Long-chain polyunsaturated n-3 and n-6 fatty acids are present in human milk, but not in the majority of infant formulas sold in Denmark. The content of the n-3 fatty acid DHA is high in retinal tissue and cerebral cortex. A number of studies have suggested that the content of DHA has a positive influence on the function of cell membranes. Preterm infants receiving human milk or infant formula with DHA have a better visual acuity than those receiving infant formula without DHA. In term infants receiving infant formula the content of DHA in plasma, red blood cell membranes and cerebral tissue is reduced compared to breast-fed infants.