Doctor's Note

For more on the subject, see Human Neurotransmitters in Plants.

For more context, see my associated blog post: Raspberries Reverse Precancerous Lesions.

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  • Veguyan


    How can we believe in any study? It seems they can always refute each other.


    By Marc Kaufman
    Washington Post Staff Writer
    Friday, May 26, 2006
    The largest study of its kind has unexpectedly concluded that smoking marijuana, even regularly and heavily, does not lead to lung cancer.

    ScienceDaily (Apr. 17, 2007) — The active ingredient in marijuana cuts tumor growth in common lung cancer in half and significantly reduces the ability of the cancer to spread, say researchers at Harvard University who tested the chemical in both lab and mouse studies.

    • John Furr

      It’s not conflicting data. The 2007 study used cannabis extract. If you want to get that same effect then you should juice a few ounces of marijuana and drink that daily. Unless you heat it the THC won’t be activated and you won’t get high..or in the case of consuming a few ounces you won’t pass out for a few day’s.

      Smoking marijuana does not provide you with nearly enough cannabinoids and you still get all the toxic effects of smoke.

      If you are going to use recreationally then either eat (after heating it..brownies) it or vaporize it to minimize the harmful combustion products.

      • Jordan

        What about vaporizing marijuana?

        “Pulmonary function in cannabis users: Support for a clinical trial of the vaporizer.”

        “These preliminary data reveal meaningful improvements in respiratory function, suggesting that a randomized clinical trial of the cannabis vaporizer is warranted. The vaporizer has potential for the administration of medical cannabis and as a harm reduction technique.”

  • Veguyan

    WELLINGTON, New Zealand, Jan. 29 — Smoking a single marijuana joint may be as carcinogenic to the lung as 20 tobacco cigarettes, researchers here determined.

    ScienceDaily (Jan. 27, 2008) — A new study finds that the development of bullous lung disease occurs in marijuana smokers approximately 20 years earlier than tobacco smokers.

    ScienceDaily (Aug. 5, 2009) — In a finding that challenges the increasingly popular belief that smoking marijuana is less harmful to health than smoking tobacco, researchers in Canada are reporting that smoking marijuana, like smoking tobacco, has toxic effects on cells.

    • Damien

      All of these, tests were done on Chimpanzees, the only way to “Make” Them smoke a marijuana cigarette is to FILL the room with smoke until they dont breath anything but smoke, further causing respiratory problems, so on so on, the actual effects of Marijuana are much less harmful then smoking Tobaco, i got cancer from smoking tobaco, and got cured by….you guessed it, MARIJUANA

    • Richard K

      wrong! get reading! I’m sooo in Cannada and you gotta read the wholes studies eh! And remember they are controlled studies by corps. and gov.s to make their drugs be in the best light. Veguyan you will be convinced of radiation and chemo, nothing I can do about that other than to get you to trust the earth dude. Be your first opinion. Meducate yourself! .trythis …

  • Veguyan


    • Michael Greger M.D.

      Thank you for bringing up this important larger point. What does one do in the face of conflicting evidence? The answer is to look at the balance of evidence and ask yourself before making any decision “What does the best available evidence show right now?” Unfortunately, sometimes the media fails to put new study results in context and so you get this kind of intellectual whiplash back and forth. In terms of the purported link between smoking cannabis and lung cancer, although doubts have been raised, the latest review continues to raise strong concerns. It seems smoke inhalation is not good for your lungs, whether from a burning building or bogie.

      • Ryan 船 Seaton

        What about the benefits of medical cannabis or drinking marijuana tea etc ? ie vs smoking it ? Currently discussing this on my Facebook page …

        • Andrew Cerone

          To Ryan.. I have the same question. Smoking anything is bad, so that does not make marijuana bad. Im sure smoking GREEN TEA is bad! We seem to be avoiding the question of whether or not the cannabinoids in marijuana are bad themselves, not the smoke. Why has this not been addressed?

          • Ryan 船 Seaton

            Hey Andrew, thanks for reminding me about this post. Cannabis Sativa (Ganja/Marijuana/Weed) has a greater deal of complexity in regards to the cannabinoids that have been found to have medicinal value with continuing studies suggesting its usefulness against diseases such as cancer and maybe more.

            HOWEVER, regarding NUTRITION, Cannabis Indica is of more interest to me as its a complete protein with only between .03-1.5% of the psychoactive compound known as Delta-9-Tetrahydrocannabinol (THC) which has higher concentration of between 5-10% in Cannabis Sativa. Since most if not all of the THC is removed in Industrial Hemp (aka Cannabis Indica) , I would like to see more nutrition facts about Hemp Milk and Hemp Seeds which imported to us here in Jamaica from America and (mostly ) Canada. Oh the Irony ….

          • Nuno MS

            …ah, sorry, it’s the other way around… C. indica is in THC than C. sativa…

      • TheLance3185 .

        Bogie. HAHAHA! How West Coastal of you.

