Sodium selenite is far more than an ordinary selenium supplement. This redox-active compound has attracted interest in cancer research because it may place pressure on cancer cells from two directions at once: increasing oxidative stress while weakening the antioxidant systems those cells depend upon for survival.

This article explores the history of sodium selenite, its effects on glutathione, thioredoxin, mitochondria and cancer-cell death, and where it may fit within a carefully coordinated Press–Pulse metabolic oncology strategy. It also examines the current research, the limitations of the evidence and why nutritional selenium and pharmacological sodium selenite should never be considered interchangeable.