New review looks at the factors influencing caffeine’s impact on the body
Genetics may partly determine how much caffeine you drink
A new scientific review has investigated different factors that influence how the body metabolises caffeine and how caffeine intake affects everyday activity. The review found that factors including gender, diet, and genetics may all influence caffeine’s effect on an individual.
The review, ‘Interindividual differences in caffeine metabolism and factors driving caffeine consumption’, suggests that genetics play a critical role in the way that caffeine is metabolised.
Humans absorb 99% of caffeine intake within 45 minutes1, where it is then distributed around the body in body fluids such as blood and saliva; before being metabolised, primarily in the liver. Caffeine’s effects will last for several hours, depending on how quickly or slowly it is metabolised by the body.
Liver disease, for example, is likely to impair metabolism of caffeine2. A few specific medical drugs, such as some types of antidepressants3, may also make it harder for the body to metabolise caffeine.
Other factors affecting caffeine metabolism range from smoking status to diet4. For example, grapefruit juice consumption is associated with slower clearance of caffeine from the body5,6, while eating broccoli increases caffeine clearance7.
The review also explores why some people are more likely to consume caffeine than others. While various environmental factors play a role, coffee consumption is affected primarily by genetic factors. For example, one study has suggested that people with a particular genetic variation can drink more coffee because their bodies metabolise it more effectively8.
Variability in caffeine intake may be partly linked to the side effects that some people experience, such as anxiety or difficulty sleeping – that is, a person may self-regulate their intake if they know they are likely to experience side effects. Genetics may play a role in determining whether a person experiences side effects from caffeine: for example, genetic variations linked to anxiety disorders may also be associated with a specific response to caffeine9. Likewise, a genetic variation leads to differences in sleep and sleep sensitivity to caffeine10.
Tolerance may develop in chronic caffeine consumers (i.e. people who frequently consume caffeine over a long period of time). Caffeine tolerance could mean that a person needs to consume more caffeine to achieve the desired effect; or it may reduce a person’s reaction to adverse effects. As tolerance to the behavioural effects of caffeine varies from person to person, people will often regulate their intake to achieve the desired effects (such as increased alertness) while avoiding potential negative effects (such as anxiety)11.
Dr Astrid Nehlig, University Paris Descartes and paper author, said: “People often talk about how coffee affects them. We now know that genetics play a big part not only in how an individual reacts to caffeine, but may even help determine how much coffee they are likely to drink in the first place. Understanding these connections in more detail is incredibly important, given that research has shown some interesting links between caffeine consumption, increased health and quality of life.”
The paper suggests that further research into caffeine could categorise populations by gene type and their likely consequence on various functions when caffeine is consumed; emphasising that a better understanding of the factors influencing caffeine intake could provide a good opportunity to identify critical factors affecting quality of ageing and/or susceptibility to disease.
Readers interested in finding out more about coffee & health can visit: www.coffeeandhealth.org
Notes to editors
- Nehlig A. (2018) Interindividual Differences in Caffeine Metabolism and Factors Driving Caffeine Consumption, Pharmacological Reviews, published online.
- This paper was funded by ISIC but this has not in any way affected the production or content of the research. The author has declared no conflict of interest.
- Blanchard J. and Sawers S.J. (1983) The absolute bioavailability of caffeine in man. Eur J Clin Pharmacol, 24:93–98.
- Park G.J. et al. (2003) Validity of the 13C-caffeine breath test as a noninvasive, quantitative test of liver function. Hepatology, 38:1227-1236.
- Culm-Merdek K.E. et al. (2005) Fluvoxamine impairs single-dose caffeine clearance without altering caffeine pharmacodynamics. Br J Clin Pharmacol, 60:486-493.
- Arnaud M.J. (2011) Pharmacokinetics and metabolism of natural methylxanthines in animal and man. Handb Exp Pharmacol, (200): 33-91.
- Fuhr U. et al. (1993) Inhibitory effect of grapefruit juice and its bitter principal, naringenin, on CYP1A2 dependent metabolism of caffeine in man. Br J Clin Pharmacol, 35:431-436.
- Fuhr U. et al. (1995) Lacking effect of grapefruit juice on theophylline pharmacokinetics. Int J Clin Pharmacol Ther, 33:311-314.
- Lampe J.W. et al. (2000) Brassica vegetables increase and apiaceous vegetables decrease cytochrome P450 1A2 activity in humans: changes in caffeine metabolite ratios in response to controlled vegetable diets. Carcinogenesis, 21: 1157-1162.
- Cornelis M.C. et al. (2011) Genome-wide meta-analysis identifies regions on 7p21 (AHR) and 15q24 (CYP1A2) as determinants of habitual caffeine consumption. PLoS Genet, 7:e1002033.
- Childs E. et al. (2008) Association between ADORA2A and DRD2 polymorphisms and caffeine-induced anxiety. Neuropsychopharmacology, 33:2791-2800.
- Rétey J.V. et al. (2005) A functional genetic variation of adenosine deaminase affects the duration and intensity of deep sleep in humans. Proc Natl Acad Sci USA, 102:15676-15681.
- Smith A. (2002) Effects of caffeine on human behavior. Food Chem Toxicol, 40:1243-1255.
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