Fun With Fiber: The Real Scoop

One of our most cherished pleasures in life happens to be challenging conventional wisdom (CW). You never would’ve guessed, right? After all the talk of meat and fat this week, we’ve been feeling, well, rather off. We figured it was the perfect time to take on everyone’s favorite gristly subject: fiber.

CW says Americans need serious fiber in their diets. And by “fiber” CW often means bran buds, whole wheat, psyllium husks – you know, sticks and twigs roughage. We’re talking that 1980’s Saturday Night Live bit about Super Colon Blow cereal. Let’s just say that the more sensitive among us, in particular, want to broach the question: “Is this really the best way?”

So, we thought we’d do some digging. Our ventures into the bowels of fiber research turned up some stimulating information. (O.K., we’ll stop.) First, let’s sit back and enjoy a brief gastronomical lesson. Anyone for some popcorn before we start? (Moving on!)

What is the point of fiber anyway? What does it do? Well, on one hand, soluble fiber (vegetables, fruit, oatmeal, and legumes that partially dissolve in water) enhances the thickness of the stomach’s contents. This slows stomach emptying. While this can give the body more time to absorb nutrients, it can also “trap” minerals like calcium or zinc, binding them up in such a way that they don’t have the opportunity to be absorbed. Insoluble fiber (like whole grains, seeds and fruit skins) increases the mass of the stool, which actually moves the stool more quickly through the intestines. Insoluble fibers pass through the digestive system relatively intact. Continuing on…

Let’s explore the reasons we’re supposed to incorporate fiber into our diets and what some sources have to say.

Fiber helps keep you regular
Some of us can reliably mark off our daily calendars, we’re so consistent. Others, well, not so much. For some of us, things come easily. Others, well, we won’t go there.

Whatever the issue, fiber can help, or so says CW. While our personal experiences don’t directly challenge that claim, our research showed a less than comforting picture of the long-term effects.

Some research shows that the very fiber we turn to with perfectly innocent intentions can become a serious monkey on our backs. It turns out, we may have to continually up the ante over time until we’re in over our heads – or behinds, so to speak.

The key to a healthy gastronomical tract is not roughage but bacteria. The large intestine’s natural bacteria, which help comprise stool bulk, maintain water content and soften the stool. (Sounds like those ads, huh?) Fiber, particularly excessive insoluble fiber, offering a quick jump start to things is not the natural catalyst for a healthy excretory system.

Finally, when it comes to long term “issues,” The American College of Gastroenterology Functional Gastrointestinal Disorders Task Force didn’t find fiber to be an effective treatment for chronic constipation.

Fiber lowers cholesterol
We’ve been talking about the cholesterol issue a lot this past week. As you’ve likely read, we believe cholesterol numbers aren’t the secret code to your health or longevity prospects.

Studies, some reliable and some not, have shown relatively minor changes in cholesterol as a result of higher fiber intake. These same changes have not carried over as predictors of heart disease. (I think I hear a broken record.) Furthermore, these “improvements” in cholesterol had a difficult price for some subjects in terms of gastrointestinal troubles.

Fiber lowers your risk of cancer
It’s usually colon cancer that people mean here, and the studies vary much more than you likely hear. The New England Journal of Medicine and The Lancet include studies that show high fiber diets do not lower the risk of cancer or incidence of polyps, a common precursor to cancer.

But maybe we’re onto something…. Some studies, including a study published in the International Journal of Cancer, break down the fiber sources of their subjects. And guess what? Researchers found that vegetable based fiber (as opposed to that from cereal and fruit) was the most cancer protective. The study focused on those with a risk of prostate cancer, but other researchers and physicians extend this claim to suggest a vegetable based high fiber diet in lieu of carbohydrate fiber sources.

Fiber helps prevent and/or treat diabetes
Here we find ourselves back to the question of what kind of fiber. The standard recommendation for diabetics is soluble fiber. A study in the Journal of Clinical Epidemiology found that high vegetable consumption (in this case, raw) was consistent with an 80% lower incidence of Type 2 diabetes. Studies using carbohydrate sources have not shown these kinds of results.

Soluble fiber slows stomach emptying, which prevents the body from being flooded with glucose at the same rate as it would be with a low fiber meal (assuming a high glycemic load in the meal). But therein lies the pertinent question: if you maintain a diet with low glycemic load, do you really need to slow the digestion process with fiber? Hmm. If that fiber were adding a plethora of nutrients, as found in vegetables, then the answer would be yes. But as for a fiber source without all those nutrients? Not so convincing.

