Nutrition and COVID-19
Nutrition is important at the best of times and essential at the worst of times. There are evidence-based nutrition and lifestyle strategies that already exist to promote a healthy immune system, but not when it comes specifically to preventing and alleviating symptoms of COVID-19. This article will summarize the research that has been done so far with nutrition and COVID-19, and it will focus on what you can do to support a healthy immune system, including reducing inflammation that can potentially increase the risk of infection and more severe symptoms. Outlandish, unvalidated claims (pseudoscience) have also emerged during the pandemic, and this article will serve to debunk those myths.
Nutrition and Lifestyle
Scientists suspect that inflammation can increase the risk of severe COVID-19 and are continuing to investigate whether an anti-inflammatory dietary approach can help to support the immune system.
The most well studied anti-inflammatory diet is the Mediterranean diet, which is high in vegetables, fruits, legumes, olive oil, whole grains, and nuts; moderate in fermented dairy products, fish, poultry, and wine; and low in ultra-processed foods and red meat. The Western diet, on the other hand, is considered to be pro-inflammatory and can lead to a low-grade inflammation state.1 It is high in processed foods, refined grains, red meat, saturated fat, and sugar. High blood sugar can lead to inflammation and it is associated with high mortality in people with severe COVID-19 infection.2 There is no harm in following a Mediterranean-style diet, so please consider giving it a try. This could be as simple as eating roasted vegetables with extra virgin olive oil for dinner, or a heart-warming vegetable soup topped with toasted pumpkin seeds for lunch.
People who are malnourished and/or immunocompromised are more susceptible to severe COVID-19 complications.1 This includes older adults, those taking medications that affect their immune system, and those with chronic inflammatory diseases, such as diabetes. There have also been associations identified with adiposity(fat)-based chronic disease (ABCD), such as obesity, that show these individuals could be at a higher risk for infection and worse outcomes.3 If you are living with obesity, adhering to a whole food diet and limiting processed foods can be helpful in reducing inflammation. Enjoyable and easy to follow regular exercise, which does not need to be vigorous, can also contribute positively.
Eating a healthy, balanced diet with enough calories, protein, fibre, and nutrients, is key to restoring and maintaining a healthy immune system, especially in these populations. Now is not the time to go on any low-calorie crash diets, as a decrease in caloric intake weakens the immune system. The goal here is to eat enough, even if that means complementing your diet with nutritional supplements and/or smoothies that are high in calories and protein.
The World Health Organization (WHO) provides up-to-date recommendations for maintaining a healthy lifestyle during the pandemic.4 Eating a balanced diet, getting enough sleep, being physically active, and reducing and managing stress are highly recommended to maintain your immune system. Please refer to the WHO resource “Food and Nutrition Tips during Self-Quarantine” for up-to-date recommendations.
Vitamin D
There is only weak evidence to support taking vitamin D for COVID-19, but some experts are recommending supplementation, given its key role in reducing inflammation. This is also because people get less sun in the winter months, and now we are spending even more time housebound due to physical distancing protocols. Some populations at higher risk of vitamin D deficiency include the elderly, infants younger than 5 years of age, those who are pregnant or breastfeeding, those who live in northern regions of Canada, and those with dark skin Taking a vitamin D supplement of 2,000 IU/day is likely safe, and you should consult with your doctor if you have low vitamin D levels as you’ll need to take more than that.5
Vitamin C
There is only weak evidence for taking vitamin C for COVID-19, and the recommendations for high doses of vitamin C given intravenously (IV) were based on observational studies.6 Vitamin C use in patients with COVID-19 infection of various severities or use of intravenous (IV) vitamin C in hospitalized patients did not reduce symptoms or time to recovery when compared to those receiving no vitamin C.7 Some experts suggest eating more fruits and vegetables to get vitamin C, and/or taking supplementation of 200-2,000 mg/day orally, for COVID-19.4,1 Go cautiously, as very high doses of oral vitamin C (>5,000 mg) can cause gastrointestinal side effects, such as nausea.
Zinc
Zinc plays a key role in the development of immune cells, and some experts suggest that supplementation of 30-50 mg/day might help control RNA viruses such as coronaviruses.8 However, zinc has not been shown in well controlled studies to prevent COVID-19 infection or improve recovery, and IV zinc also has not been demonstrated to help with hospitalized patients. Studies are lacking and further research is needed. Foods rich in zinc include nuts, seeds, legumes, meat, and dairy.
