When flu season is on the horizon, almost everyone should get an annual flu vaccination. But according to the Centers for Disease Control and Prevention (CDC), not everyone should get a flu shot without first consulting a physician. Here's who is on that list:

  • People who have a severe allergy to chicken eggs
  • People who have had a severe reaction to an influenza vaccination
  • People who developed Guillain-Barre syndrome (GBS) within six weeks of getting an influenza vaccine
  • Children less than 6 months of age
  • People who have a moderate to severe illness with a fever

Not on that list? Good for you—get a flu shot! Once you've done that, you can also boost your immune system with these easy tips.

How it all works

The immune system helps protect the body from unwanted foreign invaders year-round. Its role is very important during cold and flu season. While we can't completely avoid germs, eating a healthy diet to boost your immunity can keep the body's defenses up so that it can battle pesky viruses and bacteria. Increase your intake of the following foods and you might just avoid the sniffles or feverish flu altogether.

Fruits and vegetables

Vitamins A and C help your immune system work well. Fruits and vegetables are excellent sources of both vitamins. Fruits and vegetables also provide additional vitamins, minerals, fiber and naturally occurring plant chemicals that help keep you healthy and prevent disease.

"Oranges are very high in vitamin C, and so are red peppers," says Kerry Neville, registered dietician, a spokesperson for the American Dietetic Association. "And carrots are a great source of beta-carotene, which the body converts to vitamin A."

Add colorful fruits and vegetables, such as berries and leafy greens, to your plate to strengthen the body's defenses. Frozen fruits and vegetables work fine when fresh ones aren't available. Lightly steam or sauté vegetables or add them to soups to reap the benefits. Eat fruits whole, make them into smoothies or put them in hot cereal.

Nuts and vegetable oils

Neville recommends nuts and healthy oils, such as canola and olive oils, as good sources of fat-soluble vitamin E, another nutrient vital to your immune system. Research has shown that even a small shortage of vitamin E can make it harder for your immune system to work.

Nuts and healthy (nonhydrogenated) vegetable oils are also rich sources of unsaturated fats. That makes them good substitutes for saturated and trans fats (such as hydrogenated oils) that may hurt your immune system or cause heart disease.

Reach for a small handful of almonds or other raw nuts as a snack, and trickle canola or olive oil in salads, soups and sauces.


This flavorful food is known for its immune-boosting and antimicrobial action, making it a favorite of Dr. Glen Nagel, a naturopath in Portland, Oregon. "A constituent called alliin is converted, when crushed, to allicin, which is probably responsible for some of garlic's antimicrobial action," Dr. Nagel explains. Allicin may also increase immune-system activity.

"The best way to prepare it is to peel and crush the fresh clove of garlic, then wait five to 10 minutes and spread it on bread with olive oil," Dr. Nagel recommends. "If you cook the garlic, the healthful properties are reduced." If you do cook garlic, Dr. Nagel recommends at least adding it to the dish at the end.


Not all bacteria are bad for you. Live, active bacteria cultures found in yogurt benefit the body, strengthening your digestive system and boosting your defense from illness-promoting bacteria.

Beneficial bacteria in the gut can dwindle because of changes in your lifestyle or diet, viral or bacterial infections, or use of antibiotics that wipe out the good with the bad bacteria. This throws off your digestive system, allowing more harmful bacteria to grow. This imbalance can cause constipation, diarrhea and other problems. Eating yogurt containing live active cultures can help replace the healthy bacteria. Look for products that contain Lactobacillus or Bifidobacterium strains.

Zinc-rich foods

You need zinc so that your immune cells can grow and function. Research has shown that eating too little zinc can decrease your resistance to infection. Lean meats and seafood are especially rich sources of zinc. Eggs, milk and Brazil nuts are other foods that contain significant amounts of zinc.

In addition to these immunity-boosting foods, consider taking a daily multivitamin and mineral supplement, especially during cold and flu season. It's yet another way to up your intake of immune-supporting nutrients—an ounce of prevention, as they say.

Published on Jan. 15, 2009; updated on May 23, 2014.