Q: As I condition my horse for the spring competition season I’m looking at supplements to both support my horse’s muscle development and help performance. I see DMG and creatine are common ingredients in the supplements I am researching. What are these, and do they improve performance?
A: The acronym “DMG” stands for dimethylglycine, which is a derivative of the amino acid glycine and an ergogenic compound, meaning it’s used to improve performance, recovery, or stamina. Sometimes referred to as vitamin B15, DMG contains two methyl groups, which it can donate to various reactions within the body. These include aerobic energy production pathways that use oxygen. A version with three methyl groups exists, trimethylglycine (also known as betaine).
Dimethylglycine occurs naturally in animals and plants and is an intermediary product of choline metabolism (choline is a water-soluble vitamin involved in the metabolism and transport of fats). It’s thought to enhance muscle creatine levels.
Why would increasing creatine production or supplementing creatine improve performance?
Because the body can convert creatine to phosphocreatine, and phosphocreatine can be used to generate adenosine triphosphate (ATP), which is the energy currency of cells that allows muscle to contract.
The more ATP, the greater the energy available for muscle contraction, allowing for potentially increased power and stamina. Therefore, DMG and creatine are often found in supplements claiming to support muscle mass and recovery. Creatine is synthesized by the liver and kidney and is not prevalent in plants, so it wouldn’t naturally be a major component of a horse’s typical diet.
Phosphocreatine can anaerobically donate a phosphate to adenosine diphosphate (ADP) creating ATP, thus helping maintain the cells’ available ATP for contraction (if you remember your high school biology, this is the ATP-ADP cycle). This reaction occurs extremely rapidly and is short-lived, meaning that overall this isn’t the main way in which muscle cells generate ATP for contraction. However, inadequate phosphocreatine is generally considered a major cause of muscle fatigue during intense, short-lived exercise, such as a horse breaking from a start gate. Insuring adequate phosphocreatine would therefore be useful for generating muscle power at the start of movement, especially during explosive movements, as well as during those final moments of a sprint when you need your horse to “dig deep.”
Additionally, claims have been made that DMG supplementation increases oxygen use in muscle tissue and decreases lactic acid buildup. If true, this could lead to improvements in both aerobic and anaerobic performance. Beyond performance enhancement, DMG is also purported to improve immune function. In humans it’s been shown to result in a strong antibody response to vaccines. However, similar research in horses showed no positive benefit.
Researchers have not conclusively determined whether supplementing horses with DMG offers these beneficial impacts. In a study of racing Quarter Horses and Standardbreds, scientists found a blood lactate reduction; however, researchers on a similar study in Thoroughbreds observed no improvement. The theories behind supplementing DMG and creatine are sound, but research to date doesn’t provide much conclusive support. In fact, the equine digestive tract might not absorb creatine well.
These ingredients might result in improved performance in horses not yet fit enough for the work being asked of them. However, the research suggests that in fit horses they will have little to no effect. If the former is in fact the case–that unfit horses might be able to perform better on these supplements–this raises an ethics issue. Namely, because working a horse above its fitness level increases his risk of injury.
My preference is to create conditioning schedules with a good base of long slow work that are built on slowly and include regular breaks from intense exercise. In the long run, this is most likely to give you the best performance while at the same time insuring the longevity of your horse.