Image Credit: stevenharris / Flickr. This image has been modified.

Coffee Caveats

Last month in the American Journal of Clinical Nutrition, an editorial entitled “Coffee consumption and risk of chronic diseases: changing our views” reviewed the growing evidence that for most people, the benefits of drinking coffee likely outweigh the risks. For example, a recent analysis of the best studies published to date suggests coffee consumption may lead to a modest reduction in overall cancer incidence, as detailed in my 1-min. video Coffee and Cancer. Each daily cup o’ joe was associated with about a 3% reduced risk of cancers, especially bladder, breast, mouth, colorectal, endometrial, esophageal, liver, leukemic, pancreatic, and prostate cancers.

What about the caffeine, though? Glad you asked! Check out What About the Caffeine?

There are a few caveats. Some health conditions may be worsened by coffee, such as insomnia, anxiety, gastroesophageal reflux (heartburn), high blood pressure, and certain heartbeat rhythm irregularities. There are also compounds in coffee that increase cholesterol levels, but are effectively removed when filtered through paper, so drip coffee is preferable to boiled, French press and espresso. Pregnant women should restrict caffeine consumption to less than two cups of coffee a day.

Despite the growing evidence of health benefits associated with coffee consumption, I still don’t recommend people drink it—not because it’s not healthy, but because there are even healthier choices. In this way, coffee is like a banana, another common convenient plant product. If you have a choice, I’d encourage you to make healthier fruit choices (apples are better, berries are best). Similarly, when it comes to beverages, I’d encourage you to choose an even healthier one, like green tea.

One final note: not all routes of administering coffee are benign. Consider the title of a case reported in a medical journal last month: “Rectal Perforation…Caused by Rectal Burns Associated With Hot Coffee Enemas.”

Michael Greger, M.D.


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

32 responses to “Coffee Caveats

Comment Etiquette

On, you'll find a vibrant community of nutrition enthusiasts, health professionals, and many knowledgeable users seeking to discover the healthiest diet to eat for themselves and their families. As always, our goal is to foster conversations that are insightful, engaging, and most of all, helpful – from the nutrition beginners to the experts in our community.

To do this we need your help, so here are some basic guidelines to get you started.

The Short List

To help maintain and foster a welcoming atmosphere in our comments, please refrain from rude comments, name-calling, and responding to posts that break the rules (see our full Community Guidelines for more details). We will remove any posts in violation of our rules when we see it, which will, unfortunately, include any nicer comments that may have been made in response.

Be respectful and help out our staff and volunteer health supporters by actively not replying to comments that are breaking the rules. Instead, please flag or report them by submitting a ticket to our help desk. is made up of an incredible staff and many dedicated volunteers that work hard to ensure that the comments section runs smoothly and we spend a great deal of time reading comments from our community members.

Have a correction or suggestion for video or blog? Please contact us to let us know. Submitting a correction this way will result in a quicker fix than commenting on a thread with a suggestion or correction.

View the Full Community Guidelines

    1.  Headaches(ha) are common. It is important to correctly diagnose the type of headache you have. In my experience many patients who say they have migraines may be suffering from musculo-skeletal ha’s (most common ms ha’s  originate in upper neck and are felt along the back of the head or from temporal mandibular jt and felt on the side of the head). Caffeine withdrawal ha’s are another type of ha. Assuming the correct diagnosis of migraines… they are often associated with food triggers. In my experience avoiding foods that are high in tyramines( a naturally occurring compound which is also a breakdown product of the amino acid tyramine) is particularly helpful. It is particularly high in processed foods and increases in leftovers. The challenge is that it occurs in both animal products such as cheeses, processed and most meats and plant products such as nuts and snow peas. The best approach is to go on a plant based diet and when you get a migraine to list everything that you ate or drank within previous 24 hours. It does get tricky because it is the amount consumed that seems to be critical not stress. When under stress people tend to eat out, skip meals(thereby eating more when they eat) or eat leftovers. My patients always preferred avoiding migraines as opposed to treating them although they would occasionally “push the envelope a little for foods like chocolate”. Caffeine which is actually added to some old migraine treatments like “cafergot” seems to be able to trigger migraines but it can depend on the amount, type and brewing characteristics. Good luck.

  1. Lowrie, if you’re addicted to caffeine, for sure you’re going to get a migraine if you don’t have your coffee and you won’t be able to function until you get your fix. It’s not a nice situation and so, I wouldn’t start drinking coffee if you don’t now.
    I don’t see anything wrong with a banana. It’s a good source of vitamin B6 which neither apples nor berries have, manganese which apples don’t have and has equivalent amounts of dietary fiber and vitamin C to an apple or berries.   

