Developmental sensitivity of the brain to dietary n-3 fatty acids.

The developing brain readily incorporates dietary fatty acids, while the adult brain is refractory to changes in fatty acid composition. In order to localize the time in development when this transition occurs, chicks were fed large amounts of n-3 fatty acids from fish oil beginning at 0, 1, 2, or 3 weeks of age. Control chicks were fed a soybean oil-based diet, as were the experimental chicks before introduction of the fish oil diet. Resistance to diet-induced increases in brain n-3 fatty acid levels began at 2 weeks of age, and was substantial at 3 weeks. Docosahexaenoic acid was particularly resistant to change as the brain matured, increasing by 38% when fish oil was fed from time of hatching, but only by 8% when fish oil feeding was delayed until 3 weeks of age. Dietary fish oil caused a compensatory decrease in brain n-6 fatty acids, and this decrease occurred even at later time points when the rise in brain n-3 fatty acids was much less prominent. The liver incorporated high levels of n-3 fatty acids at all ages, and compensated by decreasing monounsaturated fatty acids at early time points and n-6 fatty acids at later time points. These results show that resistance to changes in brain fatty acid composition is evident at a relatively early age, before brain development is complete.