Experts are hoping to find hundreds of babies with Down's syndrome to help find out if food supplements could keep them healthier.

The trial, based in London and Birmingham, will test whether vitamins and minerals can have any impact on the illnesses that often plague children with the syndrome.

There are hundreds of Down's syndrome babies born in the UK each year.

As well as the trademark physical differences that characterise the syndrome - and the developmental difficulties they face - Down's children are vulnerable to a wide variety of other problems.

These include increased risks of hearing and vision defects, heart abnormalities, leukaemia, thyroid disorders, and of developing Alzheimer-type dementia in later life.

The number and extent of these problems varies widely from child to child.

However, many people with Down's syndrome can expect to live to 60 years old.

Belief tested

It has long been believed that adding certain supplements to the diets of children with the condition might stave off some of these physical problems, but firm scientific evidence to support this has been lacking.

Three Down's syndrome charities have now joined forces to fund a properly-designed study at the Institutes of Child Health in London and Birmingham.

Dr Jill Ellis, in London, said: "We know that children with Down's syndrome are more sensitive to the effects of certain chemicals called free radicals.

"We think that free radical damage may contribute towards a variety of health problems associated with Down's syndrome.

"This may include short stature, developmental difficulties, and an increase in the number and severity of infections."

Home visits

The studies will look at vitamins A, C and E, plus zinc and selenium, and a form of folic acide called folinic acid.

Some babies will get a combination of supplements, others will get nothing.

To qualify for the study the babies have to live either in the west Midlands or within the M25 area, so that researchers can make home visits.

It is likely to be some time before the trial can report results, whether positive or negative.