Nutrition & The Immune System
A dietitian’s deep dive into the link between nutrition and the immune system. We’ll discuss which key nutrients support immune function, the best food sources of those nutrients, along with easy recipe ideas to incorporate them into your diet!
I’m sure I’m not alone when I say that I’ve been absolutely bombarded with messages and companies telling me that I need to take X product to support my immunity during the current pandemic. At the same time, I know so many of us are finding ourselves cooking more at home and wondering what we can do to support the health of our families and ourselves.
It’s overwhelming and a lot to take in all at once. I want you to know that I feel you. Add to that a loss of jobs and income for many, making those expensive products seem even more out of reach.
As a dietitian, I couldn’t be more disappointed in companies trying to capitalize on people’s fears during this virus. That’s why I want to give you an evidence-based look at how nutrition supports our immune system.
The truth is that nutrition plays a very important role in our immune system function, but perhaps not in the way that many companies might make you think.
I want you to know that the majority of these key nutrients can be found in real, affordable whole foods that you can find at any grocery store. Keep scrolling to see the best foods to support your immune system function, along with with a number of easy recipe ideas for how to use them!
I hope by the end of this post you’ll feel more informed and empowered in supporting your health both right now and all year long. Because our immune health isn’t just important during a pandemic, right? Let’s get started.
What Is The Immune System?
Before we get into the link between nutrition and the immune system, let’s start by briefly defining what the immune system is.
Essentially, the immune system is a set of interconnected organs, tissues, and cells within the body. It’s principle function is to protect the host (so us humans) from becoming infected by pathogenic (disease-causing) microorganisms, like viruses or bacteria.
The interconnected parts involved in this “system” include the white blood cells, antibodies, bone marrow, spleen, thymus, lymph nodes, and the gut.
Can You “Boost” Immunity?
A “boost” in something signifies an increase or improvement. When it comes to “boosting the immune system,” it would mean that something could increase or improve our immune function.
While there are specific nutrients that are essential for an immune system to function properly, unfortunately there is no evidence to say that more of a nutrient (beyond our needs) will lead to more immune function (above normal). This is where many marketing messages go wrong.
An analogy for this is to think about a car. It needs a certain amount of fuel to run, but a car will run the exact same if the gas tank is 100% or 50% full. A tank that is 100% full doesn’t run “better,” right? And if you put too much gas in the tank, it’ll simply spill out.
It’s the same with nutrition. Our bodies and immune systems need a certain amount of specific nutrients to run, but more of those nutrients doesn’t necessarily mean it’ll run “better.” If our “tank” is full, putting more nutrition in our bodies won’t help us much. Our bodies can only absorb and use so much of each nutrient at a time.
An exception to this is if you truly are malnourished, deficient, or not getting enough of these specific nutrients (an “empty tank” if you will). If that’s the case, improving your nutrition status can help bring your immune function back up to normal (I).
Bottom line? There is no evidence to show that we can increase our immune function above normal through nutrition. In fact, an overactive immune system isn’t necessarily a good thing; it’s a key aspect of an autoimmune disorder.
With all that said, there are certain nutrients that are involved in the proper functioning of our immune systems. We CAN eat in a way that supports our immune function by way of ensuring that we’re getting these nutrients in most days. Let’s get into that next!
The Role Of Nutrition On The Immune System
First and foremost, it is essential that we are eating ENOUGH of both calories and essential nutrients. Undernutrition can compromise our immune system, which can lead to an increased susceptibility to infection (I).
In terms of individual nutrients, a key macronutrient involved in immunity is protein!
Our body needs protein to create antibodies that recognize and fight off foreign invaders, like bacteria or viruses. Protein also plays an essential role in helping your body heal and recover. This is not to say that carbohydrates and fats aren’t important, rather to simply highlight protein’s unique role.
