Milk thistle for IR horses?


I read that milk thistle powder, at a dosage of two teaspoons per day for a 500 kg horse, would not only support the liver but might help keep insulin levels down. Is there an ECIR position on milk thistle as a supplement?
Susan H TX 2021

Sherry Morse

If you're looking for a magic bullet to help IR, milk thistle is probably not it but it won't hurt an IR horse to be on it.  Would you care to share where you read this information?


It was a post from Mad Barn, the Canadian nutrition company, but I can’t find it again right now. It wasn’t overstating the case, certainly not as a magic bullet, but it said it had been shown to help with insulin regulation. Since powdered milk thistle is not super expensive, I thought I might add some for my IR mare.
Susan H TX 2021


Nancy C

Hi Susan

Not sure that Milk Thistle will lower insulin or improve insulin sensitivity and not sure MB is even saying that. It is a powerful antioxidant and has been recommended here for the liver in some specific equine cases.

This link explains a bit about what happens with milk thistle and reducing oxidative stress

About reducing iron overload (which could help with insulin sensitivity) and protection:
This from 2018 which indicates large amounts are needed.
There is some evidence the silimarin found in Milk Thistle can chelate iron and it is also an excellent antioxidant to protect the tissues.  However, to get a therapeutic amount from the whole herb you would have to feed around 6 to 12 ounces per day.  It would be more economical to get a standardized product in bulk, such as:
where a generous teaspoon once or twice a day will do it.  Also need to continue to supplement trace minerals.

Not clear to me about milk thistle and fatty liver in the equine. We have been focused on fatty liver and triglycerides a lot here recently.  I hope Dr Kellon will weigh in on the realtionship of fatty liver and using milk thistle to support the liver to "detox" when needed.

Edited to add:

Nancy C in NH
ECIR Moderator 2003
ECIR Group Inc. President 2021-2022


Eleanor Kellon, VMD

In the early 2000's there was speculation that silibinin's effects on fatty liver would also translate into improved insulin sensitivity but careful studies like this one in mice did not confirm that. .

We don't know how common fatty liver is in metabolic equines. We know that mild elevations of liver enzymes are sometimes found and we know that horses on SGLT2 inhibitors have elevated triglycerides, sometimes with elevated liver enzymes. We also know from earlier research that a small number of  metabolic horses have high triglycerides for years with no obvious signs except some weight loss.  As long as the horse is doing well and on generous calories with stable weight I don't worry about the triglycerides as long as liver enzymes are normal.  Adjusting the diet has taken care of liver enzymes so far without any need for Milk Thistle.

I agree with everything Nancy wrote, including about dosing.
Eleanor in PA 
EC Owner 2001
The first step to wisdom is "I don't know."