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Myths and Misconceptions about Insulin Resistance/Metabolic Syndrome
By Eleanor M. Kellon, VMD
Insulin resistance is an inflammatory condition. Metabolic syndrome in humans is associated with elevation of a number of inflammatory proteins called cytokines but the picture in horses is far less clear. Suagee et al 2012 found no correlation between insulin levels and inflammatory cytokines like TNF-alpha and IL-6 that are elevated in IR humans. Vick et al 2007 found a correlation between IR and TNF-alpha levels but only in mares older than 20. No other cytokine changes. Burns et al 2010 found higher inflammatory cytokine levels in the neck crest fat but no difference between normal and IR horses. Laminitis in IR horses is also not inflammatory. This is important because it explains why the response to NSAID drugs for pain in IR horses is typically poor and why these drugs do not “treat” anything.
“Whole foods” can prevent/cure insulin resistance. It’s not too clear where this idea came from but I suspect it is referring back to the difference between how things like white bread versus whole grain products produce higher glucose and insulin spikes in humans. That’s true, and it’s also true that processed (e.g. extruded) barley and corn are more digestible to glucose. However, that does not mean that whole oats or whole corn will be safe. They most definitely are not. It also does not mean that heat processed grains or co-product foods like brans or wheat midds cause IR. Food does not cause insulin resistance and many of these co-products are lower in sugar/starch and higher fiber than the whole food.
XYZ supplement or feed will make it safe for your IR horse to return to pasture. All the evidence points to IR being an inherent part of the horse’s metabolic makeup. They are born this way. When food is scarce and poor quality IR is actually a survival advantage, but not for domesticated horses. Nothing can change the way the horse was born. Proper management will keep it from being a health issue but free access to grass is rarely possible. Grass is a living tissue and its levels of sugar and starch will vary. Things like type of grass, weather conditions, stage of growth, severity of IR, level of exercise influence how safe (or not) some degree of grazing may be but no supplement will make it safe for you to just turn an IR horse out on grass. You may get away with it for a while but sooner or later there will be problems.
Glyphosate (Round Up) causes metabolic syndrome. All herbicides are potentially toxic but like all things potentially toxic there will be a dangerous level (dosage matters) and also predictable effects that are discovered in the course of toxicity studies. Glyphosate has been blamed for just about any human medical condition you can think of. More recently, claims focused on horses including that glyphosate causes EMS. The proposed mechanism for this is glyphosate substituting for the amino acid glycine in cellular insulin receptors. Problem is, this is 100% speculation with zero evidence to show this happens and at least one formal study, Kim et al 1990 that shows it does not. The people making these claims have a “Dr.” before their name by virtue of a PhD but their area of expertise has nothing to do with physiology, biochemistry, medicine, toxicology or nutrition. Would you go to your dentist for advice on a hysterectomy or to your gynecologist for a hip replacement? Don’t take advice about food choices from a computer scientist. There are often benefits to organic foods but going non-GMO won’t eliminate equine metabolic syndrome.
If you want to read an excellent, up to date, scientific article on laminitis and insulin resistance written by researchers who actually work in the field, go to https://www.sciencedirect.com/science/article/pii/S1090023317302290?via%3Dihub.