Antioxidants are the hope of the healthy. Millions of people take supplements, usually vitamins or antioxidants, in the hope that these extras will prevent chronic conditions. The supplement industry is vast but many of the popular products so eagerly ingested lack scientific evidence of benefit.
The latest casualties are selenium and vitamin E for the prevention of cancer in men. In the largest randomised controlled trial ever undertaken, comprising over 35 000 people, these substances were no more effective than placebo in reducing the rates of prostate or any other cancers in middle-aged and elderly men. The trial was supposed to last 12 years but was stopped half-way when an interim audit shown no effect of each agent or a combination (Lippman et al JAMA 2009;301:39-51).
In a second smaller trial of 15 000 male doctors - also middle-aged - vitamins E and C were pitted against placebo and, again, after 8 years there was no decreased risk of any cancer found (Gazanio et al pp 52-62).
It seems clear that healthy men and women do not lower their chances of developing cancer by taking vitamins C, E or selenium. Half of all American adults take supplements. Will these definitive studies change their habits?
At the other end of the age spectrum, other additives have also not been faring very well. Theoretically, giving preterm infants high doses of polyunsaturated fatty acids in their diets could assist brain structure and function. Babies born before 33 completed weeks of gestation are at risk of developmental and behavioural problems, but it is unclear whether standard or high dose fatty acids in their early feeds will make any difference to long-term outcomes.
Makrides et al (JAMA 2009;301:175-82) supplemented the diet of the mothers whose expressed breast milk formed the bulk of the infant's nutrition. The intervention group took capsules containing tuna oil while the controls had a standard diet, resulting in the babies receiving either high or low doses of docosahexanoic acid (DHA) from birth to the date when they would have reached term in utero. Examining both groups at 18 months there was no difference in the neuro-developmental outcome between those receiving the DHA supplementation or not. However, the girls did better than the boys which may lead to even higher dose trials.
