Dear Mark: Are Probiotics Useless, Gluten-Free Diets Dangerous, and GMOs Completely and Utterly Safe?

Probiotics Useless FinalFor today’s edition of Dear Mark, I’m answering three questions from a single reader who just read an article from Vice. The article makes pretty bold assertions about topics that have already received a good deal of attention here on the blog. First, are probiotics actually useless? A new study cited in the article seems to suggest so. Next, is your gluten-free diet killing you? That’s what the author of the Vice article says. And finally, have GMO foods been conclusively proven to be safe and indistinguishable from non-GMO foods? Is the debate, more or less, conclusively over?

Let’s discuss:


What are we to make of this article on Vice? It’s claiming that probiotics don’t do anything, gluten-free diets are potentially dangerous for people without celiac, and GMO foods have no downsides. Is it true?



The studies the article bases its arguments on are real, but the results aren’t as definitive or far-reaching as the Vice writer implies. Let’s take a look at each in turn.

“Probiotics are useless.”

That’s what the Vice writer said.

The paper was rather narrow, actually. Its goal was to assess the effect of probiotic supplementation on fecal microbiota composition in healthy subjects. That’s it. In the authors’ own words, “RCTs of solely probiotic supplementation and placebo in healthy adults that examined alteration in composition of overall fecal microbiota structure assessed by shotgun metagenomic sequencing, 16S ribosomal RNA sequencing, or phylogenetic microarray methods were included.” They ended up with 7 eligible trials.

It wasn’t assessing the health effects of probiotics. It assessed whether or not healthy people taking probiotics can expect alterations to the bacteria living in their guts.

Probiotics do lots of other things, not always by altering the composition of the resident gut bacteria.

They can improve IBS symptoms and other GI issues. They can help the lactose intolerant tolerate it. They can improve rheumatoid arthritis symptoms and reduce the incidence of upper respiratory tract infections. They can increase gut barrier stability.

This study wasn’t about those other things, though. It was about healthy adults without any health conditions, particularly ones that probiotics have been shown to help. All the other hundreds of probiotics trials are useless or flawed. It just means that they didn’t satisfy their specific and narrow requirements for consideration.

If you’re healthy, with no digestive complaints, no immune problems, then probiotics won’t change your gut composition. That’s all this study says.

This actually makes me feel good about using and selling probiotics. It suggests to me that in healthy folks, probiotics don’t try to fix what isn’t broken. They don’t “assert” themselves on an otherwise intact and healthy gut. But in unhealthy people with conditions probiotics can help, they do alter the gut in a positive way. Probiotics are “smart.” As living things, perhaps they can fix what needs fixing and ignore what doesn’t.

The next claim was “gluten-free diets are dangerous.”

The Vice writer oversteps yet again. The actual paper in the Journal of Pediatrics was fairer and more balanced, suggesting that gluten-free diets as commonly practiced increased the risk of nutrient deficiencies. I agree with this.

For many people, wheat is the “best” source of many nutrients because it’s a huge part of their diet. Then they go gluten-free and remove wheat from their diet only to replace it with more nutrient-poor grains. They’re not eating any healthier; they’re actually just swapping out wheat for other refined grains. Gluten-free foods typically use nutrient-poor starches and flours. Whereas whole wheat is perfect for making baked goods by itself, gluten-free bakers must cobble together tons of isolated, refined flours, gums, and starches to approximate the original product. This removes gluten, sure, but it also removes a lot of nutrients. Whole wheat bread is more nutritious than rice flour bread. Wheat pancakes contain more micronutrients than tapioca starch pancakes. The former examples are whole foods. The latter examples are isolated, nutrient-poor starches.

What if you went “gluten-free” by replacing your grains with meat, vegetables, fruits, and tubers? I swear there’s a name for that

“GMOs are safe.”

I’ve never taken a hard-line stance against GMO foods. I’m not particularly concerned with the act of gene insertion so much as what’s being inserted and what those insertions allow us to do. Many of you have given me a lot of flack for that nuanced position.

