Table 2. Characteristics of studies investigating an association between insufficient milk supply and breast cancer.

Author	Year of Publication	Country	Study Period	Outcome (type of breast cancer)	Age (years)	N total
Shema [15]	2007	Israel	2005	premenopausal and postmenopausal	30–75	640
Newcomb [16]	1999	U.S.A.	1992–1994	postmenopausal	50–79	1323
Freudenheim [17]	1997	U.S.A.	not available	premenopausal and postmenopausal	40–85	511
Brinton [18]	1995	U.S.A.	not available	premenopausal	<45	169
Newcomb [19]	1994	U.S.A.	not available	premenopausal and postmenopausal	<75	7454
Yang [20]	1993	Canada	1988–1989	premenopausal and postmenopausal	<75	1182
Byers [21]	1985	U.S.A.	1957–1965	premenopausal and postmenopausal	40–84	1012

^*note that all are case-control studies.