Future directions for nutrient requirements--lipids.

Recent advances in instrumentation and methodologies are redefining the study of lipid nutrition by allowing probing for subtle responses to marginal variations in nutrients. Stable isotope labeling studies allow demonstration of chain elongation, desaturation, chain shortening and resynthesis in humans. Essential fatty acid deficiency affects membrane physicochemical properties and membrane-bound protein activity. Understanding of the molecular functions of dietary fat has progressed to conceptualization of complex competing and complementary interactions and signals. The physical properties of lipids--insolubility in water and amphipathic qualities--underlie their physiological function. These findings will lead to new biomarkers of health status.