LBWIs are defined as infants weighing below 2.5kg at birth, with those weighing less than 1.5kg classified as very low-birth weight infants (VLBWIs).
LBWIs accounted for 15% to 20% of all newborns in 2014 (mostly from low- or middle-income countries) with 28% of them born in South Asia alone.
They are usually prone to mental and behavioural issues, and as vital constituents of the brain and retina, LCPUFAs are considered essential for foetal infant mental and visual development.
LCPUFA supplements such as DHA and arachidonic acids (AA) are commonly found in infant formula, acting as a selling point for many brands, especially in China.
However, researchers said it was unclear if lactation supplemented with LCPUFAs can help to boost intelligence in infants of either regular or low birth weight.
Based on this, a review led by China's Jilin University was conducted to identify research focused on the link between intelligence and LCPUFA supplementation in LBWIs.
The researchers conducted a comprehensive search of multiple databases, and selected studies that compared the Bayley Scales of Infant Development (BSID) or Wechsler Abbreviated Scale of Intelligence for Children (WISC) scores between LBWIs who had been supplemented with LCPUFAs during lactation and those who had not.
They then reported that the main outcome of the studies included in their meta-analysis was the mean difference in the mental development index and psychomotor development index of the BSID, and the full-scale IQ, verbal IQ, and performance IQ of the WISC between the controls and supplemented LBWIs.
Despite previous studies having shown that maternal intake of omega-3 PUFAs during pregnancy and lactation had positive effects on infants' nervous system development and intelligence, the researchers said their meta-analysis "could not support this hypothesis".
"Our analysis showed that there was no statistically significant difference in intelligence scores of LBWIs between LCPUFA-supplemented groups and control groups.
"Sub-group analysis of the duration of interventions or the combinations of LCPUFA had no effect on the intellectual level of the intervention group compared to that of the control group either."
The researchers said one of the limitations of the review was that among the studies involving different doses of LCPUFAs, they could not calculate the association between dosage and infant intelligence.
Other weaknesses included short intervention durations, variance in populations, and testing method limitations.
They concluded: "Future studies would benefit from using different doses of DHA and AA, or a different fatty acid ratio as a supplement for LBWIs, thereby exploring the appropriate LCPUFA supplemental doses and allocation ratios.
"Ultimately, a multi-centre, randomised quality-controlled set of experiments with a large sample size is still needed to prove that LCPUFA supplements improve LBWI intelligence, and to provide more reliable evidence."
Source: PLOS ONE
"The effect of long chain polyunsaturated fatty acid supplementation on intelligence in low birth weight infant during lactation: A meta-analysis"
Authors: Yuan Song, et al.