According to a new German study, supplementation of antioxidant vitamins may reduce cancer mortality and all-cause mortality.
In the prospective cohort study, which recruited 23,943 men and women without pre-existing cancer and myocardial infarction / strokeat the beginning of the trial, vitamin/mineral supplementation and health status were assessed at different time points, at baseline and during 11 years of follow-up (1). The study results showed that participants who took antioxidant vitamin supplements already at the beginning of the trial had a significantly reduced risk of cancer mortality and all-cause mortality compared to non-users. Initial non-users who started taking vitamin/mineral supplements during follow-up showed increased risks of cancer mortality and all-cause mortality.
The researchers concluded that supplementation of antioxidant vitamins might possibly reduce cancer and
all-cause mortality. The increased occurrence of cancer and all-cause mortality among participants who started taking supplements only during follow-up may be due to a ‘‘sick-user effect”: participants who had developed certain health problems during follow-up started supplementation to influence (not prevent) disease.
Users of any vitamin/mineral supplements were more likely to have some favourable health-related characteristic, such as being physically active and having a generally healthier diet, which was indicated by higher intakes of fruits/vegetables and milk/milk products but a lower intake of meat/meat products. Users were older than non-users and more likely to be women, have a university degree, and have been smokers for longer. Among them, multivitamins, with or without minerals, were the most commonly used supplements (28.6%), followed by antioxidant vitamins (18.1%).
Some epidemiological studies have investigated the effects of vitamin/mineral supplementation on cancer, cardiovascular disease (CVD), and all-cause mortality. However, the inconsistent findings obtained from these studies do not allow for drawing a clear conclusion. As reported by a US prospective cohort study,
long-term daily use of multivitamin supplements was significantly associated with reduced mortality due to cardiovascular diseases (2), while in another cohort study this association was not observed (3). In the Cancer Prevention Study II, use of multivitamin in combination with vitamin A, C, or E was significantly associated with decreased all-cause mortality (4). Nevertheless, multivitamin supplements alone did not show this beneficial effect in other studies (5).
See also: Topic of the Month Antioxidants in the Prevention of Cardiovascular Disease – Part 1–3