Feed a Cold, Feed a Fever is Best Advice

Nov. 25, 2008

Feed a Cold, Feed a Fever is Best Advice for Senior Citizens; Calories Needed to Fight Flu

Research shows having a body ready to fight a virus leads to a faster recovery and less-severe effects than if calories restricted,

according to research by Michigan State University nutritional immunology professor Elizabeth Gardner. Her advice applies particularly to senior citizens.

In a study published in the November issue of the Journal of Nutrition, Gardner showed that mice with a calorie-restricted diet were more likely to die during the first few days of infection than mice with a normal diet.

Caloric restriction is the practice of reducing the intake of calories to 40 percent of a normal diet, while maintaining adequate vitamins and minerals.

“If you are exposed to a new strain of influenza, to which your body has not made adequate antibodies to protect you from infection, your body must rely on cells that will kill the virus,” Gardner said.

“The natural killer cells are important in controlling the early stages of virus infection, because they act quickly once they encounter virus-infected cells. Our studies show that calorically restricted mice have increased susceptibility to influenza, and their bodies are not prepared to produce the amount of natural killer cells needed to combat the stress of fighting an infection.”

In Gardner’s research, both regularly fed mice and calorically restricted mice exposed to the virus exhibited decreased food intake as they tried to fight off the infection.

Yet the mice on calorically restricted diets took longer to recover and exhibited increased mortality, weight loss and other negative effects. Even though both sets of mice had a diet fortified with appropriate vitamins, the mice consuming normal amounts of food had their appetites back sooner and recovered faster.

“Our research shows that having a body ready to fight a virus will lead to a faster recovery and less-severe effects than if it is calorically restricted,” Gardner said.

Myth or Fact: Feed a Cold, Starve a Fever By Eric Bishop Although a few small-scale studies have suggested that “feed a cold, starve a fever” loosely represents sound medical advice, Duke medical experts caution against putting too much faith in the adage. “I think it was always pretty much dismissed as folklore,” says Denise Snyder, a nutrition scientist and clinical trials manager at the Duke University School of Nursing. “If you break it out and really think about it, there is some immune response if you eat less during a fever. But as a nutritionist, I certainly wouldn’t tell people to starve themselves.” Snyder points out that you probably won’t feel like eating anyway -- loss of appetite is your body’s natural defense mechanism for fevers, as it helps the immune system focus its energy on fighting pathogens. “You shouldn’t overconsume, but if you’re hungry you should eat,” she says, adding that fluids can only help fight the fever. As for “feed a cold,” it’s simply a matter of keeping your nutrient levels up while the virus runs its course. “Colds usually last longer than fevers,” Snyder says. “You need to be consuming food so you can fight it off -- especially fruit and vegetable juices and warm broths.” Joy doesn’t want patients to get hung up on unproven treatments. “It’s important to stress what we know makes a difference, which is getting plenty of rest,” he says. “Drinking plenty of fluids also makes a difference because it helps keep the secretions thinner and allows patients to get them out of their system lot quicker, alleviating symptoms such as a cough or nasal drainage.” Joy also emphasizes the need to practice good hygiene when you’re sick -- whether it’s a cold or a fever. “Washing your hands often, covering your mouth when you cough -- those are great ways to reduce the spread of infection that are underappreciated.” >> More at DukeHealth.org

“Adults can calorically restrict their diet eight months out for the year, but during the four months of flu season they need to bump it up to be ready. You need the reserves so your body is ready for any additional stress, including fighting a virus.”

Calorically restricted diets in general have been shown to increase lifespan in everything from yeast to primates, acknowledges Gardner. But, she says, the model used in her research can be extended to more vulnerable groups including children and the elderly, who don’t eat as much but often take vitamin supplements.

Flu shots can’t guarantee protection, in any case, since they are formulated months in advance and only can target a small handful of the many flu virus strains that might infect the population.

“If the strain of flu a person is infected with is different from the strain included in the flu vaccination, then your body sees this as a primary infection and must produce the antibodies to fight it off. A calorically restricted body is not as well prepared to do this and cannot control early infection, which impedes recovery,” Gardner added.

Gardner, an associate professor in the Department of Food Science and Human Nutrition, now is investigating the mechanisms responsible for decreased immune function during caloric restriction. Her research in nutritional immunology will lead to a better understanding of how a diet affects the immune system and the best conditions for a body to quickly and successfully fight infections.

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Research Interests: Nutritional Immunology

'Major emphasis of our lab is the response of young and aged mice to primary influenza infection'

By Elizabeth Gardner, associate professor in the Department of Food Science and Human Nutrition

Immunity decreases in aging, most well documented as an impaired cell-mediated response to antigen, i.e., reduced T cell proliferation and altered cytokine production. Aged mice also exhibit altered innate immunity, including a decrease in inducible natural killer (NK) cell activity, although such changes have not been consistent in humans. Influenza is perhaps the best characterized model for studying the immune response to virus, and influenza and its secondary pneumonias represent a major public health concern in the U.S., particularly among the elderly.

We and others have shown that the immune response to influenza vaccine is reduced in the elderly as evidenced by lower antibody titers, decreased T cell proliferative responses, reducted cytotoxic T cell activity, and altered cytokine production compared to young controls.

However, the study of immunity, particularly in the elderly, can no longer be limited to efficacy of vaccination, given the emergence of new viral strains of common viruses, such as avian influenza, and the threat of using viruses to which there are no current vaccines as agents of bioterrorism.

Therefore, a major emphasis of our lab is the response of young and aged mice to primary influenza infection at the site of infection, i.e., the lung, with a particular interest in innate (NK cell function) and cell-mediated immunity. We also study the effects of nutritional interventions, including antioxidants and nutraceuticals, on outcome to primary influenza infection or as adjuvants to vaccination.

Caloric restriction (CR) without malnutrition decreases oxidative stress and extends mean and maximal lifespan in mice. While elderly CR mice have been reported to have an increased response to influenza vaccination, the response to CR mice to primary infection is not known.

Our data suggest that a defect in NK cell function decreases survival of CR mice in response to primary influenza infection.