Written by Heather Deering, Associate Registered Nutritionist. Reviewed by Harriet Smith, Registered Dietitian
We are now several months into the coronavirus pandemic. Although work is underway to find an effective vaccine, many people’s thoughts have turned to optimising their own health and immunity.
It goes without saying, the best way to protect ourselves from coronavirus is to follow government guidance regarding social distancing and hand hygiene (1). However, having a healthy, balanced diet will support our immune system, helping us to stay safe and well.
In this article we’ll discuss how nutrition can play an important part in ensuring your immune system is as robust as possible.
Food and immunity – what’s the link?
Nutritional status is known to play an important role in immunity. Both malnutrition and obesity can negatively impact our immune response, and studies have shown that micronutrient deficiencies can result in decreased immunity (2).
As we’ll see in the sections below, there is some limited evidence to suggest that specific vitamins and minerals have immune-related benefits. The good news is that most people can get all of the nutrients they need by eating a healthy diet.
Achieving balance and variety in our diet is key as it means that our bodies are supplied with a wide range of vitamins and minerals that contribute to optimal immunity. For most healthy individuals, nutrition supplementation is unnecessary (although there is one exception to this – vitamin D).
Vitalise your body with vitamin C
Vitamin C is an essential micronutrient that has many important functions in the body, including immune benefits (3). Vitamin C is found in many foods, particularly fruits and vegetables. Foods that are especially high in vitamin C include:
· Oranges and orange juice
· Strawberries
· Red and green peppers
· Broccoli
· Potatoes
· Brussels sprouts
Although many people believe that taking high doses ocould have a protective effect against the common cold, a large-scale review of high-quality human studies found that vitamin C didn’t have a big effect on the incidence, duration, or severity of colds (4). It’s easy to get the recommended 40mg/day of vitamin C from eating a large orange or a couple of kiwi fruits. So save your money and get your vitamin C from food instead of supplements.
Don’t forget about Zinc!
Zinc is an essential nutrient for growth and development of cells as well as immunity (5). Good sources of zinc include:
· Red meat
· Poultry
· Shellfish – oysters, crab, lobster
· Cheese
· Wholegrains
· Legumes
A systematic review of the effects of zinc supplementation on the common cold found that though it wasn’t able to prevent a cold, if taken within 24 hours of the onset of symptoms, zinc did have a small effect on reducing its severity and duration (6).
It’s important to remember that beneficial effects of zinc on the common cold don’t translate to protective effects against other diseases like coronavirus. Most people can get enough zinc from eating a healthy and balanced diet.
What about the sunshine vitamin (vitamin D)?
Vitamin D is a key nutrient for healthy bones and muscles, and it’s also important for immunity (7). Known as the “sunshine vitamin”, vitamin D is found in relatively few foods (i.e. oily fish, fortified cereals and spreads), so we rely on exposure to sunlight as our main source. However, in winter months we get less sun exposure, so in the UK, supplementation with 10 micrograms per day is recommended from October to March (8).
Recently, vitamin D has received a lot of attention in relation to coronavirus and respiratory disease. Some studies suggest that vitamin D deficiency may be associated with increased risk of respiratory disease (i.e. pneumonia) (9). Data on vitamin D status is also beginning to emerge in coronavirus patients, however, it’s important to note that this data is very new and has not been critically reviewed.
Several of these new studies have found an association between high death tolls from coronavirus and vitamin D deficiency (10, 11, 12). Although interesting, these types of observational studies do not prove that vitamin D status affects prevention, treatment or outcomes relating to coronavirus. Nor does it mean that everyone should start taking high doses of vitamin D.
However, it makes sense that we should ensure an adequate intake of vitamin D through a combination of diet, sunshine exposure, and supplementation. The British Dietetic Association website recommends that people who are self-isolating or unable to go outside should consider taking a daily supplement containing 10 micrograms of vitamin D to ensure a healthy vitamin D status.
What about gut health and immunity?
