Background and Objective: Feeding long‐chain polyunsaturated fatty acids (LCP) influences immunity in adults; however, less is known about their effect during development. The aim of the study was to determine the effect of feeding LCP on immunity in healthy infants during the first 4 months of life.Patients and Methods: Formula‐fed infants were randomized at ≤14 days of age to standard term formula (Formula) or formula containing LCP (Formula+LCP). Infants exclusively fed human milk (HM) were included for comparison. At 16 weeks of age, blood was collected and phenotypes, the ability to proliferate and produce cytokines (interleukin [IL]‐2, IL‐4, IL‐6, IL‐10, IL‐12, interferon [IFN]‐γ, tumor necrosis factor [TNF]‐α, TGF‐β) after incubation with phytohemaglutinin (PHA), β‐lactoglobulin, or soy protein were measured.Results: Feeding LCP resulted in a higher than and more similar proliferation rate to PHA in HM‐fed infants, possibly because of a greater T_H1 type cytokine response and a higher percentage of antigen mature (CD45RO+) cells (P < 0.05). The response to β‐lactoglobulin did not differ among groups. After incubation with soy protein Formula+LCP, compared with Formula produced less IL‐2 and more TNF‐α and had a higher percentage of CD8+ and a lower percentage of CD20+ (CD20+CD54+) cells poststimulation (P < 0.05). Both formula groups produced less IL‐2 after PHA, had a lower percentage of CD80+ cells, and a higher percentage of CD54+ cells after incubation with food proteins (P < 0.05).Conclusions: Formula‐fed infants, at low risk for allergy, respond differently to mitogen and food proteins ex vivo than those fed HM. Feeding LCP altered some of these differences in the direction that is hypothesized to confer immune benefits.

We examined whether a ganglioside supplemented diet affected the course ofGiardia murisinfection in mice and survival ofGiardia lambliatrophozoitesin vitro. Female CD-1 mice were fed 1 of 5 experimental diets: standard lab chow as a control diet; semi-synthetic diets containing 20% (w/w) triglyceride based on the fat composition of a conventional infant formula; triglyceride diet; triglyceride diet containing a low level of ganglioside (0·1% w/w); and triglyceride diet containing a high level of ganglioside (1·0% w/w of diet). After 2 weeks of feeding, mice were inoculated withG. murisby gastric intubation and fed the experimental diets during the course of the infection. Cysts released in the faeces and trophozoites present in the small intestine were enumerated at various times post-infection. The average cyst output and the number of trophozoites during the course of the infection in mice fed ganglioside-containing diet were found to be significantly lower (3-log₁₀reduction) compared to animals fed control diets. The results ofin vitrogrowth studies indicated that gangliosides may be directly toxic to the parasites. Thus, gangliosides have a protective effect againstG. murisinfectionin vivoand affect the survival ofG. lambliatrophozoitesin vitro.