The essential trace mineral, selenium (Se) is of fundamental importance to human health. Selenium is a powerful antioxidant mineral and is found in all tissues of the body. It has a protective effect against oxidative damage to body cells, particularly the heart. Selenium deficiency has been linked to a range of serious conditions like cancer, cardiovascular disease, inflammatory diseases and other free radical related problems such as premature ageing.

Most Se ingested by animals and humans comes from the soil, through plants. Levels of Se available in soils are highly variable globally. Areas that are notably low in Se include parts of China, Siberia, Central Africa, Eastern Europe and New Zealand. Although large areas have not yet been mapped for Se, it is apparent that many people have too little Se to support maximum selenoenzyme expression.

Human Se status is sensitive to changes in the food supply. Of concern is a trend towards a reduction of Se in the food chain in certain regions, possibly because of fossil fuel burning (with release of sulfur, an Se antagonist), acid rain, soil acidification and use of high-sulfur fertilizers.

Some common dietary foods that contain Selenium in various forms include garlic, Brazil nuts, mushrooms, asparagus, wheat and many cereals. An ideal nutritional supplement would be a selenium-enriched edible plant part wherein the selenium metabolically accumulates in the form of bioavailable organic selenium compounds. Plants that naturally contain higher levels of the sulfur- containing amino acids such as those from the Allium and Brassica species are preferred for enrichment, based on metabolic criteria.