The study cited in the article discusses GMO-related reductions in “insecticide poisoning,” an acute condition affecting farm laborers who handle and come into direct contact with pesticides. The increase in GMOs engineered to produce their own endogenous insecticides has reduced the use of exogenous insecticides. Workers are applying and handling fewer insecticides, which presumably drives down cases of insecticide poisoning. This is a logical and positive development.

However, a 2012 study found that GMOs have led to a net increase in pesticide usage (herbicides and insecticides combined), primarily thanks to Roundup-Ready crops. A more recent paper found that insecticide use went down but herbicide use went up, again thanks to Roundup-ready crops incentivizing and encouraging Roundup use. More Roundup (an herbicide) is being applied than ever.

Is Roundup safe? Pro-industry skeptics always point to the relative safety of glyphosate, the active ingredient in Roundup. But surfactants, adjuvants, and other “inactive” ingredients make Roundup 25 times more toxic than plain old glyphosate. I’m not comfortable with it, personally.

So, to sum up, the Vice article doesn’t give the whole story. It’s a quick summary that probably took under an hour to write, but it’s very misleading.

What do you think, folks?

TAGS:  dear mark, gluten, GMO

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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40 thoughts on “Dear Mark: Are Probiotics Useless, Gluten-Free Diets Dangerous, and GMOs Completely and Utterly Safe?”

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  1. Surnames can contain personal information regarding origin, profession, trade, status, etc. When the day comes that I can sell my healthy poop to science because my GI is wicked awesome, I am legally changing my surname to “Poopsmith” or “Goldterd”. Maybe add a “Von” in there for additional comedic value.

  2. You aren’t going to eat Roundup-Ready cotton though. OTOH, if you eat organic, non-GMO sweet corn, it’s almost certain to have been sprayed with Bt (sarcasm) unlike GMO sweet and field corns with their inserted Bt gene (/sarcasm). Hawaiian papayas have a gene insert that resists papaya mosaic virus, not Roundup. I’m not sure what gene has been inserted into the yeast used for commercial beer production, but I’m certain that it is also not Roundup resistance! There is a single handful of GMO crops, several grown in very limited areas, available for human consumption. IIRC cotton and soy are the only crops that are RR.

    Every time I hear “GMO”, I think about the Canis lupus var. familiaris living in my house. They are so genetically modified from the original wolf even if it was only via traditional genetic modification techniques.

    I’d hang around to argue, but I need to go beat back the Bermuda grass in my yard with a little Roundup.

    1. Except that cottonseed oil is used in processed food and cotton may be one of the raw materials that the various cellulosic fibers that are being used as bulking agents in processed foods are derived from. I’m not certain about that last one, though.

      1. Plus I’ve seen cattle being fed the stalks of cotton plants as forage……

  3. Vice is a very much overrated hipster news source that is quite shoddy and from what I have read from them, seeks to goal seek their stories to create the pre-determined narrative rather than just report the facts as they find. They also censor debate on heir forums, as well.

  4. I feel the same way about GMOs and generally don’t like the entire “debate.” Actually making genetic modifications is something we’ve been doing for thousands of years to our benefit.

    The problem comes down to what modifications are being made and why. However, the debate usually turns into “flower children vs. SCIENCE!” with a lot of boring clichés.

    Genetic modification in and of itself isn’t bad at all in my opinion. However… even before modern techniques, our misguided meddling for the wrong reasons produced pretty and uniform, but tasteless tomatos, and those awful Red “Delicious” apples, a misnomer if ever there was one.

    1. Actually we haven’t been making genetic modifications for thousands of years. We’ve been practicing selective breeding to enhance characteristics that are already there. What we are doing now is literally rewriting the genome of plants and animals that could never occur naturally. We are moving forward with this on a global scale with almost no oversight or regulatory bodies in place to deal with it. But that’s not the most worrisome part. The scary part is that our food supply is become less diverse and more under the control of a handful of mega corporations. Massive mono cropping of plants that are patented and controlled by one corporation is kind of a problem. Being able to patent life itself is kind of a problem. Everyone in the world planting the exact same patented strain of corn, beans and rice is a problem. Terminator seeds are a problem ( seeds that are always sterile so you can’t make a second crop off the first crop)

      Make no mistake about it. Companies do not invest millions of dollars to patent life forms for altruistic reasons. It’s for profit and that profit can only be realized by total control of the food production chain and forcing alternatives off the market.

