Immunological Factors and Macronutrient Content in Human Milk From Women With Subclinical Mastitis

Subclinical mastitis is an asymptomatic inflammatory condition of the lactating mammary glands possibly associated with premature interruption of breastfeeding and poor weight gain in infants. However, data on human milk composition in mothers with subclinical mastitis are limited and inconsistent. Although human milk from donors with subclinical mastitis may be used after pasteurization if it meets the criteria, whether the composition is suitable for donor human milk remains unknown.

This study assessed the human milk composition of participants with subclinical mastitis and verified the safety of donor human milk, including that from mothers with subclinical mastitis.

This cross-sectional survey included 106 milk samples collected between March 2022 and January 2023. Subclinical mastitis status was assessed using the sodium-potassium ratio, which was measured using an ion-selective electrode. The concentrations of lactoferrin and secretory Immunoglobulin A were analyzed using an enzyme-linked immunosorbent assay. True protein, fat, carbohydrate, and energy levels were analyzed using a mid-infrared transmission spectroscopy.

In human milk from the subclinical mastitis group, lactoferrin and true protein concentrations were significantly increased compared to those without subclinical mastitis. A positive correlation was observed between lactoferrin and secretory Immunoglobulin A levels.

Increased immunological substances and protein concentrations in human milk are similar to those observed in clinical mastitis, indicating an inflammatory response in the body, even in asymptomatic individuals. Immunological substances and proteins are beneficial for preterm infants. Therefore, human milk from mothers with subclinical mastitis is suitable for use by milk banks.