In addition to protein, there are many different micronutrients (vitamins + minerals) that play essential roles in the proper functioning of our immune system. These include:
- Vitamins – A, B6, B12, C, D, E, and folate
- Minerals – zinc, iron, and selenium
These various micronutrients work together in many ways to support immune function. For instance, they play essential roles in:
- regulating immune responses
- synthesizing + ensuring the proper functioning of immune cells
- protecting immune cells from oxidative damage
How can we make sure we’re getting in enough of these key nutrients? In the next section I’ll cover the best food sources of these nutrients. I’ve also shared some easy recipe ideas that incorporate these foods!
Best Protein Food Sources
Both animal and plant foods can be quality sources of protein. For animal-based foods, protein can come from all meats, fish, shellfish, eggs, and dairy products.
Some high animal-based protein recipes:
- Spanakopita Frittata
- Crispy Salmon With Coconut Honey & Lime
- Healthy Breakfast Egg Muffins
- Baked Salmon With Pistachio Pesto
- High-Protein Tuna Salad
Some of the best sources of plant-based protein include soy products (like tofu, tempeh, edamame, and soy milk), legumes (beans, lentils, chickpeas), nuts, seeds, and whole grains (like quinoa, brown rice, and oatmeal).
While I encourage eating a variety of foods for everyone, if you’re on a plant-based diet this is particularly important to ensure you’re getting in all essential amino acids!
Some plant-based protein recipes:
Best Food Sources of Vitamin A
Some of the best sources of vitamin A come from orange-coloured fruits and vegetables. These foods receive their vibrant pigments from a plant compound called beta-carotene. Beta-carotene is both an antioxidant and a “provitamin” that gets converted to vitamin A in our bodies.
Orange fruits and veggies include things like sweet potatoes, winter squash, carrots, bell peppers, mangoes, and apricots.
For example, 1 cup of either sweet potatoes or winter squash will provide over 100% of your daily vitamin A needs!
Other vegetables rich in vitamin A include greens like spinach, kale, and broccoli. Seafood, eggs, and fortified milk products are also good sources.
Some recipes rich in vitamin A:
- Miso Mashed Sweet Potatoes
- Roasted Butternut Squash With Kale & Coconut
- Maple-Roasted Carrots With Harissa Yogurt
- Sweet Potato Hash With Red Pepper & Kale
- No-Bake Carrot Cake Energy Bites
- Massaged Kale Salad With Sweet Potato
Best Food Sources of Vitamin B6
Vitamin B6 is widely available in our food system! If you’re eating a varied diet, it’s likely that you’re getting enough. Good sources of B6 include:
- Meats – chicken, beef, and pork
- Fish – salmon, tuna
- Whole grains
- Legumes – chickpeas, beans, lentils
- Nuts + seeds (and their butters)
- Fruits + vegetables – bananas, avocados, spinach, carrots, sweet potatoes, peas, potatoes, squash, etc.
Best Food Sources of Vitamin B12
Vitamin B12 is primarily found in animal-based foods like meat, seafood, eggs, and dairy products. For instance, a 3-oz serving of seafood will provide over 100% of your daily B12 needs. 2 large eggs will provide about 50% of your daily needs.
Scroll up to the recipes listed as good sources of animal protein – those will be rich in B12 as well!
The only plant-based foods that contain B12 are those that have been fortified with it. Nutritional yeast is a great example – 1 serving will provide 100% of your daily needs. This recipe for a Cheesy Miso Tahini Sauce is one of my favourite ways to use it.
Best Food Sources of Vitamin C
Vitamin C is likely the nutrient we most associate with immune function. Lucky for us, it’s found in a TON of colourful fruits and vegetables, including:
- Bell peppers
- Berries – strawberries, raspberries, blueberries, blackberries
- Citrus fruits – lemons, oranges, grapefruit
- Tropical fruits – guava, papayas, mangos, pineapples, kiwis
- Brussels sprouts
- White potatoes
- Leafy greens – kale, spinach, etc.
