Epidermal growth factor and transforming growth factor-α in human milk of different lactation stages and different regions and their relationship with maternal diet
Epidermal growth factor (EGF) and transforming growth factor-α (TGF-α) are important growth-promoting factors in human milk and play an important role in a newborn's gastrointestinal function. The aim of the present study was to compare EGF and TGF-α contents in breast milk from different lactation periods and different regions and further analyze the effect of maternal diet on the concentration of EGF and TGF-α in breast milk. Breast milk samples and 24-hour food records were obtained from lactating mothers on day 1 (colostrum), day 14 (transitional milk) and day 42 (mature milk) from Hangzhou (n = 76), Lanzhou (n = 76) and Beijing (n = 76), China. EGF and TGF-α levels were determined by enzyme-linked immunosorbent assay (ELISA). The concentration of EGF in breast milk decreased over lactation periods (p < 0.001) while the TGF-α content in breast milk increased over lactation periods (p < 0.001). During all of the three lactation periods, the EGF content in the breast milk from Lanzhou participants was significantly higher than Beijing and Hangzhou participants (p < 0.001), while the TGF-α content in the breast milk from Beijing was significantly higher than that from Lanzhou and Hangzhou (p < 0.001). The concentration of EGF in breast milk decreased with the increasing intake of proteins (p = 0.042), total energy (p = 0.031), vegetables (p = 0.002), fruits (p < 0.001), soy products (p = 0.001) and dairy foods (p < 0.001), while the TGF-α content in breast milk increased with the increasing intake of carbohydrates (p = 0.023) and dairy products (p = 0.011) and decreased with the increasing intake of proteins (p = 0.008) and meat (p = 0.016). The EGF and TGF-α contents in breast milk were greatly influenced by regions and lactation periods and there was also a strong relationship with maternal diet.