Table 2.
Risk of cancer or cancer mortality associated with dietary supplements.
| Nutrient | Study Design |
Study Population | Follow Up | Supplement Intake | Risk of Cancer (p < 0.05) |
Ref. |
|---|---|---|---|---|---|---|
| Vitamin A | Double Blind RCT | 29,133 White males between 1985 and 1988 |
5–8 years | (1) α-tocopherol 50 mg/day), (2) β-carotene (20 mg/day), (3) both supplements, (4) placebo |
Higher serum retinol at baseline led to higher risk of PCA incidence. HR = 1.19 (95% CI: 1.03–1.36) |
[12] |
| Sustained high exposure to serum retinol led to greatest risk of PCA incidence. HR = 1.31 (95% CI: 1.08–1.59) | ||||||
| Vitamin A | Double Blind RCT | 18,314 Men and women, high risk for lung cancer | 24 months | (1) combination of 30 mg beta-carotene and 25,000 IU vitamin A daily, (2) placebo |
Beta-carotene and Vit A supp. resulted in excess lung CA incidence. HR = 1.36 (95% CI: 1.07–1.73) |
[13] |
| Beta-carotene and vit A resulted in excess lung CA mortality. HR = 1.59 (95% CI: 1.13–2.23) | ||||||
| Vitamin B6 | Cohort Study | 77,118 Men and women, 50 to 76 years between 2000 and 2002 | 6 years | 10 years average daily dose (mg/d) (1) non-user, (2) 0.4–1.4, (3) 1.4–3.0, (4) 3.0–20, (5) >20 |
Higher risk of lung CA after 10 y Vit B6 supp. HR = 1.82 (95% CI: 1.25–2.65) |
[15] |
| Vitamin B9 | Population-Based Study | Cancer discharge trends in Chile, 1992–1996 vs. 2001–2004 (before and after flour folic acid fortification) | N/A | Average consumption of 185 g of flour containing 410 μg folic acid | B9 supp. program resulted in additional risk of colon cancer HR = 2.9 (99% CI: 2.86–3.25) |
[16] |
| Vitamin B12 | Cohort Study | 77,118 participants 50–76 years, between 2000 and 2002 | 6 years | 10 years average daily dose (µg/d) (1) non-user, (2) 0.1–5.00, (3) 5.01–25.00, (4) 25.01–55.00, (5) >55.00 |
Higher risk of lung CA after 10 y Vit B12 supp. HR = 1.98 (95% CI: 1.32–2.97) |
[15] |
| Vitamin E | Double Blind RCT | 35,533 men between 2001 and 2004 | 7–12 years | (1) Oral selenium (200 μg/d, (2) Vitamin E (400 IU/d), (3) both agents, (4) placebos |
Increased risk of PCA Development with Vit E supp. HR = 1.17 (99% CI: 1.004–1.36) |
[14] |
| Selenium | Prospective Cohort Study | 4459 men, 40–75 years initially diagnosed with non-metastatic prostate cancer | 7.8 years | Selenium supplement μg/day: (1) non-user (2) 1–24 (3) 25–139 (4) >140 |
Increased PCA mortality, highest of >140 μg/day selenium supp. HR = 2.60 (95% CI: 1.44–4.70) |
[18] |
| Zinc | Prospective Cohort Study | 47,240 men, 40–75 years between 1986 and 2016 | 28.3 years | Zinc (mg/d): (1) non-user, (2) 1–24, (3) 25–74, (4) ≥75 |
>75 mg/day zinc supp led to increased risk of aggressive PCA. HR = 1.80 (95% CI: 1.19–2.73) |
[19] |
| >15 years zinc supp led to increased risk of PCA mortality. HR = 1.91 (95% CI: 1.28–2.85) | ||||||
| Omega-3 | Case Cohort Design Nested within SELECT trial |
834 men with PCA and 1393 men selected randomly at baseline | 4.5 years | (1) Oral selenium (200 μg/d, (2) Vitamin E (400 IU/d), (3) both agents, (4) placebos |
Higher PCA risk in men with high Omega-3 serum level. HR = 1.43 (95% CI: 1.09–1.88) |
[20] |
Randomized controlled clinical trial (RCT), PCA: Prostate Cancer, Vit: Vitamin, CA: Cancer, supp: supplementation, N/A, not applicable, SELECT trial (Selenium and Vitamin E Cancer Prevention Trial).