Expert Q&A: Can Your Diet Help You Avoid Flu?

An interview with Christine Gerbstadt, MD, RD.

Reviewed by Louise Chang, MD on December 01, 2009

During the cooler months when we spend more time indoors, the odds of getting the flu increase. The CDC estimates that up to 20% of Americans get the flu each year. And now, the H1N1 flu pandemic has pushed those odds even higher.

Health experts recommend an annual flu shot, but Americans want to know what else they can do to prevent flu. WebMD turned to Christine Gerbstadt, MD, RD, a spokeswoman for the American Dietetic Association, to learn more about what diet and lifestyle steps we can take to bolster our immunity.

Why is it important to get a flu vaccine?

Your best defense against the flu is getting vaccinated, but that alone is not a 100% guarantee. It is also important to wash hands, take good care of yourself, and eat a nutritious diet. When you get a flu vaccine, your body makes antibodies that will fight the specific illness, but it takes up to 10 days for the vaccines to take effect. Each year, approximately 200,000 people are hospitalized because of complications from flu and as many as 36,000 die from flu-related causes.

Who is at greatest risk for serious flu complications?

Population groups most at risk for the flu include people who have a chronic disease or are immune-compromised, young children, the elderly, and pregnant women. All of these people, along with caregivers, should be the first to get the flu shot to minimize the risk.

Half of the people currently hospitalized for the flu are under age 25, which is reflective of the increased incidence of H1N1 flu that is more serious for younger people.

Are some people at greater risk for flu because of diet or other lifestyle habits?

Inadequate diets that are low in protein, too low in calories (less than 1,200), or contain too many processed or fast foods will lack all the nutrients necessary to maintain a healthy immune system. Sleep deprivation and stress are other conditions that can make you more vulnerable to getting the flu.

How can a nutritious diet bolster immunity and help you avoid the flu?

The healthier you are, the healthier your immune system -- your body’s "coat of armor" to protect you from all kinds of diseases. In order to prevent seasonal influenza and other germs that can make you sick, you need to make sure your immune system is healthy. The American Dietetic Association says eating healthfully is a great way to boost immunity and prevent flu. Diets that are plentiful in fruits, vegetables, whole grains, lean protein, low-fat dairy, healthy fats, and more can provide a wide array of nutrients and antioxidants that can help boost the immune system.

Are there certain foods that fight flu?

Some experts tout specific immune-boosting foods and beverages like broccoli, red peppers, tea, sweet potatoes, and garlic. But it is more important to eat a wide variety of healthy foods from all food groups to boost your body’s immune system. There is no guarantee that eating certain foods will fend off infection, but we do know that your immune response or susceptibility to infection can be enhanced with overall good nutrition. Almost any fruit or vegetable is a good choice, especially ones rich in antioxidants --vitamins A, C, E and selenium, zinc, and beta carotene -- that help immune cells work optimally.

Lean protein is also important, because the immune molecules are made of protein.

Are there specific nutrients that play a role in bolstering immunity?

Preliminary research suggests low levels of vitamin D may be linked to an increase in seasonal colds and flu and an increased incidence of respiratory infections. Omega-3 fatty acids from foods like salmon may also play a role in promoting immunity. Most Americans fall short when it comes to getting enough of these nutrients, and would benefit from eating fatty fish twice a week and taking a supplement of vitamin D to boost immunity.

Can foods that contain healthy bacteria help prevent the flu?

Foods like yogurt contain probiotics, which add healthy bacteria to the intestinal track. A healthy gastrointestinal track can bolster your defense and help resist flu viruses. Choose yogurts with active cultures that are also fortified with vitamin D to promote a healthy gastrointestinal track and help meet your requirement for three servings a day of low-fat dairy.

Besides eating a healthy diet, what else can people do to prevent the flu?

Get adequate sleep, regular exercise, reduce your stress level, drink plenty of liquids, and eat a nutritious diet on a fairly regular schedule. Your immune system stays active, promoting a steady supply of immune cells, when you eat regularly and choose nutrient-rich foods. Studies have shown that moderate, regular exercise can boost the immune system, so finding at least 30 minutes a day to be active will help.

Good personal hygiene, including frequent and thorough hand-washing, covering your nose and mouth with a disposable tissue (not a reusable handkerchief), and minimal touching of your eyes, nose, and mouth will reduce the spread of germs. In fact, good hygiene may be the most important defense in fending off a virus.

How do you know if you have the flu?

Flu is a respiratory illness that can cause mild to severe symptoms. If your symptoms are severe, see your doctor. Symptoms include:

Stay home when you are contagious, getting plenty of rest. Most people are out 3-5 days, and should not return to work or school until they are fever-free for 24 hours.

What kind of diet should you follow when you have the flu?

Depending on the severity of the symptoms, eat what you can tolerate. Chicken soup and salty liquids are recommended because they encourage drinking and are very soothing. When your appetite improves, advance to soft solid foods like bananas, toast, and turkey. Fruit smoothies or protein shakes are sometimes well-tolerated when you don’t feel hungry. When you are feeling better, eat nutritious meals to promote wellness.