Have you ever wondered if there’s a natural way to lower your high blood pressure, guard against Alzheimer's, lose weight, and feel better? Well as it turns out there is. Michael Greger, M.D. FACLM, founder of NutritionFacts.org, and author of the instant New York Times bestseller “How Not to Die” celebrates evidence-based nutrition to add years to our life and life to our years.

Preventing Colon Cancer

New research on a leading cause of death in the United States.

This episode features audio from Should We All Get Colonoscopies Starting at Age 50?, What to Take Before a Colonoscopy, and Solving a Colon Cancer Mystery. Visit the video pages for all sources and doctor’s notes related to this podcast.


Welcome to the Nutrition Facts podcast.  I’m your host Dr. Michael Greger.  I am thrilled that you have decided to join me today.  Because the more I learn about latest nutrition research – the more convinced I am that this information can make a real difference in all of our lives.  And I like nothing better – than sharing it with you.

Today we focus on the second leading cause of cancer death in the United States – colon cancer. And here’s a really startling fact – 70% of colon cancer deaths are avoidable.  But what is the right course of prevention and treatment? 

In our first story we look at the screening recommendations for colonoscopies – and ask why doctors in the United States continue to recommend colonoscopies when other countries recommend less invasive colon cancer screening methods?

Though colonoscopies can cause serious harm in about 1 in every 350 cases, sigmoidoscopies, which are shorter and smaller scopes, have ten times fewer complications. But, do colonoscopies work better, the total risk benefit  better? We don’t know, since we don’t have any randomized controlled colonoscopy trials, and we won’t until the mid 2020’s. So, what should we do?

The USPSTF, the official prevention guidelines body, considers colonoscopies just one of three acceptable colon cancer screening strategies. Starting at age 50, we should either: get our stool tested for hidden blood every year, no scoping at all; or a sigmoidoscopy every five years, along with stool testing every three; or a colonoscopy every 10 years. And, in terms of virtual colonoscopies or the new DNA stool testing, there is insufficient evidence to recommend either of those two.

Though they recommend ending routine screening at age 75, that’s assuming you’ve been testing negative for 25 years since your 50th birthday. If you’re 75 and have never been screened, then it’s probably a good idea to be screened at least into one’s 80s.

If there are three acceptable screening strategies, how should one decide? They recommend that patients work with their physician in selecting one after considering the risks and benefits of each option. For patients to participate in the decision-making process, though, they have to be given the information. The degree to which health providers communicate the necessary information was not known, until this study. They audiotaped clinic visits looking for the nine elements of informed decision-making. Discussing the patient’s role in making the decision, what kind of decision has to be made, what are the alternatives, what are the pros and cons of each option, the uncertainties, making sure the patient understands their options, and then finally asking them what they would prefer. That’s the role of a good doctor. It’s your body; it’s your informed decision.

How many of these nine crucial elements of informed decision making were communicated to patients when it came to colon cancer screening? Care to hazard a guess? In most of the patients, none. The average number addressed? One out of nine. As an editorial in the Journal of the American Medical Association put it, “There are too many probabilities and uncertainties for patients to consider and too little time for clinicians to discuss them with patients.” So, doctors just make up the patients’

minds up for them, and what do they choose? Most often, as in this survey of a thousand physicians, doctors recommend colonoscopy. Why? Other developed countries mostly use the stool tests, the FOBT tests, with only a few recommending colonoscopies or sigmoidoscopies. This may be because most physicians in the world don’t get paid by procedure. As one gastroenterologist put it, “Colonoscopy is the goose that laid the golden egg.”

A New York Times exposé concluded that the reason doctors rake in so much money is less about top notch patient care and more about business plans maximizing revenue,  lobbying, marketing, and turf battles. Who sets the prices for procedures? The American Medical Association, the chief lobbying group for physicians. No wonder gastroenterologists pull in nearly a half million dollars a year.

And, the American Gastroenterological Association wants to keep it that way. Referring to these exposés, the president of the Association warned that gastroenterology is under attack. Colorectal cancer screening and prevention may be reduced in volume and discounted. But, they have tips for how to succeed in the coming nightmarish world of accountability and transparency.