    1. Coffee as with all plants don’t contain cholesterol. I don’t drink instant coffee but unless they add some animal product to it it should contain no cholesterol.

  2. it seems to me that any food or beverage that is habit forming and causes withdrawal symptoms when removed from the diet should never be considered as health promoting.

    Abstention from such products seems like a “no brainer’ to me.

  3. Hello Mr. Greger,
    Are you going to post any video on the possible reason for the higher incidence of colorectal cancer among vegetarians in the EPIC-Oxford study? Thank you!

    — Carlo

  4. Green Tea should be avoided when receiving treatment with Velcade for MM Cancer – it is proven to reduce the positive results. 

  5. I’ve reviewed Ray Kurzweil’s health guide.  Kurzweil is a very smart guy and very science literate, so in my mind there is, at least, a presumption of credibility.  He recommends an alkaline diet, and specifically recommends drinking alkalyzed water and avoiding coffee because of its high acidity.  Are you aware of any peer-reviewed studies supporting or opposing this recommendation?  Thanks very much, and thank you for your extremely credible and purely science-based recommendations.  

    1. Dr. Greger covers alkalized water here

      as for alkalinity,

      Almost all plant foods will produce a potential renal acid
      load (PRAL) that is negative (alkaline) because of the amino acid
      makeup. Grains are very slightly acidic but most animal products are
      several times times more acidic. The PRAL can be calculated with this
      formula PRAL = 0.49(Protein) + 0.037(Phosphorus) – 0.021(Potassium) –
      0.026(Magnesium) – 0.013(Calcium).


      You can go to the USDA nutrition database and calculate the
      alkalinity or acidity of certain foods this way using a 100 gram
      serving sample.


      Here are a list of common plant foods. A negative number indicates alkalinity whereas positive means acidity.


      Cereals, oats, regular cooked with water, w/o salt/ 2.18

      Bananas, raw/ -6.93

      Blueberries, raw/ -1.04

      Rice, brown, long-grain, cooked/ 2.18

      Broccoli, cooked, boiled, drained, w/o salt/ -3.57

      Cauliflower, cooked, boiled, drained, w/o salt / -1.33

      Carrots, cooked, boiled, drained, w/o salt/ -4.10

      Peaches, raw/ -3.11

      Beans, kidney, cooked, boiled, w/o salt/ -0.69

      Kale, raw/ -8.34


      Animal Foods


      Chicken, broilers or fryers, breast, meat only, cooked, roasted/ 17.30

      Egg, whole, raw, fresh/ 9.43

      Fish, salmon, Atlantic, wild, cooked, dry heat/ 7.57

      Beef, bottom sirloin, tri-tip, separable lean only, trimmed to 0″ fat, choice, cooked, roasted/ 12.79

      Cheese, cheddar/ 19.00


      As you can see, all animal foods are acidic. This acidity is bad for
      our bones as explained by this study. “In response to chronic acid
      stress such as is imposed by an acid-ash diet, cellular responses
      mobilize bone and calcium as a buffer.”


      This acidic environment increases the production of cortisol which further diminishes bone density.


      This chronic acid load people put on their body causes bone loss leading to osteoporosis later on in life.

  6.  If coffee has some health benefits, it’s probably due to its high content of  chlorogenic acid, an antioxidant which in the amounts in coffee may hinder iron absorption. Foods with more reasonable amounts of chlorogenic acid include green tea, sunflower seeds, artichokes, blueberries, cilantro, carrots, tomatoes and peanuts. Coffee also has its downside. I agree with Jaxon ” that any food or beverage that is habit forming and causes
    withdrawal symptoms when removed from the diet should never be
    considered as health promoting. Abstention from such products seems like a “no brainer’ ” There are many foods and beverages, such as those above which are better to eat and drink

  7. I am little conflicted your other video seems to imply you have no problem with coffee but here you say drink green tea instead? Maybe it would be good to write in the description of the video that you think that while coffee isn’t that dangerous that there are better choices. As the video implies coffee is healthy. Maybe do a more recent video saying which drink is the healthiest to drink… or the top selection of drinks that are best. And to remind people balance is key. Drinking multiple drinks.

  8. Hi Dr. Greger,

    I noticed your articles about coffee:

    However you are missing an elementary factor that could explain why people would live longer while consuming coffee despite it being bad for you:
    Those who consume the most coffee tend to have higher incomes. These population studies are biased because comparatively wealthier professionals drink more coffee. For example, lower tier jobs often don’t have break rooms or areas with a coffee maker available and you cannot just make a cup and drink it anyway even if you have an on-site coffee maker. It is well known that having more wealth and higher job autonomy leads to better health outcomes because such people have more control over their lives, they have more optimism, stronger self-belief and also much less stress, but the poor have everything against them in those regards. See Susan Rosenthal’s free e-book “Power and Powerlessness”:
    for more detail about how economic factors and workplace autonomy impact health.

