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Caffeine is an extremely common chemical typically found in things like tea, coffee, coca-cola and other products.

Caffeine works by stimulating the central nervous system, heart, muscles, and the centers that control blood pressure. Caffeine also raises blood pressure, but may not do this for people who are regular caffeine consumers. It also increases urine flow and encourages bowel movement. But again, it may not have this effect in people who use caffeine regularly.


Most commonly, caffeine is used to help ‘wake-up’ and improve on mental alertness, but also has other uses and purposes.  In this way, caffeine is consumed via liquid such as a coffee, tea or an energy drink.

Caffeine can be used by mouth or rectally in combination with painkillers, like asprin. It is used with painkillers for simple headaches, migraines and preventing and treating headaches after epidural anesthesia.

Some people find that caffeine helps with asthma, gallbladder disease, attention deficit-hyperactivity disorder (ADHD), low blood pressure and shortness of breath in newborns.

Caffeine is quite commonly used amongst athletes as stimulants. Within the limits, caffeine is accepted by the  National Collegiate Athletic Association (NCAA) as an acceptable form of stimulation, unlike steroids. Urine concentrations over 15 mcg/mL are prohibited. To put this into perspective, it takes the majority of people around 8 cups of coffee providing 100 mg/cup to reach this urine concentration.

Caffeine can also come in the form of a cream, which is applied to the skin to reduce redness, puffiness, itching and dermatitis.

People with disorders that affect the voice, singers, and other vocal professionals are often advised against consuming caffeine. However, until recently, this recommendation was not based in research. Developing research seems to indicate that caffeine may actually harm voice quality. But further study is necessary to confirm these early findings.

Side effects

Caffeine is safe from most adults, depending on health conditions, to consume when used appropriately, but it can come with some side effects, both positive and negative.



Recent studies have shown that people who regularly drink coffee (and therefore caffeine) are less at risk of developing Alzehimer’s disease of dementia but about 45%. These benefits are reserved for people who drink caffeinated coffee, not decaf. Many consider coffee to be a health drink, but like most consumables, over indulging can cause side effects.

Withdrawal and Overdose

Caffeine withdrawal is a side effect of drinking it excessively, your body learns to rely on it.

Symptoms of caffeine withdrawal include:

  • Headaches
  • Anxiety
  • Drowsiness
  • Irritability
  • In some people, withdrawal may cause tremors.
  • Achy muscles

It is also possible to overdose on caffeine, although this is extremely rare. Symptoms of an overdose include:

  • Vomiting
  • Confusion
  • Hallucinations
  • Rapid or irregular heartbeat
  • Trouble breathing

In some cases an overdose of caffeine can cause death due to convulsions. Up to 400 milligrams of caffeine is was is considered to be safe, according to the Mayo Clinic. This equals around 4 cups of coffee a day, although do be aware that the amount of caffeine in beverages varies widely.

Digestive problems

Caffeine increases the amount of acid in your stomach, therefore it may cause heartburn or an upset stomach. Left-over or ‘extra’ caffeine doesn’t get stored in your body either. It’s processed in the liver and exits through your urine. Consequently, you might have an increase in urination shortly after having caffeine.

If you have experience with stomach problems, like acid reflux or ulcers, you should consult with your doctor and ask him or her if it is okay for you to have caffeine.

Reproductive system and Pregnancy

Caffeine travels within the bloodstream and into the placenta. Since it is a  stimulant, it can easily cause a baby’s heart rate to increase. In saying this, drinking a little caffeine each day is fine and safe during pregnancy.

On the flip side, too much caffeine can also cause slowed fetal growth and increased risk of miscarriage. In most cases, a little caffeine is safe during pregnancy. According to experts, you should aim to limit your caffeine consumption between 200 and 300 milligrams per day if you’re trying to get pregnant or are pregnant. This is the case for if you are trying to get pregnant as there has been some evidence to suggest that large amounts of caffeine can interfere with the estrogen production and metabolism needed to conceive successfully.

Circulatory and respiratory systems

Caffeine is absorbed from your stomach, reaching its highest levels in your bloodstream within one hour or two at most. It can also make your blood pressure go up for a short period of time. This effect is thought to be due to an increase in adrenaline or a temporary block on the hormones that naturally widen your arteries. In the majority of people, there are no long-term effects on the blood pressure, but if you have irregular heart rhythms, caffeine may make your heart work harder. If you have high blood pressure (hypertension) or heart-related problems, ask your GP if caffeine is safe for you to consume at any point.

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