TABLE 5.

Efficacy of dietary supplements and risk of cancer¹

Factor (references)	Trials, n	RR	95% CI	I2 (95% CI), %
Calcium (36, 57)	2	0.37	0.22, 0.63	0 (NA)
Given singly	2	0.41	0.22, 0.76	0
Combined with others	1	0.33	0.17, 0.66	NA
Low dose (<1200 mg/d)	1	0.13	0.01, 2.53	NA
High dose (≥1200 mg/d)	1	0.38	0.22, 0.66	NA
Selenium2 (45, 54, 60, 87, 93)	4	0.85	0.68, 1.07	80 (47, 92)
Given singly	3	0.78	0.52, 1.18	85
Combined with others	2	0.99	0.87, 1.12	54
Low dose (<120 μg/d)	2	0.83	0.58, 1.19	27
High dose (≥120 μg/d)	2	0.84	0.53, 1.33	91
Zinc2 (combined with others and low dose, <50 mg/d) (45, 66)	2	0.91	0.77, 1.07	0 (NA)
Vitamin D (51, 55, 57, 67, 82, 84)	6	0.81	0.41, 1.62	58 (0, 83)
Given singly	4	1.42	0.46, 4.32	0
Combined with others	2	0.60	0.21, 1.74	90
Low dose (<500 IU/d)	4	0.98	0.92, 1.05	0
High dose (≥500 IU/d)	2	0.92	0.08, 10.1	78
β-Carotene2 (43–45, 59, 80)	5	1.02	0.96, 1.08	46 (0, 80)
Given singly	3	1.01	0.96, 1.07	16
Combined with others	3	1.03	0.92, 1.16	60
Low dose (<30 mg/d)	3	0.99	0.93, 1.07	51
High dose (≥30 mg/d)	2	1.09	0.96, 1.23	30
Vitamin A (combined with others) (43, 66)	2	1.16	1.00, 1.35	0 (NA)
Low dose (<25,000 IU/d)	1	1.33	0.30, 5.91	NA
High dose (≥25,000 IU/d)	1	1.16	1.00, 1.35	NA
Vitamin C2 (45, 65, 75)	3	0.99	0.91, 1.06	0 (0, 90)
Given singly	1	1.00	0.91, 1.10	NA
Combined with others	3	0.99	0.91, 1.07	0
Low dose (<500 mg/d)	2	0.90	0.77, 1.06	0
High dose (≥500 mg/d)	1	1.01	0.93, 1.10	NA
Vitamin E2 (48, 58, 60, 65, 74, 75, 80)	7	1.02	0.99, 1.06	0 (0, 71)
Given singly	6	1.01	0.98, 1.05	0
Combined with others	4	1.03	0.99, 1.08	0
Low dose (<400 IU/d)	2	1.01	0.95, 1.07	0
High dose (≥400 IU/d)	5	1.03	0.98, 1.07	0
Folic acid (given singly and high dose, ≥5 mg/d) (47)	1	1.04	0.53, 2.06	NA
Vitamin K (32)	1	3.05	0.13, 73.4	NA
EPA (85)	1	1.11	0.93, 1.33	NA

¹NA, not applicable.

²Multiarm trials were combined.