Primal Flora: Your Questions Answered

A few weeks ago, I unveiled the new and improved Primal Flora. With four new strains reflecting the latest microbiome research, I’m really happy with the results we’ve had so far. But that’s easy for me to say — I’ve been living and breathing this product for the better part of a year, including months of research, consulting with experts, and personal experimentation, so I know Primal Flora. But not everyone does. And in the comment section of that earlier post, and in emails I’ve received from some of you, many questions arose. Today, I’m going to answer as many as I can.

Without further ado:

Great stuff! Thank you. Ordered my monthly supply! When is the best time to take probiotics? With food, without food? A.M., P.M.?

Take probiotics with food or 30 minutes before meals, as they seem to survive the transit through our gut when taken this way (as opposed to after a meal).

If you think about how we’d obtain probiotics before supplements, this makes perfect sense. They’d either be attached to the food in the form of dirt (soil based organisms) or they’d be inherent to the food because of fermentation. Since many of us no longer eat plants we’ve plucked straight from the soil without washing, nor does everyone regularly consume a wide variety of fermented foods, Primal Flora taken with food is a worthy mimetic.

Do you think this product is okay for those avoiding nightshades? Referring to the potato starch ingredient.

Yes. For a couple reasons:

1. Potato starch is just starch. It contains no potato proteins and none of the nightshade alkaloids that sensitive people sometimes must avoid. This is similar to how gluten-free foods can actually contain wheat starch (and in Europe, gluten-free food manufacturers have used wheat starch for years) and still qualify as gluten-free because the residual gluten is so minimal in starch.

2. Even if it did contain nightshade alkaloids, we’re talking about 50 milligrams of potato starch. That’s like 1/16 of a teaspoon. The average blueberry is far more problematic from a nightshade standpoint than a few milligrams of potato starch.

For what it’s worth, I’ve sometimes noticed mild joint pain from excessive potato consumption, but neither large doses of raw potato starch (for the resistant starch content) nor the miniscule doses present in Primal Flora have ever given me issues.

Can the Primal formula go bad because of long overseas shipping? Can the bacteria somehow get activated & infect the body with countless diseases?

1. No. Primal Flora is completely shelf-stable, no refrigeration required. Its strains can withstand some fairly harsh conditions, like an intercontinental flight.

2. The strains in PF were chosen not just for efficacy, but also for safety. Unfortunate adverse reactions occur in some people with any supplement. That’s just the nature of consuming pharmacologically active substances, whether it’s a vitamin, a mineral, a drug, or a viable probiotic strain. And if you have an immune deficiency, certain probiotics may be counterproductive and should be cleared with a doctor. Also, these are intended for oral usage. Don’t go rubbing Primal Flora in your eye or anything. That’s a good way to get endophthalamitis. But “countless diseases”? Not likely.

Started taking them 3 weeks ago so I don’t know if I should see results by now. I chose them because there were no histamine increasing strains and even one histamine lowering strain. I can’t swallow pills that big though. I hope that they reach my gut even if I open them because it’s really pricey 1$ USD per pill.

The strains chosen are all hardy and should resist digestion. The veggie caps are there as an extra barrier just for further protection. I’ll occasionally empty a cap or two into my smoothies and I haven’t noticed any reduction of effect. And for those wondering, the capsule is a normal/average size.

Can someone with a trained eye comment on how this compares to Prescript Assist?

The only real similarity Primal Flora shares with Prescrip Assist, beyond being a soil-based probiotic supplement, is the presence of Bacillus subtilis. Everything else is different. From what I’ve gathered, Prescript Assist is a fine product that should complement Primal Flora quite well.

Does anyone know if these can be used for dogs? Our dog had just had a nail ripped off and had to go on 7 days of antibiotics, which I’m bummed about. Thought something like this could help build her gut bacteria back up.

While this isn’t designed with dogs in mind, it probably couldn’t hurt. Most of the strains used in Primal Flora have either also been used in canine probiotic supplements or appear in normal healthy canine guts. Either way, they’re probably safe and potentially quite effective.

In one study, giving Bacillus subtilis to dogs improved the consistency and quality of their poop. Dogs on the B. subtilis had less protein in their poop, indicating better digestion and assimilation of nutrients. It also improved the odor, which isn’t to say that it will make your dog’s poop smell good.

Another study found that giving a synbiotic containing Bacillus coagulans to Alaskan sled dogs improved butyrate production, reduced diarrhea (after a disease outbreak), and improved the fecal score.

