Abstract

Previously in this journal, Hlusko et al.1 hypothesised that the substitution in an exon of ectodysplasin receptor (EDAR) at position 370 (EDARV370A mutation), wich increases mammary duct branching, may enhance the transmission of vitamin D to the foetus through breast milk. However, based on current evidence, this hypothesis warrants a critical re-examination. Bernard et al.2 investigated breast density across different ancestries and found that Native American and Alaska Native women, populations known for having high frequencies of the EDARV370A allele, exhibited lower breast density compared to other groups. Similarly, Coletta et al.3 identified a significant association between the EDARV370A genotype and reduced breast density in the US Hispanic population and another group with elevated frequencies of this allele. After adjusting for key variables, such as age, body mass index, menopausal status and number of children (p = 0.0218), they concluded that carriers of the EDARV370A allele have a lower parenchymal content in breast tissue compared to non-carriers. These results challenge Hlusko et al.'s hypothesis regarding the adaptive value of the EDARV370A SNP. Breast milk composition has evolved to provide a stable and essential source of nutrition for infants.4 With respect to vitamin D, no statistically significant differences were observed in the total vitamin D activity of breast milk between non-supplemented mothers and those supplemented with 1000 IU of vitamin D₃.5 This suggests that vitamin D levels in breast milk remain relatively consistent regardless of supplementation. Consequently, this evidence casts doubt on Hlusko et al.'s1 hypothesis that carriers of the EDARV370A allele benefit from an evolutionary fitness advantage, both in terms of breast structure and vitamin D composition in milk. Further research is needed to conclusively determine the role of the EDARV370A mutation in this context.