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Consumption of a dark roast coffee blend reduces DNA damage in humans: results from a 4-week randomised controlled study



To determine the DNA protective effects of a standard coffee beverage in comparison to water consumption.


The single-blind, randomised controlled study with parallel design included healthy women (n = 50) and men (n = 50) recruited from the general Central European population. The subjects were randomised in a coffee and a control group, with stratification for sex and body mass index. The study comprised two periods of 4 weeks: a preconditioning period, with daily consumption of at least 500 ml water but no coffee, nor tea, nor any other caffeine-containing product. During the subsequent intervention period the coffee group consumed 500 ml of freshly brewed dark roast coffee blend per day, the control group consumed water instead. On the last day of each period, blood was drawn and analysed by comet assay (single-cell gel electrophoresis) to assess the level of DNA damage (strand breakage).


At the end of the intervention period the mean level of DNA strand breaks in the coffee group has decreased in comparison to the control group [difference in means 0.23% TI (tail intensity), p = 0.028]. The mean change from baseline (delta value) was − 23% in the coffee group (p = 0.0012). Effects of coffee intake were similar for men and women. During intervention, neither group showed any significant change in body weight or calorie intake.


Our results indicate that regular consumption of a dark roast coffee blend has a beneficial protective effect on human DNA integrity in both, men and women.

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Body mass index


Caffeoylquinic acid


Intention to treat




Per protocol


Standard deviation


Tail intensity


Wilcoxon rank sum test


Wilcoxon signed rank test


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We thank Thomas Hofmann and Roman Lang (Technical University of Munich) for NMP, trigonelline and creatinine measurements (compliance), and Lubica Prochazkova, Helena Nagyova, Edita Mrvikova and Zuzana Krchnava from Slovak Medical University for technical help.


This study has been supported by Tchibo GmbH, Hamburg, Germany.

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Correspondence to Dorothea Schipp.

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D. Schipp is a self-employed statistician, who has been appointed and financed by Tchibo GmbH for this and other projects.

Ethical standards

The study has been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.

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Schipp, D., Tulinska, J., Sustrova, M. et al. Consumption of a dark roast coffee blend reduces DNA damage in humans: results from a 4-week randomised controlled study. Eur J Nutr 58, 3199–3206 (2019).

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  • Coffee
  • Comet assay
  • Human intervention study
  • DNA strand breaks
  • DNA damage