It’s no secret that a healthy, diverse plant-based diet can support a healthy immune system. And now, research is emerging on how this may impact COVID-19 (1,11).

A new paper, in the European Journal of Clinical Nutrition, highlights some recent studies in this area:

  • A large survey, of more than 592,000 UK- and US-based adults, found dietary patterns characterised by healthy plant foods were linked with a 9% lower risk of COVID-19 infection and a 41% lower risk of severe COVID-19 (2). And the results were especially strong for people living in areas of higher socioeconomic deprivation.
  • In another recent study, the dietary data from 568 COVID-19 cases and 2,316 controls, from healthcare workers across six countries (France, Germany, Italy, Spain, UK, USA) with substantial exposure to COVID-19 patients, showed that those following a plant-based diet had a 73% lower risk of moderate-to-severe COVID-19 (3).

Another study, published in 2022 in the journal Nutrients, looked at the link between diet and risk of COVID-19 in 95 healthy young people living in Poland (8).

Those with a history of COVID-19 consumed lower amounts of groats (a type of wholegrain), rice, fruit, vegetables, nuts and legumes. They also had a lower dietary intake of water, plant protein, dietary fiber, potassium, magnesium, iron, zinc, copper, vitamin E, thiamin, vitamin B6, and folate.

Among the findings, eating a balanced diet, with an average daily consumption of >500g of vegetables and fruit, and >10g of nuts, was linked with an 86% lower risk of COVID-19, compared with those whose diet was not balanced and who ate lower amounts of these foods.

Did you know? Internet searches for ‘immunity booster food’ increased by 350% between 2019 and 2020! (4)

What about certain nutrients and COVID-19?

While still an emerging area of research, some recent studies suggest low levels of vitamin D, vitamin C, vitamin A, zinc, selenium, copper and magnesium in COVID-19 patients are linked with prolonged hospital stay, increased mortality rate and greater COVID-19 complications (5,10).

Food sources of these nutrients (5,6):

Nutrient Food sources include:
Zinc Meat, seafood (oysters), poultry, cereals, nuts, legumes, dairy products, whole grains.
Vitamin D Cheese, liver, eggs, oily fish (salmon, tuna), mushrooms, fortified milks and margarines.
Vitamin C Fruits (citrus fruits, kiwifruit, berries), vegetables (capsicum, tomatoes, broccoli).
Magnesium Nuts, seeds, legumes, whole grains, green leafy vegetables, cereals, seafood, dairy products.
Selenium Seafood, liver, poultry, eggs, dairy products, nuts (Brazil nuts)
Copper Liver, seafood (oysters), nuts, seeds, wholegrains, legumes, green leafy vegetables.

How do nuts fit in?

Eating a nutrient-rich, plant-forward diet (in which nuts, along with vegetables, fruits, seeds, legumes, whole grains, fish and healthy fats, are front and centre) will help your immune system function at its best.

Nuts provide plant-based protein and gut-loving fibre, and contain 28 different vitamins and minerals, and antioxidants.

Through their nutrients – such as zinc, magnesium, copper and selenium – they support the healthy functioning of our immune system, an important weapon against COVID-19.

Did you know? When it comes to the powerful antioxidant selenium, Brazil nuts are a plant food stand-out! They contain 1,917ug/100g (or 575ug in a 30g handful). Just 2-3 Brazil nuts a day will meet 100% of the Recommended Dietary Intake (RDI) for selenium.

While all nuts contain immunity-supporting nutrients, here are the top three for zinc, magnesium and copper content:

Nutrient Top 3 tree nut sources Amount (mg)/100g Amount (mg)/30g handful Interesting facts: Did you know?*
Zinc Cashews Pine nuts Brazil nuts 5.5
5.3
4.1
1.7
1.6
1.2
Two tablespoons of pine nuts (30g) provide almost a quarter of the daily zinc target for women.
Magnesium Brazil nuts Almonds Cashews 350
266
250
105
80
75
A 30g handful of almonds (around 20 almonds) contains 80mg of magnesium – a quarter of what women need daily.    
Copper Brazil nuts Cashews Hazelnuts 2.0
1.9
1.5
0.6
0.6
0.5
A 30g handful of cashews (around 15 cashews) provides half the Adequate Intake (AI) of copper for women.

