Vitamin E may reduce the risk of prostate cancer in smokers

A follow-up study from Finland reports that a supplementation of vitamin E had a preventive effect on prostate cancer development in male smokers, which lasted about eight years after the initial trial and resulted in decreased mortality.

The study determined potential long-term effects of vitamin E (alpha-tocopherol) and beta-carotene on cancer incidence and the risk of all-cause mortality in 25,563 male smokers for 18 years after a large randomized controlled trial (1). The initial ATBC study examined the impact of a supplementation with alpha-tocopherol (50 mg/day), beta-carotene (20 mg/day) or placebo for about six years on cancer incidence in 29,133 male smokers aged 50 to 69 years (2). The follow-up observation showed that the 34% reduction of prostate cancer incidence in men who received vitamin E continued about eight years after the initial trial had ended. In addition, the 16% lower mortality risk from prostate cancer in the vitamin E group was still evident about eight years after the trial. While in the original ATBC study, high dose beta-carotene supplementation significantly increased the risk of developing lung cancer among participants who reported smoking 20 ciga- rettes or more per day, the higher risk related to heavy smoking disappeared within about four years after stopping beta-carotene supplementation. No late effects were observed during the 18-year follow-up.

The researchers commented that although laboratory experiments point to several potential mechanisms for a cancer preventive effect of alpha-tocopherol, its role in prostate carcinogenesis remains unclear. A sub- study within the ATBC study suggested that alpha-tocopherol supplementation decreased serum concen- trations of androstenedione and testosterone, sex hormones thought to be involved in the etiology of pro- state cancer (3). In contrasts to the ATBC study findings, however, other trials supplementing vitamin E as 400 IU daily or every other day have found no beneficial effect on prostate cancer incidence.

The temporal effects of increased lung cancer risk among heavy smoking participants who received high doses of beta-carotene for years, which disappeared after intervention, suggest that beta-carotene seemed to accelerate the growth of already existing very early stage non-recognizable tumors, and argue against a role in initiating lung cancer development. The findings of the ATBC study are inconsistent with smaller lung cancer protective effects of increased beta-carotene intake or blood concentrations observed in prospective epidemiological studies (4). In other randomized controlled trials with smokers and non-smokers, beta- carotene supplementation did not impact lung cancer incidence (5-7).

1. Virtamo J. et al. Effects of alpha-tocopherol and beta-carotene supplementation on cancer incidence and mortality: 18-Year post-intervention follow-up of the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. Int. J. Cancer. Published online December 2013.
   
2. The ATBC Cancer Prevention Study Group. The Alpha-Tocopherol, Beta-Carotene Lung Cancer Prevention Study: design, methods, participant characteristics, and compliance. Ann Epidemiol. 1994; 4:1–10.
   
3. Hartman T. J. et al. Effects of long-term alpha-tocopherol supplementation on serum hormones in older men. Prostate. 2001; 46:33–38.
   
4. Gallicchio L. et al. Carotenoids and the risk of developing lung cancer: a systematic review. Am J Clin Nutr. 2008; 88:372–383.
   
5. Hennekens C. H. et al. Lack of effect of long-term supplementation with beta-carotene on the incidence of malignant neoplasms and cardiovascular disease. N Engl J Med. 1996; 334:1145–1149.
   
6. Lee I. M. et al. Beta-Carotene supplementation and incidence of cancer and cardiovascular disease: the Women’s Health Study. J Natl Cancer Inst. 1999; 91:2102–2106.
   
7. Lin J. et al. Vitamins C and E and beta-carotene supplementation and cancer risk: a randomized controlled trial. J Natl Cancer Inst. 2009; 101:14–23.