Serum Metabolomic Response to Low and High Dose Vitamin E Supplementation in Two Randomized Controlled Trials

Objectives Vitamin E is an essential micronutrient and critical human antioxidant that has been tested for cancer and cardiovascular preventative effects for decades with conflicting results. For example, prostate cancer incidence was reduced by a low-dose vitamin E supplement in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study, but the findings were not replicated by high-dose vitamin E trials such as the Selenium and Vitamin E Cancer Prevention Trial (SELECT). The present investigation examined the serum metabolomic responses to low- and high-dose vitamin E supplementation in order to gain biological insight into the divergent trial outcomes. Methods We examined baseline and on-study serum samples for 154 men randomly assigned to receive 400 IU vitamin E (as alpha-tocopheryl acetate; ATA) or placebo daily in the Vitamin E Atherosclerosis Prevention Study (VEAPS), and 100 men administered 50 IU ATA or placebo daily in the ATBC Study. Over 970 known metabolites were identified using an ultrahigh-performance LC-MS/MS platform. Linear regression models estimated the change in serum metabolites of men supplemented with vitamin E to those assigned to placebo in VEAPS compared with ATBC. Results Serum alpha-carboxyethyl hydrochroman (CEHC) sulfate, alpha-tocopherol, and beta-/gamma-tocopherol were significantly altered by supplementation with ATA in both the VEAPS and ATBC trials (all P-values ≤ 5.1 × 10−5, the Bonferroni multiple-comparisons corrected statistical threshold). Serum C22 lactone sulfate was also significantly decreased in response to the high-dose vitamin E supplement in VEAPS (β = −0.70, P-value = 8.1 × 10−6), but not altered in the low-dose ATBC trial (β = −0.17, P-value = 0.4). Additionally, changes in several androgenic steroid metabolites were strongly related to the vitamin E supplement-associated change in C22 lactone sulfate only in the high-dose VEAPS trial. Conclusions We found evidence of a dose-dependent vitamin E supplementation effect on a novel C22 lactone sulfate compound as well as several androgenic steroids that may have relevance to previous controlled trial findings for prostate cancer. Funding Sources This research was supported by the Intramural Research Program of the National Cancer Institute, National Institutes of Health, U.S. Public Health Service, Department of Health and Human Services.

The effect of β-carotene on the mortality of male smokers is modified by smoking and by vitamins C and E: evidence against a uniform effect of nutrient

A previous analysis of the Alpha-Tocopherol Beta-Carotene (ATBC) Study on male smokers found that β-carotene supplementation increased the risk of pneumonia 4-fold in those who started smoking at the age of ≥21 years and smoked ≥21 cigarettes/d (a subgroup of 7 % of the study population). The present study hypothesised that β-carotene increases mortality in the same subgroup. The ATBC Study (1985–1993) recruited 29 133 Finnish male smokers (≥5 cigarettes/d) aged 50–69 years. Cox regression models were constructed to estimate the effect of β-carotene supplementation in subgroups. β-Carotene increased mortality (risk ratio 1·56; 95 % CI 1·06, 2·3) in those who started to smoke at ≥21 years and smoked ≥21 cigarettes/d. Within this subgroup, there was strong evidence of further heterogeneity. The effect of β-carotene supplementation was further modified by dietary vitamin C intake, fruit and vegetable intake (P = 0·0004), and by vitamin E supplementation (P = 0·011). Thus, harm from β-carotene was not uniform within the study population. Interactions between β-carotene and vitamins C and E were seen only within a subgroup of 7 % of the ATBC participants, and therefore should not be extrapolated to the general population. Heterogeneity of the β-carotene effect on mortality challenges the validity of previous meta-analyses that have pooled many diverse antioxidants for one single estimate of effect using the assumption that a single estimate equally applies to all antioxidants and all people. Trial registration: ClinicalTrials.gov NCT00342992.

β-Carotene Supplementation and Lung Cancer Incidence in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study: The Role of Tar and Nicotine

Introduction The Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study demonstrated that β-carotene supplementation increases lung cancer incidence in smokers. Further, cigarettes with higher tar and nicotine content are associated with a higher risk of lung cancer. However, no studies have examined whether the increased risk associated with β-carotene supplementation in smokers varies by the tar or nicotine content of cigarettes. Methods The ATBC Study was a randomized, double-blind intervention trial conducted in southwest Finland. A total of 29 133 male smokers, aged 50–69 years, were enrolled and randomly assigned to one of four groups (α-tocopherol, β-carotene, both, or placebo). Cox proportional hazards models were used to estimate the hazard ratio (HR) and 95% confidence intervals (CI) of lung cancer risk by β-carotene trial assignment stratified by a priori categories of cigarette tar and nicotine content. Results The β-carotene supplementation group had significantly higher risk of developing lung cancer in all categories of tar content (yes vs. no β-carotene supplementation—ultralight cigarettes [≤7 mg tar]: HR = 1.31, 95% CI = 0.91 to 1.89; nonfiltered cigarettes [≥21 mg tar]: HR = 1.22, 95% CI = 0.91 to 1.64; p for interaction = .91). Similarly, there was no interaction with nicotine content (yes vs. no β-carotene supplementation—ventilated cigarettes [≤0.8 µg nicotine]: HR = 1.23, 95% CI = 0.98 to 1.54; nonfiltered cigarettes [≥1.3 µg nicotine]: HR = 1.22, 95% CI = 0.91 to 1.64; p for interaction = .83). Conclusion These findings support the conclusion that supplementation with β-carotene increases the risk of lung cancer in smokers regardless of the tar or nicotine content of cigarettes smoked. Our data suggest that all smokers should continue to avoid β-carotene supplementation. Implications Previous studies demonstrated that β-carotene supplementation increases risk of lung cancer in smokers. This study moves the field forward by examining the potential for modification of risk of lung cancer with different levels of tar and nicotine in cigarettes smoked, as interaction with carcinogens in these components of cigarette smoke is hypothesized to be the mechanism by which β-carotene increases risk. Our study provides evidence that the increased risk of lung cancer in smokers who take β-carotene supplements is not dependent upon the tar or nicotine level of cigarettes smoked and suggests that all smokers should continue to avoid β-carotene supplementation.