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A highly publicized study in the news this week has been used in a slew of articles to suggest that drinking several cups of coffee a day will extend your life.

Coffee, caffeinated or decaffeinated, may help extend the lives of people who drink it daily, a U.S. study found.

Men who drank 2 to 3 cups a day had a 10 per cent chance of outliving those who drank no coffee, while women had a 13 per cent advantage, according to research published Wednesday in the New England Journal of Medicine. Toronto Star

To me, this is a huge misinterpretation of the observational study (N Engl J Med), which appears to have merely correlated self-proclaimed coffee drinkers with living longer. We know of course that correlation does not imply causation, and the relationship could be due to a number of things, such as the possible fact that coffee drinkers tend to wake up earlier and have more active days, which might improve their overall health.

Is there anything in this or any other study to actually suggest a causal relationship between drinking coffee and living longer, or is this being blown out of proportion by popular media?

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Alain
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  • In spite of this study, I personally would still expect that all other things being equal, if one were to live an *identical* life, but with the addition of a few cups of coffee a day, their overall health would worsen, not improve. – Alain May 18 '12 at 17:01
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    Your odds of dying are 1. The questions are when and how. – dmckee --- ex-moderator kitten May 18 '12 at 17:10
  • @dmckee Haha, I see the mistake in my question title now. Thanks. (Was "Does drinking coffee reduce one's odds of dying?") – Alain May 18 '12 at 17:24
  • 1. Coffee contains acrylamide, which is considered to be carcinogenic [http://en.wikipedia.org/wiki/Acrylamide 2 prepared foods: beverages]. 2. Coffee deregulates your body's natural mechanisms, e.g. it can influence your sleep patterns. Also, it deprives you of significant doses of magnesium, calcium, and so on. I think what you read could have been a coffee-selling company hubbub. I don't believe anything easily anymore, thank heavens for this page. Coffee is an addictive substance and it can be harmful if overdosed. Otherwise it would be only right to serve it to children and breastfeeding –  May 20 '12 at 07:01
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    @milamilo Your point 2 is a typical logical fallacy. Lots of things, including all drugs, deregulate your body’s natural mechanisms, some in drastic ways. This *can*, but isn’s necessarily, detriment to your health. Furthermore, there’s no a priory reason to suspect a coffee company propaganda. In particular, the authors declared no conflicting interests. Your last sentence is once again a fallacy. Just about *everything* is poisonous when overdosed on, and lots of substances are harmful only to specific groups (e.g. children). – Konrad Rudolph May 20 '12 at 17:49
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    @milamilo: the acrylamide point is also moot as it stands. How much acrylamide does a cup of coffee contain? How much acrylamide and how often do you have to take to increase of how much your chances of getting a tumour? Etc etc. *Sola dosis facit venenum*. Also, the last point is ridiculous. Red wine contains various antioxydants and a non-excessive intake of red wine is healthy. That does not mean you should give it to infants. – nico May 20 '12 at 17:55
  • @Alain: *their overall health would worsen*. And that is because... – nico May 20 '12 at 17:58
  • I have no references for that claim, it's just what I would expect, hence the comment rather than putting it in my original question. In any event, I certainly don't believe coffee is particularly detrimental to one's health, I just think it's incorrect to state that it makes people live longer based on the hyped study. – Alain May 21 '12 at 01:21
  • I'm confused about the quote "Men who drank 2 to 3 cups a day had a 10 per cent chance of outliving those who drank no coffee". That's saying that 10% of coffee drinking men survive longer lives than coffee free men, and thus 90% of coffee drinkers live shorter lives. Your baseline chance for outliving anyone else is 50%. 10% is worse. Is this just a bad quote? – John Rhoades May 23 '12 at 13:08
  • @JohnRhoades The quote is verbatim, looks like they just suck at getting a point across. The likely result of the study was that if you grouped all the coffee drinkers and non-coffee drinkers together, the former group lived on average 10% longer. This isn't made clear in the original study's abstract though. – Alain May 23 '12 at 13:10

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Disclaimer - I claim no expertise what so ever in nutrition and health. Do not take my statement as fact, do your own research

Mainstream opinion seems to be that high intake of antioxidants are one big component for longevity. And coffee, according to some studies, is a powerful antioxidant.

A thought experiment: Two subjects 'A' and 'B' Subject 'A' drinks no coffee. Subject 'B' drinks 2 Cups a day. Plain black coffee from organic crops, no additives (E.g. Sugars, Spices, Milk...)

EVERYTHING else EQUAL , it seems to me that subject 'B' statistically would outlive subject 'A'. This would be based on the idea that antioxidant "protects" the body from so called "free-radicals". Additionally subject 'B' could have better health because of the additional hydration from the coffee. (This statement could potentially be wrong, the diuretic effects of coffee is debated. This blog post gives some information on the topic)

There's some weak links in these arguments: Coffee includes many other things then just antioxidants, these ingredients could possibly be harmful and thus invert the result, I.e subject 'A' outlives subject 'B'. Subject 'B' might have genetic disadvantages/differences that makes "normally non-harmful ingredients" of coffee into something that the subject can't handle efficiently. Nutrition is a really hard topic and we do not understand it all yet.

According to the book "The most effective ways to live longer" (isbn-13: 978-1-59233-340-0); "Coffee Scored at the top of the heap in antioxidant capacity among alcohol, teas and coffee."

This statement is based on the study: Pelligrini, N., M. Seafini, B. Colombi, et al. - Antioxidant capacity of plant foods, beverages and oils consumed in Italy assessed by three different assays. J Nutr 133 (September 2003): 2812-2819.

Alain
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Jerker Bengtsson
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  • Welcome to Skeptics! If I understand correctly, you're asserting that the causal link could be the antioxidation properties of coffee? Do you think that the studies mentioned in in this question support your claim? http://skeptics.stackexchange.com/questions/510/do-antioxidants-have-health-benefits I was also wondering about the quality of the coffee-- would Starbucks be better/worse than Maxwell House? – mmr May 19 '12 at 14:37
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    A few comments: First, this post is still lacking credible references, although I appreciate the effort. You have one blog post and one reference to a 'popular science' type book. While the latter references a study, note that it's only comparing the level of antioxidants in alcohol, teas and coffee. This is similar, for example, to saying "Of coke, pepsi and dr. pepper, pepsi contains the most vitamins." It really doesn't do much to put anything in perspective. – Alain May 19 '12 at 15:48
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    I believe to make your claims useful, you must show that 1) coffee contains a substantial level of antioxidants (with references), and 2) Antioxidants contribute to the longevity of life (with references). Even then, a counterclaim would be that this benefit does not outweigh the downfalls [citation needed] of drinking coffee. :) – Alain May 19 '12 at 15:49