DNA damage occurs with normal metabolism and upon exposure to toxic environmental factors. It is associated with the development of some cancers, cardiovascular diseases, diabetes, and inflammatory bowel diseases. Coffee contains a number of compounds with antioxidant properties, and previous research has shown that coffee and coffee extracts may reduce DNA damage in colon cells and white blood cells. Findings of this randomized controlled trial detail the effects of daily coffee consumption on DNA damage in healthy adults.

Coffee constituents such as caffeic acid, catechol, hydroxyhydroquinone, trigonelline, and alkylpyridinium compounds enhance cellular protection by activating Nrf2, a transcription factor that regulates the expression of antioxidant proteins like glutathione. Of these constituents, the alkylpyridinium compounds, which are produced during roasting, were the most robust activators of Nrf2. One study comparing dark and medium roast coffee blends found that both blends reduced DNA damage; however, this study did not include a control group.

The researchers recruited 100 healthy adults to participate in their study and randomly assigned them to one of two groups that were matched for weight and age. During a preconditioning period, they asked participants to consume at least 16 ounces of water per day and to avoid coffee, tea, and other caffeine-containing beverages and foods for four weeks. During the intervention period, participants in one group consumed 16 ounces of freshly brewed dark roast coffee blend per day for four weeks while the other group continued to drink water and avoid coffee. Participants gave blood samples at baseline and at the end of each four-week period for the measurement of DNA damage, using a test called the comet assay, which measures DNA strand breaks.

DNA damage did not change between the preconditioning and intervention period for participants in the water group, while participants in the coffee group had a reduction in DNA damage. Compared to their baseline intake of coffee and other antioxidant-rich foods and beverages, participants who consumed the study coffee treatment had a significant 23 percent reduction in DNA damage levels. These effects were similar between males and females.

The authors concluded that regular consumption of dark roast coffee reduces DNA damage in healthy adults compared to water consumption. They advise that future studies should compare the effects of different kinds of coffee (e.g., light, medium, and dark roast) on DNA damage and health.

• Link to full report.
• Learn more about the benefits of coffee on healthspan from Dr. Guido Kroemer in this clip.