Many people take vitamins and minerals to promote health and prevent various diseases, but are they as safe and useful as they seem at first glance? According to numerous studies carried out in recent years, vitamins with antioxidant activity not only have no efficacy in the prevention of cardiovascular and oncological pathologies, but also increase the mortality rate of patients in certain cases.

The objective of a systematic review and meta-analysis by G. Bjelakovic et al. (Denmark), was to assess the effect of taking antioxidants prescribed for the primary and secondary prevention of various diseases on the mortality rate of patients. The study authors searched the electronic databases and bibliographic sources available for the period up to October 2005. The analysis included the results of all the randomized trials identified on β-carotene, vitamins A, C, E and selenium, both as monotherapy and in various combinations compared to placebo or the absence of treatment in adult patients.

A total of 68 studies were analyzed, including 232,606 participants (385 publications). An in-depth study of work with a high and low risk of systematic errors did not reveal a significant effect of the intake of antioxidants on mortality (relative risk (RR) 1.02; confidence interval (CI) 95% 0.98-1.06) At the same time, when analyzing only 47 studies at low risk of systematic errors, which included 180,938 participants, the intake of antioxidants was accompanied by a significant increase in patient mortality (RR 1.05; 95% CI 1.02-1.08). There was a significant association between the use of β-carotene (RR 1.07; 95% CI 1.02-1.11), vitamin A (RR 1.16; 95% CI 1.10-1 , 24) and vitamin E (RR 1.04; 95% CI 1.01-1.07) both as monotherapy and in combination with each other and increased mortality, while for vitamin C and selenium, such a relationship has not been shown. The effect of vitamin A and β-carotene on mortality was dose-dependent; there was no similar dependence on vitamin E.

According to the researchers, one of the suspected mechanisms leading to increased mortality in patients taking antioxidant vitamins is the damaging effects of reducing the number of free radicals on the body's defense systems. According to another hypothesis, the antioxidants themselves can in certain cases stimulate the formation of an increased amount of free radicals, which negatively affects the functioning of various organs and systems.

Based on the results, the authors do not recommend the use of antioxidant vitamins for prophylactic purposes, preferring a balanced diet and exercise. The effect of vitamin C and selenium intake on mortality needs to be further investigated.