Insulin insensitivity or insulin resistance is a common feature of both equine Cushing’s disease (Pituitary pars intermedia dysfunction – PPID) and equine metabolic syndrome (EMS). Insulin insensitivity leads to a number of health issues, particularly weight gain and an increased risk of developing laminitis. In Cushing’s the insulin insensitivity arises because of excess production of cortisol which counteracts insulin. In EMS, which is similar to Type II diabetes in people, horses have an excessive increase in blood insulin when they eat sugary feeds. EMS is a major predisposing factor in laminitis.
Chromium (Cr) is a metal and is an additive in steel manufacture. Cr increases the action of insulin although this is still not entirely understood. In 2001 the US Institute of Medicine published a recommended intake of Cr for humans (National Academies, 2001). Cr supplementation has been used in the management of human Type II diabetes patients and a review in 2016 concluded “the available evidence suggests favourable effects of chromium supplementation on glycaemic control in patients with diabetes” (Mauro-Martin et al. 2016).
A study of 5mg chromium per day from chromium containing yeast from 2011 failed to show any effect on insulin sensitivity in laminitic, obese horses (Chameroy et al. 2011). However, a recent study by Spears et al. (2020) from North Carolina State University found that 2 or 4 mg of chromium propionate per day did increase insulin sensitivity in adult horses following a carbohydrate-high feed.
Whilst chromium propionate increased insulin sensitivity in normal, healthy horses, further trials are needed to show whether it has the same effect in Cushing’s or EMS-affected horses.
Note: At the present time, whilst legal to use in the USA, the use of chromium propionate in any feed or supplement is prohibited in the UK and EU.
San Mauro-Martin, Ruiz-León AM, Camina-Martín MA, Garicano-Vilar E, Collado-Yurrita L, Mateo-Silleras Bd, Redondo Del Río Mde P. (2016) Chromium supplementation in patients with type 2 diabetes and high risk of type 2 diabetes: a meta-analysis of randomized controlled trials. Nutr Hosp. 2016 Feb 16;33(1):27. Available HERE
Spears JW, Lloyd KE, Siciliano P, Pratt-Phillips S, Goertzen EW, McLeod SJ, Moore J, Krafka K, Hyda J, Rounds W. (2020) Chromium propionate increases insulin sensitivity in horses following oral and intravenous carbohydrate administration. J Anim Sci. 2020 Mar 25. Available HERE
Chameroy KA, Frank N, Elliott SB, Boston RC. (2011) 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. Available HERE