We’ll let you take it from here. We hope we’ve given you something interesting to chew on. Send us your perspectives and suggestions on the fiber question.

Peter Guthrie Flickr Photo (CC)

Further Reading:

Sh*t Happens

Jimmy Moore: Fiber Folly Finally Fizzled

That’s Fit: Coffee – A Good Source of… Fiber?

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31 thoughts on “Fun With Fiber: The Real Scoop”

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  1. One thing soluble fiber can be a huge help with is, as counterintuitive as this may sound, chronic diarrhea as seen with IBS. My understanding is that when soluble fiber dissolves, it creates a sort of gel, adding bulk, but in a smooth way, to what’s going through your intestines. (I’m trying to not gross people out here. Working?) Anyway, this is a case where slowing intestinal transit is *super* helpful. It also gives your intestines something to grip, so to speak, lessening the severity of the spasms that are often a part of IBS. Fun times! Taking a soluble fiber supplement (I’m talking 10, 12, even 16 grams daily) has made me a much happier, healthier person. Of course, not everyone has IBS. But in terms of what fiber can do for you, people think of it as a laxative, when, especially in terms of soluble fiber, it actually functions quite differently.

    1. Hi, Surplus. I know your post was some time ago, but if you’re still around, I’d like to share my experiences with IBS. The day I stopped eating grains (a food touted as the high-fibre panacea), was the day I never had another episode of IBS. Obviously, removing an entire food group which contains good amounts of fibre reduced my overall fibre intake. I now eat on average 15g of fibre per day. I don’t aim for that total; that’s just how it works out with what I eat. This is far fewer grams than recommended by CW. So, I’m eating less fibre but my bowel habits have improved beyond measure. Make of that whatever you wish. All the best.

  2. Mark, Gary Taubes agrees with you. Also, there are cultures such as the Inuit and Masai who traditionally ate no plant foods whatsoever. These people are very healthy as long as they stick to their traditional diets. Although I have heard reports of constipation among the Masai. Another thing to note is they both eat fermented foods. Maybe those contribute to intestinal health?

  3. I’m glad to see this post – I am a much happier person with less fiber in my diet.

    My doctor in 2002, when I first went low carb: But you’ll be constipated!
    Me: Doctor, I **** once a day. Isn’t that enough? Or did you want me to go back to my old 5 times a day habit.

  4. Very good article!

    While we should get healthy fiber from fruits and vegetables, we should avoid “bran” fiber like the plague. Bran fiber causes lots of issues related to the gut health which we have already shown is the real marker for health (and risks of cancer). The grain is not our friend…but just a cheap source of “fiber” that is marketed by any company selling processed foods…they are not selling health, just their product as “healthy”. Huge difference.

  5. Sorry for the double comment…but just came across this also in relation to the Africans and low incidence of colon cancer research…and how the “Bran” industry jumped on that bandwagon.

    “Commercial interests were quick to see the potential in the recommendation and jump on the bran wagon. Burkitt’s recommendation was based on vegetable fibre, but bran (cereal fibre) has a far higher fibre content and bran was a practically worthless by-product of the milling process that, until then, had been thrown away. Almost overnight, it became a highly priced profit maker. Although totally inedible, backed by Burkitt’s fibre hypothesis, bran could now be promoted as a valuable food. But Dr. Hugh Trowell, Burkitt’s partner and another strong advocate of dietary fibre, stated in 1974 that:”A serious confusion of thought is produced by referring to the dietary fibre hypothesis as the bran hypothesis, for many Africans do not consume cereal or bran””

    good read overall

  6. …Mr..HNY..So do we presume you have read Good Cals Bad Cals.. and what sayeth yee about it pleasum ?

  7. I love fiber in all its many forms. My problem is not getting enough of it but figuring out how much is too much before I overindulge. There’s nothing like congratulating oneself on eating plenty of fiber only to wake up the next morning with a gut full of pain and a pressing need to find the potty.

