Essential Fatty Acids and Brain Development

Nutrition of the infant is of paramount importance for at least two main reasons: (a) there is a fast rate of growth and tissue development; (b) organ specific phases of development take place, which are likely to be determinants of subsequent performance. Tissue development involves increase in size and number of cells. The fast rate of growth in infancy is reflected in the high energy requirement since the recommended energy requirement per unit weight is about three times higher (120 kcal/kg body weight/day) for newborn infants compared to adults (1). It is estimated that up to one-fourth to one-third of the total energy intake in the first few months of life is utilized for growth and that approximately 5 kcal are required for each gram of body weight gained (1). In the adult, brain occupies about 2% of the body weight and consumes one-fifth of the energy utilized by the body as a whole. In the infant, the brain is approximately 16% of the body weight and consumes in excess of 50% of the energy intake in the first few months. The brain of the human infant at birth may weigh about 450 g but at 2 to 4 years of age it will reach 1.5 kg with the most active phase of growth being in the first 6 to 12 months. Although the bulk of brain cell division occurs during fetal life, about 20% of the total adult number of brain cells is added during the first year of life; the bulk of postnatal brain growth is, however, accounted for by an increase in cell size and the formation of the connections between the cells (2). Of the materials acquired by the brain during postnatal development, approximately 60% is structural fat. Carbohydrates, fats, and proteins all contribute toward the energy content of the diet to different degrees, fat contributing the highest at about 9 kcal/g of fat. In human milk, fat accounts for about 50% to 60% of the energy, and of the fat, oleic acid is quantitatively the most significant fatty acid. Thus, fat is essential in infant nutrition in order to supply an adequate amount of energy when it is required the most. If there is no fat in the diet, then the volume of the feed would have to be increased in great amounts. Substitution with protein would lead to an increased solute load on the kidney while carbohydrate substitution could lead to digestive disturbances due to excessive load of the disaccharides on the intestinal mucosa. Fats are also required as vehicles for the fat soluble vitamins.