Can nutrition and lifestyle improve your resistance to COVID-19?

By Dr Malcolm Mackay

The COVID-19 pandemic response from our health authorities and political leaders fails to address the measures we can take to improve our immune response should we contract the virus. This is a missed opportunity to promote healthy lifestyle behaviours at a teachable moment.

The effect of nutrition & lifestyle on your immune response to COVID-19

This is a recording of a free webinar we presented on August 4, 2020 to an audience of 50 people whilst our city (Melbourne, Australia) was under stage 4 lockdown following a second wave of Covid-19 cases

The Covid-19 virus is new to the human population so most of us are susceptible to infection if we are exposed. However, the severity of the infection varies greatly from asymptomatic to fatal in a manner that is not random. Most Covid-19 deaths have been in the elderly and middle aged adults in poor health – there have been very few deaths in non-obese healthy adults. The presence of chronic disease is well documented as a risk factor for more severe infection, but undiagnosed disease processes – insulin resistance, inflammation, unhealthy arteries – are under-recognised, as is sub-optimal nutrition and shortfalls in other areas of healthy lifestyle behaviours. Artery disease is ubiquitous and begins at an early age in countries where people eat significant amounts of animal products or processed foods – most middle aged Australian men and almost all men and women over age 70yr have advanced artery disease whether or not they have been diagnosed with heart disease.

We have been looking at the research around immune response to Covid-19 and other viruses and the role nutrition and lifestyle play in this, as well as listening to presentations by authors we trust, and the information is empowering – there are actions you can take to give yourself the best chance of a quick recovery from a Covid-19 infection.

A healthy immune system needs a healthy body

The immune system is distributed throughout the body and a healthy immune system can only exist in a healthy body. The Covid-19 pandemic has shown us that unhealthy bodies are less able to cope with infection. A state of chronic disease reduces our body’s reserve capacity to keep functioning under the stress of serious infection and impairs the immune response to infection. Having a chronic disease diagnosis – hypertension, diabetes, obesity, heart disease etc – increases the chances of a more severe Covid-19 infection (Richardson et. al 2020; Simonnet et. al 2020). However, the underlying mechanisms of chronic disease – inflammation, artery endothelial function, blood glucose etc – are dynamic and modifiable with nutrition and lifestyle changes.

Chronic disease is therefore a modifiable risk factor for severe COVID-19: Whole foods, plant-based nutrition – a dietary pattern centred around whole grains, legumes, vegetables and fruit – starts working immediately, improving those disease mechanisms with every meal, effectively reversing chronic medical conditions behind the scenes. Up front, reversing obesity may seem a futile short term action to take during the Covid pandemic as it will take many months for significant weight reduction, but rest assured that some of the underlying metabolic disturbances and therefore risk of Covid complications will improve within days of transition to whole foods, plant-based diet. It’s never too late to wind back the timeline of chronic disease progression.

A ‘well-regulated’ immune system

The immune system is tightly regulated with many checks and balances. We need a ‘well-regulated’ immune system rather than a ‘strong’ immune system. A hyperactive immune system can cause a runaway inflammatory reaction to infection – an excessive inflammatory immune response can be as dangerous as an inadequate response. A well-regulated immune system needs a healthy body with low levels of inflammatory foods (animal products, processed foods) and generous amounts of anti-inflammatory foods – whole plant foods. It’s not “boost” your immune system, it’s “support” it to do its job.

The health of the immune system begins in the gut: 70% of our immune cells reside in the gut, where they receive signals from the gut microbiome. The short chain fatty acids (SFAs) that ‘good’ microbes make from dietary fibre and resistant starch help keep immune cells well-regulated, ready for duty but not hyperactive. SFA’s regulate immune response and selectively recruit the CD8 immune cells that fight viruses in lungs. Animal products, processed foods and high fat diets support the growth of ‘bad’ microbes and disrupt the gut barrier, leading to dysregulation of immune cells. A change in diet can flip the microbiome profile within 3 days (see David et al 2014) so what you eat every day counts. High fibre starchy foods are the feedstock for a healthy gut microbiome. See also our section on Gut Health.

Whole plants provide all the nutrients we need for immune health: Nutrient deficiencies from not eating enough whole plant foods can impair the immune system but supplementing nutrients beyond our needs does not improve resistance to infection. The evidence is equivocal for any benefit, even for vitamin C (see Hemila & Chalker 2013) and of little relevance to whole food plant-based adherents, who are hopefully eating a diet rich in foods that provide vitamin C as well as phytonutrients that augment its function. Whole plant foods, when eaten in abundance, provide an optimal balance of iron, zinc and other nutrients with few exceptions – a Vitamin B12 supplement is recommended for everyone and vitamin D for those lacking adequate sunlight exposure.

