Dear Mark: Easy Prebiotic Foods, NSAIDs and the Gut Bacteria, Plus Some Hydration Questions

IbuprofenFor today’s edition of Dear Mark, I’m answering a bunch of questions from readers drawn from the comment sections. First, is there a better, whole foods-based alternative to prebiotic powders, meals, and flours? Turns out there are many, and I give a few of my favorites. Next, what’s the deal with NSAIDs and the gut? Everyone knows they increase leaky gut, but can they also affect the gut biome directly? I finish up by answering several readers questions regarding hydration. Can stevia replace syrup in the hydration solution I posted? Does anything change for post-menopausal women? Does milk work?

Let’s go:


Can you give some good, practical examples of prebiotic foods? I am taking in resistant starch in the form of potato starch and it seems to be beneficial (or at least not harmful) but I know there are other options as well. I just don’t think I can eat that much raw garlic (or the people around me would appreciate it).

Any suggestions on ways to get other prebiotics in or supplements (inulin?)



Sure, there are tons of whole foods prebiotics, most of them delicious, easily accessible, and more nutritious than their equivalent in refined fibrous powders.

Instead of potato starch, eat green (or greenish) bananas and/or cooked and cooled potatoes. Potato starch is great, but it’s just resistant starch. Green bananas and cooked and cooled potatoes both give you RS plus potassium, magnesium, and a spectrum of different fibers. Cooked and cooled potato salad is a great way to get RS.

Instead of inulin powder, eat Jerusalem artichokes (fartichokes), onions, leeks, or chicory root. They are whole foods and will provide ample micronutrients.

Eat nuts and seeds. Modest amounts of most nuts and seeds will help. Almonds and pistachios seem to have the most prebiotic potential, while macadamias are quite low in any fiber at all.

Don’t forget about “animal fiber.” That’s the gristle, the cartilage, the chewy bits at the end of chicken bones that can have prebiotic effects in our guts. Plus, animal fiber provides the all-important collagen that so many modern eaters are missing from their diets.

Just eat a wide variety of plant matter. Some broccoli here, some Brussels sprouts there, a handful of blueberries, some almonds and pecans, a roasted kabocha squash, a Big Ass Salad for lunch—that sort of thing. In addition to different types of fiber, colorful fruits and veggies also provide polyphenols, which can have prebiotic effects.

And yeah, I’d lay off the raw garlic. While a couple cloves are definitely beneficial (and may even paradoxically improve your body odor), eating enough to get the prebiotic benefits is a stretch.

I’m surprised you didn’t address the negative effects of NSAIDS on the gut, or do NSAIDS affect the gut wall directly and not the biome?

Yes and no.

When gut-aware people typically caution against NSAID overuse, they focus on their ability to directly damage the intestinal lining. This is a big problem, to be sure. NSAIDs can worsen gut barrier dysfunction and increase intestinal permeability in patients with IBS (who frequently take it to deal with the symptoms). An animal study indicates that NSAID overuse may even increase gluten sensitivity by “potentiating” its barrier dysfunction.

There’s also definite evidence that NSAIDs can directly change the gut biome.

This direct effect on gut bacteria isn’t unique to NSAIDs. As Art Ayers put it recently, “all drugs are antibiotics.” Almost every pharmaceutical (and many “natural” products) interacts with the gut biome on some level. Many drugs were designed as antibiotics or derived from natural compounds whose original owners—plants—used them to fend off microbial attacks. For instance:

So NSAIDs are not alone. And it may be that these drugs, which many people take chronically, are more responsible for widespread antibiotic resistance than antibiotics, which are usually taken for just a week or two.

Two questions:

1. Does stevia count as “sugar” in the water? Carbs kill me no matter where they come from, or why I consume them.

2. What about post-menopausal women–what should THEY do lacking a luteal phase?

Unfortunately, as it has no calories stevia doesn’t work for the purposes described in the hydration post. For those who haven’t read it, I gave a quick recipe for a hydration formula: a pinch of salt and a teaspoon of maple syrup added to water. The salt provides much-needed electrolytes and the syrup provides glucose and fructose to facilitate the absorption of water through small channels in the intestines. The sugar is not going toward caloric requirements in the strict sense. It’s fueling the cells absorbing the water. Do you think a single teaspoon—4 grams of sugar—will really be too much for you? Maybe, but I doubt it.

Also, remember that this recipe is intended for athletes and other people engaged in serious training, often in warm conditions promoting heavy fluid loss. If you’re taking it easy, the salt/sugar solution is probably unnecessary. If you’re going hard enough to warrant this solution, you’ll burn right through any errant milligrams of glucose that make it past.

What about post-menopausal women? The same solution applies. My point in mentioning it was that sodium requirements may be elevated in some women during the luteal phase, so they should take special care to obtain enough sodium when exercising. If you’re post-menopause, you can still benefit from the solution, but it may not be as critical.

How about milk?

Actually not a bad idea. A surprising amount of evidence supports milk’s hydrating abilities.

In kids, drinking milk beats drinking water for hydration.

For post-workout recovery and hydration, milk beats sports drinks. If you’re lactose intolerant, lactose-free milk even works.

Milk being effective isn’t all that surprising. Breastfed babies live entirely off the stuff, obtaining all the electrolytes and fluids they need to stay hydrated, even in hot climates.

To sum up, on a hot day a glass of lukewarm milk may feel like a bad choice, but it will definitely hydrate you. Just make sure you’re tolerant; explosive diarrhea has the opposite effect on hydration.

That’s it for today, folks. Thanks for reading! Be sure to throw any tips or responses you have down below!

TAGS:  dear mark

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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16 thoughts on “Dear Mark: Easy Prebiotic Foods, NSAIDs and the Gut Bacteria, Plus Some Hydration Questions”

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  1. Great post! I love milk but i’ve heard that it is only good for you if it is raw and grass fed. This isn’t available near me unfortunately.

