Trace minerals are inorganic elements necessary for proper operation of the human body, yet they generally make up less than 0.005% of adult body weight. Trace minerals are essential for normal growth and metabolism, assimilation and utilization of vitamins and other nutrients, and for making the enzymes, hormones, and other chemical messengers required by the human body.

For some trace minerals, a specific biochemical function has not been clearly defined. For others, the biochemical function is very well-known. Iodine, for example, is needed to make thyroid hormones, which control multiple aspects of human metabolism, including body weight. Iron is another mineral with a clear biological role: it is needed for hemoglobin synthesis, which allows the human body to transport oxygen via the bloodstream.

Additionally, some trace minerals (including selenium) are used to make powerful natural antioxidants capable of protecting human cells from damage caused by free radicals.