Why is there 8 mg of iron in Soylent?


Continuing the discussion from Soylent Macronutrient Overview:

We’ve been wondering, on that thread, about whether 8 mg is an appropriate amount of iron to have in Soylent and, if so, what the reasoning is for choosing this amount. Because many feel that 8 mg is likely to be insufficient for menstruating women.

Since the staff did not intervene, I figured that after a while, you stopped checking blog post feedback threads. So I’m creating this one in hopes that @JulioMiles or @rob will be able to give us an answer.


8mg has been determined to be the adequate intake of iron by the Institute of Medicine


We do check post feedback. The body stores iron very well. Because of this it would be unwise to give everyone more than needed, as it would risk the accumulation of extra, and it is extremely unlikely a deficiency would arise in aforementioned scenario given regular adequate intake.


Thank you for your reply. In that link, the EAR for women is 8.1mg, and the RDA is 18mg.


An Estimated Average Requirement (EAR) is the average daily nutrient intake level estimated to meet the requirements of half of the healthy individuals in a group.


An RDA is the average daily dietary intake level; sufficient to meet the nutrient requirements of nearly all (97-98 percent) healthy individuals in a group.

These are the levels that are recommended by the USDA as being healthy day-by-day in the long term. So I have some followup questions based on this:

  1. Do you have any sources that support that the EAR would be “extremely unlikely” to result in deficiency for the other half of women who the USDA claims would not have their requirements met by 8mg?
  2. I assume you are implying that an “accumulation of extra” is iron overload, and dangerous, correct?
  3. Do you have any sources that support the claim that taking more than required, but well within the safe limits, over the long term would result in accumulation of extra?
  4. Wouldn’t this accumulation also occur for 50% of women who take the RDA? Since 8.1mg is sufficient for them.
  5. By this logic, wouldn’t taking 8mg of Iron/day also result in accumulation of extra for the 50% of men who only need 6mg/day?
  6. Are you aware of the fact that the USDA (pg 332/pdf pg 346) recommends that those who consume only non-heme Iron double (x1.8) their Iron intake? Do you have any thoughts on this wrt Soylent, which has only non-heme Iron?


Well now I’m just confused.

According to those charts, the “Recommended Dietary Allowances and Adequate Intakes” for menstruating women is 18mg, but the “Estimated Average Requirements” is only 8.

What’s the difference? Why is there such a large discrepancy between the numbers?! What does it all MEAN?!

Edit: Oh, I get it now. Thanks, Sintax.


Thanks for your answer. I’d still very much like it if you could say more on this though.

…And I’m looking for questions to ask, but actually I think if you answer everything @Sintax has asked, I’ll have a much better understanding of this.


@Sintax Actually you found a mistake. I am grateful you brought this to my attention.

I double checked our formula and found we actually have 21.6mg of iron in a day. The macro post was based on a spreadsheet that did not properly include the extra from the rice protein. 8mg comes from the oat flour, 13.6mg from the rice protein. Due to this we do not include any supplemental iron like ferrous gluconate.

The USDA’s RDIs and IOM’s RDA’s differ on occasion. Likely given the tolerable intake of 45mg the USDA considers 18mg / day to be the daily value by default. We are slightly in excess of this but still below half the tolerable level. This should not only provide ample iron for either gender, but account for any absorption differences between heme and non-heme iron. I do not have specific numbers on this but much research has shown that in general absorption from a liquid is superior to that from solid whole foods so I do not see much cause for concern that the iron source is non-heme. With a tolerable intake of 45mg there does not appear to be cause for concern that this slight excess will accumulate in the body to unsafe levels.

I have updated the micro blog post. Thank you @Sintax for such attention to detail

Soylent Macronutrient Overview

Excellent news!! This was my last gripe. Thank you very much for confirming this.

My wife and I get about 23mg/day from my DIY recipe, and it works out fine. To those of you who were worried about Iron Overload, please don’t. Unless you go much higher than this level of intake, diet is rarely ever the cause.


From what I have read, your body can control iron intake fairly well, based off your iron stores. Numerous places list the absorption of non-heme iron to be between 2-20%, heme-iron from 5%-35%, so the actual amount of the iron available is widely variable. I doubt anyone not suffering from a disease that affects iron absorption will have any issues with the current, updated, amount.


@sintax: do you have your recipe online in diy.soylent? how can i find it?
i’ve searche for your user there, but found nothing


Wait a minute… let me get this straight. So you had to double check your formula to find out that it contains almost three times the iron you previously thought it had?

Man… that’s pure, precise, science, right there.

One can imagine in future posts: “well… I’ve triple checked the formula and found out that it actually has 70mg of selenium instead of 70ug.”

Even better: “Just found out that we had made a little mistake in the formula of our previous shipments, we inadvertently switched chromium by mercury.”


I think the point wasn’t that they weren’t aware how much iron they had - just that when they wrote it up for the blog, they sourced the numbers from an out-of-date spreadsheet. So in the “background”, where they were actually putting together requirements, they were always working with the right number. Rob’s last sentence, “Due to this…”, seems to imply that they were in fact already using the 21.6 number for their actual calculations.

You have a valid point though, and it would be good to get a reply from @rob or @JulioMiles confirming that it was just a publication mistake, not an internal one…


I’m pretty sure the mistake comes from the fact that the people who decide what’s in Soylent and those who tell us what’s in it aren’t the same.


@shadowhawkxx It was indeed a publication mistake. The amount of iron was consistent, but when drafting the blog post I did not keep the precise amounts of every ingredient in working memory and relied on a personal spreadsheet that was inconsistent with the official formula on this one point.

It has been corrected now, facilitated by my well-oxygenated brain and finger muscles due to the abundance of hemoglobin in my bloodstream.


I’ve reread my previous reply and it sounds a bit harsh and too sarcastic, and for that I apologise.
The point I was trying to stress is that we are talking about people replacing complete meals with this product and how seriously you take it in consideration.
I don’t know about the U.S. but in my country you can’t sell lunch without having a nutritionist granting the optimal balance and the right mix of ingredients, let alone a bunch of chemical compounds mixed together.

Just my two cents.


I’m glad to see this clarified; I was concerned about the low level of iron previously posted, so this is good news for me :slight_smile:



So why then did you jump to the defence of 8mg and even provide sources to ‘back up’ yourself straight away?

What else do you believe you are right on?