FIG. 1.

Baseline plasma selenium (Se) levels of Nutritional Prevention of Cancer (NPC) and Selenium and Vitamin E Cancer Prevention Trial (SELECT) participants. Thick horizontal lines indicate the range between lowest and highest baseline plasma Se levels of NPC and SELECT study participants. As depicted by dashed vertical lines, significantly lowered cancer incidence was observed only among the Se-supplemented NPC participants whose baseline Se levels were in the first and second tertile (91–122 ng/ml Se). For comparison, plasma Se levels associated with optimization of plasma selenoproteins are marked by dotted vertical lines. Se-mediated cancer prevention in the NPC study appears to be associated with optimization of plasma selenoprotein P (SeP) levels.