Boron is known to help support the synthesizing of estrogen, vitamin D and other steroidal hormones. Boron also protects hormones from rapidly breaking down. Boron is essential in the strengthening of connective tissue structure as well as supports mineral metabolism.In humans, boron deficiency signs and symptoms have not been firmly established. Limited data suggest that boron deficiency might affect brain function by reducing mental alertness and impairing executive brain function [1,2,3]. In addition, a low-boron diet (0.25 mg boron/2,000 kcal) might elevate urinary calcium and magnesium excretion and lower serum concentrations of estrogen in postmenopausal women [2,4]. Low boron intakes (0.23 mg boron/2,000 kcal) also appear to reduce plasma calcium and serum 25-hydroxy vitamin D levels and raise serum calcitonin and osteocalcin levels in men and women [2]; these changes could affect bone mineral density. Boron toxicity can also cause headache, hypothermia, restlessness, weariness, renal injury, dermatitis, alopecia, anorexia, and indigestion. In infants, high boron intakes have caused anemia, seizures, erythema, and thin hair [5]. Extremely high doses of boron can be fatal; for example, 15,000 to 20,000 mg can cause death in adults [5,6]. So you do not need to take more than 20 mg a day is upper limit of boron if you are over the age of 19.