You probably aren't thinking about colds and flu when you're packing your lunch, cooking dinner, or gulping a quick smoothie before yoga class. But the foods you eat can have a powerful effect on your body's ability to ward off everyday bugs, whether it's the office cold everyone's passing around, or germs from the person coughing on the mat next to you in class. "The right foods have the ability to support our immune system by providing the nutrients it needs to thrive," says registered dietitian Beth Reardon, director of integrative nutrition at Duke Integrative Medicine in North Carolina. What's more, a healthy immune system isn't important just in cold season; evidence suggests that it can help protect you from a host of chronic diseases as well.
The following 10 foods are must-haves in an immunity-boosting diet. They all contain key nutrients that have a demonstrable effect on the body's ability to stay healthy, and they're delicious and convenient besides. In fact, you probably have some of them in your kitchen already. Add them to your weekly menu and be well.
Why: Among commonly consumed berries, strawberries have the most vitamin C: A one-cup serving provides 50 percent more than the U.S. recommended daily quota, which can help you ward off illness. "The immune system relies on a number of mechanisms to help protect the body from infection, including the production of white blood cells," Reardon says. "And vitamin C is especially important for the proper functioning of these immune components."
Reardon adds that vitamin C has been shown to reduce the severity and duration of symptoms associated with colds and flu. Vitamin C is also involved in making the collagen necessary for maintaining healthy skin, which is a frontline defender against viruses.
Good to Know: When frozen, strawberries retain most of their vitamin C, so you can enjoy them all year.
Use: Strawberries are equally at home in your favorite breakfast bowl, in a spinach salad with sliced almonds, in fruit salsas, or in fresh fruit smoothies.
Why: Full of live probiotic bacteria, this tangy dairy product is made by inoculating milk with a mixture of yeasts and bacteria. These beneficial critters take up residence in the intestines, where they alter the pH of the intestinal environment to a level that is unfavorable to harmful microbes. Probiotics are also thought to play a direct role in immune cell function and may even reduce the incidence, severity, and duration of symptoms associated with the common cold.
Good to Know: Kefir and yogurt are both cultured dairy products; the difference is that yogurt is made by inoculating milk with bacteria, while kefir is inoculated with a blend of yeasts and bacteria and has more beneficial probiotics that can colonize the intestinal tract.
Use: Buy plain kefir and layer it with strawberries and nuts; blend it into smoothies; or whisk it with olive oil, lemon juice, and minced garlic to make
a creamy salad dressing.
Why: You might be surprised to know that, ounce for ounce, kale is a richer source of beta carotene than carrots or sweet potatoes, which makes it a top choice for fighting off colds and the flu. "In the body, the liver converts beta carotene into vitamin A, which amps up the immune system by increasing the production of white blood cells, including ones that seek out and destroy foreign bacteria and viruses," says Reardon. She adds that vitamin A also helps maintain the lining of your respiratory and digestive tracts, which are your first lines of defense against pathogens. This robust leafy green also has high levels of vitamin C, an antioxidant that's important for immune function.
Good to Know: Conventionally grown kale can contain high levels of pesticide residues, so choose organic kale whenever possible.
Use: Fat-soluble beta carotene is better absorbed when it's in the presence of dietary fat, so try gently sauteing kale in oil, incorporating it raw into salads with diced avocado, or making crispy kale chips.
Why: Start your day with a comforting bowl of oatmeal and build immunity from the get-go. Whole grain oats contain beta-glucan, a compound shown to activate immune cells that fight infectious microorganisms. Oats are also a source of immunity-building zinc. For the most benefit, choose steel-cut or old-fashioned rolled oats rather than sugary instant varieties.
Good to Know: No time to make steel-cut oats in the morning? You can soak them overnight by boiling water, adding the oats, and removing pan from from the heat. In the morning, they'll cook in about 10 minutes.
