The Proper Balance of Essential Fatty Acids for Life

Abstract

It has been known for more than 70 years that some fatty acids are essential in the diet, but quantitative requirements for n-3 and n-6 fatty acids have been difficult to define. Recent research has established the importance of n-3 and n-6 long chain polyunsaturated fatty acids (LCPs) during infancy. Since n-6 and n-3 fatty acids compete for elongation and desaturation to biologically active LCPs that may have opposing biological effects, awareness of the n-3/n-6 balance is critical.
   Requirements for LCPs infancy have been empirically determined by comparing formula-fed to breast fed infants. The composition of human milk, and the biochemical, metabolic and behavioral responses of the breast-fed infant serve as guides to the requirements for LCPs. While n-6 LCP levels in human milk are rather constant on a global basis, the concentrations of n-3 LCPs in human milk vary widely. A balanced addition of LCPs to infant formula improves visual acuity, cognitive development, modifies the immune respose, and modulates cholesterol metabolism all to more closely resemble breast-fed infants. Unbalanced additions (n-3 LCPs with no n-6 LCPs), however, have been associated with impaired language development in males and decreased growth in low body weight (LBW) infants. Benefits of LCP supplementation extend beyond the first 6 months of life.
   Little is known about the optimal n-3/n-6 balance after weaning and in puberty, when nutrient demands dramatically increase to support growth and development. However, efforts to modify total and saturated fat intake, to prevent the beginnings of some adult diseases, have drawn attention to the importance of fatty acid balance in childhood.
   Unbalanced consumption of n-3 and n-6 fatty acids is associated with many different diseases in adulthood; n-3 LCP supplementation is linked to a decrease in the risk of hypertension, mental diseases, immune hyper-reactivity, and heart disease. Even small amounts of n-3 LCPs in the diet have been associated with reduced risk of sudden cardiac death, probably due to their antiarrhythmic effects. In vivo studies have shown that LCPs prevent arthythmias and modify heart rate variability. In cultured cardiac myocytes LCPs interact directly with ion channels to protect against arthythmic responses.
   Prospective, properly controlled studies need to be conducted to further define the role of the n-3/n-6 ratio in adolescent and adult life. By integrating our knowledge of LCP balance in infancy with current and future information cincerning requirements later in life, we will be able to establish appropriate balance recommendations for optimal balance throughout a lifetime.