20. Isoflavone and flavonoid supplemented eggs in health

Eggs are a staple item in the western diet with an average per capita egg consumption of up to 248 eggs per year in the USA alone. Eggs can serve as carriers of a variety of nutrient, such as vitamins and omega-3 fatty acids. In this chapter we will focus on the egg as a vehicle of other nutrients, such as isoflavones, otherwise found in less commonly consumed food products. Isoflavones are plant secondary metabolites and belong to the flavonoid family. Isoflavones have been shown to act as phytoestrogens and to have a myriad of potential health benefits, and they may also protect the body against breast cancer, heart disease and osteoporosis. Isoflavones are more abundant in leguminous plant, such as soybeans. Soy and soy products, however, are not a regular part of the western diet and are mainly used as livestock and poultry feed. Soy isoflavones can be transferred and accumulated in eggs yolk making them a perfect carrier for isoflavones. Commercial hen eggs have been shown to contain ~30-120 μg isoflavones/100 g of yolk. Fortification of the poultry diet with isoflavone or isoflavone reach ingreditents (such as soy germ) can result in higher accumulation of isoflavone in the eggs, with concentrations of up to 1000 μg isoflavones/100 g yolk reported. Isoflavones fortification of eggs, however, may not be always desirable. There are some concerns about potential adverse effects of isoflavone estrogen-like activities for selected populations. For that reason, we consider that information of isoflavone presence in eggs would be valuable to consumers and egg producers as well. Fortification of chicken feed with other flavonoid containing compounds can also enhances the quality of the eggs and their health benefits. Synthetic additives are often added to animal feed to prevent oxidation and prolong the shelf-life and the health qualities of their products. Addition of some flavonoid containing plants to the poultry feed instead may decrease the cholesterol and low-density lipoprotein content of the egg yolk, as well as, increasing their oxidative stabilities.