Nearly 90% of Americans drink the equivalent of about two cups of coffee daily. But whereas one person can have a rich cup of joe with dessert and sleep like a baby, another can feel hyped up on a weak cup of tea. AncestryDNA^® + Traits can tell you if people with DNA like yours are likely to consume more or less caffeine than average, which may be related to your caffeine metabolism.

What Does Caffeine Do?

There's a reason coffee and tea are two of the world's most popular beverages. It's all about their shared magic ingredient: caffeine.

Caffeine stimulates the central nervous system, making people feel more energetic and awake. It also increases both dopamine and serotonin, chemicals in the brain that help one feel productive and happy.

But the effects of caffeine consumption aren’t the same for everyone. Some people can handle several cups of strong coffee and feel great, while others find that just a little amount of caffeine makes them jittery or interferes with their sleep.

For everyone, caffeine causes increased urination. And it leads to higher levels of acid in the stomach, which can cause stomach upset.

What Science Says about Caffeine Sensitivity

Whether you feel good or not-so-good after eating or drinking caffeine is partly due to tolerance as well as factors like your age, whether you're male or female, and what medications you're taking. But it turns out there might also be a genetic component.

AncestryDNA scientists have discovered over 30,000 DNA markers that are associated with individuals’ sensitivity to caffeine. Of those genetic markers, two seem to play a role in how your body handles caffeine, specifically caffeine metabolism. One is on chromosome 7 near the AHR gene, and the other is on chromosome 15 near the CYP1A1 and CYP1A2 genes.

Variations in the genes that direct how the body processes caffeine mean that it leaves some people's systems quickly, while it lingers for much longer in others. Fast metabolizers tend to drink more caffeine than slow metabolizers.

How Much Caffeine Is Too Much?

Although consuming low to moderate doses of caffeine is thought to be safe, experts’ guidelines recommend that most healthy adults have no more than 400 mg of caffeine per day. That's equivalent to about three or four cups of coffee, depending on the strength of the cups. However, women who are pregnant or trying to become pregnant should limit themselves to one or two cups of coffee per day.

Of course if you find you have a caffeine sensitivity, you might consider avoiding caffeine altogether. Signs of caffeine sensitivity include nausea, anxiety, and sleep disruption after consuming caffeine.

According to the Diagnostic and Statistical Manual of Mental Disorders, 5th edition, Caffeine Use Disorder and Caffeine Withdrawal are diagnosable conditions.

Interesting Facts about Caffeine

Yes, caffeine is a drug—the most popular psychoactive drug in the world. Research suggests that people have been enjoying caffeine for over 1,000 years.

Although coffee and tea are two common sources of caffeine, the coveted substance can also be found in the leaves, seeds, and fruits of more than sixty plants, including guarana berries and yerba mate. It's also present in chocolate and foods containing chocolate, soda and energy drinks, and over-the-counter painkillers.

Although it's rare, you can die from caffeine toxicity. It's difficult to ingest enough of a caffeinated beverage to reach dangerous levels, so powdered forms of caffeine are often the culprits in these unusual situations.

References

Addicott Meredith A. "Caffeine Use Disorder: A Review of the Evidence and Future Implications. Current Addiction Reports. September 2014. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4115451/.

Amin N., E. Byrne E, J. Johnson J, et al. "Genome-wide association analysis of coffee drinking suggests association with CYP1A1/CYP1A2 and NRCAM." Molecular Psychiatry. November 2012. https://pubmed.ncbi.nlm.nih.gov/21876539/.

"Caffeine Content for Coffee, Tea, Soda and More. Mayo Clinic." Accessed June 2, 2023. https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/caffeine/art-20049372.

"Caffeine: Uses, Side Effects, Interactions, Dosage, and Warning." WebMD. Accessed June 2, 2013. https://www.webmd.com/vitamins/ai/ingredientmono-979/caffeine.

Cornelis Marilyn C., Keri L. Monda, Kai Yu, et al. "Genome-Wide Meta-Analysis Identifies Regions on 7p21 (AHR) and 15q24 (CYP1A2) As Determinants of Habitual Caffeine Consumption." PLoS Genetics. April 7, 2011. https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1002033.

Costa, Samantha. "Your Body on Caffeine: When Enough Is Enough." U.S. News & World Report. January 7, 2016. https://health.usnews.com/health-news/health-wellness/articles/2016-01-07/your-body-on-caffeine-when-enough-is-enough.

Josse Andrea R., Laura A. Da Costa, Hannia Campos, et al. "Associations between polymorphisms in the AHR and CYP1A1-CYP1A2 gene regions and habitual caffeine consumption." American Journal of Clinical Nutrition. September 2012. https://pubmed.ncbi.nlm.nih.gov/22854411/.

McMahon, George, Amy E. Taylor, George Davey Smith, et al. "Phenotype Refinement Strengthens the Association of AHR and CYP1A1 Genotype with Caffeine Consumption." PLoS ONE. July 30, 2014. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103448.

"Spilling the Beans: How Much Caffeine is Too Much?" U.S. Food and Drug Administration. December 12, 2018. https://www.fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much.

Sulem Patrick, Daniel F. Gudbjartsson, Frank Geller, et al. "Sequence variants at CYP1A1–CYP1A2 and AHR associate with coffee consumption." Human Molecular Genetics. May 15, 2011. https://pubmed.ncbi.nlm.nih.gov/21357676/.