Which group of coffee drinkers are you in?

Washington D.C.: Did you know that coffee drinkers are classified based on their caffeine sensitivity?A scientist, J.W. Langer, explained why everyone experiences coffee differently.Coffee drinkers fall into one of three major groups based on their caffeine sensitivity, according to study author Langer.

The report drew on existing research to explain how the body metabolises caffeine, why some people are more affected by caffeine than others, and how healthcare professionals can take this into account when advising patients.

An individual's response to caffeine is likely determined by two main genetic factors: whether their liver can metabolise caffeine quickly or slowly1-3; and whether they carry a genetic variation that makes their central nervous system more sensitive to caffeine's stimulating effects1, 4-8 Based on these genetic factors, Langer proposed three descriptive levels of overall caffeine sensitivity:

- High sensitivity to caffeine

Slow-metabolism in the liver and high binding in the central nervous system. Even small amounts of caffeine will cause a stimulating effect and higher doses may cause sleep problems, as seen in a minority of people.

- Regular sensitivity to caffeine

The balance between caffeine inactivation in the liver and binding in the central nervous system means that the individual can typically drink 2-5 cups of coffee during the day without adverse reactions or sleep disturbances. Caffeine is normally not recommended in the evening, but individual differences prevail, as seen in most people.

- Low sensitivity to caffeine

Fast metabolisers of caffeine. Higher intakes can be consumed, (although healthcare professionals should advise that they still stay within the EFSA guidelines of no more than five cups of coffee per day9). Coffee drinking before bedtime does not typically disturb sleep.

Langer explained, "It's common for people to ask their doctor questions such as why they are kept awake by one cup of coffee, while their partner easily falls asleep after five cups. The answer is that we are all unique coffee drinkers. Our genetic make-up programmes our reaction to caffeine, just as it programmes our hair colour and eye colour."

An individual with low sensitivity to caffeine probably will not experience the typically desired effects of caffeine, such as wakefulness, alertness, and increased concentration. It is important for healthcare professionals to stress that fast metabolisers should not exceed the recommended daily caffeine intake trying to achieve the desired effects.

Langer continued, "Most people will self-moderate their caffeine intake based on their personal experience of what they can tolerate. However, it's important that those with a low sensitivity to caffeine stay within the recommended daily caffeine intake of up to 400mg caffeine, which is equivalent to around five cups of coffee."

This report explained the genetic variations that affect individuals' responses to caffeine in more detail, as well as outlining some of the non-genetic factors such as smoking status, pregnancy, and age.

The report also stressed the importance of taking individual responses into consideration when healthcare professionals are advising patients and consumers on their caffeine intake.The findings are published in the Institute for Scientific Information on Coffee.