FAs, whether saturated, mono- (MUFA) or polyunsaturated, are oxidized in the mitochondria and represent the most energetic substrates of the diet. They are incorporated into phospholipids as the major components of cellular membranes or packaged into triglycerides for storage and
export. The essential PUFA of the n-3 series (EPA and DHA, found in fish oil and ALA, precursor of EPA and DHA, found in nut, soy, and rapeseed oils) and of the n-6 series (arachidonic acid -AA- and LA found in sunflower and nut oils) are precursors for different signaling molecules. Initial steps in their metabolism are desaturations catalyzed by ratelimiting Δ6 and Δ5 desaturases (Figure 3). In humans, Δ5 and Δ6 desaturase activities, and thereby the conversion
rate of ALA to EPA/DHA, are low and can further be modulated by genetic and epigenetic factors and dietary cofactors, including magnesium, zinc, and vitamin B6 [44, 45].
Therefore, exogenous sources of EPA/DHA are important as they generate the most potent n-3 PUFA-derived protective mediators [23].