Selenium is an essential micronutrient with multiple roles in the growth and metabolism of plant and animal cells. It is present in the glutathione peroxidases and tetraiodothyronine 5' deiodinases enzymes as a part of the selenocysteine amino acid and in the selenoprotein P and can act as an antioxidant with positive effects in the prevention of cancer and the neutralization of toxicity from heavy metals. According to the National Academy of Sciences of the United States, the RDA (Recommended Dietary Allowance) for supplemental selenium in humans ranges from 50 to 100 mg/day. An ideal nutritional supplement able to reverse a deficient selenium status correlated to lowered immunity to diseases is represented by the edible part of Se-enriched plants with selenium stored in the organic form, which is more available than the inorganic one.
The role of selenium as an antioxidant is also extremely interesting as regards some metabolic processes of various agricultural plant species where the possibility to slow down or delay the onset of senescence and fruit ripening may be commercially useful. Selenium enrichment may increase the post-harvest shelf life of edible plants, preserving product quality for a longer time. Knowledge about selenium storage in various parts of edible plants would therefore allow vegetable products to be offered that, because of their selenium content, may contribute to slowing the onset of aging in humans.
Trials in the selenium enrichment of fruits (apples, pears and peaches) and vegetables (tomatoes, radish, chicory, strawberry, and basil) have shown that the administration of sodium selenate in hydroponics or through foliar fertilization increases the plant’s selenium content and may delay senescence and fruit ripening. This effect may be due to a biosynthetic reduction of ethylene, the plant hormone primarily responsible for the plant’s senescence and fruit ripening. The ultimate objectives of these studies are to reduce waste along the distribution chain (general markets and supermarkets) and in the marketing of fresh and processed (e.g., dried, preserved) fruit and vegetable products having a selenium content physiologically adequate to the nutritive aspects.
Research in this field anticipates a synergy of the various scientific skills needed to produce a high nutraceutical selenium-enriched product that can modulate some biological activities in the human body and which will keep longer in comparison to one that has not been so enriched.