to diet and exercise.
• The small boost in calorie burning has not been shown to last, because tolerance builds with regular use.
• Caffeine alone has not been shown to stop a migraine; the trials tested it added to pain relievers, and quick relief on its own applies to withdrawal headaches.

How to read this:

Each use above carries its own grade. A means several good human trials agree. B means at least one good human trial. C means small, early or observational human work. D means weak or mixed human data. Insufficient means no human study on file. These are options to discuss, not advice, and this page is not a promise of results. Talk with your own clinician, above all if you are pregnant, have heart rhythm problems, or take other medicines.

What can Caffeine help prevent?

• Parkinson's disease risk reduction: consistent association in multiple large prospective cohort studies
• Type 2 diabetes risk reduction: habitual coffee consumption linked to lower incidence in large meta-analyses
• Liver disease progression: regular coffee intake associated with reduced risk of cirrhosis and liver cancer

Which foods are rich in it?

Foods and beverages rich in caffeine include:

1. Coffee
2. Tea
3. Chocolate
4. Cocoa
5. Guarana
6. Yerba Mate
7. Certain Ice Creams and Desserts
8. Certain Supplements

What are possible side effects?

Caffeine is generally well-tolerated, but excessive intake can lead to:

• Common (10-30%)
• Insomnia
• Nervousness
• Restlessness
• Less Common (1-10%)
• Stomach upset
• Fast heart rate
• Muscle tremors
• Rare (<1%)
• Anxiety
• High blood pressure
• Dependency and withdrawal symptoms

What’s the recommended daily dose?

The recommended daily dose of caffeine for adults is up to 400 mg, equivalent to about 4 cups of brewed coffee. However, individual tolerance can vary widely.

How many days does it take to work?

Caffeine's effects can be felt within 15 to 30 minutes after consumption. The full stimulating effects typically last for 3 to 5 hours.

What time of day is best to take it?

Caffeine can be consumed at any time of day, but it is generally best to avoid it in the late afternoon and evening to prevent interference with sleep.

Is it best to take it with or without food?

Caffeine can be taken with or without food. However, consuming caffeine with food may reduce the likelihood of gastrointestinal discomfort.