Iron absorption - immediately post-exercise is best

@LarissaW, here is the other thing I was mentioning about iron absorption. Sorry it took me a while to get to this…

For runners who have an iron deficiency, there is an additional problem because the release of the hormone hepcidin can be triggered from exercise-induced inflammation.

As you may already know, hepcidin is the regulator of iron metabolism. And when hepcidin levels are higher, iron absorption is decreased.

(This link may be behind a paywall, I am not sure. You can try it. But I put the key points of the entire article in the text below.)

Researchers found that inflammation and hepcidin levels significantly increased three hours after each running session, though the levels were highest following the afternoon runs, since hepcidin levels naturally rise during the afternoon hours.

They also discovered iron was best absorbed in the morning right after exercise, before hepcidin hit its high point.

In fact, when runners consumed iron within 30 minutes following their 90-minute morning run, they absorbed about 40 percent more of the mineral than when they consumed iron after an afternoon run. The morning runners also absorbed the mineral better than those who took iron in the morning, but ran later in the day.

The wiki is short and gives a very good description of what hepcidin does…

And if you want the more sciencey info on it, here is one that tells you the same thing. Same thing as above, but with more details.

And the final part is this, which we’ve already discussed, but the fact that vitamin C improves iron absorption.

So the quick and easy thing to say - you can improve your iron absorption by taking it right after you run in the morning, and also taking it with a big glass of orange juice (carbs too!! :grinning:), right after you finish!


Hey DL, thinking about this a bit. Here are some thoughts.

The idea that post-exercise absorption is best…

Perhaps this was not worded correctly in the article. It says “Running can hinder—or encourage—iron absorption.”

The problem with absorption is that inflammation and hepcidin levels increase post-run.

If I am reading it correctly, the experiment had too many dependent variables.

In one test session, they had a morning run and did the iron 30 minutes postrun and 10 hours postrun.

In the second test session, they did an afternoon run and had the iron 7.5 hours prerun or (or ?!?!?! what kind of experiment is this?!?!?) 30 minutes postrun.

Anyway, it seems that exercise is not what helps absorption, but rather that it hinders it.

And also, that taking it in the morning is better than taking it later in the day, since hepcidin levels also increase later in the day.

So my thinking is that taking it in the morning would be better, regardless of whether you run in the morning or in the afternoon.

And since I can’t always drink juice in the morning (like if I do not have a low BG), I am thinking of getting some 100mg vitamin C pills (which supposedly can increase absorption by 67%).

So…rather than taking iron after exercise, I would take it every morning with a vitamin C pill.

And since vitamin C is water soluble, that extra amount should not be a problem for me.

What do you think, Doctor L? Iron in the morning with a vitamin C pill, regardless of when I am exercising. Make sense?

(and all of this babbling, is why I needed a keyboard instead of a phone, so thanks!)

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Doctor Eric - I’ll relieve you of your talking to yourself now.

Honestly, I haven’t read the article[s] yet. I will ! When I get through finals. It sounds like however that there may not be that much that can be concluded from it because of moving variables as well as their specific and seemingly arbitrary term exercise (90 min run, right?). Well not all 90 min runs are the same, right! Same with all exercise in general, like I’m thinking aerobic v anaerobic, as well as RPE, duration, etc. So it may not be appropriate to extrapolate data from one study. (I will come back to this, read the article, and dive into the research on exercise and hepcidin though because I’m sure there is some meaningful stuff to look into).

Is there a study showing this is a significant increase? My bad if you put one above that I am actively ignoring so as not to dive down a rabbitt hole instead of studying :smiley:

Very astute of you! Pharmacies sell iron supplements with vitamin C in them already :smiley:

I’ll throw this out there as to other considerations for iron supplementation for correcting iron deficiency. I haven’t looked on the research in a few years, and I’m happy to find some sources on this later to back up what I’m saying. I believe this to be true but could be wrong if I’m remembering wrong so feel free to slap me on the wrist: Iron is best absorbed on an empty stomach when taken with vitamin C and water. Coffee interferes with iron absorption. SO, it is ideal to take iron supplements that have vitamin C with them, and it is best to take these in the morning, an hour or two before any breakfast/coffee. (unsure how exercise may affect absorption if supplement is taken before or after exercise).

Of course, not all vitamin or supplement that is taken will be absorbed, so depending on the extent of one’s deficiency then one may want to consider taking the supplement twice a day. I would doubt that if someone is iron deficient then they would be able to absorb enough iron from iron pills 2x a day that they would reach toxic levels, though iron does fall into a category that it shouldn’t be taken without considering that too high of doses may lead to toxicity.

Did I remember all this right, Doctor Eric?

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O and we can talk about iron in the diet too and what sources are absorbed best if you wanted to talk about that?? :smile:

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Right! But the Runner’s World article was just kind of dumbing it down a bit, trying not to make their reader’s eyes glaze over with the details.

I looked at the actual study, and they had a very specific criteria, which was exactly like so many other studies they do.

Sixteen endurance-trained runners (10 male, 6 female) with serum ferritin (sFer) < 50 μg·L−1 completed a 90-min running protocol (65% vV˙O2max) in the morning (AM), or the afternoon (PM), in a crossover design.

It seems like 65% of VO2 is such a standard now in all of these tests!!

The way they calculate it could be just from formulas, which can be pretty unreliable.
One of the formulas based on HR:
65% of VO2max
( ( 220 - Age - RestingHR ) x 65% ) + RestingHR )
(If I did it based on formula, that would be like an RPE of 2. It really depends on actual fitness levels. The HR calculation can be soooo lame.
“Hey researcher, can you turn the treadmill on please?!?”)

If they are using indirect calorimetry, it would be much more reliable. So who knows how they calculated 65%.

The article did not reference a study, but I assume there has been one, since they said that directly in the article - “since hepcidin levels naturally rise during the afternoon hours”. So although I do not have a study, I was simply going from their statement and trusting the Runner’s World people were not just making that up. Again, I think they are trying to just give the main points of the idea, and trying not to get to sciencey and boring in their article.

I did not know that! Thanks! I will get those next time. I am a bit behind the curve I guess. Just trying to catch up now!

Yay! Morning sounds good!

Oh no! Morning not so good!

Crap, maybe back to nighttime…

There is risk here depending on the cause of the deficiency. Some forms of anemia can be caused by a failure to absorb, so taking more does not always improve the condition.

This is definitely something to discuss with the hemat!!

I would not even want to venture a guess on what to do about increasing it over any normal recommendations. They have formulas based on your weight and hemoglobin and iron stores. This is not in my wheelhouse, so I won’t pretend. (Happy to sing a song though. :man_shrugging: )

Yes, let’s add that to the list. :+1:

I have to tell you, this is new and dangerous ground for me now, so I have to walk very carefully here! Having an endo whom I can learn from has not been my normal experience. I am getting nervous about the first appointment!

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