Since dogs have lived with humans for so long, often eating the same food (or leftovers) and living in the same living quarters as us, their ancestral gut biome might be closer to ours than other animals. They carry a lot of Bifidobacterium strains, for example. I’d say give it a shot.

Just wondering if this could be used for kids? I have a 5 year old with recurrent upper respiratory issues, so would be interested in giving it a whirl. Could the capsules be emptied into yoghurt or something to make it easier to give to a child?

This isn’t designed or intended for children, as they’re considered a special class of human with special requirements. I will say this, though:

Kids eat lots of dirt if you let them. It’s kind of what they live to do. Mud pies, dirt clod fights, a stubborn unwillingness to wash their hands before eating — kids intuitively know the importance of dirt ingestion. So while they probably don’t need a supplement if they’re getting plenty of free play out in the dirt, my personal (but not professional) opinion is that it’d probably be okay.

Besides, these aren’t foreign, harmful strains never before encountered or carried by children. In fact:

I don’t think most kids need a probiotic. But if they do take one, Primal Flora should be pretty safe.

I totally agree with you that we need to work on keeping our gut in check. I take DE (diatomaceous earth) on a daily basis to help eliminate the bad parasites as well as all the other benefits you get from it. Will the Primal flora Supplements work ok in conjunction with DE?

Yes. DE has no effect on the strains found in Primal Flora (or any strains, from what I can tell). Go for it.

That’s it for today, everyone. I hope I answered your questions, and if you’ve got an others, feel free to shoot them off down below. Thanks for reading!

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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 “Primal Flora: Your Questions Answered”

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  1. Just a tip that I’ve heard: empty the capsule into some milk or other sugar containing drink and wait a bit. Bubbles will lay to rest the death of bacteria due to transit and will also raise the total number of strains you are ingesting!
    Does anyone know though if this will cause competition between the strain species, potentially killing one or some off?

    1. Zach, it depends on which one you want to take the lead. Mark has done a great job formulating a probiotic arsenal. All of them are great for what the do. but they do different things. Adding capsule to dairy may favor the organisms that naturally thrive in dairy. The L. plantarum tends to dominate cruciferous vegetable ferments. S. boulardii is a yeast that was isolated from tropical fruit. So if your problem is travellers diarrhea, add a capsule to mangosteen juice and see what happens. Fermenting food is the best way to get probiotics. If you are going to experiment, inoculating a culture with Primal Flora is an interesting concept. I would only suggest this if you have home fermenting or microbiology experience. The purpose of probiotics is defense against the bad bugs and it is good to know what they smell like in advance. If not, taking a capsule is better than potentially infecting your family with listeria.

  2. I would love to try Primal Flora, but shipping rates from to Canada are ruinous. A $29.95 bottle costs $26 dollars for shipping. That seems incredibly high.

    Plus, since uses DHL as their shipper, the shipment will almost certainly incur a customs fee, plus a DHL fee for applying for that customs fee on the customers behalf, for an extra $20 or so. That more than doubles the purchase price of the product.

    Please note, I am not complaining about the price of the product itself. That seems quite reasonable. Just the shipping costs. I buy a lot of products from the U.S., and rarely see shipping costs like this.

    USPS would be a better option. Cheaper shipping and somehow manages to get to me without incurring customs.

    What do you think, Mark? Any help for your (would-be) customers north of the border?

    1. Take a look at shipping rates from Amazon. I can get it from Amazon in the US with no shipping costs. Maybe it’s similar, or at least cheaper, for you in Canada.

      1. Good idea! Just checked, no luck. had four suppliers, including Only one ships to Canada, and the shipping and handling fee for one bottle is $31.94. There is still the possibility of a customs charge.

        So, no dice. Still exhorbitantly expensive.

    2. Whats interesting is carries Primal Flora (sold by Primal Blueprint and Fulfilled by Amazon, thus Prime elegable), but doesn’t.

      I wonder when Mark will get around to invading other Amazons.

      1. That would be great! If Mark got his products on, I think he would be able to reach a lot of customers who won’t purchase his products now because of the price. I think the payoff, for his company, would be fairly good for the effort involved.

        Here’s hoping!

        1. I’m another one hoping for that. I just recently made an order from Primal Blueprint…$26 for shipping and another $23 for customs. Still yet to see the $AM to $CAN conversion. Won’t be doing that again.

    3. Hi there,

      If you email [email protected], customer service can work with you a different shipping options that maybe more cost effective for your area.

