Iodine is vital to human health, and iodine bio-fortification programs help improve the human intake through plant consumption. Essential processes in plants that can be altered by iodine bio-fortification include the nutritional state of plants. The main objective of this work was to determine whether mineral nutrient concentrations were affected by the application of different forms (iodide [I-] vs. iodate [IO3-]) and dosages (0, 20, 40, and 80 mu M) of iodine, to ascertain the influence of this trace element in Lactuca sativa var. longifolia plants. The application of 80 mu M of I- significantly reduced the nutrients nitrogen (N), phosphorus (P), and potassium (K) to below the optimal ranges established for this crop. The IO3- treatments represented optimal maintenance of the nutritional state for most of the nutrients and even an improvement of nutrients as important as magnesium (Mg) and iron (Fe).