Why would primary care docs push colonoscopies though? Because many doctors get what are essentially financial kickbacks for procedure referrals. Studying doctor behavior before and after they started profiting from their own referrals, it’s estimated that doctors make nearly a million more referrals every year than they would have if they there were not personally profiting.

In our next story, we look at the uses of peppermint oil to reduce the pain and discomfort of colonoscopies for the patient, as well as make insertion and withdrawal of scope easier for the doctor.

Peppermint was not officially described—by a white guy—until 1696, but we’ve probably been using it for at least a few thousand years. After-dinner mints are used to reduce the gastrocolic reflex, the urge to defecate following a meal. The stretching of nerves in the stomach triggers spasms in the colon, which makes sense—our body’s making way for more food coming down the pipe. What peppermint does is relax the muscles of the colon.

If you take circular strips of human colons removed during surgery and just lay them on a table, they spontaneously contract on their own about three times a minute. Isn’t that kind of creepy? But then if you drop more and more menthol from peppermint on them, the contractions still happen, but they’re not as strong. Well, if peppermint can relax the colon and reduce spasms, might it be useful during a colonoscopy, as first suggested over 30 years ago. See, colon spasm can hinder the progress of the scope and cause the patient discomfort. So, they tried spraying some peppermint oil out the tip, and in every case, the spasm was relieved within 30 seconds. So, the next innovation would be to just use a hand pump to flood the whole colon with a peppermint oil solution before the colonoscopy. Simple, safe, and convenient alternative to injecting an anti-spasm drug, which can have an array of side effects, whereas instilling some peppermint solution and within 20 seconds, the spasming colon opens right up.

Similar results were attained with upper endoscopy, working better, quicker, safer than the drug, and also when mixed into barium enemas. But wouldn’t it be easier to just swallow some peppermint oil instead of squirting it up the rectum? Premedication with peppermint oil in colonoscopy. Just popping a few peppermint oil capsules four hours before the procedure sped up the entire process, and increased both doctor and patient satisfaction, because reducing colon spasm reduces pain and discomfort, and makes the scope easier to insert and withdraw.

Pain and discomfort are not the only barriers to signing people up for colonoscopies, though. Even if peppermint oil makes it go seamlessly, there’s still the dreaded bowel prep, where you have to drink quarts of a powerful liquid laxative before the procedure to completely clean you out. And, aside from the pain, a fear of complications and feelings of embarrassment and vulnerability.

Serious complications occur in about 1 in every 350 colonoscopies: including perforations and bleeding to death. Perforations occur when the tip of the scope punches through wall of the colon, or because they inflated the colon too much—they have to pump in air so they can look around, or when they’re trying to cauterize some bleeding caused by like a biopsy, which, in extremely rare instances, can ignite some residual gas and cause the colon to explode on the table.

Death from colonoscopy is rare, occurring only in about 1 in every thousand procedures, but with about 15 million colonoscopies performed annually in the United States, colonoscopies kill about 15,000 Americans every year, raising the question: do the benefits outweigh the risks?

In our final story we look at the prevalence of colon cancer in Africa.   Even though modern African diets may now be as miserably low in fiber as American diets, Africans still appear to have 50 times less colorectal cancer than Americans (our second leading cancer killer).  Here’s the research. 

Colorectal cancer is the second leading cause of cancer death in the United States, after lung cancer. If you look at the rates of lung cancer around the world, they vary by a factor of 10. If there were nothing we could do to prevent lung cancer, if it just arose spontaneously, happened at random, you’d assume that the rates everywhere would be the same. But since there’s such a huge variation in rates, you assume there’s some external cause, and indeed, we now know smoking is responsible for 90% of lung cancer cases. So if we don’t want to die of the #1 cancer killer, by just not smoking we can throw 90% of our risk out the window. For colon cancer, there’s an even bigger spread, a bigger variation around the world.  So it appears colon cancer doesn’t just happen; something makes it happen. Well, if our lungs can get filled with carcinogens from smoke, maybe our colons are getting filled with carcinogens from food. Researchers from the University of Pittsburgh and the University of Limpopo sought to answer the question, “Why do African Americans get more colon cancer than native Africans?” Why study Africans? Because colon cancer is extremely rare in native African populations, like more than 50 times lower than rates of Americans, white or black.

