Is coffee a pro-oxidant or an antioxidant? I've heard that coffee acts as a pro-oxidant which damages cells and tissues causing the long-term effect of shorting life expectancy (Free-radical theory of aging), the opposite of how antioxidants are thought to work (e.g. Green tea).

However I can't find this information on Wikipedia (e.g. coffee or caffeine).

Therefore is coffee a pro-oxidant or an antioxidant?
In Spain one study showed that Brazilian Arabica 100% (A100) roasted samples presented lower antioxidant capacity (less efficient antioxidants) than Robusta coffee varieties (could be due to the higher percentage of chlorogenic acids in Robusta ground coffee than in Arabica) therefore Brazilian Arabica 100% (A100) presented the highest value of pro-oxidant activity.

However higher antioxidant activity was observed in Colombian coffees than in conventional roasted coffee blends. On the other hand, when the percentage of torrefacto coffee was increased, an increase of the antioxidant activity and a slight tendency to decrease the pro-oxidant activity were observed. Therefore addition of sugar at the end of the torrefacto roasting process may influence the antioxidant and pro-oxidant properties of coffee because sugar is one of the main precursors the Maillard reaction.

In summary, we can say that antioxidant and pro-oxidant capacity of ground coffee can be affected by several factors such as coffee variety, roasting process (e.g. torrefacto), growing climate, storage, etc. The details of the studies for further reading can be found below.

Sources:


(study) Comparison of antioxidant and pro-oxidant activity in coffee beverages prepared with conventional and “Torrefacto” coffee at Science Direct
(study) Influence of torrefacto roast on antioxidant and pro-oxidant activity of coffee at Research Gate