Breast milk fatty acids possess immunomodulatory properties, and new intervention strategies beyond supplementation of maternal diet with single oils are called for. The objective of the present study was to evaluate the effect of dietary intervention during pregnancy and breastfeeding on breast milk fatty acid and cytokine composition.

Pregnant women were randomised into three study groups: dietary intervention with probiotics (diet/probiotic) or with placebo (diet/placebo) and a control group (control/placebo). Dietary intervention included dietary counselling and provision of rapeseed oil-based food products. The probiotics used were Lactobacillus rhamnosus GG and Bifidobacterium lactis Bb12 in combination. Dietary intake was evaluated by food records at every trimester of pregnancy and 1 month postpartum. Breast milk samples were collected after birth (colostrum) and 1 month after delivery for fatty acid and cytokine analysis (n = 125).

Dietary intervention improved the quality of fat in the diet. In breast milk, the proportion of α-linolenic acid and total n-3 fatty acids was higher in both dietary intervention groups compared with control group (p < 0.05). In the diet/probiotic group, the γ-linolenic acid content was higher compared with the diet/placebo group (p < 0.05). The concentrations of TNF-α, IL-10, IL-4 and IL-2 were higher in both dietary intervention groups compared with controls, and furthermore, long-chain n-3 fatty acids were associated with several cytokines in colostrum samples.

The present intervention demonstrated the possibility of modifying breast milk immunomodulatory factors by dietary means.