The study, published in Nutrients, is reportedly the first to systematically evaluate the effects of DHA and ARA supplementation on the cognitive development of infants.
Supplementing fatty acids beyond a certain threshold and not in the correct ratio may be detrimental and reduce infant growth rates, according to researchers from Qingdao University and the National Center of Technology Innovation for Dairy in China.
Systematic review and meta-analysis of the literature “demonstrated that an optimal DHA/ARA ratio of 0.5–1 exhibits significantly positive effects on cognitive development in infants,” they wrote.
Long chain PUFAs and infant development
Long-chain polyunsaturated fatty acids, including omega-3 and omega-6, are essential for infant development.
Enzymes convert α-linolenic acid (ALA) to the omega-3 fatty acids eicosapentaenoic acid (EPA) and DHA, while linoleic acid (LA) is converted to arachidonic acid (ARA). However, this process is regulated by age and diet, and conversion rates may be below 3-5%. Additionally, some people have a genetic variant of the desaturase enzyme that weakens the production of ARA.
As the fetus is developing, DHA is delivered via the placenta. Once the infant is born, they rely on breast milk and formula as essential sources of DHA to support the development of the brain, eyes, and nervous system. ARA is an omega-6 fatty acid that supports brain development and the repair and growth of muscle tissue.
The current study notes that ARA is a metabolic necessity for every cell “functioning as a precursor for eicosanoids that influence various biological processes, particularly those involved in cerebral, cardiovascular, and immune functions”.
Getting the ratio right
The researchers note that previous studies have demonstrated that “important physiological and developmental endpoints are sensitive to the ratio of dietary DHA /ARA”.
They explain that supplementing infant formula with DHA alone could result in ARA deficiency and slow infant weight gain.
“Infant Δ-6 desaturase activity is low (only 10–30% of adult activity in preterm infants) and DHA shares the enzyme with the ARA precursor (LA), causing competitive inhibition and further reducing the efficiency of ARA synthesis,” they wrote.
Study details
The researchers conducted a systematic review and meta-analysis using relevant search words. The meta-analysis included nine randomized controlled trials (RCTs) comprising 1039 subjects.
The included studies used the Bayley Scales of Infant and Toddler Development (BSID) and Brunet–Lezine developmental quotient (DQ) test as assessment tools for cognitive function evaluation and developmental score.
The researchers measured cognitive outcomes using standardized mean difference and measured psychomotor development index (PDI) and mental using development index (MDI) using weighted mean difference.
The results showed “significantly positive effects of DHA and ARA supplementation on cognitive development in infants”.
The subgroup analysis showed positive effects on PDI and MDI when the intervention DHA/ARA ratio was 0.5–1
“The study suggests that the combination of DHA and ARA is superior to DHA or ARA supplementation alone and that strict attention should be paid to the DHA/ARA,” the researchers wrote, recommending the 0.5–1 ratio for infant formulas.
However, they noted the study’s limitations and advised carefully interpreting the findings.
Source: Nutrients 2025, 17(6), 1091; doi: 10.3390/nu17061091, “Effects of Different Proportions of DHA and ARA on Cognitive Development in Infants: A Meta-Analysis”, Authors: A. Tian et al.