Doctor's Note

The "coffee may reduce cancer risk" is a reference to yesterday’s video. There are additional cognitive benefits afforded by the phytonutrient theanine in green tea. See Dietary Brain Wave Alteration, and hundreds of other videos onmore than a thousand subjects. Note that the caffeine and pregnancy study is publicly accessible, so you can download it by clicking on the link above in the Sources Cited section.

Also, check out my associated blog posts for more context: Coffee CaveatsIs Caffeinated Tea Really Dehydrating?, and Treating Parkinson's Disease with Diet

  • Michael Greger M.D.

    The “coffee may reduce cancer risk” is a reference to yesterday’s video. There are additional cognitive benefits afforded by the phytonutrient theanine in green tea. See Dietary Brain Wave Alteration, and hundreds of other videos on more than a thousand subjects. Note that the caffeine and pregnancy study is publicly accessible, so you can download it by clicking on the link above in the Sources Cited section.

  • jkearns97062

    What about the risk of caffeine to cardiovascular health? Only recently, Dr. Caldwell Esselstyn started recommending that people avoid coffee with caffeine. “Several studies indicate it may contribute injury to the lining of the artery.” Thanks!

    • Michael Greger M.D.

      Great question! I addressed it in one of my Q&A blogs http://nutritionfacts.org/blog/2012/02/16/ask-the-doctor-qa-with-michael-greger-m-d-19/ earlier this year:

      AAs I detailed in my video The Power of NO, endothelial dysfunction is the first step towards atherosclerosis–our #1 killer–and so we need to keep the inner lining of our arteries healthy by any means necessary. Last year, a study entitled “Impact of Acute Caffeine Ingestion on Endothelial Function in Subjects With and Without Coronary Artery Disease” was published in the American Journal of Cardiology. They performed the most rigorous investigation to date, a randomized, double-blind, placebo-controlled cross-over study that found that caffeine significantly improved endothelial function. They concluded “In conclusion, acute caffeine ingestion significantly improved endothelial function assessed by brachial artery FMD in subjects with and without CAD and was associated with lower plasma markers of inflammation.” That was for the amount of caffeine found in about 2 cups of coffee, 4 cups of black tea, or 8 cups of green. Similar benefits were found previously at a higher dose (3, 6, and 12 cups respectively). So why do studies on brewed coffee, espresso, and energy drinks show negative effects? Well, there are a lot of other substances in these beverages besides caffeine, some of which may also be removed in the decaffeination process. Since there appear to be compounds in coffee that both impair and improve endothelial function (whereas in tea, both green and black, it appears to be all improvement), one might turn to epidemiological studies to look at overall risk and benefit of coffee consumption (see, for example, Coffee and Cancer and Update on Coffee). Though filtered coffee may be good, the evidence supporting the benefits of green tea are much stronger and more consistent. So I continue to recommend people drink tea instead of coffee, not because coffee is bad for you, but because green tea appears to be much better.

  • paul3917

    What about the studies that say it raises homocystine and blood pressure? And what about caffeine addiction and withdrawals: the rummy feeling until you get your morning fix, the headaches, irritability and compulsive coffee-seeking behavior. I’ve seen it in others and it isn’t a pretty picture. I never started the caffeine habit after observing it as a child in my father, how he tried and failed to quit, and I have no reason to start in now, considering that its supposed mild benefits are readily available by living a clean life and a diet full of fresh fruits and vegetables. I may not wake up fully alert, but I’m ready to take on the day within half an hour, even if I don’t go for my run first.

    • Toxins

      Dr. Greger addressed this to me too actually because I had a similair question. His response is in his blog post of Ask the doctor Q&A week 19

      “As I detailed in my video The Power of NO, endothelial dysfunction is the first step towards atherosclerosis–our #1 killer–and so we need to keep the inner lining of our arteries healthy by any means necessary. Last year, a study entitled “Impact of Acute Caffeine Ingestion on Endothelial Function in Subjects With and Without Coronary Artery Disease” was published in the American Journal of Cardiology. They performed the most rigorous investigation to date, a randomized, double-blind, placebo-controlled cross-over study that found that caffeine significantly improved endothelial function. They concluded “In conclusion, acute caffeine ingestion significantly improved endothelial function assessed by brachial artery FMD in subjects with and without CAD and was associated with lower plasma markers of inflammation.” That was for the amount of caffeine found in about 2 cups of coffee, 4 cups of black tea, or 8 cups of green. Similar benefits were found previously at a higher dose (3, 6, and 12 cups respectively). So why do studies on brewed coffee, espresso, and energy drinks show negative effects? Well, there are a lot of other substances in these beverages besides caffeine, some of which may also be removed in the decaffeination process. Since there appear to be compounds in coffee that both impair and improve endothelial function (whereas in tea, both green and black, it appears to be all improvement), one might turn to epidemiological studies to look at overall risk and benefit of coffee consumption (see, for example, my Update on Coffee). Though filtered coffee may be good, the evidence supporting the benefits of green tea are much stronger and more consistent. So I continue to recommend people drink tea instead of coffee, not because coffee is bad for you, but because green tea appears to be much better.”
      http://nutritionfacts.org/blog/2012/02/16/ask-the-doctor-qa-with-michael-greger-m-d-19/

    • http://www.facebook.com/joaoeiras João Eiras

      True. Caffeine has short term benefits, but continuous consumption will create dependency. However, the symptoms you describe are not typical from caffeine deprivation. I saw long time ago a small documentary about a study on caffeine deprivation (perhaps BBC, don’t remember). Two individuals, both had something like a liter of coffee a day. One of them was given decaf during a week. On the 3rd and 4th day, his aptitude for reflex and problem solving tests were at a all time low, he was fatigued, almost vegetative. 5th day he started recovering, on the 7th and 8th day he was normal, and the tests regular. The other individual suffered a bit of a placebo, also felt fatigued, despite the tests being regular during the entire week. I have in average two espressos a day. I have once deprived myself of coffee for two weeks, and I experimented the exact same symptoms. 3rd and 4th day very tired, hard to concentrate, fatigued. Then recovered and got perfectly ok.

