There used to be an abundance of selenium in the soil, but as intense farming practices have severely diminished the availability of it, we can longer rely on this as a valuable source. Selenium works with and links to proteins to form selenoproteins. These create glutathione, the amino acid which is the body’s natural antioxidant defence against free radicals which damage cells. One of the components of selenoproteins is thioredoxin which is involved in the regeneration of other antioxidants. Selenium helps regulate the thyroid and protects the heart and circulatory systems. Brazil nuts are the most abundant source of selenium by a long way. Other sources include: tuna, salmon and halibut, barley and couscous, and sunflower seeds.