Phytic acid: not enough of it to be an issue?


The body absorbs magnesium much more readily from supplements than it does from food, as it is receiving it in the raw mineral form. So while the RDA for magnesium is 400mg, the recommended upper limit for magnesium coming from a supplement (as most Soylent recipes have) is 350mg. And some DIY-ers have even found that to be too much. The salient point being magnesium toxicity is only associated with mineral supplements, not with food. So while you COULD consume an extra 762mg of magnesium, if you try to do it through a supplement things are not going to go well. Instead you should look for magnesium rich foods.


Thank you for the excellent explanation!


Excellent post, Nick! Thank you for writing this up.


Good job, Nick. I agree: I don’t think this closes the book on the phytic acid issue, but it certainly represents progress in the right direction. I’ve been uncomfortable about people just blowing it off without really going into it; so it feels good to see someone make this kind of effort. It seems to be an extraordinarily difficult question (like so many of the critical issues in human nutrition) due to there being too many variables to nail down comfortably.

Obviously those who have hitherto dismissed the issue as of no importance due to the high molar mass of phytic acid have not gone very deeply into the matter; the capacity of the phytic acid molecule to bind multiple molecules of various minerals means that each phytic acid molecule is a sextuple-threat binding agent. Ahother matter that hasn’t yet received serious attention here is the capability of phytic acid to inhibit amylase, pepsin and trypsin, thus interfering significantly with the digestion of both starches and proteins.

My personal hunch is that those who keep repeating that phytates are not a significant issue are indulging in highly unscientific wishful thinking and that a questionable agenda is being pursued in trying to prove that there isn’t enough phytate in oat powder to be a problem. It seems to me that a more sensible way of proceeding would be either to look for a complex carb source that is low in phytic acid and high in phytase, or else to include phytase in the formula. I lean toward the latter option myself, but either would do the job. I wonder why no one has given buckwheat flour a serious look; buckwheat is not a cereal grain, thus avoiding the gluten issue, and it has some nutritionally valuable phytochemicals like rutin.

Anyway, thanks, Nick, for opening this subject and going into it seriously; this wins you some kudos for real scientific attitude.


@J_Jeffrey_Bragg: I was looking forward to hearing from you about this! You raise a lot of good questions; I hadn’t heard anything about the ability of phytic acid to inhibit digestive enzymes. I’ll have to look into that!

My personal hunch is that those who keep repeating that phytates are not a significant issue are indulging in highly unscientific wishful thinking and that a questionable agenda is being pursued in trying to prove that there isn’t enough phytate in oat powder to be a problem.

It’s fair for you to feel that way. I think that the scientific thing to do is to look at the data that exists, and ask whether or not it says that phytates are an issue. If the data says they are an issue, then it is scientific to believe they are an issue. If the data says they are not an issue, then it is scientific to believe they are not an issue.

To be clear, are we in agreement that phytate is definitely a non-issue for calcium, phosphorus and magnesium, given sufficient quantities of those minerals? To me this part of this picture seems clear.

As far as the other minerals are concerned, I see plenty of room to continue doubting the safeness of the phytic acid in soylent. The studies I looked at suggest, in a non-rigorous way, that there will be no issue with zinc and iron given sufficient quantities of those minerals; but other studies might say different things.

However, in all fairness, I think that if you wish to say that a problem exists, you ought to find some studies which suggest that a problem exists! I.e., you ought to find some different numbers wherein the phytic acid comes out creating shortages of these minerals.

There is definitely a lot that we don’t know enough about. There are the minerals for which there is little or no data on their interaction with phytic acid; and there is the digestive enzyme issue that you have just introduced me to. So I definitely think caution is warranted in any case.

It seems to me that a more sensible way of proceeding would be either to look for a complex carb source that is low in phytic acid and high in phytase, or else to include phytase in the formula. I lean toward the latter option myself, but either would do the job.

With this I agree. Using phytase is a cleaner approach, because there are fewer things one has to be right about for it to work. If I had access to phytase then I would use it.

I think it’s useful to distinguish between figuring out what course of action to take, and figuring out what’s true. Maybe we are strongly concerned about getting enough minerals, and even a small probability that we aren’t is worth worrying about to us. Whether the chance is big enough to worry about, however, is distinct from the question of how big the chance is.

It is consistent to say that phytic acid probably isn’t giving us mineral deficiencies, and also that we want to take steps against the possibility of it doing so. To me, it seems like what’s probably true is that the effect of phytic acid in soylent is not very pronounced. As for what to do about it? Well, ideally I’d like to take steps against phytic acid anyway. Phytase is a very cheap enzyme; if I could order it quantities less than a ton, I already would have! Such is life.

Thanks for weighing in on this!


Nick, I agree in general with nearly all that you’ve said here. I haven’t gone looking for studies because my online time is limited and every time I find a promising abstract the study itself is behind an expensive paywall, making online research frustrating for me.