I know we often think of oranges as the best source of vitamin C, but it’s not the only (or the best) one! For example,
- one cup of chopped bell peppers will provide 170% of your daily vitamin C needs
- one cup of strawberries will provide 100%
- one cup of broccoli will provide 90%
In comparison, an orange will provide about 80%. It’s still a great source of vitamin C, but I just want you to know that you can get it from soo many foods!
Some recipes rich in vitamin C:
- Strawberry Tomato Avocado Salad
- Strawberry Orange Frozen Greek Yogurt Bark
- Roasted Red Pepper Cashew Cream Pasta
- Strawberry Quinoa Tabbouleh
- Chocolate Orange Oatmeal
Best Food Sources of Vitamin D
Vitamin D is unfortunately not widely available in our food system. We produce vitamin D when sunlight hits our skin, but for many of us this is an inadequate way to meet our needs, especially in the winter months. For this reason, supplementation may be necessary.
Foods that do provide vitamin D include:
- Fatty fish, like salmon, tuna, or mackerel
- Eggs, cheese, and fortified milk or milk alternatives
Some recipes rich in vitamin D:
- Mediterranean Canned Mackerel Pasta
- Easy Canned Mackerel Pasta Salad
- Healthy Tuna Pasta Salad
- Canned Salmon Potato Salad
- Eggs Benedict With Canned Salmon
Best Food Sources of Folate
Folate is a B vitamin that is widely available in plant-based foods. If you’re eating a variety of plants, you will likely be meeting your folate needs!
Particularly high sources of folate include:
- Legumes – beans, lentils, chickpeas
- Nuts + seeds – peanuts, flax seeds, sunflower seeds
- Veggies – asparagus, spinach, romaine lettuce, broccoli, green peas
- Enriched grain products (bread, pasta)
Best Food Sources of Zinc
Zinc is one of the key minerals involved in immune function. Some of best sources of zinc include:
- Meats – beef, chicken, turkey, poultry
- Shellfish – oysters, shrimp
- Dairy products – yogurt, milk, cheese
- Nuts – cashews, almonds, peanuts
- Seeds – pumpkin seeds, hemp seeds
Some recipes rich in zinc:
- Vegan Hemp Seed Pesto
- Healthy Homemade Trail Mix
- Tomato Soup With Cashew Cream
- Pasta With Cashew Cream Tomato Sauce
Tip: sprinkling nuts + seeds on top of oatmeal, yogurt, or salad bowls is an excellent way to get zinc in! For instance:
- a 1/4-cup of pumpkin seeds provides about 33% of a woman’s daily zinc needs
- a 1/4-cup of cashews provides about 15% of your daily needs
Best Food Sources of Iron
Iron is an essential mineral involved in immunity. Some of the best animal-based food sources of iron include:
- Meats – beef, poultry, pork
- Seafood – oysters, shrimp, scallops, mackerel, trout, tuna
Some of the best plant-based sources of iron include:
- Soy products – tofu, tempeh
- Legumes – lentils, chickpeas, beans, hummus
- Nuts + nut butters – almond, cashew, hazelnut
- Seeds + seed butters – pumpkin seeds, sunflower seeds, sesame seeds
- Grains – enriched pastas, cereals
- Vegetables – spinach, asparagus, beets, beet greens
- Blackstrap molasses
Tip: pair vitamin C-rich foods (see above!) with plant-based sources of iron to increase it’s absorption into the body. For example:
- have a tofu stir-fry with bell peppers and tomatoes
- add lemon to a spinach salad dressing
- or, use blackstrap molasses to sweetened a strawberry oatmeal bowl
Many of the recipes I’ve already shared in this post contain these iron-rich foods!
Best Food Sources of Selenium
Selenium is another key mineral involved in immunity. It’s found in a wide variety of foods, including:
- Brazil nuts – 1 nut provides 100% of your daily selenium needs!
