I did t take any iron supplements at all!
I had been taking the high prescription doses. I had a nightmare mix of issues that led to a kind of cfs including restless leg symptoms. Gp said to try raising ferritin from 50 to over 70 (as it did say on the print out that 50 was technically borderline). It took 3 months on 3x 200 mg a day and completely messed up my stomach. Every time I stopped my ferritin would gradually drop down (bad periods) and I could tell, more so from brain fog but I need to add I had other chronic health issues. This was just a tiny factor. by then though I developed severe ibs from the pills.
A different Gp suggested fodmaps diet and just measuring iron before and after one cycle. I knew of a few bits that caused an issue from it but I cut out milk and gluten (had hard cheese). I may have taken spatone with oj, I can't remember; I'm really not sure how much that works.
Gluten wasn't an issue but I was drinking a lot of milk during the day. It was also causing some of the ibs issues.
This programme was on air about 2 years after all my iron chaos.
I'm completely fine now ibs wise though pregnancy seems to have helped that too. I now have days where I consciously avoid some dairy if I'm going to have iron rich food to boost iron. However, my periods haven't returned yet.
There was a thread recently where someone was going to try it and had found other research on it too but I can't remember which one it was.
I think if you read around the research it's to do with maximising absorption. My point is that the body should be able to do it from diet if you're very mindful of what and when, any additional iron tablets might be best taken alternating days and only once a day. Being veggi is a bit of an additional challenge.