Even if it is a common opinion that dietetic supplements are able to protect against oxidative stresses, trials concerning this subject have never given a convincing demonstration of the real usefulness of these supplements. Now, a meta-analysis has been performed on 68 randomized trials, involving more than 230.000 subjects, of whom about 70% was in good health. Both used doses and the duration of treatments were very variable and the supplements were administered as a single dietetic supplement or as an association of various substances. Analysing the 47 trials with high methodological quality researchers saw that betacarotene, vitamin A and vitamin E, administered singularly or in association with other supplements, have significantly increased the mortality risk (RR 1,05 – 1,16 – 1,04 respectively), while vitamin C and selenium had no effects on the overall mortality.
Even if the increase in the overall mortality risk seen through betacarotene, vitamin A and vitamin E supplements is little, however the use of these substances should be not advised in primary or secondary prevention. Obviously, the results of these trials refer to chemical supplements of single substances, and they cannot be adapted to food (fruit and vegetables) consumption, rich in the same substances.
