Many owners don’t think twice before feeding their horses nutritional supplements touted to solve issues ranging from metabolic and joint problems to insect control and behavioral vices. But in many cases the science behind the powders, pellets, and liquids that these horses consume daily is lacking due to research challenges. Thus, owners need to be cognizant about selecting reputable supplements for their horses.

There are a number of issues that limit scientific research in horses. First, horses are extremely expensive research animals to maintain. Also, researchers must use disease "models" in which investigators incite a disease or ailment in the animal for research purposes; these artificially created disease scenarios do not always reflect what happens in natural cases of disease. This is also a concern when it comes to conducting studies in the laboratory setting using cell cultures to examine nutritional supplements’ effects. That is, what happens in a petri dish (in vitro) to samples of tissue or blood does not necessarily reflect what happens in the live horse (in vivo). Another obstacle is that equine studies often do not include sufficient horse numbers to give the studies enough statistical "power." Thus, if only a small number of patients are included in a study, the chances for inaccurate results are higher.

Some nutritional supplement manufacturers also rely on scientific data conducted using similar–but not identical–products, claiming that both products work the same. Finally, some manufacturers rely on data from scientific studies performed in other species, such as rats, mice, and humans. In some cases there might be physiological similarities between species; however, this is not always true. Thus, a beneficial effect of a supplement in one species might not translate to horses. Nonetheless, conducting research on these products is important. In medicine, using research-driven decision-making is referred to as "evidence-based medicine" (EBM). According to David L. Sackett, FRSC, MD, FRCP, author of Evidence-Based Medicine: How to Practice and Teach EBM, this type of medicine "integrates the best external evidence with individual clinical expertise and patient choice."

Only a handful of nutritional supplement companies have conducted scientific testing to demonstrate safety, efficacy, purity, or to determine how these products benefit horses (mechanisms of action). This means that untested products may not be doing anything or, worse, may be unsafe for equine consumption. The lack of science in this area of equine nutrition underscores the importance of striving toward evidence-based studies on nutritional supplements