      Should be ban all GMO’s? Of course not. But the way we are doing it now and the rate it’s accelerating is going to have some major blowback down the road and I don’t think we will have the ability to deal with it effectvely.

      Much in the same way the internal combustion engine and fossils fuels allowed the world’s population to explode, standards of living to increase, and allowed us to free us of the squalor of streets filled with horse urine and garbage, it’s also come a huge price that we have now have come to understand but have zero ability to do anything about. We are going to pay dearly for it and we will actually have to increase our reliance on fossils fuels just to survive it long enough to find a way out of it.

      This is the reason so many of us are uneasy about GMO’s. We don’t actually think GMO rice with enhanced vitamin A will make us sick, it’s the whole ecosystem of values, priorities, and consequences that comes with it.

      1. I would argue selective breeding is just a rudimentary form of genetic modification. It can certainly have unforeseen consequences.

        I’m not opposed to the concept of genetic modification. I realize there are potential consequences. Okay. Same goes for smart phones and global networks, which I’m okay with as well.

        I don’t disagree that the companies and agendas pushing the current crop of genetic modifications are as greedy as they are corrupt. However, that’s got nothing to do with gene splicing and everything to do with the inherent nature of large, wealthy organizations—another issue we’ve been dealing with for thousands of years.

        Profit isn’t inherently bad either. My smart phone was built for profit’s sake, not altruism. I don’t think any multinational is altruistic in any sense. So what? The current push for alternative energy isn’t being driven by altruism, it’s driven by the same forces that drove the internal combustion engine.

        I’m uneasy about GMOs in this climate. I’m simply not opposed to genetic modification of our foods or even our own species for that matter. I’m not going to be sad when we can erase hemophilia or even pattern baldness.

        Genetic modification is a completely different discussion than huge corporations abusing it and patenting it. I just think a bunch of completely separate issues keep getting wrapped up into a single blob.

        1. Consider what wheat has been through, exposure to toxins and radiation and dog know what else it should be considered GMO.

          We have no more or few amber waves of grain anymore. Mutant ninja dwarf wheat has taken over.

      2. Preach it, brother! Very much agree with your thoughtful and intelligent comment / “rant”. :).

      3. As a Midwest farmer who has relied on GMO technology for my entire farming career and listened to the emotionally charged screaming of the opponents, I am encouraged by the logical and thoughtful approach that many are taking on this issue currently. No one can say definitively that GMOs are safe, but I feel,the benefits ultimately outweigh the risk. I agree that the consolidation of massive seed conglomerates is far more disconcerting. Unfortunately the massive amounts of money required to develop and get a new trait approved has kind of forced this. So indirectly the screaming of the opponents of GMO helped to force this. I believe this technology will ultimately be the future if it is ever accepted and encouraged by the masses. The possibilities are endless when you think of the genetic traits that can easily be inserted.

        1. Good to hear from someone who is personally involved in this. I agree with the ‘nuances’ as stated above. We’ve been eating GMO modified food for some time I think. As long as we stick with basically harmless genetic traits, and study the results carefully, I see little reason to be concerned.

          The issue comes up because many have lost trust in our institutions.

        2. I’m honestly curious…why did, and do, the big companies that create,support, and use GMO’s spend billions to fight mandatory labeling if it costs so much to develop a new trait approved?

        3. Travis: “the emotionally charged screaming of the opponents” – this is really tricksy wording to attempt to undermine the overall validity of any opposition to GMOs. You use the word “screaming,” twice, in fact.

          Please at least balance it by describing the arguments those who favour GMOs as “dollar-eyed greed” – because in 99.99% of cases, that is what we’re talking about here.

          Or, better yet, let’s not attempt to label (and thereby belittle) people with opposing views derived in good faith, and from analysing the evidence? Such derisory speech has no place in rational adult discourse.

          As a secondary question, do you Travis support mandatory labelling of all foods containing any GMOs, and of all animal products where animals have been fed on GMOs?

