With the COVID-19 pandemic sweeping the globe, everyone needs to keep their immune system strong to protect themselves and the people around them. No supplement will prevent or cure disease, but looking after your nutritional health is something you can do to help your body prepare for illness, and help you fight it off if necessary.
Ensuring a strong immune system is not a simple as it’s made out to believe. You’ve probably heard about the benefits of vitamin C and garlic, but the truth is no single food or nutrient is going to stop you from getting sick. The immune system is supported by a whole range of nutrients, and so if even one is lacking, it can impact it’s function. As different foods contain different nutrients, you need to eat a variety of foods to ensure that you get nutritional adequacy. A good diet will help to ensure a strong immune response, and will not require further supplementation. The efficacy of nutrient supplementation varies and certain nutrients can interfere with the absorption of others e.g iron supplementation can inhibit zinc absorption.
In this post, I'll go over the some of the key nutrients that support the foundation of strong immune system and some foods which contain high amounts of these nutrients and come highly recommended by a registered dietitian in NZ. The intake recommendations are based on healthy adults between 18-65 years. If you are pregnant or breastfeeding, your requirements might be different. It’s important you speak to a registered nutritionist or dietitian to find out what your specific requirements may be.
First on the list is protein. Our immune system is made of protein, so while most of us know that protein is super importance for our muscles, protein is also the foundation of our immune system.
How do we know we are getting enough protein? Most adults require 2-3 serves of protein-rich foods per day to meet their requirements. People over 65 years will need 3 serves at a minimum. Some protein examples include:
- 80g of cooked meat (20g protein)
- 100g of cooked fish (20g protein)
- 1 cup of lentils (18g protein)
- 1/3 cup nuts (9g protein)
- 100g tofu (8g protein)
We also get small amounts of protein from other aspects of our diet, which all add up.
Signs of insufficient protein can be loss of muscle mass or strength, slow-healing wounds, or struggling to recover from illnesses. It is more common in the older population as protein requirements increase as independence decreases - for example those who are living in aged care. Be sure to check on your older loved ones if they are living alone and ensure that they are able to eat well.
Zinc is a mineral which plays an important role at the DNA and RNA level and appears to protect against viruses by stopping them replicating . The average healthy adult requires 8mg of zinc per day . Foods high in zinc tend to be animal-based such as meat, chicken seafood and dairy, however there also some good plant-based sources. Zinc-rich foods include:
- 6 oysters (9mg)
- 80g cooked beef (6mg)
- 1 cup cooked mussels (4mg)
- ½ cup baked beans (2.9mg)
- 30g pumpkin seeds (2.2mg)
- ½ cup cooked chickpeas (1.3mg)
As zinc is also really important for our bones, a zinc deficiency can also impact our immune health as our bones are responsible for producing our white blood cells, which are an important aspect of our immune system.
Copper is another mineral that plays an important role in our immunity. Copper helps our immunes systems “soldiers” to work properly. These are the types of cells that go out and attack invaders, such as viruses or bacteria that will make us sick. Men need slightly more than women, 1.7mg per day as opposed to 1.2mg. Copper-rich food sources include:
- 1 medium potato, skin on (0.6mg)
- Shiitake mushrooms (0.6mg)
- 30g cashew nuts (0.6mg)
- ¼ cup Sunflower seeds (0.6mg)
- 30g dark chocolate (0.5mg)
- ½ large avocado (0.2mg)
- 1 cup cooked brown pasta (0.26mg)
- ½ cup cooked spinach (0.15mg)
Like zinc, selenium seems to play a role in specifically protecting against viruses. It also seems to be a key factor in improving the immune response to vaccines . In New Zealand, we have low selenium levels in our soil and so we must take care to ensure adequate selenium in our diet, especially with a focus on eating NZ grown produce. The average male needs slightly more than women, 70ug as opposed to 60ug daily.
- 1 x brazil nut (70ug)
- 100g sardines, canned (45ug)
- 80g beef steak, (30ug)
- 100g chicken breast, (22ug)
- 1 cup low fat cottage cheese (20ug)
- 1 cup cooked brown rice, (19ug)
- 1 large egg (15ug)
- 1 cup cooked lentils (6ug).