      There’s also a live chat feature on, if you’d prefer!

      Hope this helps!

      1. Thanks, Elizabeth, I’ll give that a try! Have they been able to help you?

  3. “Also, these are intended for oral usage. Don’t go rubbing Primal Flora in your eye or anything.”

    Wait, I’m not supposed to ingest this ocularly!!!?

  4. About the dogs: your vet may have some prescription probiotics geared specifically for dogs. A few animal med websites sell the OTC, but they MAY need to be shipped refrigerated.

    Same goes for cats. I have a cat with CKD who uses prescription ones geared for consuminging the by-products of protein digestion (creatinine, phosphorus, etc.), and it’s kept refrigerated. Genrealized ones are available both prescription and OTC. The only other one I’ve used for cats is FortiFlora.

    This brand is also made for dogs. Just mix it in with the wet food–it’s liver-flavored, so there shouldn’t be any taste problem.

    1. Jarrow’s PetDophilus is a great product and you don’t need a prescription. Mercola Healthy Pets also has a great pet probiotic.

  5. Hi, long-time follower of MDA here (since 2011). Just needed to jump in with a HELL NO!!!!! Regarding this:

    “Do you think this product is okay for those avoiding nightshades? Referring to the potato starch ingredient.

    Yes. For a couple reasons:”

    I am allergic to nightshades, in particular potatoes are my main trigger. I’ve been eating really, really cleanly. And had begun intermittent fasting to further give my body a chance to heal, when I ran out of my potassium supplements.

    I dug out an old bottle of potassium from Twinlabs and didn’t even think twice. Didn’t even think to check the label. I had the worst set of boils pop up immediately. And they lingered an unusual amount of time, for three weeks.

    They just wouldn’t heal.

    A few days after they first showed up, I thought to check the label and sure enough Potato starch was in the ingredients. For some reason I reacted worse to the potato starch, than if I’d had accidental contact with oil used to fry potatoes, or even eating french fries or potato chips themselves.

    And so, NO! If you have a nightshade allergy, I’d be careful. And if your main trigger is Potatoes, then I would avoid at all costs!

    Sorry Mark, would love to get behind this, but no. On the other hand, if it was made with Tapioca Starch, I’d give it a try.

    1. People tend to think peanuts are the only dangerous allergen for people who are sensitive, but that’s not true. Allergies can occur with any food. A single sunflower seed would be enough to send my daughter to the ER. A severe allergy can morph into anaphylactic shock, which can easily kill a person. This was discussed by an EMT who posted here recently.

      In all probability, potato starch is safe for the vast majority of people. I have no problem with it myself. However, if you know you’re allergic to anything derived from potatoes, you would do very well indeed to to avoid it completely, no matter how minuscule the amount. The body can easily recognize and act upon substances that are microscopic and even smaller. This is one of the main principles of why homeopathy works.

      1. This is one of the main principles of why homeopathy works.

        It doesn’t work.

        1. Ah… Another guy who has probably never tried it and knows nothing about it…yet he “knows” it doesn’t work. Interesting how many people have bought into the allopathic mindset, thinking something has to be an overkill rife with side effects in order to “work.”

          Of course it works.

          I’ve used homeopathy successfully for myself, my son, and my animals for over 15 years. A lot depends on the experience and ability of the homeopath, who will prescribe a remedy after an in-depth consultation. Homeopathic preparations need to be custom-formulated. You can’t just go buy a tube of something labeled “homeopathic” from the health food store and expect it to work. That isn’t real homeopathy.

        2. Homeopathy works just as well as a placebo.

          But if you adjust up the baseline of ‘zero effect’ to equal the effects of a sugar pill then homeopathy have this ‘zero effect’.

          If I’m sick or down and someone lovingly brings me a hot cup of tea – I feel much better – not quite the same effect if I make it myself.

    2. Just want to second Shary’s reply – as a person sensitive to nightshades, I’ve found that potato starch is a definite trigger – leads to all the same symptoms as if I had eaten a bowl of curry.

      Definitely something to avoid if you are sensitive to nightshades! Glad to hear that it’s a very small amount but unfortunately I still get a reaction.

  6. As we’re grown up kids, isn’t it easier and cheaper for us to eat dirt also? I grow lots of my own veg, pick and eat wild berries without washing, use unwashed herbs in my salads and only clean using natural products (actually just water most of the time).

