Bitter Coffee, Better Health?

Reading time: 4 – 6 minutes

I love my coffee. Who doesn’t want (or need for all you coffee addicts out there) a cup of freshly brewed java to start their day? However, the bitterness of coffee is something most of us could do without.

Now chemists in Germany and the U.S. say they have identified the chemicals that are largely responsible for coffee’s bitterness. Their study, one of the most detailed chemical analyses of coffee bitterness to date, was presented this week at the 234th national meeting of the American Chemical Society [1].

coffee+apple.jpgContrary to popular belief, only 15% of coffee’s perceived bitterness is due to caffeine [1]. In fact, coffee is a complex mixture of chemicals and an estimated 25 to 30 compounds have been thought to contribute to coffee’s bitter taste. Surprisingly, however, the chemists found that coffee’s bitterness is due to two main classes of compounds produced during the roasting process; chlorogenic acid lactones and phenylindanes. Both compounds are antioxidants and are not present in green, unroasted coffee beans.

During roasting, chlorogenic acid, a polyphenol in raw beans, is converted to chlorogenic acid lactones. Further roasting results in the breakdown of the lactones to phenylindanes. The lactones are responsible for the mild bitterness of light- to medium-roasted coffee, while the second breakdown product, phenylindanes, produce the harsh, bitter taste of dark-roasted coffee.

Chlorogenic acid lactones have been known for some time to be produced by the roasting process [2], but their role as a source of bitterness was not known until now. Perhaps more importantly, the identification of phenylindanes adds to the growing body of knowledge investigating the health benefits of coffee.

What you say? Health benefits?

Indeed, coffee consumption offers a number of potential health benefits. The results of epidemiological research suggest that moderate coffee consumption may help prevent type 2 diabetes mellitus [3-4], Parkinson’s disease [5] and liver disease [6]. Although coffee consumption has not been found to be associated with significantly increased cardiovascular disease risk, it is associated with increases in several cardiovascular disease risk factors, namely blood pressure [7] and plasma homocysteine [8]. Some individuals may be more vulnerable to the adverse effects of caffeine in coffee, including people with hypertension, children, adolescents and the elderly. Nevertheless, habitual intake of caffeinated beverages may prevent heart disease in the elderly.

It’s been suggested that this research on coffee bitterness will lead to a “better cup of joe”. However, I wouldn’t be too surprised if the the compounds that give coffee its bitter taste also turn out to be responsible for coffee’s health benefits.


  1. Battling Bitter Coffee: Chemists Identify Roasting As The Main Culprit. ScienceDaily 2007 Aug 22.
  2. Farah et al. Effect of roasting on the formation of chlorogenic acid lactones in coffee. J Agric Food Chem. 2005 Mar 9;53(5):1505-13.
    View abstract
  3. Salazar-Martinez et al. Coffee consumption and risk for type 2 diabetes mellitus. Ann Intern Med. 2004 Jan 6;140(1):1-8.
    View abstract
  4. van Dam and Hu. Coffee consumption and risk of type 2 diabetes: a systematic review. JAMA. 2005 Jul 6;294(1):97-104.
    View abstract
  5. Ascherio et al. Prospective study of caffeine consumption and risk of Parkinson’s disease in men and women. Ann Neurol. 2001 Jul;50(1):56-63.
    View abstract
  6. Ruhl and Everhart. Coffee and tea consumption are associated with a lower incidence of chronic liver disease in the United States. Gastroenterology. 2005 Dec;129(6):1928-36.
    View abstract
  7. Noordzij et al. Blood pressure response to chronic intake of coffee and caffeine: a meta-analysis of randomized controlled trials. J Hypertens. 2005 May;23(5):921-8.
    View abstract
  8. Olthof et al. Consumption of high doses of chlorogenic acid, present in coffee, or of black tea increases plasma total homocysteine concentrations in humans. Am J Clin Nutr. 2001 Mar;73(3):532-8.
    View abstract
About the Author

Walter Jessen is a senior writer for Highlight HEALTH Media.


  1. Hmm – WordPress wiped my comment. Trying again:

    Thanks for writing this, Walter! I am an unabashed coffee addict. I’ll happily drink it in any way, shape or form – even with a knife when I worked the night shift and needed to stay awake during the early morning hours which should be wiped off the face of every clock!