*Based on the Nutrient Reference Values for Australia and New Zealand. Zinc: RDI = 14mg/day (men); 8mg/day (women). Magnesium: RDI = 400mg/day (men, 19-30yr); 420mg/day (all other men); 310mg/day (women, 19-30yr); 320mg/day (all other women). Copper: AI = 1.7mg/day (men); 1.2mg/day (women)

Did you know? Studies suggest regularly eating nuts contributes to heart health, reduces the risk of developing type 2 diabetes, assists with weight management and reduces the risk of cancer.

Chronic conditions and COVID-19

COVID-19 deaths are much more common in people with chronic conditions, such as heart disease and type 2 diabetes (1). And research suggests the effectiveness of vaccines may be reduced in people with central obesity, hypertension, abnormal blood lipid levels, or who smoke (1). In turn, these conditions are strongly linked with diet and lifestyle.

Did you know? A recent study found that a 10% reduction in the prevalence of diet-related conditions, such as obesity and type 2 diabetes, could have prevented ∼11% of COVID-19 hospitalisations among US adults (7).

The bottom line:

A “magic bullet” for COVID-19 is unlikely (10). Instead, a combination of strategies is more likely to be effective – including evidence that healthy diets, adequate sleep, regular exercise, maintaining healthy weight, and time in nature may all help to reduce the risks associated with COVID-19 (10).

When it comes to what we eat, evidence is lacking that specific types of foods can protect against COVID-19. But some interesting recent studies suggest a role for nutrient-rich, plant-based dietary patterns (11), as well as certain nutrients, in lowering the risks linked with COVID-19.

Even in pre-pandemic times, many of us needed to boost our intake of healthy, plant-based core foods like nuts, seeds, whole grains, legumes, fruits and vegetables. So, a healthy, diverse, plant-based dietary pattern should always be a priority – including during the COVID-19 pandemic!

Although, to date, no studies have looked at the effect of plant-based diets on long COVID-19, some researchers have suggested they may be beneficial (9,10). This is due to the abundance of data showing positive association of plant-based diets with improved immune function, neurotransmitter balance, pain and inflammation reduction, improved sleep, and mental health (9,10).

References

  1. Kahleova, H., Barnard, N.D. Can a plant-based diet help mitigate Covid-19?. Eur J Clin Nutr, 2022. https://doi.org/10.1038/s41430-022-01082-w
  2. Merino, J., et al. Diet quality and risk and severity of COVID-19: A prospective cohort study. [Internet, June 2021]. Available at: https://www.medrxiv.org/content/10.1101/2021.06.24.21259283v1
  3. Kim, H., et al. Plant-based diets, pescatarian diets and COVID-19 severity: A population-based case-control study in six countries. BMJ Nutr Prev Health, 2021. 4:257–66. https://nutrition.bmj.com/content/4/1/257
  4. Rachul, C., et al. COVID-19 and “Immune Boosting” on the Internet: A content analysis of Google search results. BMJ Open, 2020. https://bmjopen.bmj.com/content/10/10/e040989
  5. Altooq, N., et al. The role of micronutrients in the management of COIVD-19 and optimizing vaccine efficacy. Human Nutrition & Metabolism, 2022. https://www.sciencedirect.com/science/article/pii/S2666149722000044
  6. National Health and Medical Research Council 2006, Nutrient Reference Values for Australia and New Zealand, Canberra: National Health and Medical Research Council. Available from: http://www.nrv.gov.au
  7. O’Hearn, M., et al. Coronavirus disease 2019 hospitalizations attributable to cardiometabolic conditions in the United States: A comparative risk assessment analysis. J Am Heart Assoc, 2021. https://www.ahajournals.org/doi/10.1161/JAHA.120.019259
  8. Jagielski, P., et al. Associations of nutritional behavior and gut microbiota with the risk of COVID-19 in healthy young adults in Poland. Nutrients, 2022. https://doi.org/10.3390/nu14020350
  9. Storz, MA. Lifestyle adjustments in long-COVID management: Potential benefits of plant-based diets. Curr Nutr Rep, 2021. 10(4):352-63.
  10. Campbell, J. COVID-19: Reducing the risk via diet and lifestyle. J Int Med, 2022. https://doi.org/10.1016/j.joim.2022.10.001
  11. Leno Durán, E., et al. Influence of diet in COVID-19 infection and severity risk: A systematic review. Nutricion Hospitalaria, 2023. DOI: 10.20960/nh.04448.
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