'Feed a cold' is good advice

Parents often do not know whether to feed ill children

Experts say that when sickly patients are told to "feed a cold, starve a fever", they may be receiving scientifically valid advice.

Dutch scientists have conducted small-scale experiments which suggest that both approaches are the best way of priming the immune system to cope with different infections.

The research, reported on the New Scientist website, found that the different approaches may activate different types of immune cell.

Six volunteers were recruited for the trial, and told to fast overnight before coming for tests.

Liquid lunch

On the first occasion they were given a meal in liquid form, and on another day were simply given water to fill their stomachs.

Six hours after each experiment, their blood was tested for signs of an immune response.

After the liquid meal, levels of a body chemical called Gamma interferon had multiplied by four.

This chemical indicates that the body is using a type of immune response designed to kill cells which have become infected, and tends to be directed at viral infections.

Bacterial attack

The water-only diet, however, produced almost a fourfold increase in levels of a different chemical, called interleukin-4.

Certain foods could be given to critically-ill patients to stimulate the right immune response

Dr Gijs van den Brink

This is a sign of an immune response which launches attacks on invaders lurking outside the cells.

Most bacterial infections require this kind of response.

Dr Gijs van den Brink of the Academic Medical Center in Amsterdam said: "To our knowledge, this is the first time that such a direct effect has been demonstrated."

Food supplement

The findings do not totally support the old wives' tale - although colds are caused by viruses, so is flu, which is likely to cause a raised temperature.

Dr Van den Brink speculated that the immune response may be an energy-saving tactic by the body, responding immediately to bacterial infections, but waiting until more energy is made available before taking on viruses.

He said: "Certain foods could be given to critically-ill patients to stimulate the right immune response."

He suggested that glutamine, found in milk, meat and some nuts, boosts the "anti-viral" immune response.