Keeping your immune system healthy is very important, no matter the season.
Naturally, what you eat can majorly influence your immune health.
Certain foods may actually decrease your chances of getting sick, while others can help you recover more quickly if you do get ill.
This article lists 10 foods you should eat if you want to boost your immune system.
Iron is a mineral that plays an important role in immune function. A diet containing too little iron can contribute to anemia and weaken the immune system (, , , ).
That's why it's important to optimize your intake of iron-rich foods, such as meat, poultry, fish, shellfish, legumes, nuts, seeds, cruciferous vegetables and dried fruit.
You can also improve your absorption of iron from foods by using cast-iron pots and pans to cook, and avoiding tea or coffee with meals.
Combining iron-rich foods with a source of vitamin C can help boost your absorption even further.
That said, it's important to remember that overly high blood iron levels can be harmful and may actually suppress the immune system (, , ) Therefore, it's best to use iron supplements only if you have an iron deficiency, or on the advice of a doctor.
Bottom Line: Optimal blood iron levels help improve your immune function. Therefore, it's advantageous to include iron-rich foods in your diet.
Foods that are rich in probiotics are thought to help enhance your immune function.
Probiotics are beneficial bacteria that live in your gut and help stimulate your immune system.
Recent reviews show that probiotics may reduce the risk of developing upper respiratory tract infections by up to 42% (, , , ).
They also help maintain the health of your gut's lining, which may help prevent unwanted substances from "leaking" into the body and provoking an immune response (, , , ).
Studies also show that when people do get sick, those who regularly consume probiotics are up to 33% less likely to need antibiotics. In certain cases, regularly consuming probiotics may also lead to a faster recovery from illness (, , ).
Most studies on the topic provided participants with probiotic supplements. However, it's also possible to increase your intake by making probiotic foods a regular part of your diet ().
Great sources of probiotics include sauerkraut, naturally fermented pickles, yogurt, kefir, buttermilk, kimchi, tempeh, miso, natto and kombucha.
Bottom Line: Probiotics can help strengthen your immune system. This may reduce the likelihood and severity of your symptoms and help you recover faster when you do fall ill.
Fruits like oranges, grapefruits and tangerines are high in vitamin C, a well-known immunity booster.
Vitamin C is recognized for its antibacterial and anti-inflammatory properties. It also helps maintain the integrity of your skin, which acts as a protective barrier against infection ().
In addition, vitamin C acts as an antioxidant, helping protect your immune cells against harmful compounds formed in response to viral or bacterial infections ().
Therefore, getting enough vitamin C is a great way to strengthen your immune system and may reduce your likelihood of infection (, , , , ).
Some studies also report that upping your vitamin C intake during the common cold may help you get better more quickly (, , , , ).
That said, it might be more advantageous to increase your intake from plant foods rather than supplements, since plants contain other beneficial compounds that supplements may not.
Other foods high in vitamin C include bell peppers, guavas, dark leafy greens, broccoli, berries, tomatoes, papaya and snap peas.
Bottom Line: Citrus fruit and other vitamin-C-rich foods can help boost your immune system. This likely lowers your risk of infection and may even speed up your recovery.
Ginger is rich in gingerol, a bioactive substance thought to help lower the risk of infections ().
In fact, ginger has antimicrobial properties that may inhibit the growth of several types of bacteria, including E. coli, Candida and Salmonella (, , , ).
Studies on human cells show that fresh ginger may also help fight the human respiratory syncytial virus (HRSV), a virus responsible for many respiratory infections. However, more studies in humans are needed to support this protective effect ().
Ginger's effects may be especially potent if the ginger compounds are already present in your body before the infection occurs ().
Finally, ginger also has anti-nausea effects, which may help decrease your nausea symptoms when you have the flu ().
More research is needed to determine effective dosage guidelines.
In the meantime, simply add a sprinkle of fresh or dried ginger to your dishes or smoothies. You can also sip on a fresh ginger infusion or use pickled ginger as a probiotic-rich palate cleanser between dishes.
Bottom Line: Making ginger a regular part of your diet may help decrease your risk of infection and reduce nausea symptoms when you're sick.
Garlic also contains active compounds that may help reduce your risk of infection (, ).
For instance, allicin, the main active compound in garlic, is thought to improve your immune cells' ability to fight off colds and the flu (, ).
Garlic also seems to have antimicrobial and antiviral properties that may help it fight bacterial and viral infections (, , ).
In one study, participants given a daily allicin supplement experienced colds 63% less often than the placebo group. In addition, when they did get sick, participants in the allicin group recovered 3.5 days earlier, on average ().
In another study, participants given a daily aged garlic extract supplement became sick just as frequently as the placebo group. However, they reported 21% fewer symptoms and recovered 58% more quickly than the placebo group ().
To maximize garlic's immune-boosting effects, aim to eat one clove two to three times per day.
Crushing the garlic and allowing it to stand for 10 minutes prior to cooking can also help increase its effects (, ).
Bottom Line: Consuming two to three cloves of fresh garlic per day may help boost your immune system. Garlic seems particularly effective at reducing the symptoms and duration of the common cold and flu.
For many years, Native Americans have used berries to treat infections like the common cold ().
This could be because berries are a rich source of polyphenols, a group of beneficial plant compounds with antimicrobial properties.
For instance, quercetin, one berry polyphenol, is thought to be particularly effective at reducing your risk of getting ill after a bout of intensive exercise ().
