Prostate Health: Are you Typical or a SELECT Male with High Vitamin E Status?
Antioxidants protect us. Our bodies have many interrelated systems to protect our cells and tissues. Vitamin E (α-tocopherol) is the most abundant lipid-soluble antioxidant in our bodies. It is co-located within cell membranes to protect polyunsaturated fatty acids from peroxidization. Vitamin E, as well as other antioxidants such as vitamin C and selenium, help protect DNA and proteins from oxidation. Vitamin C is required to regenerate vitamin E.
Vitamin E supplementation reduced the incidence of prostate cancer and mortality 32% and 41%, respectively, in the Alpha-Tocopherol ,Beta-Carotene Cancer (ATBC) Prevention Study. Unfortunately, most intervention trials, and subsequent meta-analysis, have used a treatment analysis (vitamin E vs placebo) and ignored nutritional status of the volunteers.
In 2009, Lippman and colleagues reported that selenium or vitamin E supplementation, alone or in combination, did not prevent prostate cancer in the Selenium and Vitamin E Cancer Prevention Trial (SELECT). Six years after supplementation was ended in SELECT, researchers are finally reporting results involving plasma α-tocopherol concentrations with outcomes.
Baseline vitamin E concentrations, measured in 2001-2004, among the prostate cancer cases (32.6 µmol/L) and controls (31.6 µmol/L); higher than median concentrations of 28µmol/L reported for US adults for 2003-2006. Plasma α-tocopherol concentration was not associated with prostate cancer risk. An interaction was observed with selenomethionine supplementation in men with high-grade prostate cancer risk and high α-tocopherol concentrations.
Factors to consider. The highest quintile for α-tocopherol concentrations was >39.1 µmol/L. Fewer than 25% of Americans over 51y have these levels. Indeed, the median concentration for non-supplement users is 24.9 µmol/L.
In the Physicians Health Study, men randomized to the study were healthier, exercising more and eating more nutritiously than those invited but not randomized to the study. Perhaps confounders apply to SELECT. The participants may not reflect the general population. Certainly the incidence of prostate cancer was higher than expected in SELECT.
Without doubt, the nutritional benefits of vitamin E should be based on studies assessing nutrient status rather than randomization codes. It is good to see studies reported with nutritional status measures.
Albanes D, Till C, Klein EA, Goodman PJ, Mondul AM, Weinstein SJ, Taylor PR, Parnes HL, Gaziano JM, Song X, Fleshner NE, Brown PH, Meyskens Jr FL. Plasma tocopherols and risk of prostate cancer in the Selenium and Vitamin E Cancer Prevention Trial (SELECT). 2014 Cancer Prev Res doi: 10.1158/1940-6207.CAPR-14-0058
Heinonen OP, Albanes D, Virtamo J, Taylor PR, Huttunen JK, Hartman AM, Haapakoski J, Malila N, Rautalahti M, Ripatti S, Maenpaa H, Teerenhovi L, Koss L, Virolainen M, Edwards BK. Prostate cancer and supplementation with α-tocopherol and β-carotene: Incidence and mortality in a controlled trial. 1998 J Natl Cancer Inst 90:440
Lippman SM, Klein EA, Goodman PJ, Lucia MS, Thompson IM, Ford LG, Parnes HL, Minasian LM, Gaziano JM, Hartline JA, Parsons JK, Bearden JD, Crawford ED, Goodman GE, Claudio J, Winquist E, Cook ED, Karp DD, Walther P, Lieber MM, Kristal AR, Darke AK, Arnold KB, Ganz PA, Santella RM, Albanes D, Taylor PR, Probstfield JL,, Jagpal TJ, Crowley JJ, Meyskens FL, Baker LH, Coltman CA. Effect of selenium and vitamin E on prostate cancer and other cancers: The Selenium and Vitamin E Cancer Prevention Trial (SELECT). 2009 JAMA 301:39 doi: 10.1001/jama.2008.864
McBurney MI, Yu E, Ciappio E, Bird J, Eggersdorfer M, Stoecklin E, Mehta S. Vitamin E status of the US adult population by use of dietary supplements. 2014 FASEB J 28(1):1041.7
Sesso HD, Gaziano JM, VanDenburgh M, Hennekens CH, Glynn RJ, Buring JE. Comparison of baseline characteristics and mortality experience of participants and nonparticipants in a randomized clinical trial: the Physicians’ Health Study. 2002 Controlled Clin Trials doi: 10.1016/S0197-2456(02)00235-0