There is no published research that we know of regarding the use of flax seed to control the accumulation of sand in the horse's intestines. Some research from Florida suggests that removal of sand is better accomplished by feeding a high percentage of hay in the diet. The Florida workers looked at using psyllium to help remove sand from horses that were actually dosed with measured amounts of sand. They compared psyllium with different levels of hay in the diet and actually found that the higher levels of hay intake removed more sand than psyllium.

The main reason flax seed has gained popularity is due to the omega 3 fatty acids present in flax seed oil. There is actually a research report that linseed oil, high in omega 3 fatty acid, may help in managing horses with endotoxemia. Endotoxemia is another condition where endotoxins are found in the blood and are derived from gram-negative rod-shaped bacteria that may cause hemorrhages, necrosis of the kidneys, and shock. However, as mentioned before, there are no reports of flax seed or use of omega 3 fatty acid actually controlling sand accumulation or even helping to remove sand.