Use: Grind rolled oats in a food processor and substitute it for part of the flour in muffins, pancakes, and scones, or mix rolled oats with dried fruit, nuts, and pumpkin seeds for an immunity-building muesli to eat with yogurt or kefir.
Why: Rich, velvety almond butter contains three times as much vitamin E as peanut butter. When it comes to immunity, vitamin E often takes a back seat to the more commonly discussed vitamin C, "but this fat-soluble antioxidant is necessary for normal functioning of white blood cells, particularly the ones which respond to cells that have been infected by viruses," says Miranda Marti, a naturopathic doctor at the Bastyr Center for Natural Health in Seattle.
Good to Know: Increasingly available in supermarkets, almond butter is also a good source of heart-healthy monounsaturated fat.
Use: Make an almond butter sandwich with apple slices and honey; mix a dollop with coconut milk and red curry paste to make a dipping sauce for grilled veggies; or blend a spoonful into a smoothie.
Why: One of nature's most perfect foods, this staple protein is high in soluble fiber, which has been found by University of Illinois scientists to increase the production of an anti-inflammatory protein that strengthens the immune system. Beans also have an abundance of immunity-boosting anti-oxidants and folate, a B vitamin required for the production of new immune cells.
Good to Know: All beans are good sources of soluble fiber, but lima beans and kidney beans contain the most.
Use: Beans are as versatile as they are nutritious, starring in soups, stews, dips, and salads. For a nearly instant lunch, fold cooked beans, chopped tomato, arugula, and a squeeze of lime juice into a whole grain tortilla.
Why: This ceremonial Japanese tea is produced when young green tea leaves are steamed and then ground into a fine bright-green powder. Scientists at the University of Colorado discovered that, because the whole leaf is consumed in the tea, matcha provides sky-high levels of a class of antioxidants called catechins, which studies suggest can help halt the replication of the influenza virus and stimulate immune cells. Matcha has a lush vegetal flavor with a lingering sweetness.
Good to Know: Besides mixing powdered matcha with hot water, you can add it to smoothies, steamed milk, or soy milk, and even incorporate it into baked goods.
Use: Place a teaspoon in a small bowl or mug and add a few inches of simmering water. Whisk briskly and top with additional hot water to desired taste.
Why: Lauded for its nutty taste and chewy texture, this heirloom rice was called "forbidden rice" in ancient China because it was reserved for royalty and nobility. Recently, Louisiana State University Agricultural Center scientists working in the food science department discovered that black rice contains especially high levels of antioxidants (including the same anthocyanins as blueberries), which protect immune cells from oxidative damage.
Good to Know: An increasing number of health food stores and supermarkets now carry this once-rare rice variety.
Use: For a tasty main-dish salad, toss cooked black rice with dried cherries, pecans, chopped red pepper, baby spinach, and olive oil.
Why: Pumpkin seeds, which you can buy hulled in many supermarkets, are brimming with the mineral zinc, which can help you fight colds and flu. "Zinc plays a central role in immune function by increasing the production of various immune cells that are involved in the body's response to viruses," says Reardon.
Good to Know: Store pumpkin seeds, also known as pepitas, in the freezer to keep them fresh.
Use: Add to granola and top with yogurt or kefir; use in pesto instead of pine nuts; or toast in a dry skillet with sea salt and sprinkle over soups, salads, and roasted root vegetables.
Why: Fortified with vitamin D, milk is one of the few reliable dietary sources of the sunshine vitamin. T cells, the immune system's virus-killing cells, rely on vitamin D in order to become active when viral threats abound. According to a study involving nearly 19,000 subjects in the Archives of Internal Medicine, people with the lowest average levels of vitamin D were 36 percent more likely to develop an upper-respiratory infection than those with higher blood levels of the vitamin.
Good to Know: A study in the Journal of Nutrition discovered that whey, a protein in dairy products, can propel immune cells into action.
Use: Stir into oatmeal or granola, add to smoothies, or drink warm with a dash of cinnamon.