Plants provide a ‘symphony’ of phytonutrients: In addition to the nutrients that are essential for life, whole plant foods provide thousands of phytonutrients that are essential for good health. Phytonutrients enhance our physiology at all levels, from DNA expression to sports performance. Plants, and the products that our gut microbiome makes from plants, regulates immune cells, reduce inflammation and protect against oxidative stress. Supplements cannot simulate this complex symphony and may throw it out of balance and worsen our health. There is a large body of research detailing specific food components and their effects on immunity, often funded by food and supplement industries. You can find some of these at However, the WHOLE is more important than the individual parts, and the safest approach is to just eat a variety of whole plant foods every day.

A whole foods, plant-based diet has a wide breadth of effect: A high carbohydrate, whole foods, plant-based diet benefits nearly every aspect of our health and is effective in the prevention and management of most chronic diseases: it seems to be the right fuel for the human body. Breadth of effect is apparent in T. Colin Campbell’s research into chronic hepatitis B and liver cancer. More plant-based diets are associated with both a decrease in cancer risk plus an improved immune response – more antibodies against hepatitis B and lower numbers of virus particles.

Fruit and vegetables support the immune system: An adequate fruit and vegetable intake boosts antibody response to infection or immunisation. Healthy 65-85yr subjects had significantly higher antibody response to pneumonia vaccine when they increased their fruit and veg intake from 2 or less serves per day (average 1.4) to 5 per day for several months (Gibson, et al 2012). The fruit and vegetable intake of these ‘healthy’ subjects may seem unusually low but the reality is that 95% of Australians fail to meet the recommended minimum intake of 7 serves per day. It also raises the question of what the media and healthcare community mean when they report an adverse health outcome in a ‘healthy’ person.

COVID-19, endothelial cells and inflammation

The risk factors for severe infections and death are more aligned with vascular risk factors than lung conditions such as asthma. The virus may enter the body through the lungs but can then spread to infect other tissues including the endothelium, the tile-like endothelial cells that line our arteries. The lungs themselves are a meshwork of fine blood vessels around air spaces and vulnerable to vascular damage. A report in The Lancet (Varga, et al 2020) suggests that the virus does not only attack the lungs, it attacks the blood vessels everywhere starving other organs of blood supply. This may explain why it is the people with the most impaired endothelium – smoking, diabetes, heart disease, obesity – that are most vulnerable to severe COVID-19 infection. The reported increase in strokes and thrombosis associated with COVID infection may be caused by infected endothelium becoming damaged and inflamed and losing its non-stick, anti-blood clotting qualities. Damage to blood vessels may explain how Covid-19 infection causes permanent damage to the brain and other organs.

The good news is that we know how to enhance endothelial health through nutrition and lifestyle, and quickly. Studies of forearm blood flow show that a single fatty meal of animal products or vegetable oil can damage the endothelium and impair blood flow for several hours. Red meat, chicken, fish, eggs and dairy have many components that cause damage to the endothelium – inflammatory fats and cholesterol, oxidative stress, TMAO and endotoxins. Fried food, salt, oil and sugar also cause damage to the endothelium. Replacing animal based foods and processed foods with whole plant foods helps the endothelium to heal and increases blood flow. Studies by Esselstyn and Ornish demonstrated improved blood flow to the heart and reduced angina within three weeks of dietary transition. See also our section on Endothelium and Heart Health.

The beneficial effects that whole plant foods have on endothelial function are as much due to the phytonutrients they provide as they are to the absence of harmful components. Whole plant foods protect against oxidative damage, provide substrates for nitric oxide production and downregulate inflammation. The powerful anti-inflammatory properties of many whole plant foods is highly relevant to COVID-19 because it is the immune system’s excessive inflammatory reaction to the virus infection that causes a lot of the damage. Animal-based foods increase baseline inflammation – even a single meal can cause a measurable increase in cytokine inflammatory signalling in the blood. Not a good baseline for COVID-19 patients who develop the so called ‘cytokine storm’ of inflammation.

Nitric oxide inhibits replication of coronavirus: Research on COVID-19’s predecessor, SARS-CoV, demonstrated that nitric oxide (NO) generated by inducible nitric oxide synthase, an enzyme that produces NO, inhibits the replication of the virus by at least two mechanisms (Akerstrom, et al. 2009). This is the same enzyme that endothelial cells use to produce the nitric oxide that plays a central role in keeping arteries healthy. What is good for endothelial NO production is probably good for lung cell NO production. Eating whole plant foods, particularly green leafy vegetables, enhances the production of NO. See also our page on Hypertension.

If you get the virus, what foods you should eat?

