Vanadyl sulfate is a compound of vanadium, sulfur, and oxygen with the chemical formula VOSO4. At standard atmospheric pressure (100 kilopascals, or 1 bar), it has a melting point of 221 °F (105 °C) and is a blue solid at room temperature. It can imitate some of the effects of insulin. It is a popular ingredient in nutritional supplements, especially those intended to aid in strength training, though its efficacy for that purpose in humans has not been scientifically validated.
It is commonly produced in the process of extracting vanadium from the environment. It is most commonly the result of the reaction of vanadium (V) oxide (V2O5), also known as vanadium pentoxide, with sulfur dioxide (S2O4), sulfuric acid (H2SO4), and water (H2O). Vanadyl sulfate is the form in which the average person is most likely to encounter vanadium, but it is rarely found in nature.
Vanadyl sulfate has insulin-like effects, and scientific studies have shown that it can improve insulin sensitivity in diabetics. However, it also frequently causes problems in the gastrointestinal tract when people start taking it, resulting in cramps, nausea, and diarrhea that usually last about one week. More seriously, studies on human patients indicate that vanadyl sulfate decreases hemoglobin levels, possibly by interfering with the collection of iron in red blood cells. Long-term effects in humans are unknown, but existing human and animal research suggests that long-term accumulation of vanadium may cause health problems due to its toxicity at high levels.
Nutritional supplements containing vanadyl sulfate are commonly marketed as an aid to weight training and bodybuilding due to the substance's supposed ability to improve strength and muscle development. This idea is based on vanadyl sulfate's insulin-like properties. Insulin supplies cells with energy by helping glucose pass through cellular membranes to the insides of the body's cells, where the glucose is metabolized to produce energy. Insulin also aids the entry of enzymes that build and repair cellular structures and aid in muscle growth. Thus, it has been proposed that vanadyl sulfate could supplement the body's natural insulin to increase these desirable effects.
However, medical research has not supported this idea. When muscles need more energy during intense physical exertion, they increase their glycogen intake by becoming more sensitive to insulin rather than through a body-wide increase in insulin levels. Thus, artificially increasing the amount of insulin or insulin-imitating chemicals in the bloodstream did not have the helpful effects hoped for, and test subjects who took vanadyl sulfate as a supplement to strength training in scientific tests have not shown any improvements in performance compared to other subjects.