Plant-Based Foods to Support Your Immune System

Rachel Hawkins (Accredited Practicing Dietitian & Nutritionist)

Stay healthy with these immune supporting plant-based foods.

Good nutrition is essential for building and maintaining a strong immune system. The immune system helps to keep you healthy by working to identify potential threats to your health (e.g. bacteria, viruses and parasites) and fighting them off to defend the body against infection.

A healthy immune system relies on a balanced mix of vitamins and minerals, all of which can be found in everyday foods. Dietitian Rachel Hawkins discusses some of the plant-based foods that will help to support your immune system and keep you healthy all season.

Kiwifruit

Kiwifruit is a fuzzy-skinned fruit that has a sweetish-tart flavor. Kiwifruits are a fantastic source of vitamin C, a water-soluble vitamin that helps to protect the body from infection by increasing the production of antibodies (proteins that fight off foreign threats to the body) and boosting the immune system.¹ The body cannot produce or store vitamin C, so it is essential to consume it regularly in the diet.² One small kiwi fruit provides 63mg of vitamin C, which equates to 140% of the recommended dietary intake (RDI).³ Gold kiwifruits are even more impressive, containing a whopping 131mg of vitamin C… 291% of the RDI.³

Sunflower Seeds

Sunflower seeds come from the large flower heads of the sunflower plant.⁴ They have a mild, nutty flavor and are particularly high in vitamin E. Vitamin E functions as a powerful antioxidant, which helps to boost the immune system by protecting the body against free radical damage.⁵ One serving (30g) of sunflower seeds provides 10mg of vitamin E, which is the daily intake level that is deemed adequate for good health.⁵

Sweet Potato

Sweet potato is a sweet, starchy root vegetable. Golden sweet potatoes are a rich source of vitamin A, a fat-soluble vitamin that helps to regulate the immune system and protect against infection by keeping the tissues in the mouth, stomach, intestines, and respiratory system healthy.^1,6 Half a cup of cooked sweet potato provides 7745mcg of vitamin A, or 860% of the RDI for men and 1106% of the RDI for women.⁶

Legumes

Legumes include chickpeas, beans, peas, lentils, and lupins.⁷ All legumes contain substantial amounts of zinc, a mineral that is known to play a key role in the immune system by acting as an antioxidant and promoting wound healing.^8-9 Legumes also contain phytates—antinutrients that inhibit the absorption of zinc and other minerals.⁹ This means that zinc from legumes is not as easily absorbed by the body as the zinc found in animal products. Soaking your legumes in water before cooking is a simple way that you can help to reduce the phytate content of legumes, thus ensuring you get the most from their nutritional offering. Half a cup of cooked legumes (75g) provides 1.5mg of zinc, which is 11% of the RDI for men and 19% of the RDI for women.¹⁰

Mushrooms

Mushrooms are one of very few plant-based foods that are a good source of vitamin D, a nutrient that is essential for normal immune function.¹¹ Much like humans, mushrooms can synthesize vitamin D when exposed to UV light.¹² Because different mushrooms receive different levels of exposure to UV light based on varying food production and handling methods, it is difficult to quantify exactly how much vitamin D there is in a serving of mushrooms.

However, what we do know is that placing store-bought mushrooms in the sunshine for 30-60 minutes before eating is enough to boost their vitamin D content.¹³ Thus, putting mushrooms on your windowsill to soak up the sunlight before eating makes a great strategy for maximizing your vitamin D intake from mushrooms.

Brazil Nuts

Brazil nuts have a smooth, buttery flavor and are a rich source of selenium. Selenium is a mineral that plays an important role in our immune health by acting as an antioxidant that helps to lower oxidative stress, reduce inflammation, and enhance immunity.^14,15 Interestingly, selenium deficiency has been shown to be detrimental to immune function by slowing the body’s immune response.^14,15 One serving (30g) of brazil nuts provides 580mcg selenium, which is 967% RDI for women and 829% RDI men.¹⁶

References

1. Academy of Nutrition and Dietetics. Eat Right: Protect your health with immune-boosting nutrition. Accessed 17/2/2020 https://www.eatright.org/health/wellness/preventing-illness/protect-your-health-with-immune-boosting-nutrition
2. National Health and Medical Research Council. Vitamin C. Accessed 18/2/2020. https://www.nrv.gov.au/nutrients/vitamin-c
3. Love Kiwis. Nutrition Information. Accessed 17/2/2020. https://lovekiwis.com/nutrition-information/
4. Are sunflower seeds good for you? Nutrition benefits and more. Accessed 17/2/2020 https://www.healthline.com/nutrition/sunflower-seeds#nutrition
5. National Health and Medical Research Council. Vitamin E. Accessed 18/2/2020. https://www.nrv.gov.au/nutrients/vitamin-e
6. National Health and Medical Research Council. Vitamin A. Accessed 18/2/2020. https://www.nrv.gov.au/nutrients/vitamin-a
7. Grains and Legumes Nutrition Council. Types of Legumes. Accessed 17/2/2020. https://www.glnc.org.au/legumes/types-of-legumes/
8. Prasad A. S. (2008). Zinc in human health: effect of zinc on immune cells. Molecular medicine (Cambridge, Mass.), 14(5-6), 353–357. https://doi.org/10.2119/2008-00033.Prasad. Accessed: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2277319/ (zinc)
9. Shankar, AH & Prasas, AS. (1998). Zinc and immune function: the biological basis of altered resistance to infection. American journal of Clinical Nutrition. 68:447S-463S. doi: 10.1093/ajcn/68.2.447S. Accessed: https://www.ncbi.nlm.nih.gov/pubmed/9701160 (zinc 2)
10. National Health and Medical Research Council. Zinc. Accessed 18/2/2020. https://www.nrv.gov.au/nutrients/zinc
11. Prietl, B., Treiber, G., Pieber, T. R., & Amrein, K. (2013). Vitamin D and immune function. Nutrients, 5(7), 2502–2521. https://doi.org/10.3390/nu5072502. Accessed: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3738984/ (vitamin d)
12. Simon, PR., Borzelleca, JF., DeLuca, HF et al. (2013). Safety assessment of the post-harvet treatment of button mushrooms using ultraviolet light. Food Chem Toxicol, 56: 278-289. doi: 10.1016/j.fct.2013.02.009. Accessed: https://www.ncbi.nlm.nih.gov/pubmed/23485617 (Mushrooms)
13. Australian Mushrooms. Mushroom facts. Accessed 17/2/2020. https://australianmushrooms.com.au/did-you-know/
14. Hoffmann, P. R., & Berry, M. J. (2008). The influence of selenium on immune responses. Molecular nutrition & food research, 52(11), 1273–1280. https://doi.org/10.1002/mnfr.200700330. Accessed https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3723386/
15. Huang, Z., Rose, A. H., & Hoffmann, P. R. (2012). The role of selenium in inflammation and immunity: from molecular mechanisms to therapeutic opportunities. Antioxidants & redox signaling, 16(7), 705–743. https://doi.org/10.1089/ars.2011.4145. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3277928/
16. National Health and Medical Research Council. Selenium. Accessed 18/2/2020. https://www.nrv.gov.au/nutrients/selenium