If you follow a plant-based diet, it’s especially important to include a daily portion of nuts or seeds and ensure that you have plenty of wholegrains within the diet such as brown rice, pasta, or bread, as they tend to have a higher mineral concentration than the refined versions.
Iron is a more well-known mineral, and for good reason. Among it’s many roles, it carries oxygen around the body, which is why when we have low iron stores we can find ourselves feeling tired. It also plays an interesting role in immunity. Where there is iron inadequacy, it seems to negatively impact immune function, as well as where iron is in excess, such as through over-supplementation. This reinforces the concept that iron supplementation should only be taken if iron stores have been checked and identified as low. With the help of a registered dietitian, most people can get enough iron through their diet. Due to menstruation, women of child-bearing age have higher requirements than men and post-menopausal women, 18mg compared to 8mg per day. High iron foods include:
- 80g cooked red meat (3mg)
- 100g cooked chicken or fish (1.3mg)
- 1 large egg (0.6mg)
- 1 tablespoon sesame seeds (1.6mg)
- ½ cup baked beans (2.5mg)
- Iron-fortified breakfast cereal. Check label for iron per serve.
While some plant-based foods are high iron, the body is not able to absorb it as well as iron from animal sources. If you are vegetarian or vegan, take extra care that you include iron-rich sources of food in your diet every day, and get your iron levels checked annually.
Overall, the key message is to ensure that the diet contains a wide variety of foods to ensure that you get enough of each nutrient. It's important to cook more often at home to avoid heavily processed or refined food, plan your meals, and take special care if you follow any sort of restrictive diet. Restrictive diets often cut out or heavily reduce certain foods which can increase your risk of nutrient deficiencies. Do not hesitate to consult a registered dietitian in NZ to help you develop meal and nutrition plan to help support a healthy immune system.
- Zinc, Nutrient References Values Australia and New Zealad. Sourced from https://www.nrv.gov.au/nutrients/zinc on 20/7//21.
- Kaushik, N., Subramani, C., Anang, S., Muthumohan, R., Shalimar, Nayak, B., ... & Surjit, M. (2017). Zinc salts block hepatitis E virus replication by inhibiting the activity of viral RNA-dependent RNA polymerase. Journal of virology, 91(21), e00754-17.
- International Zinc Nutrition Consultative Group (IZiNCG). Hotz C and Brown K eds. Assessment of the risk of zinc deficiency in populations and options for its control. Technical Document #1. Food and Nutrition Bulletin 2004;25: S99-S199.
- Ministry of Health. NZ Food: NZ people. Key results of the national nutrition survey. Wellington; Ministry of Health, 1999.
- Broome, C. S., McArdle, F., Kyle, J. A., Andrews, F., Lowe, N. M., Hart, C. A., ... & Jackson, M. J. (2004). An increase in selenium intake improves immune function and poliovirus handling in adults with marginal selenium status. The American journal of clinical nutrition, 80(1), 154-162.
- Thomson CD. Selenium and iodine intakes and status in New Zealand and Australia. Br J Nutr 2004a;91:661-72.
- Ahluwalia, N., Sun, J., Krause, D., Mastro, A., & Handte, G. (2004). Immune function is impaired in iron-deficient, homebound, older women. The American journal of clinical nutrition, 79(3), 516-521.
- Calder, P. C. (2020). Nutrition, immunity and COVID-19. BMJ Nutrition, Prevention & Health, 3(1), 74.
A Bit About Me…
I’m Nicole, a Registered Dietitian in Auckland, NZ. I provide online, after hours and weekend consultations to clients who want a dietitian for weight loss, heart disease, prediabetes or diabetes.
Also a qualified nutritionist, I ensure that the nutritional strategies for my clients are based on scientific evidence and so are guaranteed to achieve results. As an after hours dietitian and nutritionist, you can get quality advice in the comfort of your own home, or feel free to skip the traffic and take your consultation in a private room at your work.
My online dietitian services can be found by clicking on “Nutrition Services” on my website. If you are wanting a nutrition service that is not listed, please don’t hesitate to contact me. I do offer nutrition advice outside my stated specialties, or otherwise I can help you find a dietitian who is suited to your needs.