Studies also show that berries and their polyphenols have the ability to protect against the influenza virus responsible for the flu (). They may even offer a defense against Staphylococcus, E. coli and Salmonella infections (, ).
Berries also contain good amounts of vitamin C, which adds to their immune-boosting properties.
Bottom Line: Berries contain beneficial plant compounds that may help reduce your risk of viral or bacterial infections.
Coconut oil contains medium-chain triglycerides (MCTs), a category of fats with antimicrobial properties.
The most common type of MCT found in coconut oil is lauric acid, which is converted into a substance known as monolaurin during digestion.
Both lauric acid and monolaurin have the ability to kill harmful viruses, bacteria and fungi ().
For instance, researchers report that coconut fats may help fight off the types of bacteria that cause stomach ulcers, sinusitis, dental cavities, food poisoning and urinary tract infections ().
Researchers also believe that coconut oil may be effective against the viruses responsible for influenza and hepatitis C. It may also help fight Candida albicans, a common cause of yeast infections in humans (, , ).
You can easily add coconut oil to your diet by using it instead of butter or vegetable oils in cooking or baking.
Consuming up to two tablespoons (30 ml) per day should leave enough room to continue including other healthy fats in your diet, such as avocados, nuts, olives and linseed oil.
However, you might want to increase your intake gradually to avoid the nausea or loose stools that can occur with high intakes.
Bottom Line: The type of fat found in coconuts may help protect you against various viral, bacterial and fungal infections.
Licorice is a spice made from the dried root of the Glycyrrhiza glabra plant.
It has been used in traditional herbal medicine in Asia and Europe for thousands of years.
Studies show that licorice has the ability to fight some fungi and bacteria, including E. coli, Candida albicans and Staphylococcus aureus ().
Licorice may also be able to fight the viruses responsible for the flu, gastroenteritis and polio (, ).
That said, many products containing licorice are also very high in sugar. Those trying to reduce their sugar intake should look for lower-sugar options, such as licorice tea.
In addition, consuming too much licorice may have a number of adverse effects, including high blood pressure, abnormal heart rhythm and an increased risk of premature birth (, , ).
Individuals at risk of these should limit their consumption.
Bottom Line: Licorice may help your body fight various viruses, bacteria and fungi. However, excessive intake may increase the risk of certain adverse effects, including high blood pressure.
Nuts and seeds are incredibly nutrient-rich.
They're rich in selenium, copper, vitamin E and zinc, among other nutrients. All of these play a role in maintaining a healthy immune system (, , , , ).
Sesame seeds and almonds are particularly good sources of copper and vitamin E, while pumpkin seeds and cashews are rich in zinc.
As for selenium, you can meet your daily requirement by eating just a single Brazil nut per day.
Nuts and seeds are also great sources of fiber, antioxidants and healthy fats, all of which are beneficial for health (, , ).
Bottom Line: Nuts and seeds are good sources of selenium, copper, vitamin E and zinc, all of which play an important role in immune health.
Sweet potatoes are not only delicious — they're also rich in vitamin A.
Not consuming enough foods rich in vitamin A can lead to a deficiency, which studies link to a weaker immune system and a higher sensitivity to infections ().
For instance, one study reports that vitamin-A-deficient children were 35% more likely to suffer from respiratory symptoms, compared to those with normal vitamin A levels ().
Another study reports that giving infants vitamin A supplements may help improve their response to certain vaccines ().
However, excessive vitamin A intake can lead to adverse effects such as nausea, headaches, weaker bones, coma and even premature death — especially if you take the vitamin A in supplement form ().
High intakes of vitamin A supplements during pregnancy may also increase the risk of birth defects. Therefore, it might be safest to meet your vitamin A requirements through diet instead of supplements ().
Besides sweet potatoes, other foods that are high in vitamin A include carrots, dark-green leafy vegetables, squash, romaine lettuce, dried apricots, red peppers, fish and organ meats.
Bottom Line: Sweet potatoes and other vitamin-A-rich foods may help boost the immune system and lower the likelihood of infection.
A well-functioning immune system requires a good intake of various nutrients.
People consuming a well-balanced diet rich in the foods described above should have no difficulty reaching their daily requirements.
However, some may be unable to meet their recommended daily nutrient intakes through diet alone.
If this is the case for you, consider adding the following supplements to your diet:
- Probiotics: Ideally Lactobacillus or Bifidobacterium strains in amounts between 2–3 billion colony-forming units (CFUs) per day ().
- Vitamin C: Consider taking about 75–90 mg per day. Increasing your daily dose to up to 1 gram per day may provide extra benefits during illness (, ).
- A multivitamin: Look for one containing iron, zinc, copper, vitamin E and selenium in amounts sufficient to help you meet 100% of the RDIs.
- Zinc lozenges: Doses of at least 75 mg per day at the first onset of cold symptoms may help reduce the duration of the infection ().
In addition, low blood levels of vitamin D may increase the risk of respiratory infections, including the flu, sinus infections and bronchitis ().
Therefore, those living in northern climates, where sunlight is limited, might also want to consume at least 600 IU (15 mcg) from vitamin D supplements per day ().
Bottom Line: The supplements above may help boost immune function in individuals who are unable to meet their daily nutrient requirements through diet alone.
Your diet plays an important role in the strength of your immune system.
Regularly consuming the foods listed above may help reduce how frequently you get sick and may help you recover from illness more quickly.
Those unable to add these foods to their diets might want to consider taking supplements thought to have immunity-boosting properties.