Background and aims:
This study aims to provide a first overview of fatty acid (FA) concentrations in human milk (HM) throughout lactation using pooled data analysis of existing literature, which has not been done before.

Methods: 
A Medline search was conducted with specific search terms on FAs in HM. The search was confined to English language and with a time limitation from January 1980 until August 2018. Studies providing original data on HM samples from healthy mothers were included. Main exclusion criteria were usage of packed columns for FA chromatography, undefined lactational stage, pooled milk samples across mothers or lactational stages, maternal dietary restrictions and reviews.
After data extraction and standardization, weighted least squares means (WLS) and SE were calculated for the most commonly reported FAs, palmitic-, oleic, linoleic- (LA), arachidonic- (ARA), α-linolenic- (ALA), eicosapentaenoic- (EPA), docosahexaenoic- (DHA) acids in colostrum (0-5 days post-partum), transitional milk (6-15 days) and mature milk (16-60 days) using a random effect (k >5) model.

Results: 
The literature search resulted in a total of 54 studies (4295 HM samples) worldwide. Table 1 shows that LA, palmitic and oleic acids seem to remain relatively stable throughout lactation, whereas DHA and ARA seem to decrease, ALA to increase over time and EPA to peak in transitional milk decreasing thereafter. 

Conclusions: 
Our pooled data analysis provides an overview of FA concentrations across lactational stages narrowing a scientific gap. Distinctly different temporal patterns seem to exist in HM FA concentrations.

TEMPORAL CHANGES IN FATTY ACID PROFILE OF HUMAN MILK: A POOLED DATA ANALYSIS