  7. I currently take Megaflora but would be curious how this compares to that. I’ve heard some talk that Megaflora has difficulty surviving the shipping process whereas PrimalFlora is shelf stable. Any comparisons would be helpful.

  8. Very timely post! Yesterday I decided after one month on Primal Flora to get a monthly automatic renewal to get free shipping. I asked Shasa who took the order why I needed to take PF every day. I hoped the colonies of helpful bacteria would establish themselves and I wouldn’t need an every day capsule. She wasn’t sure but was going to check with someone in production who could answer the question and she would e-mail me back. It is a treat to see all these questions posed and answered. I’m not sure I’ve noted much improvement in bowel function in a month. I’m willing to give PF a longer trial. I think I’ve taken the capsule more after breakfast than before or with. Will see what happens with better timing. I wonder if PF would help my ancient mother (94 recently diagnosed with celiac disease) with some of her digestive problems. She has trouble gaining weight. She is still 6 ft tall and weighs on a good day 127 libs. Not enough. Any thoughts? Anyone?

  9. A cup of sauerkraut several days a week works great for me. It is so delicious that it is tempting to eat more!

  10. Is there any evidence that these strains colonize the gut?

    We’re cycling through several probiotics as part of an attempt at treating my wife’s autoimmune arthritis. Right now we’re using Prescript Assist and Primal Flora–after those we’ll cycle in AOR’s, (mainly for the C. Butryicum.)

    After that batch I’m trying to decide whether to cycle back in the PA or PF.

  11. I’ve taken probiotics on and off for a few years now. I had gotten out of the habit recently and decided to give this a try a couple weeks ago. I have to say this is the first and only probiotic where I’ve actually experienced a difference…and fortunately the difference was good. As a result from the Primal Flora success, I’m contemplating Mark’s Damage Control but the price tag is high and I tend to get light headed with anything containing ginko biloba so not sure on that one yet.

    1. First off, Mark’s products are one of the few I really trust.

      You may also want to be aware of B9 present as Folic Acid in the Master Formula. What we really need is the folate form of B9 as many people can’t metabolize Folic Acid efficiently and this can cause issues downstream (in methylation). Master formula is wonderful but I am not too keen on having folic acid every single day.

  12. Thanks Mark for your thorough answer of my previous inquiry.I have another one .I’ve never taken a probiotic supplement in my life. What to expect when I start to take the primal flora? Should I expect gut pain, stomach cramps, gas , fever or diarrhea?
    What’s normal & what’s abnormal?
    At which point should I stop taking the supplement ?
    How long can I go on taking the primal flora should everything go normal & no adverse reactions are encountered?

  13. The question about giving it to dogs made me laugh. I take a combination of VSL #3, Prescript-Assist, and another probiotic. The Prescript-Assist I keep on the counter along with a couple other supplements because it doesn’t need refrigeration. This is next to the basket where I keep the dogs supplements (Dasuquin, an antihistamine for her mast cell cancer, and something for incontinence).

    I gave strict instructions to my husband about which pills to give the dog twice a day. One day I happened to see him prepare the food for the dog. Sure enough, he was giving her one of my Prescript-Assist capsules with every meal!

    I knew it wouldn’t hurt her, but geez, it sure put a dent in my wallet that month!

  14. What are probiotics?? Some probiotic supplements offer prebiotics too. How do these work?

    1. Probiotics are living strains of baceteria. So a capsule may have something like 1 Billion CFU (colony forming unit).
      Pre-biotics is like food for the biota (microbiome or gut bacteria).
      Both are needed. You want the good guys to be living and thriving in your gut and then you want to feed them too. Veggies like artichoke, leeks, asparagus will give you plenty of pre-biotic fibre.

  15. I think some newer research is showing that some gut bacteria configurations promote or prevent depression and other issues of the like. Thoughts?

  16. Mark,
    What do you know about taking immunoglobulin (antibodies derived from mammal colostrum or extracted from chicken egg yolk)?

    Immunoglobulins are produced by the immune system to bind to pathogens (bad bacteria, virus, parasites, cellular debris). That way the pathogens are identified for destruction and rendered impotent because they have an antibody attached! Kind of like trying to walk with someone on your back.

    I have read research that immunoglobulin from mammals IgE, IgA (cows, goats) stimulate inflammation and rH Factor but immunoglobulin from chicken eggs (IgY) is effective in attaching to pathogens but does not stimulate inflammation since has a slightly different shape.

