This **selenium** supplement delivers a full 200 mcg dose for thyroid and antioxidant support, right at the top of the typical supplemental range and built on L-selenomethionine, the form your body absorbs and retains most efficiently. Selenium powers the enzymes that activate thyroid hormone and recharge your cells' antioxidant defenses, so one capsule effectively covers both goals.

The thing to know is selenium's narrow safety window. The daily upper limit is 400 mcg, and most people in well-fed regions already get enough from food, with one or two Brazil nuts meeting a day's needs. At 200 mcg you stay comfortably under that ceiling, but only if this is your sole selenium source; pairing it with a multivitamin or other selenium products can push you toward excess, which over time causes hair thinning and brittle nails. Supplement if your intake is genuinely low, less so if your diet already covers you.