Title: PUFAs and Infant Formula
Key words: Essential fatty acids, PUFA, infant formula, breast feeding
Date: June 1999
Category: 4. Food Data
Author: Dr van Rhijn
PUFAs and Infant Formula
The Rationale For The Addition Of Long-Chain Polyunsaturated Fatty Acids To Infant Formula
Observational studies suggest that breast feeding may advantage the infant in cognitive and intellectual development in comparison with infants fed on formula milk, even if various confounding variables are controlled for. There is speculation that one of the beneficial components of breast milk in this regard may be long chain polyunsaturated fatty acids (LC-PUFAs). The evidence for this hypothesis will be discussed.
What are LC-PUFAs
Two parental essential fatty acids (EFAs), Linoleic Acid (18:2 n-6) and Linolenic acid (18:3 n-3 LNA) are converted to LC-PUFAs by a series of desaturation and chain elongation steps into their functional derivatives Arachidonic acid (20:4 n-6 AA) and Docosahexaenoic acid (22:6 n-3 DHA) respectively. Neural, retinal and vascular development in the foetus and neonate is dependent on an adequate supply of LC-PUFAs, especially AA and DHA1, 2, 3, as 60% of the structural material of the brain is lipid (> 50% PUFAs).
Supplementation with DHA enhances maturation of electroretinographic (ERG), improve visual-evoked potentials (VEP) and forced-choice preferential looking (FPL), reflecting a rapid retinal development4. Supplementation with LC-PUFAs resulted in shorter fixation duration scores (releasing attention), which is inversely related to intelligence5. This increased ability to process information (faster reaction times), reflects developmental maturity of frontal eye fields and cortex (Parietal & Prefrontal), secondary to an accumulation of LC-PUFAs in cell membranes6. This may be due to dopaminergic and serotonergic neurotransmission promotion. DHA is essential for normal rhodopsin7 function.
Rational for Fortification
Reports on brain lipid composition confirm that breast fed infants have higher DHA levels compared to those fed on formula8,9. DHA levels only increased to similar levels when formulas were supplemented with fish oils rather than with the precursors LA or alpha-linolenic acid. This supports the evidence that preterm infants may be unable to convert EFAs10, 11, resulting in deficiencies at a critical stage of Central Nervous System development12. No correlation with visual function was associated with the parent LNA. Deficiencies (non-fortified formula milks) may result in impaired neuro-development, poor visual acuity13, 14. Breast-feeding may confer prospective long-term benefits on neurological development15, as well as higher IQ scores at 8 years of age in pre-term infants16. Studies have demonstrated improved visual acuity in those infants receiving supplemented formula17, 18, but conflicting results with regard to cognitive function19, 20.
Many of the above mentioned studies lack proper randomisation and utilise different measuring tools for vision tests. The results are difficult to interpret if different maturation rates and age of individual testing are taken into consideration. Infants with intrauterine growth retardation may receive more benefit from supplementation with LC-PUFAs with regards to cognitive function, making a case for early supplementation with EFAs during pregnancy.
More research, controlling for the number of experimental variables, as well as consensus about the optimum quantities, duration, safety and source of LC-PUFA supplementation appropriate for pre-term and term infants are required before major changes in diet formulas are made.