The maxim “feed a cold, starve a fever” may be right after all, researchers have discovered.

Until now, most doctors and nutritionists have rejected the idea as a myth. But Dutch scientists have found that eating a meal boosts the type of immune response that destroys the viruses responsible for colds, while fasting stimulates the response that tackles the bacterial infections responsible for most fevers.

“To our knowledge, this is the first time that such a direct effect has been demonstrated,” says Gijs van den Brink of the Academic Medical Center in Amsterdam. At a Christmas dinner, he and his colleagues decided to take blood samples to see if alcohol affected the immune system.

To their surprise, later analysis suggested that alcohol had no effect but food did. So the team got six people to fast overnight and then come into the lab for tests. On one occasion they were given a liquid meal, on the other just water to distend the stomach.

The results were striking. Six hours after the liquid meal, the volunteers’ levels of gamma interferon had more than quadrupled. Gamma interferon is a hallmark of the cell-mediated immune response, in which killer T cells destroy any cells that have been invaded by pathogens. “This type of immunity is mainly directed against viral infections,” van den Brink says. “It seems to be stimulated by food.”

But when the volunteers drank only water, levels of gamma interferon fell slightly, while levels of another chemical messenger, interleukin-4, nearly quadrupled. Interleukin-4 is characteristic of the humoral immune response, in which B cells produce antibodies that attack pathogens lurking outside our cells. This response is needed to tackle most bacterial infections, van den Brink says.

Comfort food

“It fits exactly with what we recently found,” say Paul van Leeuwen of the Free University Hospital, also in Amsterdam. His team has discovered that glutamine, an amino acid common in milk, meat and some nuts, boosts the cell-mediated immune response. Van Leeuwen’s colleague Petra Boelens presented the findings at a recent conference on intensive care in Australia.

The work followed an earlier study in The Lancet that showed intensive care patients are less likely to succumb to infections if given glutamine supplements.

Van den Brink speculates that the immune response that follows eating evolved as an energy-saving ploy. Whereas most bacterial infections need an immediate response, he says, tackling a virus to which we have already been exposed can wait until we have more energy.

He cautions that people should not change their behaviour based on such a small study. But he thinks finding out exactly what stimulates the different responses will be useful: “Certain foods could be given to critically ill patients to stimulate the right immune response.”

Journal reference: Clinical and Diagnostic Laboratory Immunology (vol 9, p 182)