Solaray Selenium 200 mcg VegCapsules For Immune Support & Thyroid Function is the high potency selenium supplement provides 200 mcg of absorbable selenium as selenomethionine, a superior form found in nature, thought to be more bioavailable than other forms. An essential trace mineral naturally found in thyroid tissue, selenium may be involved in the healthy functioning of the all-important thyroid gland. Selenium may also provide support for a healthy immune system, antioxidant processes in the body and cellular health.