Skeptical Raptor's Blog hunting pseudoscience in the internet jungle

Despite the meme on Facebook, bananas do not cure cancer


This article was published on 29 July 2012, and has had over 70,000 views. This is the number one article I’ve ever written, I enjoyed writing it, but I never thought it would be such a big hit. It basically arose from a meme I saw on Facebook that claimed that bananas with dark spots had anti-cancer compounds in it. And it was all based on a misreading of a published article, a lack of knowledge about tumor necrosis factor, and a complete misunderstanding of human physiology and immunology. And this is my number 1 favorite, and number 1 most popular article for 2013.


Note: this article was rewritten and revised–please read and comment on the updated version of this article.


Last year, I wrote an article about how to critically analyze pseudoscience and misinformation to get at the scientific evidence which may help you accept or reject something you might read on the internet, even if it appeared to be accurate. On Facebook, Twitter and many internet sites (including Wikipedia), there is an amazing tendency of individuals to accept what is written as “the truth” without spending the effort to determine if what is written is based on accurate science. Twitter, of course, limits itself to 140 characters, which means you either have to click on a link to get more information, or just accept that the 140 characters are factual. And if you can make a complex scientific argument in 140 characters, I’m impressed.

Facebook is filled with false memes on just about everything from politics to medicine. The anti-vaccination crowd fills Facebook with their amusing and highly inaccurate memes. For more than a year, there have been dozens of  photos of bananas with a few words that some Japanese scientists claim that ripe bananas have high levels of “tumor necrosis factor“, so eat bananas to cure cancer and maintain a healthy immune system. Facebook is famous for these things, little pictures with a few words, no sources of the information, and broad conclusions. Eat bananas. Cure cancer. And people share them with a click of the button and move on to the next cute cat picture. It’s really the lazy person’s way of learning. Although who doesn’t enjoy the cute cat pictures?

bananas-tnf-newBut what are the facts? What can bananas do nor not do? Let’s start at the beginning.

The mysterious Japanese Study

The actual study was published here (pdf) (or here, also pdf) in Food Science and Technology Research in 2009.  I have several issues with the article with respect to the banana meme, especially in trying to make any conclusion that bananas have anything to do with “curing cancer” in humans:

  1. The authors do not make one single claim (as best as I can tell) that there is tumor necrosis factor in a banana. No, this article does not say anything about bananas having TNF. Really, nothing else I write about this article really matters, because they just don’t make any claim whatsoever about TNF and bananas.
  2. The study is in a mouse model, and many animal model experiments just don’t transfer to human clinical research. It’s not that it is impossible, but until it does, it’s difficult to make an appropriate prediction from such an experiment. So, even if the authors claimed that bananas had TNF (and that would be Nobel Prize winning research), we have no clue as to whether it has any clinical impact. But let’s not forget that the authors make not a single claim that TNF is in bananas.
  3. The article is published in a low impact journal. This journal has an impact factor of less than 1.0, which indicates a very low quality journal and it’s not even indexed in PubMed, which further indicates its low value.
  4. The bananas are not fed to the mice, the are injected into the peritoneal cavity. I am not sure why the authors did that, and I am unclear what it is supposed to prove. That it induces TNF activity might be expected since the body would react to any foreign substance (an apple, viruses, bacteria, anything) injected into the peritoneum, and production of TNF might be expected. But the TNF does not flow out of the banana, it is just the immune system’s reaction to a banana injected into the body.
  5. What is the clinical significance of what was induced? In other words, is there actually TNF isolated from the bananas in a form that actually can do something? Or is there some other effect just because there’s a blob of intraperitoneal banana extract which induces some other immune response.
  6. Bananas produce small amounts of serotonin (5-hydroxy tryptamine) and dopamine, depending on their stage of ripeness. These can have a stimulatory effect on neutrophils and macrophages in a living organism, and these can in turn produce the touted TNF-a, Interleukin-12 (IL-12) and other cytokines. In this role serotonin and dopamine are said to serve as a “biological response modifier” (BRM). In plain English, the stuff in ripe bananas can (but not necessarily will) stimulate a subset of white blood cells to produce chemical signals to deal with a variety of threats. However, this is a small effect, and it will not help you fight off cancer.
  7. No one has repeated this experiment, and certainly no one has shown this effect in humans. There is not a single double-blind clinical trial to show that bananas induce a TNF-alpha response in humans. And one more point to remember: bananas do not produce TNF. It is simply an evolutionary impossibility, unless through some amazing instance of evolutionary convergence, the banana plant evolved the ability to produce the TNF molecule for a completely different purpose for the banana plant. This would violate several principles of evolution, since there are reasons why the TNF molecule evolved in mammals and not in plants.
Let’s ignore the paper, let’s focus on the TNF producing bananas!
Let’s review–I dug up the original “Japanese scientific paper”, and what I found was essentially simple–bananas do not produce TNF, but that wasn’t even the point of the article. Whether the article has some future relevance into the study of the immune system is unknown, but through a completely ignorant reading of the article, people keep pushing the point that bananas cure “cancer.”
So let’s look at this pseudoscience even more carefully:
  • The “Japanese scientists” made no claim that there’s TNF in a banana, but the junk medicine pushers continue to make the claim, facts be damned. The problem is that anyone with a basic comprehension of biochemistry would understand that tumor necrosis factor (TNF) is a fairly complex protein, with a highly specific role in the human immune system (something notably lacking in a plant), so the chances that a banana would have some substance that exactly mimics or copies TNF is so tiny as to be close to impossible. A banana has no need for TNF, since it lacks an immune system of a vertebrate, so evolving a complex protein like TNF would be crazy; in fact, if it did, we’d have to rewrite our understanding of evolution. Let’s make this clear–we don’t have to rewrite evolution, because there is no TNF in bananas.
  • Even if we could assume that a banana makes TNF, the digestive tract would break down the complex proteins and substances, such as TNF, into its constituent components, such as amino acids, simple sugars, and fats, before being absorbed into the bloodstream. The TNF probably wouldn’t survive intact within the digestive tract. The true scientific skeptic would, even if they thought that maybe a banana evolved a TNF molecule by some strange mechanism, know that it could not enter the body.
  • Since TNF has a very specific action on the immune response, and not directly on cancer cells, how do we eat sufficient bananas (even if it did have TNF and it could be absorbed into the bloodstream) to increase the level locally to actually cause the appropriate immune response? And which one of the 200 or so cancers would it effect? It is clear that the name, tumor necrosis factor, leads one to believe that a drop of it on a cancer immediately kills the cancer. I would have to write a 20 page paper just to describe how TNF is regulated and disregulated within the immune system both locally and generally in response to a wide variety of immune challenges, including cancers. It is incredibly complex, and the name is simply one given without consideration to future alternative medicine pushers who jump on it as the the “cure” to all cancers. It isn’t.
  • Which leads us to how TNF causes many of the clinical problems associated with autoimmune disorders such as rheumatoid arthritisankylosing spondylitisinflammatory bowel diseasepsoriasishidradenitis suppurativa and refractory asthma. So, if a banana had TNF, if it could pass into the bloodstream from the digestive system, and if it could reach high enough levels to actually do something, it probably wouldn’t have any effect on any of the cancers, but it could have serious side effects. However, I wouldn’t worry about it, since there are so many “if’s” that it’s just not possible.
  • And this “boost the immune system” myth?  The immune system is an incredibly complex system, with an almost infinite number of interactions between various proteins, compounds, organs, factors, and cells. As long as you’re healthy, so is your immune system, there is nothing you can do to make it stronger, better, or “boostier.” Well, vaccinations help, but they rely upon an appropriate immune response. So even if you won the Nobel Prize by finding some miracle compound that “boosts the immune system,” it would work on one tiny part of that system, and it would have a zero net effect.

So here we go again. Someone reads that some scientists discovered bananas cure cancer. They didn’t dig up the actual paper to find out that the scientists didn’t actually say that it did. They didn’t think through the problem that bananas wouldn’t actually contain tumor necrosis factor or that the digestive tract wouldn’t actually absorb it. Or that you couldn’t possibly eat enough bananas to get enough TNF to do any good. Or that if you could that it would have some very bad effects.

If you want to eat a banana, go ahead. It does have some benefits I’m sure. But it isn’t going to prevent cancer. It’s not going to cure cancer. It’s not going to do make you live longer. It’s just going to provide nutrition.

Key citations

Comments (221)
  • kay ger

    The way I understand this blog, is that ripened bananas have less of a chance of fighting-off cancer than, let’s say, a carcinogenic pathogen cancer treatment, such as chemotherapy or radiation, which is proven to cause secondary cancers and weaken the immune system. Who pays you to write the smear campaigns for alternative cancer care, is it the FDA, AMA, or the Pharmaceutical (drug) companies?

    • Skeptical Raptor

      No, the way you should understand this article is that bananas have no ability to cure any type of cancer based on the pseudoscience pushed out in internet memes.

      There are over 250 different cancers, all with different pathophysiology, genetics, causes and treatments. There are no “cures” for “cancer”. There are treatments for any of the 250 different cancers, all shown to be effective through clinical trials published in peer-reviewed journals.

      Alternative “cancer” cures do not exist. Unless you show them to scientifically work, which can’t. So I don’t get paid by anyone, but I do have a substantial scientific research background that allows me to think. You on the other hand are an ignorant little dumbass.

      • kay ger

        No cures for cancer? That is an ignorant arbitrary statement if one was ever stated. You don’t know anything more than you what you are made aware to know. Perhaps, I might be a good subject as to what natural foods keep cancer at bay as well as other people who are now cancer free due to alternative cancer treatments. Go to the American Cancer Society website, it has  a lot of misleading statistical info, such as, “more people are recovering from cancer than ever before”, yet it doesn’t say a higher percentage of people are recovering. On other pages of the same site, it say’s more people are being diagnosed with cancer than ever before, so it makes sense that more people do recover (remission) from cancer; yet, the recovery rates from chemo or radiation is the same as it was 50 years ago. You are the moron and too thin skinned to be humored with sarcasm, so instead you reply with personal attack. That is your your caliber of a person and a denial of an ignorant self. I cant wait to post your email on my blog site. You reply to me in email instead of your forum  because you don’t want your forum to know publicly how sleazy you really are.