  8. What a coincidence that you chose to cover this topic- I just completed research into this matter 2 weeks ago, as my 1 year old twins have been constipated since birth. Doctors told me that screaming and rectally bleeding while having a bowel movement once a week could be “normal” for someone, while going as many as 4 times a day could be “normal” for someone else. I knew this wasn’t true. After trying all their useless recommendations of adding fiber, drinking water and fruit juice, I finally came across a website called This guy (a Ukrainian nutritionist named KONSTANTIN MONASTYRSKY) is the world’s biggest expert on poo and he agrees with this post, Mark. He has a book called The Fiber Menace and takes it one step further saying that relying on fiber in order to help IBS or to have a bowel movement is actually detrimental and can lead to longterm major problems. People loading up on fiber in their 20s and 30s are going to pay for it big time in their 50s and 60s. According to Monastyrsky, the biggest cause of constipation is disbacteriosis, when the good bacteria in your gut aren’t thriving or plentiful enough. So, I bought some Kefir and added it to my kid’s food. WITHIN ONE DAY, 13 months of constipation was gone and they have been having perfect, regular, soft BMs everyday since. This guy also sells supplement packs, but he discloses the ingredients in them. He says a couple of weird things I don’t agree with but for the most part, his advice falls inline with a primal lifestyle and his website is worth a read. I hope this helps some of you with IBS or diabetes.

    1. I just found Gutsense and was glued to the screen for the last hour. Came to MDA and searched for “fiber” to see if Mark had ever talked about it.

      My husband and his brother have historically had bad digestive issues. I helped my husband a lot through better eating habits, but he has already had a benign polyp removed during a colonoscopy three years ago.

      His brother has not fixed his issues yet. I’m going to send him a link to Gutsense and have a talk with him.

      The deeper you delve into the havoc CW has created, the scarier.

    2. The book Fiber Menace was a real eye opener. Not only is the science right on, but also, one gets an intuitive sense that, finally, the truth! It’s healthy gut flora we’re looking for, not fiber–and certainly not added fiber or water, which just exacerbate gastrointestinal issues. This book should be shared with doctors, including gastroenterologists who essentially try to fix what could have been avoided in the first place and who do not provide the preventive information that could have avoided our problems in the first place. To think that I could have avoided gallbladder removal had I known about Paleo and about the perils of fiber in the diet. No one should overlook this book.

  9. i do those. and NO they dont help in the slightest.
    not one bit, neither do enzymes. only fiber, and milk of mag.
    and often chewable fibers w/ the veggie fibers. annoying. i dont care, as long as i get the job done each morning.

  10. I have been diagnosed with IBS. I went primal six weeks ago. The issues I had prior to going primal are almost completely gone. The key fruits and veggies. I could not believe it. The fiber powers have not left the can since I went primal. Thanks Mark for the good work and thanks gang for all the great comments. Another Observation my GI doc likes his diet coke, makes me think how CW is soooo wrong.

    Keep it going.

  11. I’m only a few weeks in, but I’m seeing improvements. I’ve been hypothyroid and I’ve had trouble with constipation. I’m eating a lot of vegetables and some fruit, along with meat, cheese and yogurt. But I feel like a lot more is coming out than is going in. Sorry, I know that’s sort of icky. But I’m thinking that I’d been holding on to a lot and eating Primally is not just helping me not simply with being more regular, but letting go of old stuff that was (ew,ew,double eeeew) stuck.

  12. But don’t you notice that when you eat bran or oatmeal or other grains, you have regular bowel movements more frequently whereas with veggies and fruit only it’s slower and less?
    Is that a problem? It just seems like everything is just sitting in your gut for an awfully long time without the bran/oatmeal/grain. It seems like the grain is necessary to “push” everything out. Gross, but just an honest question.

    1. I agree in part. I recently added some sprouted grain bread into my diet and noticed that my BMs come out with minimal effort. They’re also much bigger. I have also found that when I’m not eating grains and am having problems, it means I’m not eating enough vegetables. But even if I increase the amount of veggies, it’s still not the same. However, what I found out from GutSense is that we don’t WANT big poos. Apparently the increased size can damage our intestines over time, since they’re not meant to handle that kind of bulk. But you’re right, it’s much easier with the grains. I think each person needs to find what works best for them. I suggest keeping a food journal for a few weeks and noting your BMs etc.

      1. I have had the exact same experience. I’m kind of waffeling on primal, I like most aspects of it, my energy is much higher despite naturally eating fewer calories on the primal diet. The only problem is constipation. I’m kind of hoping it’s just a temporary thing while my intestines adapt. I’d be interested to hear your or anyone elses opinion on this.

        1. When you’ve been on a high fiber diet (which is everyone consuming grains) then your gut is stretched out, not as firm and has damaged nerve endings.