If you are not already eating this way, changing to a whole foods plant-based diet may help even after the virus has struck. However your appetite may be suppressed during a flu-like illness. If you are able to eat it would seem a good bet to include green leafy vegetables several times per day to enhance endothelial function and suppress inflammation. Dr Baxter Montgomery has reported success (in The Exam Room Podcast – interview starts at 28m 30s) with treating hospitalised COVID patients with green smoothies. A small amount of whole grains and legumes – perhaps in a soup – may  provide the carbohydrates you need to maintain energy as well as providing the fuel for the gut microbiome to produce short chain fatty acids for their immune regulating and other health benefits. Adequate hydration is also particularly important.

Beyond nutrition – lifestyle and immune health

Nutrition will get us most of the way to excellent health but to truly thrive we need to engage all the foundations of health: nutrition, physical activity, sleep, good stress/bad stress, psychological well-being and positive social interactions. There is good reason to assume that moving towards optimising all aspects of health behaviour will also have a positive effect on our ability to withstand and overcome a COVID infection. There has never been a better time for healthier lifestyle practices.

Physical activity leads to improvements in the underlying mechanisms of health and disease, reduces the chance of getting a chronic disease and improves outcomes. Exercise enhances immune system function. A 2011 study found that a single bout of moderate exercise enhanced circulating immune cells and antibodies (Nieman 2011). Participants in the 12-15wk program of near daily moderate exercise reported 25-30% less upper respiratory infections. However, extreme bouts of exercise and chronic overtraining can suppress immune function – not something that most of us need to worry about.

Adequate sleep is important for immune health. Inadequate sleep, sleep apnoea and shift work are associated with chronic diseases including hypertension, insulin resistance, weight gain and poor mental health. Even short-term sleep deprivation may impair the immune response to an infection or vaccine. A study of young ‘healthy’ men found that restricting sleep to only 4hr per night for several days before an influenza vaccine halved their antibody response in the first 10 days after the vaccine, a critical period if it were a live viral infection (Spiegel, et al 2002).

Alcohol is an immunosuppressive drug: There is no truly safe level of intake for alcohol. Alcohol depletes nutrients and antioxidants. Alcohol suppresses the immune system. The COVID-19 pandemic is a good time for a no alcohol challenge or at least reducing intake to small amounts infrequently. See our page on Alcohol.

Smoking – quit for the duration of the pandemic: COVID-19 adds urgency to the quit smoking message. Smoking causes damage to both the airways and the blood vessels and may, in part, account for the disproportionate number of males dying of COVID -19. It’s never too late to quit smoking even if it’s just for the duration of the pandemic.

Mental health during lockdown: Stress, depression and social isolation adversely impact physical health as well as mental health. Many people report lapses in healthy plant-based eating under these conditions. This is a time when we may need to be proactive about our mental health. Everything we do to support a healthy body supports a healthy mind. Social isolation can be mitigated through video meet-ups, telephone calls and in-person interactions when safe and permitted. Maintaining a regular daily routine of meals and sleep will help your physical health as well as your mental health. Catastrophising over COVID is not helpful. Make time to switch off the media, destress and engage in your usual hobbies and interests or take the opportunity to learn something new. Many people find meditation, mindfulness practices and yoga helpful. When we focus on what we can do, rather than that which is beyond our control, we replace anxiety with empowerment.

There’s never been a better time to make healthy lifestyle changes

Nutrition and lifestyle can make a huge difference to the way your body responds to an infection. However, we have respect for this novel coronavirus and the havoc it can wreak within our bodies – our approach is to be humble about the virus and it’s unknowns, whilst giving people hope that there is much you can do to take control of your health. Even if you are already plant-based, there’s never been a better time to make healthy lifestyle changes. Our 7-day Plant-Based Nutrition & Healthy Lifestyle Immersion Retreat can help you kickstart these changes or our 10-week online lifestyle medicine program. Or check out our shorter 4-part webinar series based on our ‘Power of Plant-Based Nutrition’ one-day seminar – see Plant-Based Nutrition Webinar Series

Please note: The main author of this page is Dr Malcolm Mackay, a GP from Melbourne, with editorial assistance from nutritionist Jenny Cameron. Dr Mackay is available for telehealth consultations for anyone within Australia. If you wish to work with a lifestyle medicine practitioner to improve or reverse your chronic disease please contact Dr Mackay via this link: Book a telehealth consultation with Dr Mackay

NB there is no Medicare rebate for GP telehealth consultations unless you have seen the GP face to face within the last 12 months or are currently in COVID-19 isolation or quarantine because of a State or Territory public health order (e.g. within 7 days of testing positive for covid, or are isolating as a household contact).


Peer reviewed articles

Page created 1 May 2020
Page last updated 25 August 2020