Some preliminary research is beginning to emerge suggesting a link between gut health and coronavirus. One study found that a specific profile of gut bacteria could predict who is likely to become seriously unwell with COVID-19 despite being otherwise healthy (13). Additionally, COVID-19 patients who reported symptoms related to the poor gut health (such as diarrhoea and nausea) were found to have worse outcomes (14). However, it’s important to note that optimising your gut health through diet won’t prevent or treat coronavirus.
One of the best ways to maintain a healthy and diverse gut microbiome is through eating a diet which is high in fibre. Prebiotic foods (such as onion, garlic and leeks) should also feature regularly in your diet. Prebiotics are types of dietary fibre that help the friendly bacteria in your gut to flourish.
And finally…
As mentioned earlier, the best way to protect yourself against coronavirus is by following government and public health advice. However, you can optimise your immune system by following a healthy and well-planned diet.
It’s not just about our diets – try to ensure that you’re taking care of all aspects of your lifestyle. Aim to get enough sleep, drink plenty of water, exercise regularly, and manage your stress effectively, as these elements can also impact on our health and immunity. If you’re having problems sleeping, you might be interested in our blog post on 5 tips to get a better night’s sleep.
Finally, if you need support with achieving a balanced and varied diet, look no further than Reset Your Health – an online nutrition plan, based on an algorithm, which is personalised to your dietary and medical needs.
References
1. Coronavirus (COVID-19): what you need to do [Internet]. GOV.UK. 2020 [cited 10 May 2020]. Available from: https://www.gov.uk/coronavirus
2. Chandra R. Nutrition and the immune system: an introduction. The American Journal of Clinical Nutrition. 1997;66(2):460S-463S.
3. Chambial S, Dwivedi S, Shukla K, John P, Sharma P. Vitamin C in Disease Prevention and Cure: An Overview. Indian Journal of Clinical Biochemistry. 2013;28(4):314-328.
4. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews. 2013.
5. Roohani N, Hurrell R, Kelishadi R, Schulin R. Zinc and its importance for human health: An integrative review. J Res Med Sci. 2013;18(2):144-157.
6. Singh M, Das R. Zinc for the common cold. Cochrane Database of Systematic Reviews. 2011;16(2).
7. Nair R, Maseeh A. Vitamin D: The “sunshine” vitamin. Journal of pharmacology and pharmacotherapeutics. 2012;3(2):118-126.
8. PHE publishes new advice on vitamin D [Internet]. GOV.UK. 2020 [cited 10 May 2020]. Available from: https://www.gov.uk/government/news/phe-publishes-new-advice-on-vitamin-d
9. Zhou YF, Luo BA, Qin LL. The association between vitamin D deficiency and community-acquired pneumonia: A meta-analysis of observational studies. Medicine (Baltimore). 2019. Available from: https://www.ncbi.nlm.nih.gov/pubmed/31567995
10. Alipio, M. (2020). Vitamin D Supplementation Could Possibly Improve Clinical Outcomes of Patients Infected with Coronavirus-2019 (COVID-2019). Available from: https://ssrn.com/abstract=3571484
11. Daneshkhah A, Agrawal V, Eshein A, Subramanian H, Roy H, Backman V. The Possible Role of Vitamin D in Suppressing Cytokine Storm and Associated Mortality in COVID-19 Patients. 2020.
12. Rhodes JM, Subramanian S, Laird E, Kenny RA. Editorial: low population mortality from COVID-19 in countries south of latitude 35 degrees North supports vitamin D as a factor determining severity. 2020. Available from: https://onlinelibrary.wiley.com/doi/epdf/10.1111/apt.15777
13. Gou W, Fu Y, Yue L, Chen G, Cai X, Shuai M et al. Gut microbiota may underlie the predisposition of healthy individuals to COVID-19. 2020;.
14. Pan L, Mu M, Yang P, Sun Y, Wang R, Yan J et al. Clinical Characteristics of COVID-19 Patients With Digestive Symptoms in Hubei, China. The American Journal of Gastroenterology. 2020;115(5):766-773.