I cope with my own phytate anxieties by (reluctantly) soaking my cereal grains with lemon juice and/or whey from homemade yoghourt. My crock pot won’t hold a low enough temperature to soak at 90-120F and I see no point in soaking too hot because it only denatures the phytase. I always put buckwheat in the mix, which has a surplus of phytase. I can’t soak everything that contains phytic aci d, though – imagine a peanut butter sandwich with soaked peanut butter! :frowning:

My homemade soylent uses ground oats; I also include buckwheat and spelt, though. And I DO soak the cocoa and peanut butter powders along with the grain.

Fair comment about the abundance of calcium – my own soylent has a full cup of high-yield dry skim milk in it, so I’m well covered for calcium. However, I am still concerned about the overall balance of the calcium - phosphorus - vitamin D triangle. Because there should be an optimum ratio of those three items, it’s not that good a solution just to throw more calcium at the problem and hope for the best, yet that is what nearly all of us are doing. We can’t know how much calcium – or phosphorus – is tied up in phytates, and I doubt that any of us actually knows how much vitamin D we ought to be consuming relative to our uncertain amounts of calcium and phosphorus. Do you see the problem here?

Damn right – far too little is known about these non-urgent grey areas of nutrition. Just because people aren’t dropping dead of deficiencies does not mean that everything is beautiful, our dietary intake (soylent or otherwise) is perfectly balanced, and all’s for the best in the best of all possible worlds! Ramiel Nagel does a good job of outlining the concerns associated with diets high in cereal grains and phytate vegetables in countries where nutrition may sometimes be marginal. Soylent consumption needs to be considered as analogous in one way to those countries – because it is a NON-DIVERSE kind of diet, so whatever might be lacking in its ingredients is reinforced by daily repetition and is not covered by diversity, unless perhaps the consumer uses soylent only 50% of the time or less. So I would say, if we’re going to consume 100g of oat powder (I’ve seen some formulae as high as 400g BTW) every single day, we need to be aware of all possible nutritional ramifications entailed by constant consumption of that particular ingredient.

We must not forget that what we are doing here is EXPERIMENTAL. Just because our intention is “perfect nutrition” with all RDIs satisfied does not mean that we shall automatically fulfil that goal. Some things may be missing from our fomulae; absorption of some things may be poor; absorption of some things may be blocked; some ingredients may have extra unintended consequences. Only time and widespread usage – plus some large-scale controlled experiments – will tell whether we have achieved optimal nutrition or not. Wouldn’t you agree?


Thank you for the response!

I haven’t gone looking for studies because my online time is limited and every time I find a promising abstract the study itself is behind an expensive paywall, making online research frustrating for me.

I can feel you there. Not being in university at the moment, I have the same problem.

It’s cool that you’ve got a lot of measures in place to deal with phytic acid. I’d almost certainly be soaking and cooking my soylent, if I was planning on having a kitchen in the foreseeable future. I’m sure it would help with things besides phytic acid – such as the flatulence that I am more or less just hoping will get better over time.

Regarding the peanut butter, if you were sufficiently determined you could possibly make your own peanut butter, using your own soaked peanuts. Nut butters are made simply by putting nuts in a food processor (or similar) for several minutes. I imagine it wouldn’t have great shelf life, due to the added moisture.

However, I am still concerned about the overall balance of the calcium - phosphorus - vitamin D triangle.

This is new to me; can you explain the idea, or point me to somewhere I can read up? Thanks!

Your final two paragraphs make a lot of great points, and I’m in agreement about all of them.


Basically, Calcium and Phosphorus need to be present in the correct ratio for proper calcium absorption and bone formation and maintenance, and correct vitamin D intake must also be there for Ca absorption in the small intestine as that vitamin is needed for hormonal regulation of proteins responsible for Ca absorption. If these relationships are not in proper balance then Ca absorption is shot to hell and you get rickets, osteoporosis and other associated ills.


your links are kinda broken. There’s some random string attached to the end of each URL.
Also the 4th link is the same as the 3rd. Maybe you didn’t copy-paste correctly?
Otherwise, interesting results on Ca:P ratio. I knew about their competition for absorption but wasn’t aware of the effect on bone turnover. But that would make sense.
I’ve been just taking calcium and phosphorus at different times during the day to maximize absorption for each kind, but if their ratio is to determine bone turnover, then I need to be more careful about the amounts as well.

Kept reading and found this to be a good overview


Yeh, sorry about the links – I had a 3-way battle with this dumb laptop and the app, looks like I was the loser there. App refused to post the 4 links nicely on 4 lines and ran them all together – I tried to fix it and only made things dramatically worse.

Tldr = Google “calcium, phosphorus, vitamin D” and read all about it. :frowning:


I am currently attending university, so if you need to look at a study, feel free to PM me.


Great work on OP Nick! It’s encouraging to see some preliminary calculations to suggest this is probably not an issue. Something worth considering I think is that there’s a reasonable chance that the phytic acid present in soylent constituents like oats is probably already bound to a bunch of the oat nutrients. Would there be so much that it could still bind with additional minerals (in the rest of the soylent), or just enough to severely harm the oats’ nutritional value? Is the binding factor of PA considered when the nutrient profile of oats is measured, or not?

Another thought is that there literally must be sources for phytase in smaller quantites. Labs use it for research, ergo it must be availabe via lab suppliers in lab-appropriate quantities. Does anyone have relevant industry knowledge here?


