What does Caffeine do to your Body?

Caffeine is an alkaloid compound, which is odourless and tastes bitter in its pure form. It is found naturally in leaves, seeds and fruits of more than 60 plants including: tea leaves, coffee beans, cacao, yerba mate, guarana, yaupon holly and cola nuts. Most people consume caffeine to combat feelings of sleepiness or fatigue. How does caffeine do that exactly? And what effects does it have on your body?

Caffeine and Your Body

Caffeine Absorption

Caffeine enters the bloodstream through the mouth, oesophagus, stomach and small intestine. The effects of caffeine can be felt within 15 minutes after ingestion. It is completely absorbed within 45 minutes of consumption. Caffeine cannot be stored in your body, but it hangs out for a while; only half of the amount you consumed is eliminated in your urine after 4 to 6 hours.

When adenosine is created in your brain, it binds to its receptors. This binding causes you to feel drowsy and slows down activity between nerve cells. Caffeine looks a lot like adenosine and is able to bind to adenosine receptors. However, caffeine does not slow down nerve cell activity, like adenosine would. Because caffeine is “stealing” all the adenosine receptors, the nerve cells fail to slow down and, instead, speed up. Caffeine also causes the brain’s blood vessels to constrict, which limits adenosine’s ability to open these vessels up to more adenosine. The pituitary gland senses this odd activity in your body and releases hormones that signals the adrenal glands to produce adrenaline which has these effects on your body:

  • Pupils dilate
  • Airways open up
  • Heart beats faster
  • Blood vessels on the surface constrict to slow blood flow from cuts
  • Blood flow increase to muscles
  • Blood pressure rises
  • Blood flow to stomach slows
  • Liver release sugar into the bloodstream for extra energy
  • Muscles tighten up, ready for action

Caffeine Addiction

Caffeine is considered to be a mildly addictive substance. Eighteen to 24 hours after consuming caffeine, a person may feel the symptoms of caffeine withdrawal. These symptoms can be as mild as a headache or as serious as depression and loss of focus. Fatigue is very common in people who are in caffeine withdrawal. If you are looking to “quit” caffeine, it is recommended that you do so gradually to reduce the symptoms of withdrawal. Those who stop ingesting caffeine after regular use should feel no negative withdrawal symptoms after one week of caffeine abstinence.

More On Caffeine

Pain Relief

If you are not a regular coffee drinker, caffeine can help speed pain relief. Used in conjunction with pain relievers, caffeine can be 40% more effective in treating headaches than if the sufferer were to take the pain reliever by itself. Hence, a lot of over-the-counter pain relief medication contain caffeine.


Caffeine destroys the lining of your gastrointestinal tract, which produces ulcers and other forms of gastric irritation and damage.

Preventative Effect on Type 2 Diabetes

Caffeine has antioxidant and mineral content (magnesium and chromium) which are thought to help the body use the hormone insulin more effectively. Insulin helps your body regulate blood sugar.

Preventative Effect on Cognitive Disorders

Studies show that those who drink coffee regularly have decreased risks for cognitive impairment, such as dementia, later in life.


Decaffeinating coffee is made by first soaking the beans in water. Then caffeine is extracted from the beans with an activated carbon or solvent. The beans are soaked again in the decaffeinated water in the initial step to reabsorb flavor. Decaffeinated coffee contains on average 8.6mg to 13.0mg of caffeine.

Caffeine “Overdose”

Consuming too much caffeine in a short amount of time can cause negative symptoms. These include: restlessness, nervousness, excitement, insomnia, flushed face, diuresis and gastrointestinal upset.

Caffeine Intake

The average American consumes 280mg per day. The US Food and Drug Administration (FDA) define low, moderate, high and heavy amounts of caffeine intake as follows:

  • Low to Moderate: 130mg to 300mg per day
  • Moderate: 200mg to 300mg per day
  • High: 400mg+ per day
  • Heavy: 6,000mg+ per day