Table 2.

Summary of human research on sex-specific human milk (HM) composition.

Study	Country	Sample Size	Collection Methods	Infant Age at Collection	Findings	Limitations
Yahya et al., 2009 [53]	Iraq	109 (52 M, 57 F)	Foremilk collected	Not specified	↑ calcium for females, ↑ volume and phosphorus for males	Composition not representative of hindmilk
Powe et al., 2010 [49]	United States of America	25	Breast was emptied by pump expression (mother’s pump or study pump).	2–5 months	↑ energy content (derived by carbohydrates, protein and lipid content) for males	Small sample size, inconsistent sampling time and use of instruments for milk collection, inconsistency of stage of lactation at sampling
Hahn et al., 2016 [51]	South Korea	478 (244 M, 234 F)	Sample collected during day time	0–3 months	↑ carbohydrate and energy content for females	Inconsistent sampling time, Absence of information on maternal diet and anthropometry, inconsistency of stage of lactation at sampling
Fujita et al., 2012 [50]	Kenya	83 (47 M, 36 F)	Foremilk collected in the morning by manual expression	Not specified	↑ fat for females only in mothers with a low socioeconomic status	Composition not representative of hindmilk
Quinn, 2013 [52]	Philippines	103 (52 M, 51 F)	Sample collected in the morning by manual expression after mother nursed the infants for approximately 3 minutes	0–18 months	No significant differences were found between male and female infants in HM composition	Composition not representative of foremilk, inconsistency in stage of lactation at sampling
Fields et al., 2017 [54]	Australia	37(16 M, 21 F)	Breast emptied by pump expression	1 and 6 months	↑ insulin and leptin for females born to obese mothers	Small sample size

F, female infant; M, male infant; ↑, higher compared to the opposite sex.