A healthy immune system is essential to help your body fight off foreign invaders such as bacteria, viruses, and toxins, but did you know the importance your diet is in supporting a healthy immune system?

Unfortunately, poor diets are becoming more common in western cultures that are often full of processed foods, junk foods, and refined sugars. However, if you substitute these foods with healthier alternatives you can start to take control of your health and naturally boost your immune system!  

Rather than buying a bunch of supplements that can sometimes do more harm than good, you can simply eat a well-balanced full of foods that are abundant in essential nutrients to help your immune system thrive to fight off infection and disease.

In this article you’ll learn all about what nutrients are essential for the immune system and what foods to eat to obtain these nutrients! 

1. Vitamin A

Vitamin A is a fat-soluble vitamin and antioxidant that is essential for cell growth, eye health, and immune function. 

Vitamin A supports the immune system through the healthy maintenance of mucous membranes that are a protective barrier that help to trap infectious agents such as bacteria and viruses from entering (1).

Mucous membranes are one of the first lines of defence of the immune system that are found inside your mouth, nose, eye lids, stomach, intestines, lungs, and many other parts of the body.

Vitamin A also helps to produce white blood cells that fight foreign invaders including bacteria and viruses. In fact, a deficiency in vitamin A can increase your risk of infection and delay your recovery (2, 3).

There are two forms of vitamin A found in food.

Retinol is preformed vitamin A that is found exclusively in animal products such as dairy, meat and fish.

While carotenoids are provitamin A that are found predominantly in plant foods, in particular ones that are coloured bright orange or red such as carrots, sweet potatoes, pumpkin, butternut squash.

2. Vitamin C

Vitamin C is antioxidant that is required for the growth and repair of tissues and helps to keep the immune system healthy.

Vitamin C supports the immune system in multiple ways. Firstly, vitamin C helps to produce white blood cells that fight infection (4).

Secondly, vitamin C acts as an antioxidant to fight free radicals that cause inflammation and suppress the immune system (5).

Thirdly, vitamin C is essential to support skin health that acts as a barrier to prevent pathogens (eg. bacteria and viruses) from entering the body (6).

Studies have demonstrated that taking a vitamin C supplement can shorten wound healing time. However, vitamin C supplementation may not be necessary (7, 8).

Instead, you can eat foods that are high in the vitamin C including broccoli, cabbage, citrus fruits, leafy greens, cauliflower, capsicums, kiwi fruit and papaya. 

3. Vitamin E

Vitamin E is a fat-soluble antioxidant that protects your cells from damage and is also one of the most effective nutrients that supports immune function.

Vitamin E supports the immune system by regulating the healthy growth and development of immune cells, while vitamin E deficiency has shown to impair the normal function of the immune system, that can be restored through vitamin E repletion (9).

Although vitamin E deficiency is rare, vitamin E supplementation above dietary recommendations has shown to enhance immune function and reduce infection in older adults (9). 

Vitamin E can easily be obtained in diet by eating foods such as hemp seeds, almonds, sweet potato, peanuts, avocado and sunflower seeds.

4. Vitamin D

Unlike most other vitamins, vitamin D is in fact a hormone that has important role in modulating the immune system.

Vitamin D receptors (VDR) are found in every cell in the body including immune cells. Calcitriol (active vitamin D in the body) can regulate the activity of immune cells by turning genes on or off.

While vitamin D deficiency is associated with the increased risk of autoimmune conditions and infection (10, 11).

Only small amounts of vitamin D are found in foods (5-10%), with most of our vitamin D being produced inside the body through UVB exposure on your skin from the sun.

There are two forms of vitamin D in the diet. Vitamin D3 (cholecalciferol) is found in fatty fish (eg. salmon, mackerel, tuna, sardines) and eggs & Vitamin D2 (ergocalciferol) is found in mushrooms, and yeasts.

Vitamin D3 has demonstrated to increase blood levels of vitamin D by almost double compared to vitamin D2 (12, 13, 14).

To learn more about how to get enough vitamin D click here.

5. Folate 

Folate is a water-soluble B vitamin found naturally in foods, while folic acid is a synthetic form of folate commonly used in supplements and fortified foods.

Folate has many different roles in the body including DNA and protein production, energy production, and maintaining cell health.

Folate supports your immune system through its role in cell health, with folate deficiency decreasing the number of immune cells (15).

However, studies have also shown that high doses of folic acid supplement can suppress immune function by reducing protective immune cells. Suggesting that high doses could negatively affect the immune system, therefore it’s probably better to get folate from the diet (16, 17).

Folate is found in a number of different foods including spinach, kale, broccoli, avocado, citrus fruits, eggs, and beef liver. While folic acid is added to foods such as flour, commercial cereals and bread and is also found concentrated in supplements.

6. Zinc

Zinc is an essential mineral in the diet that is crucial for the normal development and function of immune cells with zinc deficiency affecting the healthy production of immune cells. Zinc is also an antioxidant that can neutralize free radicals that cause inflammation (18).

