Absorption rates of nutrients?


When the official Soylent formula is being blended, are they simply putting in the 100% RDA for nutrients without taking into account for a non-100% absorption rate? Considering Rob and others seem to be doing fine I am sure it is not a big deal but I am curious for my own blending.

Vitamin/Mineral Interactions

It’s a good question, especially if investigation may reveal that certain ingredients may cut absorption rates of others by anywhere from 20% - 50% or higher. If we had that data available to us, it would certainly allow us to make modifications so that we were not unnecessarily adding ingredients that weren’t working anyway.

I’m not saying this is probably what’s happening, only that we don’t know whether it is happening or not and therefore it is a worthy avenue of investigation.


For my own mix, I take my calcium separate from my iron, and I’m not using anything with phytic acid, like oat powder.

For the official mix, Rob and his team and his team are having blood tests done on the test group, so they can spot any absorption problems and bump up the amounts to compensate.

The testing and fine adjustment of micro-nutrients is the only thing I prefer about the official mix over my own. If they start selling the micro-nutrient mix as a separate product, I’ll use it.


I agree, whilst I am interested in the whole product, I am sure that the micro-nutrient mix on its own would find a good market…


Oral consumption. To be fair, no one ever really gets 100% nutrients, and we’re not sure if food consumption absorbs that much better than single nutrient powders.


Most of the amounts listed in the dietary reference intake are probably the amounts you should be consuming, but a pharmacist I talked to insisted that the recommended amount of iron is the amount you need to absorb. She told me that we tend to absorb about 10% of the elemental iron we consume and this varies from person to person. This makes sense, because the iron pills I buy each contain 35mg of elemental iron. The RDA for men is 8mg.

Currently, I take 2 iron pills per day, totalling 75mg of elemental iron. My spreadsheet shows 10% of that as a guess at how much I am absorbing (I haven’t had any blood work done).

What I don’t know is what food labels mean when they list amounts like “7% of the RDA of iron” per portion. They must be guessing at the absorption rate.


Eventually at that level you are going to overdose on Iron. You take 18mg because most peoples reserves are full and only need slight replenishment. My guess is you will need to give blood if you keep it up.


Wikipedia, citing an article in the New England Journal of Medicine (pay-walled, and I don’t have access, sorry), puts average daily normal iron loss at about 1mg/day for men, and 1.5-2mg/day for women. At about 10% absorption, that requires an intake of about 10mg/day for men and 15-20mg a day for women to maintain your iron levels. RDA is 8mg for adult men and post-menopausal women, 18mg for women with regular menstrual cycles. Based on that, it seems that the RDA is factoring in the fact humans don’t absorb all the iron they consume.

My understanding is that the larger amounts such as 35mg, 65mg, or 108mg are for treating anemia, where the body’s iron stores are depleted and so daily absorption needs to be increased well beyond normal loss, and then only until the body’s stores are restored (this article says three months).


Indeed, also the wikipedia article states ‘Absorption of dietary iron in iron salt form (as in most supplements) varies somewhat according to the body’s need for iron, and is usually between 10% and 20% of iron intake’.

Bear in mind then, even 8mg could be too high (if 20% is the actual figure). If you aren’t fully soylent (and eat meat) - as iron seems to be more readily absorbed with meat sources (and most are high in iron) you might want to be very careful with the amount of iron you supplement.

Jonathan, 75 mg isn’t a good idea.


Thanks mathfarmer. It seems the pharmacist I talked to had it a little mixed up.


I’m pretty sure labels show the elemental mass and don’t guess anything.