Vanadate (a salt of vanadic acid which is derived from vanadium) is an essential trace element in most body tissues of mammals but has an unknown function. However, both the vanadate and vanadyl forms of vanadium have been shown to stimulate possible insulin-like effects. Its effects have been reported to diminish the diabetic effect by either substituting for and replacing insulin or possibly enhancing the effects of the existing insulin in the body on diabetic rats. Oral vanadate, however, seems to have little effect on plasma glucose levels in non-diabetic rats. Another study done on rats found that despite the improvement of the rat's diabetic state, vanadate-treated rats did not gain more weight than the untreated rats, and in fact, in some studies, caused a decrease in bodyweight in control and diabetic rats due to decreased food intake. In real life, I have found that vanadyl sulfate seems to increase the pump from workouts and by some mechanism allows the pump to remain for some time after a workout.
It have also been noticed that it seems to increase hardness and vascularity. The problem for anabolic dieters stems from the fact that it either works with insulin, or by itself acting like insulin. As you know, insulin on the 5 high fat days of the diet is chronically low, and glycogen levels are chronically elevated for very good reason. By taking the vanadyl sulfate during this time it won't work for 2 reasons. Low insulin levels, and little or no carbohydrates in the diet to stimulate the insulin or the vanadyl sulfate. Therefore stay away from it on the high fat days. On the other hand, if you want to take it on your 2 carb-loading days, that is fine, and the vanadyl will work for you properly.