Here is a warm, fuzzy, unscientific article on the benefits and drawbacks of iron supplementation:
I question this guy's explanation of why iron is constipating. It's an easy read and easy to believe, as is a certain RLS website that is constantly recommended on here. I think both are sincere but just plain wrong and thus dangerous. About the only thing that is somewhat reliable are the results of animal and human trials, especially animal trials where they are able to dissect the animal and know what happened chemically as a result of the introduction or withholding of certain substances. Thus everything I say and recommend is completely dangerous too.
Anyways, this author states with great certainty that the reason iron is constipating is because it stays in the gut and feeds our resident bad bacteria that are normally kept in check by the good bacteria. When the bad bacteria get out of hand it causes bloating and constipation. I know for a fact that all life on earth (with the exception of two or three strange sounding micro-organisms) need, want and love iron. So that would include the good bacteria. They should get big and strong as well as the bad. Secondly, when the bad bacteria get out of hand, just like when we get the stomach flu or food poisoning, our bodies usually pour water into the colon in an effort to rid itself of the bacteria, resulting in diarreah, not constipation. The author states that by switching to a better (meaning more bio-available) form of iron, constipation will be eliminated because the iron won't stay in your gut and feed the bad bacteria.
I, for one, find that even the bio-available form of iron slows my motility. So I did some research and found "scientific experiments" that indicate that there are dopamine receptors in our intestines and that when these receptors are stimulated and release dopamine, motility/transit time is slowed. In one article, the scientists actually knocked out the d2 receptors from the guts of rats and found that they had greatly increased transit time. So that's why dopamine agonists that we take for RLS and Parkinson's also cause us constipation. I know of no drug that has built in radar and only goes to the destination we want it to. If Mirapex helps the d2 receptors in our brains it also helps the ones in our guts. Iron is a dopamine agonist, maybe the finest dopamine agonist of all times, but it comes with a price. Just wanted all of you to be aware of that inconvenient fact.
And also, be very cautious about RLS websites that recommend getting your iron stores up over 50, just for the sake of getting them up over 50. Where's the scientific experiments that prove that this helps RLS???