      The point being, like all drugs, you get a boost if you have a decent dose caffeine while not being used to it. If you are used to it, then you need it to keep on doing your daily stuff, while not having the benefits of the boost a non-caffeine consuming person does.

  • ekgrey

    i have read that consuming caffeine within an hour of eating can negatively affect the absorption of many nutrients, particularly iron and various vitamins. as a vegan, i could be at risk for an iron deficiency, and though i do not believe that this is the case given my diet, i want to give my body the best chance of getting the most out of everything that i eat. so where do you stand on caffeine close to meals?

  • GeorgeI

    I read on Jack Norris’ site that caffeine contributes to osteoporosis. I love my tea, but I think I will be sticking to just one cup a day. Kale seems to be the most friendly vegan calcium source and it doesn’t “cut the mustard” against the recommended DVs for calicum and Norris thinks vegans need just as much calcium as omnis.

  • GM

    Well, all research points to how healthy the green tea is. I love it, the greener the better( sencha is my favorite). Unfortutanely I have discovered that I got addicted to it. I have troubles concentrating without it, very irritable too. I am from Russia and I grew up drinking lots of black tea. For 5 years in my 20ies I stopped all tea and anything with caffeine. After childbirth, I restarted drinking green tea and haven’t stopped since. I have developed chest pains and bone pain that goes away after I stop  drinking anything with caffeine( My doctor and I couldn’t figure out any other reasons-all tests were negative). I drink on average 4-6 cups of Organic Rishi Sencha( loose leaf, very grassy). I am 115 pounds and 5.4 so maybe I have developed a sensitivity to caffeine due to low weight and lower  rate of detoxification?  Regarding addictive quality of caffeine, do you think it is just with alcohol and alcoholics , who  can not stop after tasting a drop of it ?They often talk about benefits of alcohol or dark chocolate when ‘moderately  consumed’? But what is “moderation” to an addicted brain?

  • Jerome Kellner

    Dr. Greger, can you tell me where the caffeine added to drinks and non-drink products comes from? Or direct me to source that may answer this? My intuition is that it’s synthetic and about as safe as cyclamates. Or thalidomide.

  • Smitty

    I have A Fib, and was advised to avoid all caffeine. How about decaf green tea? Is it as healthy, and how much caffeine remains in the tea?

  • Fidel Castrati

    Even a single cup of coffee can raise anxiety to very uncomfortable levels for sensitive individuals. Caffeine is a drug which some people can tolerate much better than others.

    • LynnCS

      Keeping it simple, Fidell. Yes! Very uncomfortable. Buuuut, I am convinced it is something more than just the caffeine because I can have a little caffeine in other things, but noooo coffee. I am 5 days off coffee now, again, and can’t believe the relief. I am having some Yerbe Mate tea, but not the reaction I had with the coffee. Even if I had a half cup of coffee, I would be in such a state and light headed, bladder problems, and on and on, that I couldn’t stand to be in my own skin. I love it, but it’s a no go.

  • Leo

    In the case of serious research on the acute effects of coffee and caffeine, it is necessary, I think, to distinguish between the effects habitual caffeine drinkers experience and effects experienced by those who rarely or never ingest caffeine.

    When we habitually start drinking coffee, caffeine receptors are created on the cell walls. These receptors require regular caffeine. Similar mechanisms for other alkaloids.

    I think it’s quite comical to ascribe coffee an energizing effect, when coffee is the cause of the fatigue.

    My personal experience is this. I avoid coffee and caffeine drinks if I can. When I drink a cup of coffee, I can feel a very slight stimulating effect after 5-6 hours. That is all. I am fully refreshed and clear in my head when I wake up in the morning. The same absence of fatigue between meals.

    Maybe I’m an exception. I’ve been a vegetarian / vegan for 60 years.

  • http://www.facebook.com/ryanseaton Ryan 船 Seaton
  • Brian Whaley

    I’ve heard that it “drains your adrenals over time.” Is that laughable or…?

  • Sebastian Tristan

    What about the caffeine in tea and macha?

    • http://www.DonForresterMD.com/ Don Forrester MD

      Caffeine is less in tea than coffee and is absent in some teas. Some of my patients are very sensitive to caffeine and others not. Given the half life of about 6 hours if you consume 120 mg of caffeine( about 1 cup of coffee) at 9 AM you will still have 30 mg of caffeine in your blood at 9 PM. If you have trouble sleeping this could be a contributing factor. We have seen many detrimental things being attributed to caffeine over the years but most are due to the other things that coffee drinkers tend to do. From my perspective it depends on the individual but like many things as pointed out in this video… the dose is important. Even too much water can be fatal as one Sacramento area radio station found out in their contest…. hold your Wee for a Wii contest that Dr. Greger mentioned in one of his earlier video’s…

      • Sebastian Tristan

        My sleep doesn’t seem to be affected by caffeine too much. My only concern is health.

  • Kerry R

    Let’s be honest about our addiction and stop trying to justify it by claiming that it’s healthy. It’s not. The real reason we started drinking coffee was because of the kick it gave us. Now that we’re addicted to it, we no longer get that same kick, if any at all, we just drink it because we’re hooked on it and can’t function otherwise.