Selenium biofortification of lettuce: study of selenium bioaccessibility and speciation in the edible portion of the plant

Abstract

Whereas selenium (Se) is quite important for human health and well-being it has not been comprehensively addressed in this Doctoral Thesis. Therefore, the objective of this work is to focus on this essential element during the internship to be developed abroad. Selenium is a biologically powerful element that has been linked to biochemical processes in plants, microorganisms and especially in animals and humans. In humans, selenium is an essential element, being incorporated as selenocysteine in enzymes and proteins; it plays a role in several physiological processes by acting with thyroid hormone and insulin and participates in the regulation of cell growth and fertility maintenance. Selenium deficiency leads to risk of heart failure, liver disease, and may cause hair loss, infertility, and other diseases, and it has been associated to increased risk of certain types of cancer. The recommended intake is generally 55 ¼g/day for humans, even though higher dietary intakes may be necessary for optimization of the activity of specific selenoproteins. Seafood and beef liver are rich in this element while grains and other meats, as well as fruits and vegetables, contain smaller amounts of Se; nevertheless cereal grains are generally major contributors to selenium intake mainly due to large consumption. It has to be considered that, however, the total amount of the element in food is not a good predictor of the amount absorbed by the human body, considering that the absorption process critically depends on the form of the element that is released in the gut after gastrointestinal digestion. One area that merits further investigation is Se levels in leafy vegetables such as lettuce, which are poorly characterized in Brazil, as well as the species that are effectively absorbed by the human body. In principle, if these food items provide a significant amount of selenium in a bioavailable form they could be effective means to facilitate the achievement of an optimal Se status in the context of an healthy diet. Thus, this study aims to explore Se biofortification in lettuce and evaluate its bioaccessibility and speciation after in vitro simulated human gastrointestinal digestion. The possible effect of Se on the absorption of other elements like Fe, Cd and Zn will also be investigated. (AU)