Genetic differences help explain why everyone experiences coffee’s effects differently
07 June 2018 – Coffee drinkers fall into one of three major groups based on their caffeine sensitivity, according to physician and author Dr J.W. Langer, in a new report authored for the Institute for Scientific Information on Coffee.
The report, Genetics, Metabolism and Individual Responses to Caffeine draws 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, Dr Langer has 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.
Dr Langer, author of the report, explains: “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.
Dr 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 explains 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 stresses the importance of taking individual responses into consideration when healthcare professionals are advising patients and consumers on their caffeine intake.