Caffeine Sensitivity

Caffeine Sensitivity

Caffeine is found naturally in tea and coffee. It is now being increasingly added to a variety of food and beverages. Caffeine acts as a stimulant of the brain and nervous system. It can help you to stay alert and prevent the onset of tiredness, but drinking too much caffeine, or having a lower rate of caffeine metabolism, can lead to high blood pressure. High blood pressure is a precursor to hypertension and heart disease.

What is the CYP1A2 gene?

The CYP1A2 gene encodes an enzyme called cytochrome P450, which is involved in caffeine metabolism in the liver. The enzyme breaks down caffeine into theophylline, theobromine, and paraxanthine. These molecules then travel through the body to perform a variety of functions.

What is the effect of genetic variation at the CYP1A2 gene?

Having an allele at the CYP1A2 gene reduces the activity level of the enzyme it codes for, which results in slow caffeine metabolism. Caffeine therefore remains in your blood and acts as a stimulant for longer than those with no SNP. This means that caffeine will increase blood pressure in individuals with an allele more and for a longer period of time, which gives them a higher risk of heart disease.

How does caffeine act as a stimulant?

Caffeine is absorbed after consumption from the gut into the bloodstream. It travels in the blood to the liver, where it is broken down. Having been broken down, it can now act as a stimulant.

Caffeine blocks the effects of adenosine - a molecule that makes you feel tired. It binds to adenosine receptors in the brain which stops adenosine molecules binding. This reduces the effect of adenosine and stops the feeling of tiredness.  Caffeine also increases the levels of adrenaline in the blood, which is a hormone that increases brain activity.

This combination further stimulates the brain and promotes a state of arousal, alertness and focus.

A caffeine intake of up to 400 mg per day, is generally considered safe. This amounts to 2–4 cups of coffee per day. However, it is very important that pregnant women limit their daily intake to 200 mg or less.

Why should caffeine intake be reduced during pregnancy?

It is recommended that pregnant women do not consume more that 200mg of coffee a day.

High levels of caffeine in pregnancy can result in babies having a low birthweight, which can increase the risk of health problems in later life. Too much caffeine can also increase the risk of miscarriage.

Does the presence of an allele affect caffeine intake?

Yes. Individuals with an allele on average consume less caffeine.

Individuals who have an allele metabolise caffeine more slowly, therefore caffeine remains circulating in their blood for longer, which results in them consuming less caffeine.

Individuals with no SNP, metabolise caffeine more quickly and this leads to a fall in the amount of caffeine in the blood. Consequently, these individuals increase their caffeine intake in order to avoid abstinence. This would lead to a craving for caffeine, leading in turn to higher daily caffeine intake.

What is caffeine withdrawal?

Caffeine withdrawal occurs when an individual suddenly stops consuming caffeine after regular and high consumption. Symptoms include headaches, anxiety and irritability.

When wanting to considerably decrease caffeine intake, it is best to decrease your daily consumption slowly to avoid the symptoms of caffeine withdrawal.

Backed by Science

Our in-house scientists have sorted through thousands of studies and we only use genes that are backed by a significant body of peer-reviewed research. Check out Nell’s Science Standard for more information.