ByBrian Handwerk
Published December 5, 2023
• 8 min read
Chicken soup. Half a grapefruit. Steaming hot tea. When you’re sick everyone from grandma to the next-door neighbor has a helpful suggestion for food that will put you on the road to recovery. What should we make of this wisdom—do some foods really help us feel better, or even actually get better?
And if so, why does illness often stifle our appetite when we might think nutrition is needed most?
“When someone who is feeling ill loses their appetite, or their thirst, it’s typically a sign that their immune system is working in overdrive,” explains Colleen Tewksbury, a dietician and professor of nutrition science at the University of Pennsylvania. That’s a challenge, she adds, because our bodies need fluids, as well as proteins, carbohydrates, vitamins, and minerals. “If you don’t feel hungry or thirsty, you just feel awful and you’re trying to rest, it’s really difficult to meet those needs.”
(Got a cold? Here’s how your immune system is fighting it.)
But it can be important to try. “Balanced nutrition can speed up your recovery, increase energy levels, and help to build up your immune system,” says Shea Mills, a registered dietitian nutritionist at the Mayo Clinic in Phoenix. “Overall, it is important to consume a healthy, balanced diet when sick.”
Read on for expert guidance on the reasons why you might not feel like eating when you’re ill, and tips about what to eat and drink until you’re back on your feet.
Starve a fever?
The reasons why we often can’t stomach eating while we’re sick are complex and not entirely understood.
The immune system requires a lot of energy to fight infection, which is why it’s good to consume healthy food during illness. But Yale University immunobiologist Ruslan Medzhitov says our bodies are ultimately optimized not for making us feel better, but for survival—and they might not always perceive an infection as their greatest threat. “That’s what’s counterintuitive,” Medzhitov says.
Our bodies unconsciously calculate trade-offs that may include some evolutionary mismatches with modern life, like the costs and risks once associated with sourcing food. Before pizza delivery was an option, getting food while sick meant exposing a weakened body to encounters with predators. And finding food also meant exerting more energy. Though life has changed, some theorize that these evolutionary holdovers may still play a role in curbing our appetite during illness.
(7 herbs that may help fight cold and flu.)
The body also makes physiological tradeoffs to get energy during an illness, Medzhitov notes, and scientists are still exploring how they work. Normally, the body is fueled primarily by glucose from food. When fasting, including during illness, it taps into fatty acids as a stored source of high energy. This switch of energy sources may provide protection for bodily tissues and organs against inflammation caused by some pathogens—but for others the opposite may be true.
For example, Medzhitov and colleagues found in a 2016 study that mice infected with the influenza virus benefitted greatly from feedings, while those infected with a bacterium, Listeria. This doesn’t mean you should starve a bacterium and feed a virus—studies in mice can only tell us so much about humans. But the research reveals the complex relationship between eating and illness.
Further, Tewksbury adds that different people may also respond differently to the same illnesses. “From a physiological standpoint it’s basically a stress response, and everyone responds to stress differently,” she explains.
What should you eat and drink when you’re sick?
Your body craves a specific range and combination of nutrients, levels of protein, carbohydrates, vitamins, and more—although Medzhitov says those preferences are a moving target, changing with health statuses from pregnancy to growth spurts or illness.
“The way it shifts during illness depends on the type of illness, and that’s the part that we don’t know well,” he says. “It becomes a very interesting and complex question: What’s the right range and combination of nutrients?”
(Here’s the truth about immune-boosting supplements.)
Mills suggests that eating more frequent, snack-sized portions may be more palatable than the bigger-sized meals we’re used to when healthy. By aiming to add protein, carbs, and a fruit or vegetable, you can maintain a good balance of vitamins, minerals, and macronutrients.
That formula is where the legend of chicken soup originated.
“Broth-based soups have all those components, along with vitamins and minerals and electrolytes,” Tewksbury says. Hot and steamy soups can also help break down mucus in upper respiratory tract infections. “It checks a lot of boxes.”
Mills says some vitamins and minerals might also be targeted as part of a healthy diet for the sick. Vitamin C, sourced from fruits and vegetables, is a powerful antioxidant that supports immune cells as they prevent and fight off infections, she says, while vitamin D may also improve immune response and decrease the duration of sickness. Oily fish, mushrooms, and red meat are among the few foods naturally full of vitamin D, but some dairy products and cereals are fortified with extra amounts.
Mills also notes that it’s important to focus on drinking. Hydration is a key part of battling almost any illness, and it can be especially challenging when the body is losing fluid from vomiting, diarrhea, or sweating out a fever.
“Sip on decaffeinated beverages like herbal tea, water, 100 percent fruit juices, and low-sugar electrolyte-containing drinks like coconut or cactus water to promote hydration,” she says. Drinking a protein shake or smoothie can also add essential nutrients when your appetite isn’t up for solid foods.
(Salted? Alkaline? Here’s what you actually need to hydrate.)
Supplements may also play a role—when used properly. “Zinc supplementation at the beginning of certain types of upper respiratory tract infections has been shown to reduce the intensity and duration of certain viruses,” Tewksbury says. But it must be done early—within 24 hours of symptoms emerging—and isn’t intended to be a long-term supplement because it can cause damage at high doses.
In fact, the use of any supplements to counteract colds or other sickness is best vetted by the experts. “If you want to try a nutritional or medicinal supplement to help recover from an illness, speak with your doctor, dietitian, or healthcare professional first to ensure they will not interact with any of your current medications along with learning the correct dosage for you,” Mills cautions.
Listen to your body
While foods don’t cure illness, some can bring relief: Hot tea or a cold popsicle may be soothing, for example, depending on your ailments.
But other foods can both help and harm, depending on the person. Capsaicin, found in chili peppers, can help break up mucus and open the airways—but it can also cause nausea, or even drive the production of more mucus. Ice cold drinks, too, might help with a sore throat, Tewksbury explains, but “if you’re having a lot of mucus production, it might actually make it worse.”
Ultimately, she says, “Seeing what brings you comfort is trial and error, there’s not one straightforward answer.”
Medzhitov believes that just listening to your body and its preferences during sickness is likely the best strategy. What you crave, presumably, is more often than not what your body wants.
“I think that, as a general rule of thumb all these factors that we are trying to understand are already factored in,” Medzhitov explains. When sick, your desire for one type of food and distaste for another aren’t random preferences. They’re signals that millions of years of evolutionary selection have taught your body to recognize. “If your body needs vitamin C, you will have craving for something that contains it, even though sometimes we don’t know what that craving is for.”
So rest when tired and eat what seems appealing in the portions that are satisfying? Yes, says Medzhitov. “I think that’s probably the best wisdom that we can use.”
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