Table 1. The characteristics of included studies.

Study(Year)		Breast cancer patients			Healthy controls
	Areas	Mean age	N	Zn(mean ± SD)	Mean age	N	Zn(mean ± SD)
Serum zinc levels
Cavallo et al.(1991)	France	53.10	47	90.8 ± 10.3	53.10	46	85.4 ± 10.2
	Italy	49.60	206	101.8 ± 15.8	47.10	212	87.9 ± 14.6
Gupta et al.(1991)	India	47.00	35	99.4 ± 26.5	46.00	30	115.1 ± 16.1
Yucel et al.(1994)	Turkey	48.00	31	0.479 ± 0.130	50.00	30	1.355 ± 0.289
Piccinini et al.(1996)	Italy	58.60	38	86.43 ± 23.46	56.80	22	74.03 ± 24.22
Singh et al.(1998)	India	N	10	26.3 ± 5.3	N	5	17.0 ± 7.3
Huang et al.(1999)	China	48.00	35	1.14 ± 0.28	44.50	35	1.13 ± 0.17
Magálová et al.(1999)	Slovakia	55.6	73	14.54 ± 2.11	51.7	87	14.99 ± 1.89
Zowczak et al.(2001)	Poland	N	8	13.0 ± 3.3	N	21	13.8 ± 2.0
Kuo et al.(2002)	China	N	25	753.77 ± 86.35	N	26	976.734 ± 92.25
Siddiqui et al.(2006)	India	46.84	25	8.49 ± 1.53	42.37	25	4.74 ± 0.62
Arinola et al.(2008)	Nigeria	47.17	29	143.27 ± 6.62	46.07	30	143.38 ± 7.54
Veras et al.(2011)	Brazil	N	29	69.69 ± 9.0	N	26	65.93 ± 12.44
Saleh et al.(2011)	Kuwait	47.20	50	0.99 ± 0.39	46.90	150	3.6 ± 1.1
Sarita et al.(2012)	India	N	21	13.0 ± 2.0	N	30	38.5 ± 3.9
Hair zinc levels
Piccinini et al.(1996)	Italy	58.60	38	162.30 ± 27.20	56.80	22	156.32 ± 30.07
Kilic et al.(2004)	Turkey	53.00	26	147.0 ± 21.40	55.00	27	293 ± 35.15
Wang et al.(2006)	China	54.20	50	247.6 ± 121.7	52.20	50	195.9 ± 50.2
Joo et al.(2009)	Korea	47.10	40	145 ± 7.23	47.80	144	163.54 ± 4.93
Yoo, et al.(2010)	Korea	47.08	37	14.33 ± 0.72	47.75	144	16.35 ± 0.49
Cihan et al.(2011)	Turkey	50.30	52	29.374 ± 20.367	47.40	52	63.7 ± 6.187
Gholizadeh et al.(2013)	Iran	N	21	12.3 ± 5.3	N	10	24.0 ± 6.0