Table 2. Epidemiological Studies on Selenium and Colorectal Cancer and Adenoma^a.

—ordered by study design and publication year

1st Author, pub. Year, reference	Country	Cases/controls	Outcomeb	Results (OR for highest vs. lowest quantile)			Selenium assessment
				OR	95% CI	p-trend	Specimen	Mean/medianc
Randomized Trials
Clark 1996[3]	United States	8/19d	CR	0.39	0.17–0.90	0.03	Plasma (at baseline)	114
Nested Case-Control and Case-Cohort Studies or Cohort
Peters 2006[175]	United States	758/767	A	0.76	0.53–1.10	0.01	Serum	134
Jacobs 2004[59]	United States	403/310	AR	0.67	0.43–1.05	0.21	Serum	131
		247/251	AR	0.66	0.40–1.10	0.13	Plasma	134
		362/190	AR	0.57	0.34–0.95	0.04	Serum	131
		pooled		0.66	0.50–0.87	0.006		132
Garland 1995[55]	United States	89/89	CR	2.04	0.88–4.75	0.12	Toenails	0.843
van den Brandt 1993[54]	The Netherlands	105e/2569	C	1.07	0.61–1.88	0.55	Toenails	0.535 in men; 0.560 in women
		76e/2569	R	1.12	0.49–2.55	0.89
Bostick 1993[57]	United States	212/35004	CR	0.60	0.27–1.32		Supplement	-
Criqui 1991[43]	United States	30/55	GI	Mean selenium levels lower in GI cases than controls by 9 ng/ml (p<0.1)			Plasma	149
Knekt 1990[26]	Finland	32/64	CR-men	0.69	Not reported	ns	Serum	64
		59/118	CR-women	1.26	Not reported	ns		65
Ringstad 1988[44]	Norway	11/11	GI	Mean selenium levels lower in CR cases (124 ng/ml) than controls (129 ng/ml) (p=0.3)			Serum	130 ng/ml
Schober 1987[41]	United States	72/143	C	0.71	0.29–1.67		Serum	115
Coates 1988[51]	United States	28/51	GI	1.00	Not reported	0.89	Ser./Plas.	162/148
Nomura 1987[52]	Hawaii Japanese	82/293	C	0.56	Not reported	0.33	Serum	123
		32/293	R	0.63		0.66
Peleg 1985[50]	United States	19/38	GI	Mean selenium levels not different between GI cases (115 ng/ml) and controls (116 ng/ml)			Serum	116
Salonen 1985[47]	Finland	18/18	GI	Mean selenium levels lower in GI cases (54.9 ng/ml) than controls (60.1 ng/ml) (p>0.05)			Serum	61
Salonen 1984[46]	Finland	21/21	GI	Mean selenium levels lower in GI cases (48.6±3.2 ng/ml) than controls (54.3±3.4 ng/ml) (p not provided)			Serum	54
Willett 1983[49]	United States	13/26	GI	Mean selenium levels lower in GI cases (114 ng/ml) than controls (134 ng/ml) (p=0.01)			Serum	134
Case-Control Studies
Fernandez-Banares 2002[40]	Spain	24/35	CR	Mean selenium levels lower in CR cases (41.9±4.3 ng/ml) than controls (64.9±6.3 ng/ml) (p=0.006)			Serum	89 in ≤60y 45 in >60y
	Spain	28/35	A	In subjects ≤60 years (n=30): Mean selenium levels lower in adenoma cases (57.9±4.3 ng/ml) than controls (88.9±8.0 ng/ml) (p=0.002)
Ghadirian 2000[18]	Canada	92/202	CR	0.42	0.19–0.93	0.009	Toenails	0.91 ng/mg
Scieszka 1997[48]	Poland	25/25	CR	Mean selenium levels lower in CR cases (51.4±14.1 ng/ml) than controls (38.4±12.6 ng/ml) (p=0.0018)			Plasma	51
Russo 1997[45]	United States	37/36	A	0.24	0.06–1.04	0.09	Plasma	120
Nelson 1995[56]	United States	139/138	A	1.8	0.9–4.0		Serum	123
		25/138	CR	1.7	0.5–5.9
Clark 1993[42]	United States	28/20	A	0.24	0.07–0.80	0.04	Plasma	128
Zhao 1990[53]	China	202/404	CR	Selenium levels lower in CR cases (135 ng/ml) than controls (150 ng/ml) (p<0.01)			Blood	150

^aEcologic studies and observational studies using dietary questionnaires to assess selenium intake were excluded

^bA=adenoma, AR=adenoma recurrence, C=colon cancer, CR=colorectal cancer, GI=gastrointestinal cancer, R=rectal cancer

^cMean (or median) selenium levels in controls only, serum and plasma selenium levels in ng/ml and toenail selenium levels in ng/mg

^dNumber of colorectal cancer cases in selenium supplementation group/placebo group

^eCases diagnosed during 1st year of follow-up were excluded. Results including all cases are for colon cancer (n = 216): OR, 0.79; 95% CI, 0.50–1.25; rectal cancer (n =102): OR, 1.05; 95% CI, 0.57–1.94 for highest versus lowest quintile.