What is caffeine and how does it work?

Caffeine is a natural stimulant that is most commonly found within tea, coffee and cacao plants. It works by stimulating the brain and central nervous system. One of the ways caffeine works within your body is it blocks adenosine receptors within your body, preventing you from feeling fatigued. Once the blocked receptors become free (this happens naturally) the built-up adenosine can make you feel tired suddenly which is more commonly known as crashing.

As mentioned before, caffeine affects the brain causing neural excitement. The pituitary gland is located within the brain also known as the master gland. As it governs other glands and their hormone production it perceives this excitement as an emergency and releases adrenaline.

It is important to also note that a lot of caffeinated drinks that you can buy contain extra sugar, in which also down to personal preference some people add more sugar too. Christmas drinks in particular are heavily loaded with sugar. We're not saying to not enjoy these over the festive period, but just to be mindful that your body will need to process this extra sugar. 


Here is a list of a few scientifically-backed benefits of caffeine. There are more benefits caffeine can do for you, but below gives you the main benefits as caffeine has a wide-reaching effect on the human body:

  • Can improve energy levels and reaction times: by releasing epinephrine (adrenal), it stimulates the body to produce and use more energy.
  • Can help you burn fat: several studies show that caffeine can increase fat burning and boost your metabolic rate
  • Can drastically improve physical performance: caffeine can increase adrenaline levels and release fatty acids from fat tissues. 
  • May protect you from Alzheimer disease and dementia: studies show coffee drinkers have a much lower risk of getting Alzheimer’s disease
  • May lower your risk of Parkinson’s disease: because of the effect caffeine has on the brain, coffee drinks have up to 60% lower risk of getting Parkinson’s disease
  • Can fight depression: as mentioned in the introduction, the uptake of dopamine from caffeine’s effect on adenosine.


While there are no hard guidelines to follow about the quantity of consumed caffeine. British Dietetic Association (BDA) and the National Health Service (NHS) suggest that most people can safely consume up to 300mg per day. Furthermore, it is suggested that pregnant women should not consume any more than 200mg per day.

Coffee drinks

Size in oz, (mL)

Caffeine (mg)


8 (237)



1 (30)



8 (237)



Size in oz, (mL)

Caffeine (mg)

Brewed black

8 (237)


Brewed green

8 (237)


Ready to drink, bottled

8 (237)


Other drinks

Size in oz, (mL)

Caffeine (mg)

Energy drink

8 (237)


Energy shots

1 (30)



8 (237)


*Above are a few examples, the caffeine content does vary depending on the brand.

Other factors to consider

Additional nutrients are commonly found aside from caffeine such as sugar. This does increase the energy-boosting effect of caffeine, however sugar is more presently found in foods, which can lead to overconsumption of sugar (Adults not having more than 30g of free sugar per day, roughly equivalent to 7 sugar cubes).

While 300mg is the suggested guideline, there are other considerations that can affect your daily recommended guidelines.

  • Weight
  • Gender (men are more susceptible to caffeine side effects than women)
  • Anxiety disorders (if any)
  • Medications

Side effects

  • Sleeplessness
  • Nervousness
  • Irritability
  • An upset stomach
  • A quickened heartbeat/ heart palpation
  • Muscle tremors
  • Dehydration
  • Dizziness
  • Anxiety

Please just be mindful of sugar intake over the festive holiday and look after yourselves. We hope you have a great Christmas and a Happy New Year.