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Zinc levels in breast milk, a potential clue to breast dysfunction

Posted:  Wednesday, December 16, 2015

Much has been said and written about zinc and its role in the human body. Now a new study finds that this mineral could serve as an eye-opener to breast function too. A study by the Penn State health researchers showed that zinc levels in breast milk may serve as an indicator of breast function during the lactation period.

The study published in the Journal of Mammary Gland Biology and Neoplasia looked at how genetic changes can influence zinc levels in breast milk and breast function. The study singularly focused on the protein ZnT2, which is crucial for zinc secretion into breast milk.

The researchers built on previous work which showed that women with mutations in the gene that codes for ZnT2 have considerably lower levels of zinc in breast milk. Exclusively breast-fed infants who do not get enough zinc are likely to develop severe zinc deficiency and growth and immunity problems.

Interestingly, the researchers reported that among 54 breast-feeding women, 36% of them had at least one mutation [non-synonymous single nucleotide polymorphism (SNP)] in the protein ZnT2. These women had abnormally low or high zinc levels in their breast milk. Women who have mutations, or SNPs, in ZnT2 may also experience problems with breast-feeding. This is because zinc is needed for the growth and function of the mammary glands.

Taking the study further, the researchers sorted the women into four groups based on the zinc levels in breast milk (from low to high). They found that 79% of the women in the group with the lowest levels of zinc had ZnT2 variants. Contrastingly, in the group with the highest zinc levels, 29% of the women had ZnT2 variants. However, no ZnT2 variants were detected in those with normal milk zinc levels.

Charting a different course, the researchers also looked at the ratio of sodium to potassium (Na/K) in the breast milk from these women. This ratio is a recognised indicator of breast dysfunction, including breast infection and inflammation. They found that the women with the ZnT2 variants, T288S and D103E, had a significantly higher Na/K ratio compared with women who had no ZnT2 variation. These findings indicate that genetic variation of ZnT2 could modify breast function.

The results from this study show how zinc levels in breast milk can help recognise women who have difficulty breastfeeding as well as breast-fed infants who are at risk for zinc deficiency. However, the researchers ask for further investigation to unravel the link between the genes, zinc and breast function.

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