Both the amount and quality of dietary fat consumed can affect growth and development. The consumption of adequate amounts of essential acids especially long chain polyunsaturated fatty acids (LCPUFA) is also important for normal growth and development. Arachidonic acid (AA) and docosahexaenoic acid (DHA) are particularly important for brain development. Breast milk is a good source of these fatty acids. Particular problems exist for those infants and for preterm infants who had an insufficient intra-uterine supply of arachidonic acid and DHA and who were born with low fat reserves. ⁽¹⁾

During neonatal life, there is a rapid accretion of arachidonic acid and DHA in infant brain, DHA in retina and of arachidonic acid in whole body. It has been found that in preterm infants, giving n-3 LCPUFA improved visual attention and cognitive development. Improved developmental scores at 18 months of age have been reported for infants fed both arachidonic acid and DHA.⁽²⁾ LC-PUFA are essential parts of phospholipids, so play a role in the formation of membranes and the brain.⁽³⁾ Animal studies have shown that LC-PUFA function as specific precursors for production of eicosanoids (prostaglandins, thromboxanes and leukotrienes) which regulate numerous cell and tissue functions such as phagocytic capacity of mononuclear cells, decreased production of proinflammatory cytokines ⁽⁴⁾ as well thrombocyte aggregation, vasoconstriction/vasodilatation.⁽³⁾ Infant dietary lipid intake has a profound affect on cholesterol metabolism and has shown to be associated with cardiovascular morbidity and mortality later in life.⁽³⁾

Two important LC-PUFA that have been recognized for cognitive development are DHA (a n-3 fatty acid) and Arachidonic acid (a n-6 fatty acid). DHA is a major component of retina reaching concentrations of 30-40% of total fatty acids in the rod photoreceptor in human retina.⁽³⁾ There is a growth spurt in the human brain during both last trimester of pregnancy and first post natal months with a large increase in the cerebral content of AA & DHA.⁽³⁾ Thus LC-PUFA are associated with improved visual and cognitive development. It has been found that breast fed children have higher IQ scores compared with children who received on infant formula that did not contain LC-PUFA.⁽⁵⁾ Also, mothers whose children were found to be allergic have shown to have lower levels of DHA in their breast milk as compared to milk from mothers of non-allergic children.⁽⁶⁾

A number of studies have shown that consumption of foods such as fish oil containing n-3 fatty acids; eicosapentaenoic acid (EPA) and DHA is associated with decreased risk of coronary heart disease.⁽¹⁾ However, since n-6 and n-3 fatty acids complete for same enzymes and have different biological roles (often opposing effects) on smooth muscle cells, platelet aggregation and vascular permeability, the balance between n-6 and n-3 fatty acids in diet is of considerable importance.⁽¹⁾ Thus for preterm infants, LC-PUFA intake should be similar to that of human milk with AA to DHA ratio of 1.5 and a DHA content of 0.4%.⁽²⁾ Addition of LC-PUFA in infant formulas with appropriate regard for quantitative and qualitative quality enables the formula fed infant to achieve the same blood LC-PUFA status as that of breast fed infants.⁽²⁾

A cochrane analysis of 11 randomised trials comparing LC-PUFA supplemented formula milk Vs non-supplemented formula milk in term infants found that 3 studies found beneficial effect of LC-PUFA on visual acuity whereas no beneficial effect was seen on physical growth.⁽⁷⁾ However no adverse effect of LC-PUFA have been noted when supplemented to formula.

Both fetus and newborn infant are dependent on maternal supply of DHA which is in turn related to mother's long-term dietary intake.⁽⁸⁾ For healthy infants, breast milk supplies LC-PUFA. If infant formula is given, 0.2% DHA & 0.35% of AA of total fatty acids is useful. For preterm infants, since they are born with much less total DHA & AA, they will need an infant formula that includes at least 0.35% DHA and 0.4% AA.⁽³⁾

Long chain-polyunsaturated fatty acids are associated with improved visual and cognitive development. Randomized clinical trials involving preterm infants have shown a clear requirement for DHA for full visual and neural development.

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