The immune system, like all our bodily systems, thrives off of eating a wide variety of whole foods and lots of vegetables. It doesn’t do well with tons of sugar and processed foods. In fact, eating excessive simple carbohydrates and sugars delivers a blow to immune function by impairing phagocytosis (the process whereby certain white blood cells, specifically neutrophils in this study, “eat” bacteria) for up to 5 hours.
The good news is that every time you sit down to eat a meal, you have the opportunity to make the choice of feeding health or feeding disease. And while we are not robots and do not need to be aiming for perfection (goodness knows I don’t!), what we can do is make the choice to nourish our immune system the vast majority of the time. Aiming for 90-95% of what you ingest to be supportive of health is still fantastic! Save the other 5-10% for feeding your soul because, hey, we all need that chocolate bar or extra glass of wine here and there ;)
Below you can learn about some of the key micronutrients required for optimal immune function and some good food options for getting them into your diet. Think about including a variety of these foods in your diet to support your body with the vitamins and minerals that we know support your immune system in doing its job. You’ll also find some general recommendations for supporting optimal immune system health with food at the end.
Micronutrients that nourish the immune system
Vitamin A
Vitamin A is needed to support proper innate and adaptive immune function and produce healthy epithelia and mucosa, the first line of defense against pathogens. This makes vitamin A an essential micronutrient for defense against multiple infectious diseases. Food sources high in vitamin A include beef liver, broccoli, dark green leafy vegetables, carrots, cod liver oil, eggs, sweet potatoes, squash and pumpkins.
Vitamin C
Also known as ascorbic acid, vitamin C is an anti-oxidant and plays an essential role in immune function and also support healthy epithelia. We need vitamin C for our bodies to mount an appropriate response to microbial infections (viruses, fungi, bacteria, parasites) without excessive damage to our own cells in the process. In the United States, over 40% of adults are deficient in vitamin C. Humans are one of a few species that are unable to make their own vitamin, so it’s super important to make sure that you eat plenty of foods high in vitamin C every day. Ex. guava, kiwi, leafy greens, bell peppers, strawberries, oranges, cantaloupe, grapefruit papaya, broccoli, cauliflower, bell peppers, Brussels sprouts, tomatoes, persimmon, pineapple. It is ideal to eat foods raw when eating them for vitamin C content, as high temperature cooking can result in significant loss of vitamin C from the food.
Vitamin D
Vitamin D is a very important modulator of immune function. Immune cells, including B-cells, T-cells, monocytes, macrophages and dendritic cells, require vitamin D for proper function. A deficiency in vitamin D impairs healthy immune function and increases risk of autoimmune disease and infection. Low levels of vitamin D are rampant in the United States. It’s difficult to get everything you need from food and I recommend working with your naturopathic doctor to get lab testing done to figure out appropriate vitamin D dosing for you.
Vitamin E
Vitamin E is an antioxidant that plays an important role in the maturation, function and regulation of a variety of immune cells, including NK cells, T-cells, B-cells and macrophages. Good sources of vitamin E include nuts and seeds, such as almonds, walnuts, sunflower seeds, and hazelnuts. Vitamin E is also found in dark leafy greens, egg yolk, wheat germ oil, whole grains, and avocado.
Selenium
Selenium supports immune function by increasing NK cells activity, supporting T cell proliferation and supporting innate immune function. It is also involved in glutathione production, your body’s “super antioxidant”. A deficiency of selenium weakens your defenses against viral infections and may increase viral pathogenicity. The easiest way to get close to your daily dose of selenium is by eating a brazil nut. Other good sources of selenium include sunflower seeds, eggs, seafood, legumes, mushrooms, asparagus, and meat.
Zinc
Zinc is required for normal development and function of neutrophils and NK cells, is needed for signaling in the immune system and a deficiency in zinc increases susceptibility to infection. Best dietary sources include oysters, red meat, crab and lobster. Can also be found in cheese, chicken beans, cashews, legumes, whole grains, seeds and nuts.
Additional considerations
Protein is essential for proper immune function. Not sure if you’re getting enough protein for your age/activity level? A general guideline can be found here, but ideally talk to your health care provider to get an individualized evaluation and recommendation.
Multiple studies have shown that a diet high in fruits and vegetables improves the immune system function. Make sure to eat your veggies every day and remember to eat the rainbow to make sure you’re getting all the required nutrients for optimal health.
Reduce refined sugar and refined carbohydrate intake, as this can impair white blood cell function for hours (see above).
Eat mushrooms! Mushrooms contain beta-glucans, that have anti-carcinogenic effects and help your immune system respond to infections. The immune modulating effects of mushrooms are well known, so why not includes some mushrooms in your diet to support your own immune system. Learn more here.
Use herbs and spices liberally, ex. turmeric, garlic, ginger, coriander, cinnamon, cumin. A lot of herbs and spices have supportive effects on your immune system, anti-inflammatory properties and/or antimicrobial properties.
Drink plenty of filtered or spring water.
Remember that in some cases supplementation can be beneficial to support your immune system, but food as medicine should always be the foundation. For individualized supplementation recommendations talk to your naturopathic doctor.
Be well.