I think everyone may be ignoring the most obvious way to determine if phytic acid is a problem or not: blood testing. Phytic acid is only a problem is you’re actually deficient in something, and a blood test should prove that out. Sorry if I’m being overly simplistic about this, but generally speaking, I find simple solutions to be the ones I’m most likely to actually try.

That said, we’re also assuming that the phytic acid is still present in the oat powder as the primary source of phytic acid. My understanding is that it’s largely in the outer coating of the oat, which is removed in processing. I could see it still being an issue in the flax seed, since the hull is still present, but I suspect the oat powder is not going to have enough phytic acid to be a problem. Regardless, any time you’re experimenting on yourself, blood tests are prudent.


I decided to go further in trying to calculate whether PA would be an issue in a given recipe. We already know that there isn’t much phytic acid in soylent relative to the quantity of minerals. The question becomes, will the phytic acid be bound to one mineral out of proportion to its frequency of binding to other minerals, to such an extent that there is no longer enough of that mineral which PA likes especially well?

We don’t have sufficient empirical data on that question. An approach we can take in the absence of empirical data (what can I say, I like a priori solutions) is to use a prior probability distribution to consider all the possibilities for how the PA distribution could be biased, and see what proportion of them (adjusted for likelihood) cause problems. If the proportion is low, we can say that we are safe.

I wrote all of this up into a paper, ultimately specifying a calculation that you could perform to see whether your recipe was safe according to this standard. I haven’t yet written software to perform the calculation, but if there is interest in this let me know. I’d also be quite happy to hear any feedback on the paper, in the way of comments, questions, errors, doubts about my assumptions, etc.


Very Interesting, I’m not saying I understand everything in there, but I would be interested in the software you mentioned in the last paragraph of your post.


I wasn’t aware of this touchy calcium/phosphorous/vitamin D relationship. My current recipe has 130% RDA calcium, 250% phosphorous, 500% vitamin D. Should I be worried?


That’s a pretty interesting calculation method! I suspect you didn’t get much replies since people are not familiar with the math involved, but that many people would be interested in a tool to run through the calculations.

(Incidentally, the “PA” in your paper looks like “Peano Arithmetic” to me :smile:)


It’s worth noting that in polydentate ligands like phytic acid or citric acid, the rate equations mean that unless your counter-ion concentration is really high, you’re much more likely to get lower binding ratios than maximum.

So, for example, in phytic acid, theoretically there are six or more binding points, but realistically more than one of those binding points (and from a quick inspection of the geometry, I’d guess probably up to four) is going to be binding the same mineral ion. I might check some literature and do some calculations on this later when/if I find the time.


That’s great information, @Minant! Thanks! I’d certainly be interested in seeing those calculations, especially if I could use them to improve my probability formula.


I don’t want to alarm anybody, but I found a unit conversion error in the numbers for Iron here.

These numbers work out if the phytate content of the rolls were 2g, not mg. Also, the phytate dose was per roll, so it should be doubled. The rolls were served as part of a full meal, but they only tracked the Fe absorption from isotopes in the rolls themselves. If we only count the calories from the rolls, I think it should be closer to 300mg.

So we should have 3.45g x (300/2000) = 518mg of phytate equivalent per meal or 259mg phytate equivalent per roll. From the same source:

The inhibition of Fe absorption was strongly related to the amount of phytate added; 2 mg inhibited absorption by 18%, … 25 mg by 64%, … and 250 mg by 82%

So in the example given, of 3.45g/2000 calories of soylent, we may actually be looking at 82%+ of Fe inhibition.

I don’t know what that means, exactly. But it does sound quite high. In the USDA DRI handbook page on Iron (page 332), they state:

the bioavailability of iron from a vegetarian diet is approximately 10 percent, rather than the 18 percent from a mixed Western diet. Hence, the requirement for iron is 1.8 times higher for vegetarians. It is important to emphasize that lower bioavailability diets (approaching 5 percent overall absorption) may be encountered with very strict vegetarian diets.

They’re saying that the DRIs are set assuming that you only absorb 18% of what you eat. Which makes sense considering this:

Adult men need to absorb about 1 mg/day to maintain iron balance. Menstruating women need to absorb about 1.5 mg/day, with a small proportion of this group needing to absorb as much as 3.4 mg/day

That explains the DRI for men of 8mg (1.44mg absorbed), and 18mg for women (3.24mg).

But is it just a coincidence that the numbers 18 and 82 keep showing up? Are they making that 18% assumption precisely because of the phytate issue? I think it’s a coincidence.

It’s likely that what this means is that the phytate content in soylent effectively pushes us towards that 5% overall absorption. In which case it may be a good idea to triple our DRI for Fe. This could be problematic for women, who start with a DRI for Fe of 18mg. 27mg while pregnant.

With 5% absorption, even taking the maximum upper limit of 45mg only gives you 2.25mg absorbed vs the 4.8mg needed by a pregnant woman or 3.24 needed by menstruating women.

(As far as I understand these estimates assume none of the benefits to absorption from protein and vitamin C)