      • kay ger

        You are talking to a person diagnosed with cancer in the lymph nodes now in remission without conventional radiation treatments or chemotherapy. Good dieting does help. There are so many nutritional research studies specific to foods that are proven to fight different cancers. No self-proclaimed scientific jerk should be so ignorant to argue that good nutrition and a select diet is unable to help a cancer sufferers.

      • kay ger

        Hey, ignorant big dumbass, no where does it say $100,000 dollars of chemo can cure cancer, yet it is proven to cause secondary cancer; banana’s don’t. I don’t give a crap about your scientific background, because science is continually disproving its own facts.

        You make a statement in your blog concerning a boosted immune system is misleading; no where is anything in the study stated to suggest nutrition will supercharge a healthy immune system, but boosting a depleted immune system; however, is entirely possible.

      • kay ger

        Neither can $100,000 dollars of chemo can cure cancer, but it is proven to cause secondary cancer and banana’s won’t. I don’t give a crap about your scientific background, because science is continually disproving its own facts.

        The USA is owned by corporate lobbyist that don’t want anything published or sold regarding alternative cancer research, and the FDA will take any action necessary to smear any such research, Non patentable compounds or foods that are helpful to cancer sufferers, could crash a multi-billion dollar cancer industry the pharmaceutical companies do not want to loose.

        One of several misleading statements in your blog states it is impossible to boost the immune system. No where in this study is anything stated to suggest that nutrition will supercharge a healthy immune system; however, boosting a depleted immune system is entirely possible.

        • Skeptical Raptor

          Your comments call into question your knowledge about cancer. Typically, analysis of cancer treatments are 5 year survival rates, because unless you know of a way to ascertain that 100% of cancer cells are removed from the body, and you can’t, we don’t know if the cancer has actually been killed, or gone into hiding or remission.

          The only way to boost your immune system is to get vaccinated. And there are vaccines for cancer that will soon be on the market. Well, you can get the HPV vaccine which prevents a whole class of HPV related cancers.

          Your immune system only gets “depleted” as a result of chronic malnutrition or a chronic disease. Too late then.

          OK, well, I’m glad you’re here to show off your ignorance. It’s been a pleasure. And since I don’t sit at my computer moderating comments all day, if the Disqus filter catches you, deal with it. It’s nothing personal. Or get that psychiatric help I suggested.

      • kay ger

        Hey big dumbass why did you erase all of my posts? I guess you can’t handle controversy, Hell, you don’t even identify yourself, but claim you have so much scientific research experience, but you know I know who you really are. Where are your credentials a-hole, you’re about page is all fabrication without identification, a fraud you are.

        • Skeptical Raptor

          Beautiful comment. Typical of your type, paranoid and delusional.

          Because you are a new Disqus user, who only comments here, your posts are all flagged for moderation.

          I can give a few numbers for psychiatrists. Or I could sign off on a 72 hour hold.

      • kay ger

        I’m not going away either!

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    • kay ger

      To many people believe anything they read here too.

      • Skeptical Raptor

        You’re still ignorant.

        This article has been read over 100,000 times, shared nearly 10,000 times. It’s used a reference on Snopes to debunk this banana myth.

        YOU, on the other hand, present nothing but ad hominems. That’s the position of those who lack real scientific data.

        • kay ger

          You on the other hand are a FDA plant.

        • kay ger

          Or the position of those who are too close minded and egotistical to be open minded enough to be objective in their research, Any researcher in the USA who goes outside of the AMA FDA guidelines is smeared to being a quack, but it is now my new mission to see you discredited for your nonsense on this blog, For the simple fact you keep deleting my posts because you can not deal with the fact you are the quack.

        • kay ger

          You are the ignorant fool who has a blog that acts as if an expert, but no where do you even show your true identity, you won’t post my comments, because you don’t want to be debunked, but my mission is now to identify, smear, and debunk you. I’ll see you in Queensland, you have underestimated your privacy. You want to f with me.

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    • kay ger

      Debunked? How? There is no more proof here about anything, it is just an opinion with a lot of opinionated references. However, here is a fact: Japan receives USA protection and the USA is owned by corporate lobbyist who does not want anyone discovering a cure for Cancer because it is a multi-billion dollar industry that will never let a cancer cure be known. Cure cancer and a multi-billion dollar industry will fall on its face. Keep donating your money to cancer research, the drug companies love your support.

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    • kay ger

      Pull the banana off the tree in Peru and let it set in the sun until it ripens, then it will get spots too, or maybe your Peruvian bananas are miracle bananas that would be better suited for cancer research than the Peruvian bananas that are imported into the USA..

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