Does it seem like everyone around you is coming down with a nasty case of the flu? AdventHealth Centra Care physicians are reporting an increase of influenza. In fact, flu is up across all locations. We all know to practice good hand-washing habits, and hopefully you got your flu shot earlier in the year, but don’t forget about your kitchen. It holds some surprising flu-prevention power. A well-functioning immune system is the key to keep away bacteria and viruses, like colds and flu. Did you know there are certain immune-boosting nutrients which you can get from common healthy foods, which can help bolster your body's internal defense network?
Vitamin A
Vitamin A plays a number of important roles in immunity, and vitamin A deficiency impairs gut barrier function, alters immune responses, and increases susceptibility to a range of infections. What’s more, vitamin A deficiency diminishes the body’s production of natural killer cells, key components of the body’s internal defense network. The following foods are some of the best sources of vitamin A:
- Sweet potatoes
- Carrots
- Spinach, kale, and other dark, leafy greens
- Winter squash
- Bok choy
- Cantaloupe
- Bell peppers
- Broccoli
Vitamin C
Vitamin C is probably the most notorious immune-boosting nutrient, and while there has been controversy as to whether it lives up to the hype, several components of the immune system indeed rely on vitamin C to function properly. Along those lines, a vitamin C deficiency results in a reduced protection against certain pathogens while a higher supply enhances several immune system parameters. Having said that, while studies show that vitamin C may slightly reduce the duration of illness, it does not affect its incidence or severity. Thus, there’s no need to supplement with megadoses of vitamin C; you’ll be able to get plenty from whole foods, and citrus fruits are among the richest natural sources of vitamin C:
- Pomelo
- Oranges
- Grapefruit
- Clementine
- Lemons
- Limes
- Tangerine
- Ugli fruit
- Papaya
- Bell peppers
- Broccoli
- Brussels sprouts
- Strawberries
- Pineapple
- Kiwifruit
- Cantaloupe
- Cauliflower
- Dark leafy greens
- Cabbage
- Bok choy
- Tomatoes
Vitamin D
Nearly every tissue in the body has a receptor for vitamin D (which actually functions as a hormone), including cells of the pancreas, thyroid gland, skin, stomach, colon, and you guessed it, the immune system. With that in mind, it shouldn’t come as much of a surprise that inadequate levels of vitamin D have been linked to reduced immunity. Indeed, studies suggest that supplementation with vitamin D during winter months significantly lowers the risk of getting the flu. The BEST way to optimize vitamin D status is to spend time outdoors in the sunlight, as the body naturally produces vitamin D when it’s exposed to UVB light from the sun. Unfortunately, most people don’t get nearly enough sunlight (with their bare skin exposed), and although there are few foods that naturally contain vitamin D, those that do may sound familiar:
- Salmon
- Sardines
- Tuna
- Eggs
- Mushrooms
Vitamin E
Vitamin E is the major fat-soluble antioxidant in the body, and it fights free radicals and prevents the oxidation of the fats that make up our cell membranes, a process called lipid peroxidation. Free radicals and lipid peroxidation both suppress the immune system, and as a result, vitamin E helps enhance immunity. Here are some of our favorite foods rich in vitamin E:
- Spinach
- Swiss chard
- Turnip greens
- Beet greens
- Mustard greens
- Kale
- Collard greens
- Sunflower seeds
- Asparagus
- Almonds
- Broccoli
- Bell peppers
- Tomatoes
Zinc
Zinc plays a profound role in supporting the immune system and warding off infection. Deficiency in zinc impairs many aspects of the body’s internal defense network, including the production of natural killer cells. Consuming adequate zinc lowers the likelihood of respiratory infections, and you can ensure you’re getting enough by consuming a variety of the following foods:
- Beef
- Lamb
- Sesame seeds
- Pumpkin seeds
- Lentils
- Garbanzo beans
- Cashews
Iron
A deficiency in iron leads to a reduction in the body’s ability to ward off pathogens, increasing susceptibility to infection. While many foods contain iron, where you get it matters. For instance, (non-heme) iron from plant-based foods (e.g., spinach, lentils, beans, sesame seeds) is not well absorbed. On the other hand, heme iron, which is found in beef and other animal-based foods, is much more readily absorbed. Interestingly, combining sources of heme iron with non-heme iron (e.g., beef plus veggies) increases the amount of non-heme iron absorbed. This is often referred to as the “meat factor” of iron absorption. In addition, vitamin C, which helps bolster the immune system in its own right, facilitates the absorption of non-heme iron when the two are combined. Dark, leafy greens commonly pack the combo of iron plus vitamin C.
Selenium
Selenium plays a key role in supporting the body’s antioxidant defense network. In particular, selenium is involved in the production of glutathione peroxidase, which protects the body against oxidative stress, thus acting to enhance immune function. Not surprisingly, selenium deficiency has been show to lower immunity and increase susceptibility to infection. Brazil nuts are an excellent source of selenium, and have been shown to boost blood levels of selenium more effectively than supplementation. In addition, the following are selenium-rich foods:
- Tuna
- Shrimp
- Sardines
- Salmon
- Turkey
- Chicken
- Lamb
- Scallops
- Beef
Probiotics
The digestive system houses over 70% of our immunity, and it relies on a healthy balance of gut bacteria. Thus, getting your gut in order can have a big-time impact on your immunity, and you can start by consuming more of the following fermented foods:
- Greek yogurt, yogurt, and kefir
- Kombucha
- Sauerkraut and pickles
- Kimchi
- Natto and tempeh
So there you have it; you are now armed with the nutrition knowledge that you need to fortify your internal defense network and fight off the pesky cold and flu.