          The primal diet forms small, soft blobs that are easy to pass….but if you have nerve damage and a stretched colon you might not get the triggers to move things.
          And this is normal. K. Monastyrsky explains all of this in details.

          I read his book and ordered 3 months worth of his supplements to heal my colon. It worked. I may not have bowel movements like a child but for having (or had) a severely damaged colon 1x within 48 hours isn’t bad at all.
          Other times I get 3 movements in 1 day.
          Even if you only go once every 3rd day that’s still okay for someone with damaged intestines. It’s the quality that counts, not the quantity.

          K. Monastyrsky also sells a powder (mixture of vitamin C and a couple minerals) that moistens your colon.

  13. I used to be dependent on laxatives since I was a teenager. Every week or twice a week I gulped down nasty Milk of Mag. in order to trigger bowel movements….very annoying.
    I could not figure out wth was causing me to have hard stools AND constipation until I stumbled upon MDA and read Fiber Menace.

    Apparently sugar sucked bio-organic sodium (the slime on your gut lining) right off my intestinal walls which slowed the bowles down and fiber glumped up into giant bolders. Both together wrecked havoc on my colon.

    I ditched sugar and grains, took probiotics to repopulate my gut and made sure I get all minerals back into my body to produce efficient bio-organic sodium (which is also in your joints btw).

    I never have hard stools anymore, I don’t go every day but every other day and that’s fine (compared to before sometimes not going for 2 weeks).
    Also, I’ve noticed, the more saturated fat I add to my meals the more efficient the end product.

    1. Yeah, the times I did resort to a bowl of oatmeal or a laxitive all the poop that was backed up was near perfect. It’s just that it doesn’t seem to want to come out on its own despite it being good poop. I may just try waiting it out and not panic if I go a few days without going. Another thing I always wondered about is I have a history of constipation from being a kid. When I was two or three I had horrible constipation for like a year because I was kind of taught to hold it, and probably in part because my doctor had my parents put me on a diet of low fat products (corn syrup solids peanut butter anyone?). The doctor felt it would heal up, as I was still small, but I always thought it never did fully as I’ve always been prone to constipation as a health problem. If you have any other input or thoughts on this it would be appreciated :).

  14. As veggies go I have found that Lebanese cucumber is particularly good – I have read that it is due to the high silica content; also read somewhere recently about leeks being a good veggie for fibre

  15. What about eating chia seeds? They have a lot of fiber. Is this also bad for me?

  16. Hello there

    Can anyone perhaps give me a straight answer here please, i cannot seem to find a direct confirmation 🙂

    when counting carbs (Max 50per day) do i minus the fiber ? so e.g – sweet potato – 26.76 g carbohydrates minus the fiber of 5g = 21,76g ?

    so would i could on my carbohydrates total or my Net carbs as my total Carbs per day ?

    1. Me personally, I subtract the fiber from the carb count. Using your example, I’d go with the 21 g figure

  17. These blogs are bogus. and taken out of context. Phytates (Phytic Acid) has been shown to be not only preventive in cancer mutations but restore cancer cells back to normal cells. There are not cited evidence here to legit scientific evidence. They are beliefs no different than a religious belief. Basically, eat what taste good, and let’s make claims to things that are truly healthy and label them as bad for you. This is cherry-picking the science to fit an agenda. If this paleo/primal/low carb way of eating is so spectacular how come there are supplements being sold all over blogs like these? Here is a study I randomly searched for the keywords fiber and cancer. This is from the same journal he referenced and says quite the opposite.

    I am all for looking at the science. I even have done my own blood work various times and genetically produce high cholesterol. I eat high cereal and legumes. I have not gut issues, my CRP is 0.3. Which is basically no inflammation. I know there are some people that produce more carbohydrate enzymes in the mouth. Regardless fiber is excellent for health mainly as a whole food form. It took me some time to adjust eating legumes from eating a high meat diet. We expect a quick turnover after consuming years of one kind of food. We expect things to change over in a few weeks or months when we have been damaging our gut for years with crappy foods. We call gassiness and bloating irritable bowl or other trend words because our bodies have not adjusted to the new fiber-rich diets. My advice to critical thinkers is to stop looking for blogs for information and look at the science for yourself. Spend the time and do the research.

    Sad to see such misinformation being thrown out there on the internet. But if someone wants to hear good news about their bad habits they will continue on this path. “Because bacon tastes good it must be good for you” Ignorance is bliss.