Educational information, not medical advice — ask your doctor or midwife.
Coffea is the plant genus that gives us coffee. The two species that matter are Coffea arabica and Coffea canephora, often called robusta. Both are native to Africa.
The seeds, which we call beans, are roasted and brewed into a drink. Their main active part is caffeine, a mild stimulant. Leaves, raw green beans and extracts are also sold.
The short-term effects of caffeine on alertness and tiredness are well proven in people. Most wider health claims come from studies that watch coffee drinkers, not from trials. Long traditional use is not proof that a remedy works, and it is not proof that it is safe.
The main active part is caffeine, and its effect on alertness is well established in people.
Caffeine blocks adenosine, a brain chemical that builds up through the day and makes you sleepy. Blocking it delays the feeling of tiredness. It does not replace sleep you have lost.
Caffeine also lifts adrenaline a little. That can raise heart rate and blood pressure for a short time. In trials it makes some pain relievers (analgesics) work slightly better.
Coffee also holds chlorogenic acids. In cell and animal studies these appear to slow sugar uptake and act as antioxidants. Whether that changes health in people is not settled.
Coffee speeds up the gut for many people and raises stomach acid. This has been shown in human studies. Decaf does it too, so caffeine is not the only cause.
Large studies link regular coffee drinking with lower rates of type 2 diabetes and liver disease. Those studies follow people over time. They cannot show that the coffee is the cause.
Coffea reaches most people as a drink, and also as a supplement.
Common forms: - roasted whole or ground beans for brewing - instant coffee powder and cold brew - decaffeinated coffee, which still holds a trace of caffeine - green (unroasted) coffee bean extract capsules - caffeine tablets, gums and energy drinks - coffee leaf tea, drunk in parts of Africa and Asia
Homeopathic Coffea cruda is also sold, usually for sleep problems. It is diluted so far that little or no caffeine remains. Good human evidence that it works is lacking.
The brewing method changes what ends up in the cup. Paper filters trap cafestol and kahweol, the oils linked to higher cholesterol. French press, boiled and Turkish coffee leave more of them in.
Coffea arabica grew wild in the highlands of southwest Ethiopia, in the region once called Kaffa.
Oromo people were recorded pressing crushed beans with animal fat into small balls. These were carried as food on long journeys and prized for stamina. The written records are later than the custom itself.
By the 1400s the brewed drink was in use in Yemen. Sufi orders drank it to stay awake for night prayer. From there it spread to Cairo, Istanbul and, in the 1600s, Europe.
Folk healers in Africa, the Middle East and Europe gave coffee for tiredness, headache and breathing trouble. Roasted grounds were sometimes packed onto wounds. These were customs of their time, not tested treatments.
Get urgent medical help if, after a large caffeine dose, you have chest pain, a racing heartbeat that will not settle, fainting, repeated vomiting, confusion or a seizure.
See your doctor if coffee brings on panic attacks, broken sleep, tremor or heartburn that will not settle.
Talk to a doctor or pharmacist before big changes if you take lithium, clozapine or a thyroid medicine. Steady intake matters for these drugs.
In the UK, EU, US, Canada and Australia, coffee is an ordinary food and drink. Caffeine supplements and energy drinks are sold freely but carry warning labels.
Pure and highly concentrated caffeine powder is restricted. US and EU regulators have acted against it after deaths.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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