Fish and Fish Oils
Fish and high-quality fish oils contain anti-inflammatory omega-3 fats. Eating 2-4 servings of fish per week has been associated with a reduction in all-cause mortality,9 but it is still not clear at this time if it will help in any way against COVID-19.1 There has been some theorizing and studies around omega-3 fats and reducing the duration of symptoms, improving survival rates as well as decreasing the risk of kidney and lung complications. This may be related to the potential benefits of omega-3 fats in having anti-inflammatory, immunomodulating, and even some antiviral effects.10
Gastrointestinal Tract and Fibre
The virus that causes COVID-19 can affect the gastrointestinal (GI) tract as well as the respiratory system. Potential GI symptoms include loss of appetite, nausea, vomiting, diarrhea, and abdominal pain.11 Fibre, some types of which are prebiotic, helps to promote a healthy microbiome, feed beneficial gut bacteria, and maintain gut barrier function. Studies have shown that fibre lowers the incidence of bacterial translocation across the gut, which may help reduce infection and enhance the immune system.12 It is not yet known if fibre protects against COVID-19, but it is still an excellent idea to continue eating the recommended 25-38 g of fibre per day. Foods rich in fibre include vegetables, fruits, legumes, nuts, seeds, and whole grains.
Probiotics
There is currently no reliable evidence that probiotics can help cure or prevent COVID-19. China’s National Commission did advocate for the use of probiotics for patients with severe COVID-19,8 however, we need good quality evidence before this claim can be made. The WHO does not recommend the use of probiotics for COVID-19 at the time of writing this article.3
For those who experience diarrhea as a symptom of COVID-19, there are observational studies reporting probiotics may shorten the duration of diarrhea. Research is ongoing and for now, the use of probiotics in COVID-19 remains a personal choice.13
Adaptogens
Adaptogens, such as ashwagandha and astragalus, have risen in popularity since the pandemic started. They are herbal products used in Ayurvedic medicine and might help mitigate stress. As of October 2020, evidence for use of adaptogens and COVID-19 is lacking, and they are also not safe for everybody to take. For example, people with thyroid disorders should not take ashwagandha as it may stimulate the production of thyroid hormones, which can complicate these conditions.14 In addition, there is concern that ashwagandha may cause fetal harm when taken during pregnancy. In general, it is best to avoid using adaptogens for COVID-19 prevention and treatment since the risks may outweigh the benefits in certain populations.
Pseudoscience
The internet has a plethora of false claims for potential COVID-19 prevention strategies and treatments that evidence does not support. Some of these are even harmful. This includes tips to take hot baths and/or drink water every 15 minutes. Products containing colloidal silver are unsafe and could cause serious side effects, and should be avoided.15 Oleander extract is a chemical taken from a flowering shrub that has been promoted as a potential treatment for COVID-19. It is poisonous and it is not safe to take even in tiny amounts. Toxic effects include vomiting, respiratory paralysis, heart problems, and death.16 Be cautious and verify the sources of information on any product that claims to help treat COVID-19, as charlatans are taking advantage of pandemic fears to make money from promoting baseless, and even harmful, claims.
Summary
| Nutrition and Lifestyle Strategies | Recommended? |
| Mediterranean diet | might help |
| Western diet | no |
| healthy balanced diet | might help |
| low-calorie diet | no |
| sleep (8 hours/day) | might help |
| regular physical activity | might help |
| vitamin D | might help
consider taking 2,000 IU/day orally |
| vitamin C | might help
consider taking 200-2,000 mg/day orally |
| zinc | might help
consider taking 30-50 mg/day orally |
| fish oil | not enough data |
| fibre (25-38 g/day) | might help |
| probiotics | not enough data |
| adaptogens | not enough data
avoid ashwagandha if thyroid disorder |
| taking hot baths | no |
| drinking water every 15 minutes | no |
| colloidal silver | no
unsafe |
| oleander extract | no
unsafe |
Conclusion
There is no single food or supplement that will prevent or treat COVID-19, but there are nutrition and lifestyle strategies that will promote and maintain a healthy immune system and reduce inflammation. Still, it is a good idea to take vitamin D supplementation, especially if you are working at home or are under self-quarantine and have less sun exposure. Vitamin C and zinc also look promising, and research is underway. Now is not the time to go on any crash diets to cause you to lose weight, as not eating enough calories will dampen your immune response. Stay healthy and focus on what you can do.