    My only secret about brewing coffee is to grind the beans and commence the brew within 5 minutes of the grind. That seems to work for me.

    I appreciate your analysis and research on this oh-so-important topic!

  2. I have to agree N=1, a quick “grind and brew” is the only way to go. I’ve also found that I prefer the taste of coffee from beans that aren’t ground too fine.

    I wonder if anyone else thinks the first cup just after brewing tastes better than subsequent cups from the same pot?

  3. “I wouldn’t be too surprised if the the compounds that give coffee its bitter taste also turn out to be responsible for coffee’s health benefits.”

    I agree with that that statement. Just as dark chocolate has more of a bitter flavor to it than milk chocolate does, we’re told it’s the dark chocolate has that the better antioxidants.

    I drink both coffee and tea. You two talking about freshly ground and brewed coffee, makes me want to go make a cup right now.

  4. Great post, Walter, thanks. At the office here at Healia, we are definitely fans of strong coffee. Unsurprising, perhaps, as almost all of us live in Seattle. 🙂 I’ve been following the news about coffee’s health benefits with increasing interest.

    Have a good weekend!

  5. Geesh, sorry I messed up on my comment. I see I stutter and am dyslexic in text. he, he. Guess I should have had my coffee, or tea before commenting. 🙂

  6. Walter – Read about this a few days ago – who would’ve thought that drinking coffee would be beneficial. Yippie!
    Regarding your query as to taste of first cup vs. next cup – of course the first cup always tastes the best. Just like the first bite of a wonderful desert, or whatever. To insure your additional cups of coffee taste as best as they can, simply pour the pot of coffee into a pre-warmed carafe.
    Regarding grind – it makes a difference as to what kind of coffee maker you use. If your filter is cone shaped, the grounds should be finer, if the filter is basket shaped the grounds should be coarser. The reason is the flow of water through the filters are different. Most baristas prefer the cone shaped filters. Then there’s the question of French presses, percolators, and espresso machines. But that’s another story.

  7. After several years of managing a road side cafe and drinking pots of coffee every day; I gave up coffee for tea.
    I am glad to see that the references included tea in the studies because I have become addicted to the extra strong bergamot Earl Grey
    I get at a little known online tea shop I now drink several cups of tea a day and it doesn’t upset my system the way coffee used to.
    Thanks for the article.

  8. I used to drink strong coffee all the time Jonathan. As I’ve gotten older, it’s less and less potent. Like Chrysalis, lately I’ve been drinking both coffee and tea – coffee in the morning and tea later in the day, although some days I’ve gone entirely without coffee. Tea’s got some great health benefits too!

    Chrysalis, I had to read through your comment five times before I saw what you were talking about. Guess I should have read your comment *before* I drank all that coffee. 😉

    Morgan, when I work from home or on weekends, I do use a carafe. You’re absolutely right … keeping the coffee from oxidizing or burning makes a huge difference in taste! Your explanation of grind makes sense, I hadn’t thought about it from the viewpoint of the basket shape.

    Jerry, I’ve been working on an article about the health benefits of tea – I promise I’ll publish it soon. And thanks for the recommendation on the tea shop!

  9. Hi Walter,
    Really interesting chemistry this…..I love the thought that I am actually swallowing healthful, helpful molecules instead of the gunk that sometimes goes gullet diving. 😉 I was reading a while back about the possible (?) beneficial link between coffee and prevention of skin cancer. (link: Any idea how that one’s progressing? I am somewhat sceptical because my dear uncle died from malignant melanoma yet ran 10 miles every morning and drank a mug of black coffee on his return along with rehydrating himself with mineral water and an orange. He did live in San Francisco and I realise that one case that disproves the rule does not scrub the whole hypothesis…but, any thoughts?

  10. I think common sense has a great deal to do with how healthy a cup (or pot) of coffee can be. Obliviously if it is hopped up with a ton of sugar and creamer it might have a different effect than just straight black. Walter, thanks for the well written article! It is comforting that there is potentially some beneficial value to what I drink.

    If I understand correctly: the darker the roast, the higher the anti-oxidants. I do wonder if the process of decaffeination may remove some of the beneficial anti-oxidants and nutrients. I guess the next thing they could start adding is vitamins.