- Meat + poultry
- Eggs + dairy
- Whole grains
The Immune System & Gut Health
More recent research has shown that our gut plays a huge role in immune system function. In fact, it’s thought that our gut-associated lymphoid tissue (GALT) represent about 70% of our entire immune function (I).
Our gastrointestinal tract is a large barrier to the outside world. Because of this, one of it’s primary functions is to decide what gets absorbed into our body and what stays out.
From a nutritional standpoint, what can we eat to support gut health?
- A variety of FIBRE-rich foods.
- Fibre is found in plant-based foods like fruits, vegetables, whole grains, nuts, and seeds.
- Luckily, mainly of these fibre-rich foods are also great sources of the key nutrients we just discussed above!
- Fermented foods can be a source of beneficial gut bacteria:
- Fermented dairy – plain yogurt, kefir
- Fermented soy – tempeh, miso
- Fermented cabbage – kimchi, sauerkraut
Some gut-friendly recipes:
- Savoury Kimchi Oatmeal
- Maple Kefir Chia Seed Pudding
- Easy Kimchi Quinoa Bowl
- Honey-Poached Pear Yogurt Bowl
What About Supplements?
If you’ve made it this far, I hope you can see that there are many accessible and affordable foods out there than can keep our immune systems strong. For most of us, it really isn’t necessary to drop lots of $$$ on fancy supplements and superfoods.
When it comes to supplementation, there is research to show that it usually only helps if we are DEFICIENT in a nutrient. Like the car analogy at the beginning of this post, more of a nutrient beyond what we need won’t necessarily help.
Research that looks at vitamin C (I, II) and zinc supplementation (I, II, III) has found that it might lead to a slightly shorter duration and severity of colds, but neither appear to reduce the incidence or occurrence of colds or flus. Translation: supplementation may help when you are already sick, rather than preventing you from getting sick.
Vitamin D supplementation has been shown to possibly prevent acute respiratory tract infections in those who are deficient (I). Because it’s not found in many food sources and because we’re likely not producing enough of it during the winter months, supplementing vitamin D might be something to consider.
But before you reach for just any probiotic, do know that the research here is really early. We simply don’t have clinical recommendations for specific strains or doses of bacteria when it comes to immunity just yet.
Ultimately, supplementation can help fill in any gaps missing in your diet, but they’re not meant to replace a healthy diet. They’re called “supplements” for a reason!
For personalized supplement recommendations, work one-on-one with a dietitian to help address your unique needs. As always, you should check with your doctor, pharmacist, or dietitian to make sure that a supplement doesn’t interfere with any medications you’re taking.
Other Lifestyle Factors
Like everything else in health, nutrition never works in isolation. There are many other lifestyle factors that have a major impact on immune function, too. These include:
- Moving your body
- Not smoking
- Getting adequate sleep
- Managing stress!
While eating a healthy, balanced diet is great, it can only do so much if these other areas of your life are lacking. A big reason why it’s essential to take a holistic approach to health!
I truly hope that this post helps to bring some clarity and peace of mind during this stressful time. To recap the key takeaways about nutrition and the immune system:
- From a nutrition standpoint, a diet rich in a variety of whole foods like fruits, vegetables, quality proteins, healthy fats, nuts, seeds, and whole grains is one of the best ways to keep your immune system strong.
- We can (and should) eat in a way that supports our immune system all year round, not just during this current crisis or during cold and flu season.
- Supplementation plays a role in deficiencies, but is not always necessary in a healthy population. For personalized recommendations, it’s best to speak with a dietitian one-on-one.
- It is impossible for one food, nutrient, or supplement to strengthen your immune system on it’s own. It’s also WAY too early to have any conclusive research that any food or supplement will protect you from COVID-19. Companies are capitalizing on our fears, but by staying informed and educated you don’t need to fall for their false promises.
Do you have any more questions about nutrition and the immune system? Let me know in the comments below! I hope you found this article helpful. For more simple, healthy recipe ideas and nutrition tips, be sure to follow along on Instagram and Pinterest.