Insulin Resistance and Iron Overload

Q. Thank you for your article on the research connecting insulin resistance (IR) and iron overload. Do you know of any research on how to reduce iron overload in horses that already are insulin resistant and have foundered? Is there an equine equivalent of chelation (a process that binds a mineral to an amino acid) therapy to flush out toxins or heavy metals?

Jeanne Bradbury, via e-mail

A. Great question. First, while we did find a correlation between insulin resistance and serum ferritin, the point of our study was to see if the reason iron was accumulating in black rhinos is possibly because they were insulin resistant. This is as opposed to finding out if they were insulin resistant because they were accumulating iron. There is a big difference between the two. Most captive rhinos are overweight (similar to horses) and likely do not receive adequate exercise (again, similar to horses).

My first suggestion, rather than to concentrate on the iron in the diet, is to get rid of the factors that made the horse insulin resistant (such as being overweight and not receiving adequate exercise). By correcting those issues, iron in the diet is likely a non-issue.

That being said, once the problem has developed, feeding a diet lower in iron might be prudent, though there is no good evidence that it can correct insulin resistance (or even that excess dietary iron contributes to insulin resistance). Regardless, if you have concerns, testing your feed/hay to determine iron concentrations can answer the question as to whether it is high in iron.

The National Research Council recommends a minimum of 40 to 50 ppm of iron in the feed (this would be an average of all feed provided). The optimal amount may be, and likely is, higher. This should provide a starting point in determining whether you are providing feed that is high in iron or not.

But to answer your specific question, to my knowledge there are not any recommended chelating agents currently being used. Even if you could remove the excess iron, it would not remove the factors that caused the horse to become insulin resistant in the first place. Those are probably even more important to focus on, though decreasing excessive dietary iron (if found to be doing so) would not hurt.

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