    I started to drink coffee at the office. The motivating factor: free. It was not the flavor. I figured that since it involved hot water it might be safer to drink than the local drinking fountain. I realized this logic was flawed in many ways, but it served me well and reduced the impact on the wallet.

    One thing I have noticed about coffee, that if the pot of coffee starts out extra bitter, that over a matter of 2 to 6 hours at a constant hot temperature, that it tends to mellow and sweeten out. I never wanted to dwell upon the cause of this change in flavor, but I would like to believe that it is linked more to oxidation than to bacterial changes. 😉

    This brings up a few interesting questions in itself.
    1) Is the use of Styrofoam cups more of a health hazard than its contents (ignoring its environmental impact)? Perhaps off subject?
    2) How bad is the sugar and creamer that is used? I think it is easy to weigh the effects of the added calories, but what about those “other” ingredients?
    3) Does the process of decaffeination remove some of the beneficial anti-oxidants and nutrients?
    4) What are the motivating factors that have lead to your daily preference for coffee? I would like to think I am not the only one who developed a taste for the beverage due to cost alone.
    5) Do artificial flavors really cover up the bitterness? Personally I find some flavors goes well with coffee, and others not so well. Chocolate never tastes right, and vanilla can tend to be too weak even when the aroma is very enticing. Some of the nuttier flavors tend to carry well along with Caramel Truffle. Of course the brand can have a great deal to do with the quality and richness of the added flavors.

  11. Very interesting Sisyphus. I missed that article. I looked over the paper referenced in the article and the authors essentially show three things:

    (1) Oral administration of low-dose caffeine together with running wheel exercise in mice had a greater effect on tissue fat – that is, decreased thickness of the dermal fat layer – than either treatment alone.

    (2) Oral administration of low dose caffeine (0.1 mg/ml) together with running wheel exercise in mice had a greater than additive effect in enhancing UVB-induced apoptosis (cell death), as measured by increases in apoptotic sunburn cells and caspase 3 (a protein that plays a central role in the execution-phase of cell death) positive cells, than either treatment alone. Additionally, high dose caffeine (0.4 mg/ml) was less effective than low dose.

    (3) Oral administration of low-dose caffeine together with running wheel exercise in mice had a greater than additive effect on UVB-induced formation of phospho-p53 (phospho-p53, or phosphorylated-p53, is the stabilized form of the protein tumor suppressor protein p53).

    p53 plays an essential role in the regulation of the cell cycle and mutations of p53 frequently occur in a number of different cancers. Following DNA damage, p53 is phosphorylated (stabilized), and its accumulation triggers expression of DNA repair proteins and proteins that stop the cell cycle.

    The implication of this research is that caffeinated beverages such as coffee together with exercise may be beneficial in the prevention of skin cancer by inducing cell death. However, none of this was shown by the study. There are a couple of things that come to mind that we need to remember:

    (1) Mice are being used as a model system for the human disease. However, what happens in mice may not happen in people.

    (2) Coffee was not tested, nor for that matter was the concentration of caffeine in a cup or two of coffee.

    (3) The incidence of cancer was not measured, rather the thickness of the dermal fat layer. In an earlier study, the authors found a significant inverse relationship between the number of tumors per mouse and the thickness of the dermal fat layer, suggesting a tumor-promoting effect of tissue fat.


    Lu et al. Voluntary exercise together with oral caffeine markedly stimulates UVB light-induced apoptosis and decreases tissue fat in SKH-1 mice. Proc Natl Acad Sci U S A. 2007 Jul 31;104(31):12936-41. Epub 2007 Jul 30.
    View abstract

    Lu et al. Inhibitory effects of orally administered green tea, black tea, and caffeine on skin carcinogenesis in mice previously treated with ultraviolet B light (high-risk mice): relationship to decreased tissue fat. Cancer Res. 2001 Jul 1;61(13):5002-9.
    View abstract

  12. Thanks for looking at that, Walter. It is a help for me to see your analysis of the research and makes good sense as well as giving me more to think about. I love this site!

  13. I sure hope drinking coffee has health benefits, I drink enough of it 🙂


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