Boron has been found to play a key role in the regulation of hormonal vitamin D and testosterone. When boron nutrition is adequate, the body retains more calcium than it loses (known as positive calcium balance). Athletes and anyone who aspires to healthy muscle tone may be interested in boron. Adequate boron nutrition from diet or phyto-boron supplementation may help to build and strengthen bone and connective tissue, as well as support lean body mass and fat metabolism. Taking Vitamin D3 and calcium in conjunction with boron is a great way to maximize their absorption.