"The current study suggests that higher serum concentrations of alpha-tocopherol (up to 13 to 14 milligrams per litre, which is within the normal range) are associated with moderately lower total and cause-specific mortality in older male smokers," wrote lead author Margaret Wright from the National Cancer Institute, National Institutes of Health.
The link between vitamin and so-called all-cause mortality has previously been reported by a meta-analysis published in the Annals of Internal Medicine in 2004 that made the controversial statement: "Those who take greater than 400 IU of vitamin E a day are about 10 percent more likely to die than those who do not."
However, while the new research appears to challenge this, co-author of the new study Professor Jarmo Virtamo from the National Public Health Institute, Helsinki, Finland told NutraIngredients.com that no comparison of the results could be made.
"The meta-analysis was based on supplementation trials and the new study on a follow-up cohort," he said. "They are totally different situations"
Indeed, the new study, published in the November issue of the American Journal of Clinical Nutrition, appears to highlight the difference between dietary and supplemental sources of the vitamin.
Vitamin E, an antioxidant, actually refers to a group of eight compounds: four types of tocopherols and four tocotrienols. While alpha-tocopherol is the form mostly found in supplements, a balanced diet will provide all eight types in varying concentrations.
The new research examined the link between baseline serum alpha-tocopherol concentrations and death from certain causes and death from all causes, based on 29 092 Finnish male smokers (average age 57, average BMI 26 kg per sq. m) who took part in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study.
Alpha-tocopherol levels were measured at baseline (average value 11.9 milligrams per litre) and only ten per cent reported using vitamin E supplements at the start of the study, showing that the majority of vitamin E was from the diet.
After 19 years of follow-up the researchers had documented 4518 deaths due to cancer and 5776 due to cardiovascular disease (CVD). Dr. Wright and her co-workers report that men with the highest serum alpha-tocopherol levels (more than 13.5 mg/L) had significantly reduced risk of cause-specific mortality than those with the lowest levels (less than 10 mg/L).
Mortality due to lung cancer, prostate cancer, coronary heart disease, stroke, and respiratory diseases were found to be reduced by 21, 32, 16, 36, 42 per cent, respectively, for men with the highest serum levels, compared to men with the lowest levels.
Total mortality for cancer and cardiovascular disease was reduced by 21 and 19 per cent, respectively, said the researchers.
So-called all-cause mortality was reduced by 18 per cent if serum alpha-tocopherol levels were above 13.5 mg/L, compared to those with the lowest levels.
"Continuous serum alpha-tocopherol values indicated greater risk reductions with increasing concentrations up to about 13-14 mg/L, after which no further benefit was noted," said the researchers.
The results do contrast with the results of supplementation trials, including the actual ATBC study which reported that a daily supplement of 50 mg synthetic all-rac-alpha-tocopherol had no effect on all-cause mortality.
"Because supplemental vitamin E has not been shown to reduce mortality in randomised trials, efforts to improve vitamin E status through dietary means may be warranted, particularly if future prospective studies show similar serum alpha-tocopherol -mortality associations in diverse populations, including non-smokers," concluded the researchers.
While the study results cannot be extended to other subsets of the population, like young men, women, non-smokers, and other racial groups, it is relevant to many smokers, a group who normally have lower antioxidant levels than the general population.
Tobacco smoke contains over 4,000 compounds, of which 60 are known carcinogens. The oxidative stress levels of smokers are significantly greater than non-smokers, and as such there is a bigger drain on the levels of antioxidants in the body.
Source: American Journal of Clinical Nutrition, November 2006, Volume 84, Number. 5, pages 1200-1207. "Higher baseline serum concentrations of vitamin E are associated with lower total and cause-specific mortality in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study" Margaret E. Wright et al.