      • Jordan Jordan

        What about cannabis vaporization?

        • REDCOMMIE

          EXACTLY! But no they will not see your question. Their aim is to LIE about cannabis effects. Ant this video is so obviously wrong that its actually funny.

  • Donna Magrina

    what? one cig of marijuana causes cancer? Breathing air not smoke is definitely better; even so, I have a hard time believing one marijuana cig does all that damage

    • psychwoman1

      That is not what the statement is. The statement basically is that one joint is equal to roughly 20 regular cigarettes.


        Yes and that statement is almost the same as saying that one joint causes cancer because if you could smoke one pack of cigarettes in the time needed to smoke one cannabis joint you would surely go into coma! So quit pretending you don’t see the fallacy in this video because it’s wrong in so many ways.

  • HereHere

    Anyone who thinks that incense is ‘cleaning the air’ is completely delusional. As the Dr says, any kind of smoke inhalation is not good for your lungs. This is due to the toxicity of small particulates. I heard a lecture about small particulates about 15 years ago from an air quality expert. By the way, to all smokers, it makes your breath, your clothes, your car, and your house smell very bad, too. You can’t really cover up the smell, it still seeps through the other smells, but your nose is used to the smoke, unlike everyone else’s noses.


      More than 1000 (one thousand) carcinogenic compounds found in regular cigarettes and not ONE beneficial for your body! Cannabis? More than 400 cannabinoid (btw, word “cannabinoid” is not in auto correcting dictionary on this website so that says a lot about who these guys are) compounds in one cannabis joint and just a few carcinogenic particles made by burning the plant and those are almost the same for burning any other plant. Tobacco is one of the most dangerous plants when it comes to smoking it. Cannabis is one of the least dangerous ones. So quit pretending you don’t see what this video is about.

  • justsomedude

    It seems like eating or drinking cannabis would be safer and healthier. That’s why “a friend of mine” always eats his pot.

  • Procyan

    So we should you know smoke tea right, heh

  • kerleyc

    Hi Dr. Greger…excellent information, as usual. I’m just wondering are there other foodstuffs which can influence cannabinoid receptors? Thanks…

  • Charles Worl

    decaf or regular!?!?!?!?!?!?!?!

  • Aksel

    Hey, does herbal teas ( like hibiscus tea ) stimulate endocannabinoid receptors too? or in the video does all kinds of tea stimulate them?

    • Dr. Connie Sanchez, ND

      Herbal teas, such as hibiscus, are not truely teas because they are not part of the Camellia sinensis family. Teas in that family, such as green and white tea, contain catechins. Catechins stimulate cannabinoid receptors found in the brain.

  • Francesca

    Dr. Greger I have a question. The fat foods stimulate the endocannabinoid receptors and they cause a sort of addiction, why we can’t stop eating chips but we don’t feel the same when we drink green tea?

  • Becky

    Can you do more videos on all aspects of marijuana and its different forms of consumption


      No they cannot because it would be too obvious that they are lying like it is in this video.

  • Simon


    I don`t have the patience to read all the comments. :)

    So, you maybe have get this question before; Is it just tea thats stimulates cannabinoides?

    Or are there any other supplement or food that stimulates cannabinoides?

    Kindly regards/ SImon

  • Mirko
  • Frank

    There is NO evidence that smoking marijuana causes cancer.

  • mark

    What about smoker’s vaporizors?.. which can be used with marijuana extract cartridges.

  • Sebastian Tristan

    What about Marijuana tea? Meaning, what about when Marijuana is not smoked but drank? I’m not a user and neither for or against, I’m just curious.

  • Kosmos

    Ah, there is a documentary I watched today about medicinal marijuana and they don’t recommend smoking it for treatment BUT said that there was an epidemiological study that found no connection between smoking marijuana and lung cancer.

    Just wonder who has the write info here Doc.

    This is the doco I watched –

    I think its somewhere in the second half they cite a study they did to find that.

  • NoSmokin

    I was discussing medical marijuana use with my neighbor, who said that a Dr. William Courtney M.D. advocates drinking un-heated juice that is juiced or blended from cannabis leaves. The doctor asserts that CBD and THCA are powerful antioxidants that are beneficial in the treatment of many forms of cancer.

    Your thoughts Dr.?

  • Jay

    Isnt that study talking about cannabis cigs that are mixed with tobacco? because my friend told me about a study that sounds very similar to this and when I googled it I came across some info that what the study failed to mention was that in england (where it took place I guess) they add tobacco to the cannabis mix, and because when you smoke weed you hold it into your lungs, mixing it with tobacco makes it to where you are not just holding cannabis in your lungs but also tobacco! and holding the tobacco is the reason for the increased risk of cancer, since cig smokers never ever hold in a cig but they do when its mixed with the cannabis in an attempt to hold in the goodys.

  • Jonathan Ahern

    I invite anyone interested to do further research into: smoking cannabis and lung cancer; ingesting raw cannabis; cannabinoids present in cannabis and their effects; us government patents on cannabinoids. It’s mind blowing (even without smoking it) what this plant is capable of, despite how it was demonized for decades.