  5. Two thumbs up for your view on GMOs. We have been doing things ad hoc for centuries. Having a precision tool that could allow us to rationally affect outcomes is a potentially good thing. The issue is what genes we modify and towards what end.

    1. The Sorcerer’s Apprentice comes to mind though, especially when the the Apprentice thinks mainly about the current quarter and next year is blue sky.

  6. I have found at least with myself that most probiotics are in fact useless for me. The exception to this is the SBO(soil based organism) probiotics. Normal probiotics can’t survive the stomach acid to make it into the intestines. Still the best sources of probiotics is eating an extensive variety of fermented foods like sauerkraut and kimchi. Even though it’s not strict paleo fermented dairy is excellent too for two reasons. One, it has the usual lactobacillus strains but it also has the rare and elusive thermophillus and bulgaricus strains as well. These aren’t found in fermented vegetables. Two, the fermentation of dairy turns it’s fats into short chain fatty acids that produce energy for your gut, fermented dairy is all around an excellent food for the gut. Plain(no added sugar) full fat yogurt is my favorite, but kefir is good too.

  7. I couldn’t help myself but giggle at the assertions made by Dr. Yoni Freedhoff by proxies of Vice. On the subject of probiotics, we don’t know if the subjects ate pasteurized yogurt or not (plus they didn’t address Mark’s points). 2nd, naturally, those succumbing to consuming industrialized gluten free products in general and those based on rice in particular, will be at risk of consuming Arsenic and other junk. And lastly, why risk consuming GMO products, when what’s hidden from us, surpasses what we are being told? And lets not forget the fact that the Monsanto executives of yesterday, end up as the policy makers at the FDA (past & present) and vs-a-versa.

    And as far as kale, cabbage is drastically cheaper per pound and just as healthy. And frankly, I’d rather spend my hard earned money on berries and grass fed butter the a few green leafs (-:

      1. Yummy… You should try grilled Cabbage []

  8. I only take probiotics, (Mark’s brand) on weekends. Better, I think, is to eat a variety of fermented foods. I eat different brands of raw kraut and kimchi daily, but on weekends where I fast, the only thing I have in the morning is one probiotic pill.

  9. I am wondering if a combination of helminths and [more traditional] probiotics could be a game-changer for those with a depleted microbiome and immune issues?

  10. I don’t take probiotics now but have in the past and found them helpful. If I ever have to take an antibiotic again I would certainly take them afterward. As far as the whole GMO debate I have not done enough research but chose to avoid them. And completely agree that going on a “traditional” gluten free diet is not very healthy. You
    are just replacing processed crap with even more processed crap. But eating gluten free the way I have for the past six or seven years is amazing…I’ve never felt better!

  11. I will continue to nurture my gut biome which includes eating a primal / Mediterranean diet, fermented food, drinking a little ginger tea and taking probiotics. I will continue to eat vegetables, berries, chicken, fish, nuts, healthy oils, a little wild rice and quinoa and avoid bread, pasta, sweets including products that contain wheat. Finally … I eat fresh food and don’t believe I’m consuming any GMO products … but what could POSSIBLY go wrong with genetically modifying food??? 🙂

    Thanks for another informative article Mark and hope everyone is having a great day.

  12. There is a different scenario possible with GMOs. Glyphosate interrupts the shikimate pathway in plants. The pathway is a necessary metabolic route for the biosynthesis of aromatic amino acids. Without it plants die. The goal of GMOs, in regard to glyphostate, is to engineer plants with biosynthesis not shut down by glyphostate. Thus the when the engineered crop was sprayed it does not die but all the weeds around it do. Human’s do not have the shikimate pathway thus it was assumed that glyphostate would not have an effect on humans. But bacteria do have shikimate pathways. Thus glyphostate might be affecting our gut bugs. And in a nod to fairness when glyphostate was formulated we did not know much about the human gut bacteria and its function. Thus it was regarded as safe because it was not an aspect tested. So while GMOs might not be bad for us glyphostate could. By the way Tamiflu is highly refined shikimic acid and works by limiting an enzyme the virus needs to successfully reproduce and spread the infection. Thus it would not be a surprising if tamiflu et ali negatively affects our gut biome as well.

