Preliminary studies with selenium-enriched garlic suggest that the incorporation of selenium into a plant rich in sulfur compounds enhances its chemopreventive potential.

Selenium-enriched garlic was found to induce glutathione S-transferase activity on oral administration to rats. An increase in the level of this enzyme would facilitate the conjugation of carcinogen with glutathione, and its subsequent removal from the body.

The natural abundance of sulfur in garlic and the putative substitution of sulfur by selenium in selenium-enriched garlic, is believed to be responsible for the latter's enhanced biological effects.

Selenium also functions as a cofactor for an antioxidant enzyme glutathione peroxidase (GPx). Glutathione peroxidase functions as a second line of defense against hydroperoxides, inhibiting their formation before they can damage the cell membrane and its components.