It's that time of year again, when getting sick can keep you down. This isn't just folklore. Research shows that flu outbreaks peak from December through March, with February having the highest number of occurrences. So with this in mind, here are 10 foods that can help bolster your immune system — along with explanations of why they do it.
Half a cup of broccoli contains 85 percent of your Daily Value (DV) of vitamin C, which helps the immune system stay in top working order due its involvement with white blood cells.
A good rule of thumb is to include at least one source of vitamin C–rich food in your daily diet. Other sources include red and green peppers, oranges, tomatoes and potatoes. See the full list.
Don't miss our tasty broccoli recipes >>
This orange favorite is an excellent source of vitamin A, containing 184 percent of your DV per 1/2 cup. When the body doesn't get enough vitamin A, immunity suffers and the risk of infection increases.
Just like with vitamin C, make sure foods with vitamin A make a daily showing. Other good sources include butternut squash, sweet potatoes, peppers and pumpkin. See the full list.
Fermented dairy products like yogurt contain live and active cultures of healthy bacteria called probiotics, which help maintain a healthy gastrointestinal (GI) tract. Because the GI tract is the biggest organ involved in the immune system, it plays defense against harmful bacteria and toxins.
The goal is to fill the GI tract with healthy bacteria to inch out the unhealthy bacteria. So include yogurt for breakfast or a snack, add kefir to smoothies, eat sauerkraut at dinner and try some miso soup (which contains fermented soybean).
Another way to increase the good bacteria in your GI tract is to give them food. Bananas are a source of prebiotics, a nondigestable food that increases the growth of beneficial bacteria because it is a source of fuel for them.
So look for ways to eat bananas and other sources of prebiotics like onions, garlic, asparagus, whole wheat, oatmeal, legumes, barley and rye.
5. Nuts and seeds
Vitamin E is found in nuts and seeds, with the best sources including sunflower seeds, almonds and hazelnuts. Vitamin E is an antioxidant that helps to protect cells from free-radical damage.
If you can't eat (or don't like) nuts, try avocado, wheat germ and vegetable oils. See the full list.
Salmon is one of the few foods that is a good source of vitamin D, with 112 percent of your DV per 3-ounce serving. Cells in your immune system contain vitamin D receptors, and when levels drop too low, your defenses can suffer.
While vitamin D sources like salmon, milk and eggs are helpful, the sun remains the best source. Most people need to take additional vitamin D during winter months to meet the 600IU recommended daily allowance.
Check out some creative ways to make salmon >>
A 3-ounce serving of beef contains 47 percent of your DV for zinc, a trace mineral that keeps immune cells functioning at full capacity. When the body is low in zinc, the body's ability to fight infections deteriorates. (But too much zinc isn't good, either!) And because it can't be stored by the body, daily sources of zinc are necessary.
Other good sources include poultry, beans, dairy products and certain types of seafood and nuts. See the full list.
Not only are grapes delicious, but they contain polyphenols, which are phytonutrients found in the grapes' skin that protect the grapes from harm. While more research is needed, emerging evidence suggests that grapes and grape juice may help bolster the immune system.
Other sources of polyphenols include wine, onions, blueberries and certain nuts.
For centuries, garlic has been praised for its healing power. Today, we know garlic has many benefits, including its antimicrobial properties. One study showed that people who took garlic supplements for 12 weeks had far fewer colds than those who took a placebo pill.
See this video on how to prepare and use garlic >>
10. Chicken soup
Since the 12th century, chicken soup has been used to ease symptoms of the flu. A 2000 study published in Chest Journal showed that chicken soup does have an anti-inflammatory effect: It keeps neutrophils in white blood cells from migrating.