That @ekf post was indeed gold.
I’ll add:
If you know you’re lower-iron via blood testing, or even just low-normal range, as an endurance athlete, you can just take more iron (sometimes a LOT more), and get rechecked to ensure labs are in range.
In my wife’s case, unless she’s choking down 8-10 iron pills per day. (no affiliation, just an example) If she takes that much she remains not not anemic and perfectly mid-range for all iron-related labs.
Only side effect = mild constipation, which can be managed via eating more leafy greens.
I am not a medical doctor. (I am a sport physiologist.) Don’t take this as a personal medical recommendation. Just random academic discussion 
No amount of special heme bioavailable this-and-that supps had any measurable effect until we just started ramping up dose of standard cheapo OTC iron supps.
She also does most of what @ekf mentioned with regard to timing/pairing/avoidance etc.
Just thought I’d share in case it was useful to you or anyone else here.