Vitamin E is an umbrella term for a group of 8 fat soluble antioxidants including alpha-, beta-, gamma-, and delta-tocopherol, and alpha-, beta-, gamma-, and delta-tocotrienol, though alpha-tocopherol is believed to be the primary form used by the human body.1 Vitamin E prevents production of reactive oxygen species by fat oxidation and is important for immune/endothelial cell function.
Several, large, randomized controlled trials have evaluated the effect of vitamin E supplementation on cancer incidence.
alpha-Tocopherol, beta-Carotene (ATBC) Cancer Prevention Study
The ATBC study randomly assigned 29,133 male smokers aged 50 to 69 living in Finland to receive beta-Carotene (20 mg daily), alpha-tocopherol (50 mg daily), beta-Carotene (20 mg daily) plus alpha-tocopherol (50 mg daily), or placebo for a median follow-up of 6.1 years.2 Compliance was excellent, with a median 99% of capsules taken across intervention groups.
The incidence of lung, colorectal, liver, urinary tract, and aerodigestive tract cancers were similar among subjects who received alpha-tocopherol compared with placebo.2-6
Physicians’ Health Study II
The double-blind Physician’s Health Study II randomly assigned 14,641 men aged at least 50 to receive alpha-tocopherol (400 IU), vitamin C (500 mg), a multivitamin with or without beta-carotene, or placebo for a mean follow-up of 8 years.7 The incidence of lung, prostate, colorectal, or other cancers was similar among the vitamin E and placebo groups, which was further confirmed by a long-term follow-up.8
Selenium and Vitamin E Cancer Prevention Trial (SELECT)
SELECT randomly assigned 35,533 men aged 50 or older to receive selenium, alpha-tocopherol (400 IU daily), the combination, or placebo.9 The initial analysis found a nonsignificant increased risk of prostate cancer with vitamin E supplementation compared with placebo (relative risk [RR], 1.13; 99% CI, 0.95-1.35; P = .06).
During long-term follow-up, the researchers found an increased risk of prostate cancer with vitamin E supplementation compared with placebo (hazard ratio [HR], 1.17; 99% CI, 1.004-1.36; P = .008), with an absolute increased risk of 1.6 per 1000 person-years.10 The combination of selenium and vitamin E did not increase prostate cancer risk.
Another analysis found similar incidences of bladder cancer in the vitamin E and placebo groups.11
Women’s Health Study
The Women’s Health Study randomly assigned 39,876 female health professionals aged 45 or older living in the United States to receive beta-Carotene (50 mg every 2 days) with or without aspirin (100 mg every 2 days) and/or vitamin E (600 IU every 2 days), or placebo.12 The trial lasted for 12 years, though the beta-Carotene component ended after a median treatment duration of 2.1 years. Current smokers comprised 13% of the cohort at baseline. Vitamin E supplementation did not lower the risk of total cancer or cancers of the breast, lung, or colon.
Other studies also recorded no change in overall cancer incidence or death, or incidence of lung, oral and pharyngeal, colorectal, breast, melanoma, prostate, or liver cancers with vitamin E supplementation, even among high-risk patients.13-15