Caffeine Intake and Tolerance are Related to Genetic Disposition 

This web page was produced as an assignment for an undergraduate course at Davidson College.



Crystal Structure of Human Microsomal P450 2A6 with Coumarin Bound (Coumarin not shown). Shows the location of CYP2A. Image from

Science is a rapidly changing filed that relies on communication. However, translating scientific discoveries for public understanding can lead to misleading information and a view of science as a linear process, rather than circular and ongoing (Kua et al., 2004). This web page will review two presentations of research: one popular press article, Researchers from UNC, other schools find genetic link to caffeine craving to a primary journal article Genome-Wide Meta-Analysis Identifies Regions on 7p21 (AHR) and 15q24 (CYP1A2) As Determinats of Habitual Caffeine Consumption. The analysis of these articles is intended to examine how the content of the primary journal article is presented in different contextual formats.

Scientific Paper
Caffeine can have both beneficial and ill effects on health. Understanding the genetic causes of caffeine intake can provide insight into mechanisms that can be used to provide more comprehensive studies on the health effects of caffeine.


  1. Caffeine intake was assessed using a food frequency questionnaire including questions on consumption of caffeinated coffee, tea, soft drinks, and chocolate.
  2. Meta-analysis of genome-wide association studies (GWAS) from population-based cohorts of 47,341 individuals of European descent, from five studies done in the US.
    1. Adjusted for age, sex, smoking, and eigenvectors of population variation.

Found two loci that reached genome-wide significance. 7p21 (P=2.4X10-19) near AHR and the other 15q24 (P = 5.26X10-14) between CYP1A1 and CYP1A2. Each loci are plausible biologically candidates for heritable or habitual caffeine consumption as both AHR and CYP1A2 are associated with caffeine metabolism. CYP1A2 metabolizes caffeine in the liver and AHR regulates CYP1A2.

Conclusion/Future Research
Illustrates that GWAS is a reliable method to identify genetic determinants of behavioral traits. Further investigation is needed to understand the effects of caffeine and carcinogens, such as cigarettes metabolized through the actions of CYP1A2 and AHR.

Popular Press Article
The News and Observer article opens by framing the scientific paper through a real world perspective. The article tries to gain the reader’s attention by providing context and a frame of reference. As a result, the article as a whole navigates from the research being reported (Kua et al., 2004). By providing statistics like, “9 out 10 American adults use caffeine every day” (Smith, 2012) paired with statements like, “caffeine. Some people can’t live with it, and others can’t live without out” (Smith, 2012) the article appeals to the emotions of the reader instead of presenting a logic based argument of research presented in the scientific article. Therefore, the beginning of article becomes a series of isolated facts due to the reader’s lack of scientific knowledge (Kua et al., 2004 and Smith, 2012).
After introducing the effects of caffeine intake the article shifts the focus to how genetics could play a role in caffeine consumption. The article explains that genomes were scanned looking for SNPs and data was collected from surveys about caffeine intake, but fails to demonstrate what scanning and survey methods were used. Therefore, there is a gap of knowledge providing misleading information about the implications of the study. Then, the article reports the results of the scientific paper and states that there are more genetic links than the two found, but fails to qualify the results or tell why the results are not sufficient. The scientific paper explains how the evidence supports a genetic link to caffeine consumption, but fails to explain why some people experience different caffeine tolerances or effects of caffeine. The news article interprets the results for the reader and focuses on the benefits of future research instead of the research presented in the scientific paper. Therefore, the conclusion presented to the reader is distorted. The news article draws the conclusion that genetics is the main cause of caffeine tolerance and intake, but this conclusion cannot be made from the scientific article (Kua et al., 2004; Smith, 2012).

