Nutrition during lactation not only satisfies energy and nutritional needs of lactating women, but in addition influences the composition of breast milk. The study included 83 lactating and 76 non-lactating women from the area of Primorsko Goranska County which were controlled in 3 phases (after first, third and sixth month postpartum period). During each visit were examined anthropometrics (body weight, muscle mass, fat tissue, visceral fat, and BMI), dietary intake (24-hour dietary recalls) as well as were collected milk samples. Analysis of fatty acids in breast milk samples was quantified by gas chromatography. The results of the food intake of both groups showed a continuous decrease in energy intake and in all macronutrients during postpartum period. Dietary intake was lower than recommended for all participants. Significant decrease (p=0.004) in body weight and proportion of body fat (p=0.034) were determined in lactating group during the period of 3 to 6 months postpartum, while in non-lactating group 1 to 3 months postpartum (p<0.001). Share of muscle mass was unchanged in both groups. In breast milk, the average proportion of monounsaturated fatty acids were 42.26%, trans fatty acids 2.46%, saturated fatty acids 34.95% and 20.01% of long-chain polyunsaturated fatty acids. Statistically significant correlation was confirmed between the average contents of docosahexaenoic acid in breast milk and intake from the food (r=0.52; p<0.006).