When evaluating supplements for horses prone to high insulin levels there are two basic areas to consider – the active ingredients and the base.On the ingredients front, some things to generally avoid include:
- Added iron. These horses often have iron overload. Hays already have plenty of iron. Iron is often not listed in the analysis so you have to check the ingredients list for items that say iron or ferrous.
- High doses of vitamin C (over 5000 mg). High C intake can increase iron absorption and worsens oxidative stress in a high iron environment.
- Glucosamine. While glucosamine does not disrupt glucose metabolism in normal individuals, there is evidence from humans that when there is insulin resistance it can make it worse.
- Yucca. This herb contains compounds very similar to cortisol.
- Asian Ginseng. It stimulates insulin release. North American Ginseng or Rhodiola are safe.
- Anti-diabetic herbs used for humans. Most of these stimulate insulin release. Some examples are bitter melon (Momordica), Gymnema sylvestre and Holy Basil (Ocimum sanctum).
Of great concern to many owners are the ingredients used as the base/carrier for supplements. Dextrose (glucose), maltodextrins, molasses and grains all directly stimulate insulin release but the dose also matters. Rice and wheat brans also have starch levels high enough to trigger an insulin release.
If you spot a risky ingredient the next step is to look at the dose. We may be talking about the difference between one bite from a Hershey kiss and the whole bag! Let’s say your supplement dose is 20 grams and contains 10 grams of glucose. You are adding it to a meal of 2 lbs of 6% sugar and 0.3% starch hay pellets. The pellets are providing 54.5 grams of sugar. Adding the supplement takes the meal total to 64.5 and the % sugar to 7.1% – still well within safe limits. Supplements and grain replacers/”balancers” fed in larger amounts are usually the ones you have to watch. If in doubt, get help determining the sugar and starch content.
Alfalfa is another potentially problematic element. For reasons that are still unclear, some horses have worsening of laminitis signs when they eat alfalfa. However, unless it is a true allergic reaction, where even tiny amounts could trigger a response, this is also a matter of dose. A small serving of a supplement with alfalfa in the base isn’t likely to be a problem.
There is some evidence (Loos et al, 2019) that high protein intakes may cause an exaggerated insulin response in EMS horses. In that study, horses were fed a 12.5% ESC + starch, 31.1% protein feed, two meals of 2 g/kg (2.2 lbs for an 1100 lb horse), 30 minutes apart, for a total intake of 4.4 lbs.
This is at least 4 times more than what would normally be fed. We also don’t know what the reaction would have been if the sugar + starch level was lower. For now, the best course would be to divide high protein components into multiple small meals if you need to feed them, and feed with other foods.
It takes a little vigilance to build a diet for a metabolic horse but the effort is well worth it to reduce laminitis risk.
Eleanor Kellon, VMD