A major feed company has decided to promote chromium for horses with metabolic syndrome.
The bottom line for metabolic syndrome horses is that unless the hay was grown on alkaline soil there is enough chromium in the diet already.
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The first mention of a chromium connection to glucose metabolism in humans was back in the 1950s. A chromium-containing "glucose tolerance factor”, which helped cells take up glucose, was discovered later.,,
Fast forward to the early 2000s and work done by the USDA really pushed chromium to the forefront as a possible aid in treating type 2 diabetes, which has underlying insulin resistance as its cause.
That USDA work didn't look at insulin levels, but I contacted one of the researchers who felt it should help horses with high insulin, even when their glucose is normal. Members of the Equine Cushing's and Insulin Resistance Group tried it. It didn't work to lower insulin but some horses had lower glucose when given chromium. Apparently the amount of lowered glucose wasn't making enough of a difference to lower insulin.
It wasn't just our group either. Formal research confirmed this in Dr. Cartmill's PhD thesis. Chameroy, et al., actually found resting insulin rose over time with no change in insulin sensitivity in EMS horses getting a magnesium and chromium supplement. Gentry, et al., (1999), similarly found no change in insulin with supplementation of horses on a hay diet.
A review of chromium levels in forage and other plants turned up the likely reason. Chromium is available to plants from all soils and they easily take it up. One exception to this is hays grown on alkaline soils because that decreases availability. A rule of thumb here is that if your region's hays have adequate to high selenium, chromium may be low.
A case can be made for chromium supplementation in horses on mixed grain and hay diets. Rapidly growing and very active horses may need grain to hold weight and maintain their glycogen levels. Grains were not part of the ancestral diet and hay chromium levels may be insufficient for the high starch intake. Several studies have indeed shown improved glucose handling with supplemental chromium in that scenario.
Chromium in supplements can only help with glucose disposition if it was deficient in the horse's diet. The bottom line for metabolic syndrome horses is that unless the hay was grown on alkaline soil there is enough chromium in the diet already and more won't help. You are much better off concentrating on the minerals that are commonly deficient — phosphorus, magnesium, copper, zinc, selenium and iodine.
About ECIR Group Inc.
Started in 1999, the ECIR Group is the largest field-trial database for PPID and EMS in the world and provides the latest research, diagnosis, and treatment information, in addition to dietary recommendations for horses with these conditions. Even universities do not and cannot compile and follow long term as many in-depth case histories of PPID/EMS horses as the ECIR Group.
In 2013 the Equine Cushing's and Insulin Resistance Group Inc., an Arizona nonprofit corporation, was approved as a 501(c)3 public charity. Tax deductible contributions and grants support ongoing research, education, and awareness of Equine Cushing's Disease/PPID and EMS.
THE MISSION of the ECIR Group Inc. is to improve the welfare of equines with metabolic disorders via a unique interface between basic research and real-life clinical experience. Prevention of laminitis is the ultimate goal. The ECIR Group serves the scientific community, practicing clinicians, and owners by focusing on investigations most likely to quickly, immediately, and significantly benefit the welfare of the horse.
1 Schwarz, K, Mertz W. A glucose tolerance factor and its differentiation from factor 3.
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2 Schwarz, K, Mertz W. Relation of glucose tolerance factor to impaired intravenous glucose tolerance of rats on stock diets. Am J Physiol. 1959 Mar;196(3):614-8. doi: 10.1152/ajplegacy.19126.96.36.1994.
3 Schwarz, K, Mertz W. Chromium(III) and the glucose tolerance factor. Arch Biochem Biophys. 1959 Nov;85:292-5. doi: 10.1016/0003-9861(59)90479-5.
4 Schwarz, K, Mertz W. A physiological role of chromium (III) in glucose utilization (glucose tolerance factor). Fed Proc. 1961 Sep;20(3)Pt 2:111-4. PMID: 13909776
6 Cartmill, JA. Leptin in horses: influences of body condition, gender, insulin insensitivity, feeding, and dexamethasone. 2004 Louisiana State University and Agricultural and Mechanical College. https://digitalcommons.lsu.edu/cgi/viewcontent.cgi?article=3016&context=gradschool_dissertations
7 Chameroy KA, Frank N, Elliott SB, Boston RC. Effects of a supplement containing chromium and magnesium on morphometric measurements, resting glucose, insulin concentrations and insulin sensitivity in laminitic obese horses. Equine Vet J, 2011 Jul;43(4):494-9.
8 Gentry LR, Thompson DL, Fernandez JM, Smith LA, Horohov DW, Leise BS. Effects of chromium tripicolinate supplementation on plasma hormone and metabolite concentrations and immune function in adult mares. J. Equine Vet. Sci. 1999. 19:259–265. doi:10.1016/S0737-0806(99)80330-X
Article by Eleanor M. Kellon, VMD - Press release by Nancy Collins