  • Poster

    What about eaten cannabis or eaten CDB(non-carboxylated non-THCA active) or cannabis oil (descarboxilated THCA active)?

  • Visibleperson

    have there been any documented cases of lung cancer in people who only smoke marijuana & not cigarettes?

  • Jane’s Addiction

    Now that cannabis has become legal in more states and in more contexts, what if anything is known about the health benefits or risks of consuming cannabis or cannabinoids that have been absorbed into cooking oils, as is done in edible cannabis foods (marijuana brownies and the like)? Is any of the cancer danger that we see in cannabis smoke lessened or eliminated if the cannabis is consumed as a food instead of as smoke? (Obviously, there are health concerns associated with eating brownies at all, since they’re typically made with refined flour, sugar, and oil, so my question is more to do with the cannabinoids alone and not with the risk that’s inherent in eating refined oils and the like.)

  • Arjan den Hollander.

    Too good not to share:

  • Jimmy Johnson

    I would suggest, that when your videos become outdated, as your sources to support them, please remove them so you’re not passing on false claims.

  • Pim

    How do you feel about this article on fasting regularly to stimulate white blood cells during chemo treatment. it sounds a bit counter productive. But anything is a worth a go.

  • newjumpswing

    Aloha,While I agree 100% that smoking anything is bad for your health, I would think that Jamaican Rastafarians would all be dead or dying by now if the one joint equals 20 cigarettes were completely true. Here is a group for which one joint (spliff) would be the equivalent of 5 regular joints. If this particular study were to be validated, I would think research on Rastafarians in Jamaica would tell the tale. Something to remember, the diet of Rastafarians is Ital (plant based). A big concern for me is people who are rolling cannabis with tobacco leaf or cigars( blunt).

  • dorange

    Is this true to white tea, too?

  • Wade Patton

    Study finds no relationship between habitual cannabis smoking and lung cancer risks:

  • newjumpswing


    While I completely agree that the smoking of any substance introduces pollutants and irritants into the lungs, there are not only ways to reduce those pollutants(vaporizer, water pipe with baking soda or granulated charcoal) but just as importantly, there are no studies to date to show where Jamaican Rastafarians have the highest rates of lung cancer in the world.If a joint is equal to a pack of cigarettes, then a spliff should be equal to a carton! Rastas should be extinct by now. How do you explain the fact that they are not?Could it be that the Ital diet(vegetarian) of the true Rasta is negating the negative effects of smoking large quantities of cannabis? Foods of the islands such as mango. papaya,sorrel(hibiscus),sweet potatoes are all part of the local diet and very much a part of the Ital diet.A good comparison of health effects would be Rastas who use water pipes and those who use tobacco leafs to roll their cannabis.Also those who practice Ital and those who don’t.

  • Blaice

    Webmd still states That out of over 2,000 people (half with cancer) even the most habitual marijuana smokers did not get, or have, lung cancer. It seems the subject really needs to be studied more. I’m not advocating smoking, but comparing a single joint to a pack or more of cigs with things like formaldehyde, urine, nicotine, etc. in them seems a BIT far-fetched to say the least.

    This study almost seems like it was funded by the tobacco industry, which would not surprise me. I did read the paper, which is about two pages long.

    I’d agree with Jimmy Johnson that videos like this should be removed or reformulated to reflect true validity.


    Ok, ok, ok… Smoking is obviously the worst thing you can do to your body along with drinking alcohol. BUT!!! Saying that ONE cannabis joint makes damage to your health a one pack of cigarettes is just a plain and obvious LIE! Cigarettes these days are filled with all sorts of chamicals foe a nuber of reasons from flavoring to faster burnout of cigarettes. Also tobacco is one of the poisonous plants in nature that you can smoke and not drop dead immediately after. So to say that a cannabis joint which in it self contains a very beneficial cannabinoids and terpenes is 20 times more dangerous than a tobacco cigarette which contains ZERO beneficial compounds is so wrong and an obvious LIE. I say LIE! And this guy is obviously a well educated nutritionist so he must know he is wrong and he is purposely misinforming the public about cannabis smoking effects. People who already had cancer from smoking cigarettes start coughing it out when they start smoking cannabis joints. There are a lot of examples of that. If you need any information do not hesitate to contact ANYONE WHO IS A CANNABIS ACTIVIST and they will overwhelm you with evidence of cannabis smoking CURING LUNG CANCER. Not the opposite.

  • Michael Suede

    A nice rebuttal to the Aldington study claiming cannabis smoking causes lung cancer.

  • Reason

    Nutrition facts continuing to support this refuted and flawed study ruins your credibility on other topics. Just like the US govt listing of cannabis as a schedule one drug along side heroin when the science is clear that it is neither highly addictive and does has medical value. I turn to this site to getting the BS free data and scrutiny of junk science with an agenda. Disappointing really.