Topping up on iron, ideally before you feel low

It is common for runners and ultrarunners to suffer from iron deficiency, and there is still ongoing debate about the root causes of these deficiencies. 

Recently, an article appeared on my feed, discussing two possible causes I had never heard before. 
One is iron loss through sweat, which can be a cause of iron deficiency for endurance athletes who sweat profusely during prolonged exercise.
The other is foot strike hemolysis, which is the destruction of the red blood cell membrane and the consequent release of both hemoglobin and iron into the surrounding plasma. 

While these theories make some sense, I have not verified the information and it could be partially or completely BS!

Nevertheless the consequences of iron deficiency in runners are real: fatigue, weakness, poor athletic performance, and a weakened immune system. 
Personally, I found that the best way for me to stay on top of my iron levels is by using supplements every few months. I also encourage the runners I coach to have frequent blood tests, particularly during intense period of training.