The results of a study just published in the November 2008 Scandinavian journal Acta Veterinaria Scandinavica will likely start to show up soon in connection with many supplements containing MSM (methylsulfonylmethane). Twenty-four competing show jumpers were divided into three groups, unsupplemented, MSM-supplemented (8 mg/kg of bodyweight) or same-dose MSM plus 5 mg/kg of vitamin C (ascorbic acid). The study period was five weeks, with blood samples taken before supplements began and at weekly intervals, following a jumping test over 16 jumps at speeds of 13 to 15 mph.
The study looked at markers of oxidative stress (oxygen free radicals produced in the mitochondria during exercise), as well as the activity of natural antioxidant enzyme systems in the blood of the horses over a five-week period when they were actively competing. They found higher markers of oxidative stress and lower antioxidant enzyme levels in the unsupplemented horses. Horses supplemented with MSM only had a partial restoration of their antioxidant enzyme status, while those supplemented with both MSM and ascorbic acid had full restitution to normal levels.
While the differences between the supplemented and unsupplemented groups were large, we’re not ready to put all performance horses on MSM and vitamin C. One detail absent from the study was the base diet of these horses. The drops they showed in their antioxidant enzyme systems were large compared to other studies using workloads that were just as demanding, if not more. This suggests their diet may well have been lacking in basic antioxidant nutrients such as vitamin E, selenium, copper and zinc. Inadequate intakes of branched chain amino acids, methionine and glutamate could also explain the results.
Generation of oxygen free radicals is an inevitable consequence of exercise. Under normal circumstances, the horse’s body responds to this by ramping up its production of defense systems. When that does not occur, it’s either because the horse is not being given sufficient rest periods or the diet is not adequate or both. It’s better to give the horse the nutrition he needs to function properly than look for damage control with supplements.
The doses used amounted to 40 grams per day of MSM and 25 grams of vitamin C for a 500 kg (1,100-lb.) horse. That level of vitamin C would cause diarrhea in many horses. While MSM is claimed to be fully nontoxic, this dose is massive even compared to those used for control of obvious inflammation and far exceeds what normal intake would be even for a horse on fresh pasture.