Furthermore, by denoting little space to presenting the research the article focuses the reader’s attention elsewhere. As the article progresses it shifts from presenting the results of the study to DNA testing and the reader’s ability to know if they are pre-dispositional to have a higher caffeine intake. Again, appealing to the emotions of the reader the research is presented as a series of linear isolated facts. As a result, information about the scientific study is left out providing an in-cohesive argument (Kua et al., 2004; Smith, 2012).
 The last part of the news article delivers a science lesson about how caffeine works in general rather further presenting and explaining the research presented in the journal article (Kua et al., 2004). By mixing information about the ill effects of caffeine with qualifying statements such as “results will help us understand why the effects caffeine vary from person to person, and help flag patients who are more likely to suffer negative effects” (Smith, 2012) gaps are formed in the logical argument of the research presented. Caffeine effects individuals in different ways and understanding the genetic components involved in caffeine metabolism can shed light into this issue however, the results of this scientific paper do not demonstrate how caffeine effects different individuals. The results of scientific paper only indicate that GWA is an effective method to screen for genes involved in behavioral preferences. Therefore, the connection between the two gene variants found in the scientific paper and the different effects of caffeine on individuals is misleading, as the new article inserts qualifying statements and fails to present a cohesive argument (Kua et al., 2004; Smith, 2012).

The translation of scientific evidence into public knowledge is difficult and often leads to a gap of knowledge and misleading information. The main difference between the scientific paper and the news article is not in the language used, but in what is said (Kua et al., 2004). Yes, there is more scientific jargon that makes the scientific paper denser and harder to understand, but the news article reports more on what is already known about caffeine instead of what is becoming known (Kua et al., 2004). The news article lack information regarding the scientific process assuming the reader has limited background knowledge and is unable to make the connection between the research done and the results (Kua et al., 2004). The reader does need to understand the scientific context of caffeine’s effects but it should not be at the stake of prohibiting the reader from making conclusions for themselves (Kua et al., 2004).

Caffeine – most widely consumed psychoactive substance that blocks adenosine in the brain, which promotes the urge to sleep (Cornelis et al., 2011).
Genome-wide association (GWA) - study of single nucleotide polymorphism (SNPs) genotyped from individual samples (Magi and Morris, 2010).
Meta-analysis - detects loci from a sample population by increasing the sample size over a study (Magi and Morris, 2010).
SNPs – DNA variation of a single nucleotide (US National Library of Medicine, 2013)

Cornelis, C, Marilyn, Monda, L., Keri, Yu, Kai, Paynter, Nina, Azzato, M., Elizabeth, Bennett, N., Siiri, Berndt, I., Sonja, Boerwinkle, Eric, Chanock, Stephen, Chatterjee, Nilanjan, Couper, Davidsn, Curhan, Cary, Heiss, Gerardo, Hu, B. Frank, Hunter, J., Davids, Jacobs, Kevin, Jensen, K., Majken, Kraft, peter, Landi, T., Maria, Nettleton, A., Jennifer, Purdue, P., Mark, Rajaraman, Preetha, Rimm, B., Eric, Rose, M., Lynda, Rothman, Nathaniel, Silverman, Debra, Stolzenberg-Solomom, Rachael, Subar, Amy, Yeager, Meredith, Chasman, I., Daniel, van Dam, M., Rob, and Caporaso, E., Neil. 2011. Genome-wide meta-analysis identifies regions on 7p21 (AHR ) and 15q24 (CYP1A2 ) as determinants of habitual caffeine consumption. PLoS  Genetics 7(4).

Eunice Kua, Michael Reder, and Martha J. Grossel. 2004. Science in the News: A Study of Reporting Genomics. Public Understanding of Science. 13: 309–322.

Magi, Reedik and Morris, P., Andrew. GQAMA: software for genome-wide association meta-analysis. 2010. BMC Bioinformatics 11:288.


Smith Robin, “Researchers from UNC, other schools find genetic link to caffeine craving”. Newsobserver. 02 Jan. 2012. 22. Jan. 2013.

US National Library of Medicine. 17 Jan. 2013. What are single nucleotide polymorphisms (SNPs)?. Genetics Home Reference: Your Guide to understanding genetic conditions. 22 Jan. 2013.

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