The trial aims to recruit 26 lower selenium-status participants of initial selenium-status approx. 70μg/L, and 26 higher selenium-status participants of initial selenium-status approx. 100μg/L (n=52). (Initial screening sample approx. n=120.) On initial screening, potential participants recording a selenium-status of under 28μg/L or over 400μg/L will be excluded (and their GP informed) for safety reasons.