Studies have indicated that 80-92 mg day of zinc/day can reduce the length of the common cold by up to 33%. Furthermore, zinc supplements promote healthier immune responses and significantly reduce the risk of infections in older adults (19, 20).

You can find high amounts of zinc in oysters, lean meats, poultry, lentils, chickpeas, beans, pumpkin seeds and hemp seeds.

7. Selenium 

Selenium is also an essential mineral and antioxidant in the diet that you may not have heard of before, this is because we only need small amounts of selenium. However, selenium has some very important roles in the body that include supporting thyroid health and the immune system.

Selenium plays an important role in keeping your immune system healthy by exerting antioxidant effects in the body that help to lower inflammation that take the load off the immune system (21).

Selenium is also needed to regulate glutathione in the body that is sometimes referred to as our ‘master antioxidant’. While studies show that selenium deficiency reduces immune cell function and slows our immune response (21).

Brazil nuts are extremely high in selenium (68–91mcg per nut) with other food sources of selenium including seafood, meat, poultry, and cottage cheese.

8. Iron

Iron is an essential mineral that has an important role in energy production and keeping the immune system healthy.

Iron supports the immune system by assisting in the healthy growth of immune cells, in particular a type of immune cell called lymphocytes required for healing infections. Studies have shown that iron deficiency reduces your immune response (22).

Iron also helps to support the immune system by providing oxygen to damaged cells, tissues and organs that are required for the body’s ability to fight diseases and infection (23). 

There are actually two different types of iron found in foods haem and non-haem iron, with haem-iron being the better absorbed form of iron (24). 

Iron found in animal products is around 40% haem-iron and 60% non-haem iron, and is typically found in beef, lamb, kangaroo, chicken and fish.

Plant-based sources of iron are 100% non-haem and can be found in wholegrain cereals and breads, beans, legumes, dark green leafy vegetables, dried fruits, nuts and seeds (including hemp seeds!).

To learn more about getting enough iron in a plant-based diet click here   

9. Omega 3 fatty acids

Omega 3 fatty acids are a type of polyunsaturated fatty acid that can’t be made by the body and are therefore required in the diet. Omega 3 fatty acids have an important role in brain health, eye health and regulating inflammation (25). 

Omega 3 fatty acids strengthen the immune system by reducing inflammation that can suppress the immune system and support the structure of immune cells (26, 27).

Furthermore, omega 3 fatty acids may be beneficial for a number of autoimmune conditions including rheumatoid arthritis, Crohn’s disease, ulcerative colitis, psoriasis, lupus erythematosus, multiple sclerosis and migraine headaches (28). 

Omega 3 fatty acids can be found in hemp seed oil, flax seeds, and fatty fish (eg. sardines, mackerel, salmon). 

10. Protein

Proteins are made up of amino acids that have a variety of functions that include growth and repair, energy, and keeps the immune system strong.

Protein supports a healthy immune system by helping to produce antibodies. Antibodies are proteins in the blood that help fight off harmful pathogens such as bacteria and viruses (29).

Amino acids also have an important role in regulating the immune system by activating immune cells. While protein deficiency is known to impair immune function and increase the risk or disease (30).

Dietary protein can be found in both animal and plant-based sources.

Animal sources include meat, chicken, seafood, and dairy. Plant-based sources include hemp seeds, soy products, legumes, nuts, seeds, and whole-grains.

In fact, 13 seeds hemp protein powder contains a whopping 50g of plant-based protein per 100g!

Aim to eat 1g (sedentary lifestyle) – 1.6g (active lifestyle) of protein per kg/bodyweight a day to ensure you’re getting enough protein.

11. Fibre

Fibre is the indigestible parts of plant foods, such as vegetables, fruits, grains, beans, seeds and legumes.

Fibre is important as it helps to keep our digestive system healthy by feeding our gut bacteria (gut microbiome). When you eat fibre our gut bacteria produce short chain fatty acids (SCFA) that exert an anti-inflammatory effect that supports the immune system (31, 32).

A healthy gut microbiome can also strengthen your immune system by helping to keep harmful pathogens (eg. bacteria and viruses) from entering your body through the digestive tract. This is important as approximately 70% of your immune system is found in the gut! (33) 

Aim to eat 30-40g of fibre/day to keep your gut and immune system healthy. 100g of hemp seeds contains approximately 7g of fibre (34). 

So, what's the bottom line?

Now you know that you don’t need to go out and break the bank on expensive supplements to boost your immune system, instead you can just focus on eating a well-balanced diet that provides all the nutrients you need. 

If you can eat these foods regularly while also limiting processed foods, junk foods, and refined sugars this can help to further strengthen your immune system.

Living a healthy lifestyle by exercising regularly, managing stress and getting enough rest are some simple lifestyle tips that take the load off your immune system.

It’s important to note that while eating a healthy diet and living a healthy lifestyle can support a strong immune system it will not make you immune to the covid-19 virus.

If you have any questions or need support with your health, feel free to email our head nutritionist Ben at ben@13seeds.com.au

Disclaimer:

This article does not constitute as medical advice and does not take into consideration your personal circumstances. Please see your medical professional before implementing the above.

References: 

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