    1. Not true. Optimal, but not required. Grass fed can probably be found, if not, there at least organic in the store!

  2. Hey mark. Not sure if this has been covered lately, but it’s relevant to me and probably a lot of other people(although not to this particular blog post) The topic is the effect on health of natural gas exposure. I’ve recently developed a series of health conditions which seemed to slightly correlate with diet, but now seem to correlate most powerfully with exposure to the combustion byproducts of natural gas. Workplace and home exposure both contributed to the development of the issue. With the popularity of natural gas, especially in the context of the (often under-ventilated) home kitchen, it might be a good topic to do a post on. A number of people i know who work and live under similar circumstances have seen increasing incidence of inexplicable health conditions, particularly of the lungs and skin. My intuition has always said that it’s obviously dangerous and toxic, but it’s hard to quantify dose, and the effects seem to vary a lot. Most states don’t seem to have solid regulations on the books with regards to air quality. Any words of wisdom would be appreciated.

    1. Natural gas is actually a very clean means of heating if properly installed and vented. Get a qualified technician to check your furnace, and have the power company check for gas leaks. If you have a gas stove, you might want to swap it for an electric one. You could file a formal complaint where you work. Doing so might force them to check their heating/cooling system for dirty filters, mold, mildew, etc.

      1. That “properly installed and vented” is the problem–as an architect doing lots of remodels, properly installed mechanical systems are the exception. If using gas, sealed combustion furnace and water heaters are the only way to go; and a vented hood over a gas stove is a must: CO is a byproduct of partial combustion.

  3. A great prebiotic is mock potato leek soup. Recently I have been substituting sun chokes instead of potatoes. I sauté the diced sun chokes in Kerrygold, add chopped leeks to the sauté, top off with homemade chicken broth, add salt and a few sprigs of fresh thyme and simmer away. Sometimes I hit it with a stick blender to cream it up a bit. I little bit goes a long way in the prebiotic department.

  4. Interesting read as always.

    I’m not advocating this, just pointing out there are some life extension physicians and scientists who take Metformin based on studies indicating even for the non-diabetic population it has many benefits that may increase lifespan. I think the primary concern is it may affect the liver and lowers certain B vitamins such as B12, so they supplement accordingly.

  5. Off topic, but I’ve been locked out of the MDA forum for days. Seems that at least a few others are having the same problems. The first time I requested password reset, the new password emailed didn’t work. With subsequent password reset requests, I never receive the email even after it says it has been sent. Hopefully there are a few Worker Bees or Admin staff around that can sort out the problem.

    1. Hi I noticed your post here some time after I posted a similar one below.

      Yes I’m sure plenty of accounts are affected though only regular users will notice of course. The posting interval is very slow as I guess there very few active members able to get on the forum.

      Note : even after requesting/getting new passwords they don’t work either ( so that is a waste of time in any case) – the spambot from the Amazon network in Oregon seems to keep trying and the retry limit is always used up when we go to try.

      Anyway looks like this could go on in to the new year – maybe now’s a good time to do other things 🙂

  6. I take quite a bit of Metformin. My doc checks my liver regularly. He says that as long as there isn’t a change in liver health, Metformin is safe. I don’t always trust docs but there is a lot of evidence that Metformin is beneficial.

    I also take low dose aspirin and sometimes Advil. Yes, there are dangers from them. Having had a heart attack and maybe a TIA, low dose aspirin is recommended for me. Sometimes I need Advil. I rotate it with Tylenol. One or the other most days. I also do all sorts of alternative stuff.

  7. Interesting set of questions! I never thought of “animal fiber” before. That was an eye opener. Now that I think about it, it makes perfect sense. And the collagen is healing to the gut as well!

  8. I don’t have assess to grass fed milk so I use organic 2% milk to make kefir. Do I still get all the health benefits- probiotic, protein, fat and whatever else? Thanks:-)

  9. Dear Mark,

    Any chance of fixing up the recent forum login lockout issue of many of the legitimate forum members?

    The lockout is approaching a week now, no response to the emailed issues on the subject.

    Surely the spambot hacker’s address from Amazon in Oregon can be blocked allowing the legitimate members in.

    General read-only access to the forum shows it’s a ‘ghost-town’ there – the site stats must be reflecting this.

  10. My thoughts on the supplements vs the real thing are slightly different. Food is better. Period. But today’s vegetables are cultivated to be less tough (less fiber) and sweeter (more calories). So I do what I can diet-wise, but make up for things with supplemental fibers. A green banana is great, but it’s a huge hit in calories. Potato starch has practically no calories. The right answer is in the middle, I guess.

    The parts normally thrown away from vegetables are good. The green parts of leeks. The skins of onions and garlic. (Yes, the are edible.) The stems of broccoli, collard greens, and kale.

    Don’t forget dried apricots, prunes, and figs.

    Seeds. Spices. Black pepper. Cumin. Chile peppers. All those great prebiotics.

  11. Resistant Starch

    Today’s post (really interesting…) has no mention of rice whereas previous articles have generated lots of references (cold rice pudding, sushi etc.)

    I noticed rice scored poorly on the (FreeTheAnimal) PDF referenced previously.

    Has rice fallen out of favour as a source of RS?

  12. As a follow-up to previous post could I also add that generally potatoes score poorly in the (FreeTheAnimal) PDF referenced previously unless they are roasted and cooled.

    100g Roasted and cooled provides 19.2 RS


    100g Cooked and Cooled (the phrase used in your post, today) provides only 3.2RS, and 100g Steamed and Cooled provides 5.8 RS

    On the basis of that data how you ‘cook’ your potatoes changes appreciably the RS content.