Vanadium is a micronutrient found naturally in mushrooms, shellfish, black pepper, parsley, dill, grain and grain products. It exists as both vanadyl sulfate, the form most commonly used in supplements, and vanadate. We're not sure exactly how much vanadium the body needs; the typical diet provides less than 30 micrograms daily. In the past, vanadium was promoted as a cure for various illnesses at doses ranging from 15 to 100 mg of vanadyl sulfate daily – that's 1,000 times the dietary dose, but no scientific evidence supports the use of these large amounts, which may be toxic. The small amounts contained in most multivitamin/mineral products – 10 micrograms in my formula – are too low to raise concern about toxicity.
A few small studies have indicated that higher doses of vanadium can improve insulin sensitivity and reduce blood sugar in people with diabetes; however, the dosage and long-term safety of this strategy has not been established.
Some animal studies have suggested that vanadyl sulfate may help lower blood pressure, but no human studies have been done. Unless a benefit is proved, I see no reason to take vanadium for this purpose. Nor is there any evidence demonstrating that vanadium can improve athletic performance and increase muscle mass, even though vanadium supplements are widely used for these reasons.
As far as manic depression (bipolar disorder) is concerned, some evidence suggests that blood levels of vanadium may be elevated during manic episodes and also high during depression, particularly when it is accompanied by delusional thoughts or other symptoms of psychosis. I've seen recommendations that a low vanadium diet may be helpful for those with bipolar disorder, but considering that the body absorbs only about five percent of the vanadium in the food we consume, I'm not sure how you could get intake any lower. In any event, I'm not convinced that there's a connection between vanadium and mental disturbance. Even if there were, I do not think the small amounts of vanadium in multivitamin/mineral supplements are an issue for those with mild depression.
Andrew Weil, M.D.