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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?

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    You say you can't find it on Wikipedia, and all of your links are indeed to Wikipedia. There are over 200 citations and references for further reading on the main coffee Wikipedia entry alone. Have you consulted those or other sources, e.g., such as the three links attributed the polyphenols having "little or no direct antioxidant food value"? Can you explain, or give a reference, to where you have heard this? Or have you heard this in the sense of speculation only?
    – hoc_age
    Commented Feb 13, 2015 at 16:15
  • @hoc_age I've heard it long time ago from many people (maybe TV) that coffee is a pro-oxidant which shortens the human life span, but I don't remember where and who. That's why I'm asking.
    – kenorb
    Commented Feb 13, 2015 at 16:24
  • I appreciate your fervor in asking coffee-related health questions, but it may be a slippery slope to permit asking speculative questions without attribution to a concrete reference. Let's keep it clean! :) This is especially so when the topic pertains to health (which is not the primary topic of this site; but there is a site-proposal for that!
    – hoc_age
    Commented Feb 13, 2015 at 16:35
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    If this is just a simple question of whether coffee is an anti-oxidant or not, it is probably okay; but if we start delving into the effects on cellular chemistry in the human body, that is simply too far outside the expertise/focus of this site. Commented Feb 13, 2015 at 17:22
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    @kenorb I am saying that as asked, the question may not be answerable. The study you cited listed specific varieties and roast levels. What I am saying is that your question "...is coffee a pro-oxidant or an antioxidant?" is not answerable because it probably varies by a number of factors (as also stated in the cited study). The antioxidant properties of coffee decrease with roast level, for example. Commented Feb 14, 2015 at 0:08

3 Answers 3

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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:

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    This is the "it depends" answer I thought was coming. Commented Feb 14, 2015 at 20:31
  • @ChrisinAK Personally I would still think that a coffee is pro-oxidant in general, but I'd have to check and consolidate more studies.
    – kenorb
    Commented Feb 14, 2015 at 21:47
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To clarify: as stated in another post, the type and roasting process affects the antioxidant benefits of coffee on a case by case basis, but overall it has been proven that coffee is a (fairly) potent antioxidant.

In fact, when compared against cocoa and black tea coffee is actually more potent in a cup for cup basis.

Source: Comparison of the Antioxidant Activity of Commonly Consumed Polyphenolic Beverages (Coffee, Cocoa, and Tea) Prepared per Cup Serving.

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Pro-oxidative stress is not necessarily a bad thing in moderation. According to this article, green tea is thought to induce longer lifespan by increasing the antioxidant capacities within cells by having a pro-oxidant effect. (https://www.news-medical.net/news/20211203/Green-tea-shown-to-increase-the-defensive-capabilities-of-cells.aspx) The same could be assumed to apply to coffee. Both coffee and tea (and most other plant foods) contain a complex combination of both pro-oxidants and antioxidants. Consuming them requires the body to regularly increase its antioxidant capacity, which then extends lifespan. Think of it as strength training for your mitochondria.

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