    1. I think there might a difference between glyphosate and “Round Up” in its final product form as well.

  13. According to evolutionary theory, every toxic plant is the result of genetic mutation. Every one of the things that we have found out the hard way, that we shouldn’t eat or shouldn’t eat in quantity.

    Plant breeding in the past has been simply selecting favoured mutations, and graduated to encouraging mutations at a higher rate, but the mechanism of random genetic mutation has not changed.

    The problem with random mutation is that for most of history we have not known what other mutations have been going on in the background that we don’t even know to test for.
    On the contrary, gene-splicing means that we DO know which genes we are changing and we have a better – although not perfect – idea of what should change and what to test for.

    Like anything, it’s a science that can be used well, or abused. Talk all you like about corporate greed, but consumer greed – the kind that wants to spend an ever-smaller proportion of our income on food – also has a lot to do with it.

  14. Probiotics aren’t useless. They espoused for a variety of ills, everything from constipation to cancer treatment. Scientists believe that probiotics work by repopulating the gut with good bacteria, which can be eliminated along with bad bacteria during a course of antibiotics.

  15. The issue with GMO’s is exactly as you said Mark, it’s what they allow us to do, and what we do with them is continue to destroy the environment. Gene insertion in and of itself is not inherently bad. The mass majority of GMO’s are produced so that we can use pesticides/herbicides which are mostly neurotoxins. They kill beneficial insects and soil bacteria, promote monoculture which in and of itself also depletes soil nutrients. The whole intention has begun to express itself as promoting this wildly out-of-control continuous growth of sprawling fields of GMOs that continue as justification for deforestation, etc.

    It’s really just a bad scene altogether that, if we care for the planet, no one should be supporting. It’s not necessarily about the science being wrong or evil, it’s that the science is in the hands of those who are sick with the greed of profiting from the decline of our ecosystems.

  16. “What if you went “gluten-free” by replacing your grains with meat, vegetables, fruits, and tubers? I swear there’s a name for that…”

    Oh man…too early in the morning…caught me off guard….I laughed so hard I almost snorted my peppers and steak breakfast. Dinner was so yummy I had it again this morning.

  17. First – the Vice article. Your debunking probably didn’t take too long to produce. Why couldn’t the writer reach out for a different opinion from someone? That would be the more professional approach.

    Probiotics – I have started making my own sauerkraut and love it. I started using Life Extension’s flora assist and have been able to quit my decade long usage of a PPI (prescribed by my GI dr!). I’ve suffered from side effects from using it. Skipping it for more than a day or two would result in serious stomach pain. But after starting Flora Assist, I no longer had any pain. I’m supposed to return for a colonoscopy and other procedure this year and hope to hear than things are better.

    I plan on taking Culturelle soon due to scientific research that has shown that strain of bacteria to be helpful for some other issues I’m having. It really is a case of experimenting if you’re not 100% GI healthy.

  18. My opinion is people who think Roundup is safe should be required to drink an entire jug as it’s sold at the hardware store and in front of everybody to prove it.

    1. I live surrounded by corn and bean fields. One week ago tonight, the fields were doused with Roundup. Walking out my back door was like being gassed. One week later, the air still has a stench to it. It’s a little unnerving. And disgusting.

  19. i use regular Roundup on my farm for certain things: poison ivy, and invasive non-native perennial plants such as five leaf akebia. The plain Roundup without any special additives is the one I recommend. I am careful: I wear a Tyvek suit when I use it (which is probably overkill), and gloves, and I take a shower afterwards. I think glyphosate has a place in management of the land, especially when it comes to controlling invasive non-native plants. You can also paint it on the stump of a vine or shrub after cutting it down. Brush it on full strength. If you are careful and use it judiciously, I think it’s a good tool.

  20. I figured the article from Vice overreached a bit. I’ve seen too many successful examples of probiotic supplementation for me to doubt it.

    I do agree with the idea that you can’t fix what isn’t broken, though. I’ve taken probiotics when I didn’t need them, and I didn’t see many changes. I noticed pretty good results the first time that I took them, though.