Micronutrient requirements linked to body weight?

Unfortunately I couldn’t find anything regarding this topic, maybe someone here can enlighten me:

Usually macro requirements are given dependent on body weight (like X g protein per kg body weight, or Y kcal per kg). But for micronutrients all I can find are fixed numbers.

Does it make sense that a 50 kg person needs the same amount of vitamin Z as someone weighing double that?

I could understand that the numbers for some micro nutrients that are the same if they are, say, most relevant for brain functions or something like that.
But some others surely have to be required in different amounts depending on total body weight / muscle mass?


@JamesCollier I’m interested to hear if there’s any consensus on this in the nutrition world

Very good question. The RDAs are defined as the amount of a micronutrient necessary to meet the needs of 97.5% of the population. So in the example of iron (which has an RDA in the EU of 14mg), 97.5% of people will have their iron needs met with a daily intake of 14mg. It is likely, however, that the actual amount needed is dependent on body weight (though I don’t know the specifics on which micronutrients are dependent on weight and which aren’t off the top of my head). So what this essentially means is that a smaller person may only need 10mg of iron per day, while a larger person would need closer to 14mg. However, because the RDAs are set to meet the needs of 97.5% of the population, unless you fall in the 2.5% for whom this is insufficient (which is generally due more to issues of absorption as opposed to body mass), consuming the RDA amount should be sufficient for you.

There are also different RDAs from different nutritional boards around the world (eg the new US Daily Values have a recommended intake of 18mg for iron), but they all aim to provide a value sufficient for 97.5% of the population.

Thanks for your answer @IcyElemental - I read about the 97,5 percentile before, but I am still unclear what that includes. Does it fit the requirements of 97,5% of ‘standard humans’ (some average weight, maybe half male and female?) or 97,5% of the actual population? If the latter, which data is used? I would guess that average body weight differs quite a bit between e.g. the US and Europe, and even within regions.

According to an official German report the average adult weighs 77kg at 172cm. I don’t think that they could maintain body weight at 2000kcal/day?

For some of the micronutrients the suggested intake and suggested maximum intake are quite close, e.g. sodium. (Iron was specifically addressed here.) If intake requirement is not dependent on body weight, one would come very close to the upper limit by consuming upwards of 3500 kcal/day, which might not be too out of the ordinary for bigger, active people.

A similar question / discussion came up before and didn’t really go anywhere.

My own thoughts now are that this is a really complex area, with no simple answers and the posts above and elsewhere touch on some of this. I have very little nutritional knowledge though and really only what Ive picked up in the last year or so, with much of it on here.

I’ve recently come to the conclusion, that when I was restricting calories to lose weight (fat), I would’ve been significantly under on micro nutrients. Unfortunately no blood tests or anything measurable to back that up.

fI I were doing it again, i’d likely take a daily multivitamin/one of the micronutrient powders I spotted on reddit recently or at the very least look into it more. I don’t think I’ve seen anything much here about the potential for a micronutrient deficit, quite surprising to me, as it looks like many here are restricting calories. Maybe there are posts and I’ve just missed them.

Now I’m more or less where I want to be, I appear to still need less than 2000 calories, unless I’m doing something regularly active. That’s happening less than I’d like and with autumn& winter coming I expect it to get worse.

So I may be in the same position, just with less of a deficit than previously. My current plan is to mix Huel with a competitor that offers the RDA on less calories, but no phytonutrients and to potentially take a multivitamin / powder micronutrient mix.

Interested in others thoughts and ways of dealing with a regular diet of less than 2000 calories.

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