Over 150 babies with Down's syndrome received daily supplements of selenium, zinc, vitamins A, C and E, and folinic acid for 18 months, with no benefits observed, according to results published in the British Medical Journal .
"As Down's syndrome has a profound effect on the lives of children and their families, parents will probably have a low threshold for trying interventions," wrote lead author Jill Ellis from University College London's Institute of Child Health.
"Parents who choose to give supplements to their children need to weigh their hope of unproved benefits against potential adverse effects from high dose, prolonged supplementation," she added.
Down's syndrome (trisomy 21) is the most common genetic cause of learning disability in the UK affecting around one in 1,000 new born babies.
According to background information in the article, children with Down's syndrome are reported to have increased activity of the antioxidant enzyme superoxide dismutase (SOD) that can cause oxidative damage to neuronal cells by increasing concentrations of hydrogen peroxide.
Antioxidants therefore may protect against this oxidative damage.
"There have been many claims over the years that nutritional supplements can make a difference to the development of children with Down's syndrome," explained Carol Boys, chief executive of British charity the Down's Syndrome Association, who funded the study.
"In an attempt to find out whether or not there was any benefit to be gained from giving vitamin and mineral supplements to children with Down's syndrome, we commissioned this, the largest study to be done anywhere in the world."
Ellis and co-workers assigned the babies to one of four groups, and supplemented them with a daily dose of antioxidants (selenium 10 micrograms, zinc 5 milligrams, vitamin A 0.9 mg, vitamin E 100 mg, and vitamin C 50 mg), folinic acid (0.1 milligrams), a combination of antioxidants and folinic acid, or placebo.
All the supplements were given in a powder that could be mixed with food or drink.
After 18 months, the researchers found no difference to the biochemical outcomes between the groups, with no significant improvements in language or psychomotor development.
Independent comment In an accompanying editorial, Tim Reynolds, a consultant chemical pathologist at Queen's Hospital in Burton on Trent (Enlgand) said that it was logical to test whether antioxidants could offer benefits for children with Down's Syndrome since "in theory, the genetic defects in Down's syndrome could act through excess oxidant stress that causes neurodevelopmental damage."
However, "antioxidants, vitamins, and miscellaneous food supplements are often believed to cure all manner of ills.
In many cases, however, belief in food supplements flies in the face of the evidence," he said.
"The food supplement industry can use beliefs in the benefits of their products to support a profitable business.
Understandably, parents will try any potentially effective treatment in an attempt to improve the health of their child with Down's syndrome.
"Giving vitamins to 6 month old babies with trisomy 21 does not improve their educational achievement, and until evidence of any benefit of expensive vitamin supplements is available, they cannot be recommended," concluded Reynolds.
Down's Syndrome Association' Carol Boys added: "The findings of this study provide no evidence to support the use of Vitamin and Mineral supplements in children with Down's syndrome and we would hope that parents will think very carefully before giving these sometimes very dangerous 'therapies' to their children."
Source: British Medical Journal Published online ahead of print, Online First , doi:10.1136/bmj.39465.544028.AE
"Supplementation with antioxidants and folinic acid for children with Down's syndrome: randomised controlled trial" Authors: J.M. Ellis, H.K. Tan, R.E. Gilbert, D.P.R. Muller, W. Henley, R. Moy, R. Pumphrey, C. Ani, S. Davies, V. Edwards, H. Green, A. Salt, S. Logan Editorial: British Medical Journal Published online ahead of print, Online First , doi: 10.1136/bmj.39475.655058.80 "Giving antioxidants to infants with Down's syndrome" Author: T. Reynolds