    Here is evidence of the income disparity involved in coffee consumption:
    “Demographic and Preferences of Coffee Drinkers in America”

    “Coffee Use Increases with Household Income
    “Seventy percent of Americans who report annual household incomes of $150,000+ drink coffee compared with 54% of those with household income less than $25,000.”

  9. Dr. Greger,
    What can you tell us about acrylamide in coffee? The American Cancer Society says acrylamide can be found in “potato products, grain products, and coffee.” Thank you.

  10. Please respond to this regarding coffee:

    Coffee: more addictive than pot – and more toxic

    Coffee is a strong psychoactive drug; its direct pharmacological effects are more powerful than those of cannabis. Dependence on it has a marked physiological component. In objective terms, coffee is a stronger drug than pot, with a greater potential for toxicity.

    Coffee is a powerful stimulant drug, causing dependence (even 1 cup/day) and illness – bladder irritation, stomach upset, headaches, anxiety, restlessness, heart palpitations, insomnia, elevated serum cholesterol, hypertension, prostate problems, etc.

    Coffee contains 39 alkaloids, decaf coffee 38. And these are not inert, producing the same health problems as regular coffee.

    Coffee’s true identity as a drug has been defined out of existence – socially and legally – but it is a powerful drug with serious health consequences.

    –Dr. Andrew Weil
    From ‘Natural Health, Natural Medicine’ (1995)

    1. You are asking us to respond to many questions about article written on coffee. I feel you are concerned with coffee but I am not sure what kind of response you are looking for Dr. Greger clearly references the studies in the “sources cited” if you have issue with a specific one please let me know I’ll do my best to clarify. I do appreciate your posts!

  11. Please respond to this article:

    Decaf gives the same kick as regular coffee

    Jeremy Laurance Health Editor
    November 19, 2002

    It may be a decaf but it still carries a kick. Scientists studying coffee have found that a triple espresso has a marked effect, regardless of whether it contains caffeine.

    The beverage caused an increase in the activity of the nervous system in both occasional and regular coffee drinkers, and the blood pressure of occasional drinkers rose.

    Roberto Corti, a cardiologist at the University of Zurich who led the study of 15 volunteers, said it was the first time such disparities had been reported. He said the results, published in Circulation, the journal of the American Heart Association, suggest an unknown ingredient in coffee other than caffeine stimulates the heart. Coffee contains hundreds of different substances.

    “Until now we have attributed the cardiovascular effects of coffee to caffeine, but we found non-coffee drinkers given decaffeinated coffee also display these effects,” he said. “This demonstrates how little we know about the effects of one of our most popular beverages.”

    One implication of the findings is that the potentially adverse effects of coffee on the heart could be less hazardous in regular drinkers with normal blood pressure. Whether people with high blood pressure should avoid decaffeinated coffee remains unclear.

    1. The link does not appear to work. Can you find the actual studies and post here? I’ll be sure to investigate. Thanks, Bortog

  12. Although coffee is brewed and filtered, there is still this probelm:

    Crisps and coffee highest acrylamide levels, warns U.N.

    07/03/2005- A global risk analysis of nearly 7000 food items finds French fries, potato crisps and coffee recording the highest contamination levels of the carcinogen acrylamide, warns UN committee, writes Lindsey Partos.

    Scientists from 15 countries meeting under the aegis of JECFA, the UN’s committee on food additives, caution that the harmful contaminant acrylamide in certain foods may be of public heath concern since it has been shown to cause cancer in animals.

    In April 2002, acrylamide came to the attention of the food industry when scientists at the Swedish Food Administration first reported unexpectedly high levels in fried, baked, grilled, toasted or microwaved carbohydrate-rich foods, for example chips, roast potatoes, crisps and bread.

    Since then, an international effort of more than 200 research projects has been initiated around the world with their findings co-ordinated by national governments, the European Union and the United Nations.

    In the absence of any health-based guidance values (tolerable intake levels) for acrylamide, and a bid to construe a way forward to slicing this potential carcinogen out of the food chain, scientists meeting in Rome last month assessed national dietary intake data for 17 countries.

    “The major contributing foods to total exposure for most countries were potato chips (16-30 per cent), potato crisps (6-46 per cent), coffee (13-39 per cent), pastry and sweet biscuits (10-20 per cent) and bread and rolls/toasts (10-30 per cent). Others foods items contributed less than 10 per cent of the total exposure,” the committee reports.