It’s the fiber, right? Dr. Burkitt was the first to describe the low incidence of colon cancer in native Africans, ascribing it to their traditional staple diet that was high in whole grains and, therefore, fiber content. Seems you get about a 10% reduction in risk for every 10 grams of fiber a day. So hey, if it’s a 1% drop for each gram, and they’re eating upwards of 100 grams a day, well that could explain why colon cancer is so rare in sub-Saharan Africa.

But wait a second, the modern African diet is highly processed and low in fiber, and yet there has been no dramatic increase in colon cancer incidence.

The modern African diet has a low fiber content, as most populations now depend on commercially produced refined cornmeal. And we’re not just talking low fiber intake; we’re talking United States of America low, down around half the recommended daily allowance. Yet colon disease still remains rare; still 50 times less colon cancer.

Maybe it’s because they’re thinner and exercise more? No, they’re not, and no, they don’t. If anything, their physical activity levels may now be even lower. So if they’re sedentary like us, eating mostly refined carbs, few whole plant foods, little fiber—like us–why do they still have 50 times less colon cancer than us? Well, there is one difference. The diet of both African-Americans and Caucasian-Americans is rich in meat, whereas the native Africans’ diet is so low in meat and saturated fat they have total cholesterol levels averaging 139, compared to over 200 in the U.S.

So yes, they don’t get a lot of fiber anymore, but they continue to minimize meat and animal fat consumption, supporting evidence that perhaps the most powerful determinants of colon cancer risk are the levels of meat and animal fat intake. So why do Americans get more colon cancer than Africans? Maybe the rarity of colon cancer in Africans is not the fiber, but their low animal product consumption.

There is a divergence of opinion as to whether it’s the animal fat, cholesterol, or animal protein that is most responsible for the increased cancer risk, as all three have been shown to have carcinogenic (cancer-causing) properties, but it may not really matter which component is worse, as a diet rich in one is usually rich in the others.

We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition.  Go to nutrition facts.org forward slash testimonials. We may share it on our social media to help inspire others.

To see any graphs charts, graphics, images or studies mentioned here, please go to the Nutrition Facts podcast landing page.  There you’ll find all the detailed information you need – plus links to all of the sources we cite for each of these topics.

Be sure to check out my new “How Not to Die Cookbook.”  It’s beautifully designed, with more than 100 recipes for delicious and nutritious, life-saving, plant-based meals, snacks, and beverages.  All proceeds I receive from the sales of all my books goes to charity.

NutritionFacts.org is a nonprofit, science-based public service, where you can sign up for free daily updates on the latest in nutrition research via bite-sized videos and articles.

Everything on the website is free. There’s no ads, no corporate sponsorship.  It’s strictly non-commercial.  I’m not selling anything. I just put it up as a public service, as a labor of love – as a tribute to my grandmother – whose own life was saved with evidence based nutrition.

Thanks for listening to Nutrition Facts.  I’m your host, Dr. Michael Greger.

20 responses to “Preventing Colon Cancer

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  1. As an African, wish we could all go back to our traditional healthy whole foods plant-rich diet but it is great to hear that refined cornmeal, one of modern Africa’s highly processed foods, does not raise the risk of colon cancer – health news from Africa is usually not positive. Was wondering, is there no resistant starch in refined cornmeal which would effectively imply higher fibre intake?

  2. My friebd and her husband seem to me to be essential oil addicts and her husband goes through bottles and bottles and bottles of peppermint.

    It is creepy to me.

    I am developing a dislike for essential oils and see them as what people do if they aren’t WFPB.

    My friend stops and whiffs her hands every few minutes now and takes capsules and also uses essential oil cleaners and takes vitamins and diffuses. My cousin started doing the same thing.

    Plus, the sales pitch reminds me of Amway.

    Creepy creepy creepy step ford industry

    1. They tell me it will replace my medicibe cabinet but I can’t remember the last time I used any medicine or had pain or got a cold or the flu.

    2. Ooooh, I have family members who are involved in that whole thing as well. They go on and on about keeping away from chemical cleaners and such (I use only plant based cleaners btw) but then post recipes for every possible combination of meat and cheese. I just smile and don’t say a word! :)

  3. I am interested in whether turmeric essential oil is better than turmeric, for instance.

    They are taking the things I am using as spices and are putting it in capsules and throughout the day put it under their tongues and on their neck and smell their hands and diffuse the room and clean with it and take vitamins of it and use roller balls with mixtures of scents and put drops of it in their water.

