Controversy in fatty acid balance.

It is uncertain whether preterm infants can synthesize C20 and C22 (omega-6) and (omega-3) fatty acids required for structural lipids. Dietary intake of C18:2 omega-6 and C18:3 omega-3 in formulae lacking long-chain polyunsaturated fatty acids can result in reduced levels of C20 and C22 homologues in membrane phospholipids as compared with breast-fed infants. Supplementation of fish oil has been shown to alleviate this problem in part only, as synthesis and incorporation of arachidonic acid into membrane phospholipids is reduced. Presently, infant formulae do not contain C20 and C22 fatty acids. Feeding an experimental infant formula with a balance between C20 and C22 (omega-6) and (omega-3) fatty acids within the range of human milk results in plasma phospholipid levels of C20 and C22 long-chain polyunsaturated (omega-6) and (omega-3) fatty acids similar to those in breast-fed infants. On the basis of clinical studies and evolutionary data, an increase of the linolenic and a decrease of the linoleic acid content in infant formula are suggested. Balanced incorporation of both (omega-6) and (omega-3) long-chain polyunsaturated fatty acids seems advisable in view of the lack of knowledge concerning the neonate's ability to chain elongate and desaturate essential fatty acids. Recommendations for the essential fatty acid content of preterm infant formula are suggested.