    Tackling this figure, the UN group urged national food safety authorities to work towards improving food preparation technologies that “lower significantly the acrylamide content in critical foods.”

    Acrylamide appears to form when dietary items, typically plant commodities high in carbohydrates and low in protein, are subjected to high temperatures during cooking or other thermal processing.

    Scientists now know that the most important precursor is the free amino acid asparagine which reacts with reducing sugars in the Maillard reactions that also form colour and flavour.

    Since 2002 research has shown that although trace amounts of acrylamide can be formed by boiling, significant formation generally requires a processing temperature of 120 C degrees or higher.

    Most acrylamide is accumulated during the final stages of baking, grilling or frying processes as the moisture content of the food falls and the surface temperature rises, with the exception of coffee where levels fall considerably at later stages of the roasting process.

    Acrylamide seems to be stable in the large majority of the affected foods, again with the exception of ground coffee for which levels can decline during storage over months. Since formation is dependent on the exact conditions of time and temperature used to cook or heat-process a food, there can be large variations between brands of the same product and between batches of the same brand. Large variations are also to be expected during cooking although this aspect has been less well documented.

    The composition of the food also has an influence, crucially the content of free asparagine and reducing sugars. Varietal, storage and seasonal variations can occur. Within ranges of natural variation, the limiting precursor in cereals is asparagine while fructose and glucose are more important in potatoes. Other important factors are pH and water content.

    In a review submitted to the UN group by Europe’s €600 billion food and drink industry (CIAA) apparently recent investigations have achieved a 30 to 40 per cent reduction in acrylamide levels of potato crisps by introducing several adjustments in the existing production procedures.

    But the UN committee states: “The detailed data behind this calculation were not reported and it is not known to what extent it has been applied by crisp producers.”

    Significant reduction was also reported from process-optimisation for non-fermented crispbread, while little progress was obtained so far in reducing levels in various other important intake sources, for example, roasted coffee and breakfast cereals.

    According to findings from the additive group the most efficient reduction has been achieved by using the enzyme asparaginase to selectively remove asparagine prior to heating.

    “Although tested both in cereal and potato models, the use is probably limited to specific food products manufactured from liquidised or slurried materials,” says the group.

    Several other means of lowering the precursor levels can be applied at various stages of the food chain, for instance, by variety selection and plant breeding, controlling growth and storage factors affecting sugar concentrations in potatoes, pre-treatment of potato pieces by soaking or blanching, and prolonged yeast fermentation time in breadmaking.

    Other mitigation possibilities include alteration of the product composition: addition of competing amino acids or acidic compounds, and alteration of process conditions – lowering the frying temperature.

    But a key obstacle to this progress is the fact that the feasibility of adapting these methods to large-scale food processing has not been ‘completely studied’ in most cases.

    Furthermore, any major changes would need to be checked for consumer acceptability, nutritional quality, and the possible increased formation of other undesirable substances.

    In its final recommendations, the committee urged: continued efforts to cut acrylamide concentrations in food; and continued work on using PBPK modelling to better link human biomarker data with exposure assessments and toxicological effects in experimental animals.

    In addition, the committee highlighted the need for more occurrence data on acrylamide in foods consumed developing countries.

    1. Thanks for the information! Feel free to share any studies on coffee and acrylamide here. We’ll look into!

  13. ~Trying to divorce the effects of caffeine contained in their perspective sources from everything else therein, and placing them on opposite sides of the scale, weighing the so called “pros against cons” is as futile as weighing refreshing water against its impurities in polluted tap. You cannot do it. Whether the stimulant acts suddenly or stretched over a time released process, its use of the system has the same result. That which is consumed is also assimilated. The seeming positive effects are nothing more than the excitability behaviors of the “” stimulant. It is a positive evil. Taking that which promotes healing and repair along with a counter agent as in the healing properties of green teas as well with the caffeine, is like putting together a puzzle of a healthy system, and at the same time tearing it apart.

    I would like to hear your thoughts on issues such as California passing regulation laws placing cancer risk warning labels on coffee.

  14. Does caffeine negatively affect people’s microbiome? Some research shows coffee grounds shouldn’t be used in the garden because it slows plant growth, kills worms, and harms microorganisms in the soil. Not sure if decaf does the same. And cocoa and tea have caffeine, too.

    Then I wonder if it can be used to remove parasites from the digestive tract. And, would it work on my rescued chickens or goats?

Leave a Reply

Your email address will not be published. Required fields are marked *

Pin It on Pinterest

Share This