    I have been taking a product called Vector450 (it’s also called IGYImmune) and it cleared up a gut problem I had (constipation) which I just lived with for 5 years. I have also noticed a quick recovery from hard workouts or cross country ski races. Which as a 60 year guy is kind of nice.

    The research out of University of North Texas is indicating that IgY acts as an immune modulator; that is it helps a depressed immune system come back to normal and it also calms down an overactive immune system (think autoimmune issues). The Vector450 product certainly eased my allergy symptoms for two years but not this year. Illinois has been horrible for allergies and only Nasacort has brought me back to normal. However, when I stopped the Vector450 the allergies got even worse. I have to say that Nasacort OTC is fantastic for my allergies.

    I was so impressed with the Vector450 that I invested in the company. It is a private firm based in Thunder Bay Ontario. I introduced it to many Ironman and cross country ski professionals and they think it has been terrific for recovery and allergy relief.

    I am thinking that it can help anybody get rid of pathogens and clear the runway for the probiotics to proliferate.

    What do you think?

  17. I’ve completed one bottle of Primal Flora. I’ve noticed, for lack of better, a “charged” sensation in my gut area. It’s hard to describe — something askin to a highly energized state from my solar plexus into my legs. Sleeping had become difficult even though I’m approaching exhaustion after multiple nights of very little rest. I know correlation isn’t necessarily causation but there’s been no other change in my diet except for taking fish oil with Primal Flora. What do you think: Is there a relationship between the capsules and what I’m experiencing?

  18. I like fermented foods and I choose to incorporate them into my diet and assume they are quite healthy but still I wonder about their regular necessity or importance if you already seem to have decent gut flora and how much better fermented veggies really are than those not fermented, since fermentation in the gut is essentially how we digest our plants, so aren’t they all fermented after you eat them anyway?
    Something I’ve been wondering about is a previously opened jar of sauerkraut at my campsite that I recently retrieved and ate after more than two and a half months and it didn’t seem to have changed, or maybe just barely. Maybe the freezing and thawing cycles of the end of the winter killed any bacteria inside or the vinegar/salt content prevented bacterial proliferation?
    Or maybe it was the sulfites. I wonder about sulfites in fermented foods and am a bit suspicious of them (though I just reread Mark’s blurb about them in wine and he doesn’t caution against them). Maybe I should research them when I have a bit more time.
    Life is so hectic lately! I’m trying not to complain too much. Law enforcement people are trying to ban me from my home town because of a stupid probation condition: “reside where approved by your [insert euphemism for expletive] probation officer”, who doesn’t like me anymore and is trying to give me a hard time, and some cops were giving me a hassle there (plus someone messed up my shelter – I think it was police) so I have to avoid camping there at all or at least not get caught. I’m squatting somewhere (a tent-shed full of junk) but got discovered and have to move on soon, though luckily the guy who owns it is letting me stay there for now. There’s more complications though I won’t elaborate excessively on all my woes and the library computer timer is about to run out, same old story.
    I’ve read about gut bacteria controlling stress/anxiety and improving mood, and affecting all sorts of psychological conditions, and wonder how much mine affect my stress level, which often feels like it tends to be uncomfortably close to or into the red zone, and what fermented foods could possibly help.

  19. Hi there,

    I have been told by my functional doctor to take 7 strain probiotics for my SIBO. He has suggested that I take Metagenics Ultra flora spectrum probiotics which have a blend of 7 beneficial probiotic strains including L. acidophilus NCFM®, S. boulardii, B. Lactis Bi-07, B. Lactis Bl-04, St. thermophilus, L. salivarius, and L. plant arum.

    How does this compare to Primal Flora?

    I’m very confused about the topic of probiotics and which ones I should take.


  20. Hello! I´ve been doing a thorough research on ncbi/pubmed about bacillus clausii and bacillus subtillis, and couldn’t find any evidence that both do not raise histamine levels. There is one research that points out that some strains of Bacillus Subtillis decrease the histamine content in food, whereas there are others that increase it. On Bacillus Clausii, I could’t find anything relating to histamine, other than that it decreased rhiniitis scores in children and adults (that does not prove it lowers or is neutral in histamine, as lactobacillus reuteri has some anti-allergic properties but does raise histamine). Can you possibly provide us scientific evidence that the strains in Primal Flora DO NOT raise serum histamine? Research also shows that some strains of B. Subtillis, B. Cereus and other spore forming bacillus do not only increase serum histamine (Taylor et al 1978) but also raise pro-inflammatory cytokines like TNF-alpha and IL-6 ( What do you have to say about that ?