    Are essential oil vitamins less dangerous than other vitamins? Is essential oil rurmeric better than turmeric? Or do you end up with anemia?

    I don’t mind using it to scent the room, but dogs have been poisoned by that, are we sure kids aren’t getting poisoned by diffusing it, too?

    My cousin using it while pregnant – is that okay? My friend’s husband using it every single day for headaches, could it be causing the headaches in the first place? My friend sniffing Her hand all day and wearing a necklace to sniff and diffusing the room are we sure that is risk free? I had never worried about scents before but I used to like air fresheners, are we 100% sure it isn’t like the VOC’s?

    I guess I just don’t trust it as an industry because of watching my friends and relatives who get involved in it.

    1. Okay, so is putting the Orange and lemon in the water 10,000 times better than putting slices of citrus in the same glass?

      Does it have 10,000 times more nutrition in that concentrated drop?

      Does it feed the gut microbiome the same way fruits and vegetables do and do we know it was organic oranges and lemons used in the essential oils?

      1. Reality is that they have an oil to replace many of the spices and the people using them use them instead of the foods and I don’t get if they are whole food plant based. They don’t taste it. They also baked with them instead of lemon itself and the lemon bars taste stronger and you get used to it, but is it better for me than lemon?

        If so, the lemon and grapefruit and orange and turmeric might be what I would use and would put up with their taste in my water and chili.

  4. I work in radiation oncology and our facility treats GI cancers of the lower bowel. Over the past 6-8 years I’ve really noticed an increase in younger people with rectal cancer. We’ve had patients in their upper 20’s into their 30’s, which is something I never saw 20 years ago. We’ve had two teenagers with colon cancer. Sadly, neither of them survived. The statistics bear out my observations as both colon cancer and rectal cancer are affecting younger people. What thoughts do you have about this? I know diets are terrible but I don’t feel like my generation ate much better. In my 20’s, I ate more than my share of fast food although I grew up eating lots of vegetables and LOTS of beans and rice. White rice but still, lots of beans. :) Thank you for all that you do to bring the truth into the world. I point people to your website all the time.

  5. Thank you for all the great information about preventing Colon Caner and peppermint oil 4 hours before going
    in for the scope.

    I find this very interesting, and will do it on my next scheduled appointment,

    Can you please tell me how much peppermint oil, one should take 4 hours before the test, and should it be diluted or just straight?

    Thank you
    Ardith WILLNER

  6. Hello I love this site,

    I have a few Questions I have had a colonoscopy it removed
    9 tubulovillous Adenomas with no evidence of high grade
    Displasia. I also have 7 Thyroid Nodules scheduled for a biopsy
    soon. I have been trying a plant based diet but its not
    balanced because I struggle with knowing the amount of each food
    i should eat on a daily bases and also what types of food for cancer prevention. Any suggestions ?

    Does anyone have a example of a daily or weekly meal list :)
    I am also interested in trying essential oils for healing
    And there are zillion of websites its confusing,
    Any trustworthy essential oil companies ?

    what would you recommend if it was you ?
    Types of supplements, herbs, teas, spices and antioxidants ect

    Thank you I am very grateful for this site.

    1. A great resource for balancing a whole food, plant based diet is Dr Greger’s Daily Dozen. Here is one of several videos on this topic. https://nutritionfacts.org/video/dr-gregers-daily-dozen-checklist-2/

      Here is also a great video, “The Best Advice on Diet and Cancer,” that can help answer your questions. Dr Greger, his staff, and his volunteers eat this way for all of its demonstrated benefits. https://nutritionfacts.org/video/the-best-advice-on-diet-and-cancer/

  7. Hi I’m a RN health support volunteer. That is a great question. It does have a short term effect. I think mostly because you are taking away the glut flora’s food source. But you are certainly not sterilizing the gut. The bacteria will still be there in some amount. Nothing wipes out your gut flora like broad spectrum antibiotics which kill the good bacteria. If you resume your normal (hopefully healthy) diet afterwards and give that gut flora good prebiotics to feast on, it should resume.


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