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Nutritional Immunology Toolkit

This frequently updated resource is a full list of vitamins & other nutrients helpful for Long COVID recovery for both you and your doctor’s use.


‘Nutritional immunology’ is a new and rapidly developing field of science examining the impact of foods and nutritional components on systemic immune function. (Ref: J Sun. Editorial: Immunomodulatory Functions of Nutritional Ingredients in Health and Disease. Frontiers in Immunology, Jan 2019)

These foods and concentrated nutrients can help in different ways to support your immune system and support recovery from Long COVID, depending on what your requirements are and what your starting point is. Examples include; vitamins, minerals, plant extracts (also known as botanicals or herbals), amino acids, omega 3’s, enzymes, synbiotics, and other specialised nutrients. 

There is a substantial evidence base to support the efficacy of these nutrients both individually and collectively. Under each nutrient below, we have listed relevant scientific references - just click on the phrase ‘Scientific References’ to access.

IMPORTANT NOTICE: This article is designed to be informational but it should not be considered medical advice. If you are currently under medical supervision please always check with your doctor, physician or healthcare professional.

A resource for you and your healthcare professional.

This page is designed to be a toolkit that you and your doctor or healthcare professional can access as a resource.  

We have listed both the food sources and supplement options for each nutrient. We also give dosage guidance tailored specifically for Long COVID, which you can access by clicking on the button titled ‘Recommended supplement intake’. 

All inclusions are evidence based using peer reviewed scientific sources and were short-listed after a review of over 2000 scientific papers. This list is being added to continuously as we receive new information regularly from medical and patient-led groups.

Please note: You will not necessarily need to consume each nutrient, as in many cases some overlap in function. Check with your doctor and/or healthcare professional to work together to devise a tailored plan specific to your needs. Or, to get started faster, see our top suggestions here: Long COVID Supplements.

Long COVID Supplements

Updates: We update and add to this list regularly. If you do try any of these suggestions, or if you have a suggestion for something that has worked for you, please remember to let us know with the button below that states “Suggestions or Amendments”.

Content reviewed and updated: 

28 March 2023 (BST)


Zinc is vital for immune system function as it helps cells in the immune system grow and differentiate. An abundance of evidence has accumulated over the past 50 years to demonstrate the antiviral activity of zinc against a variety of viruses, making it one of the best natural mineral antivirals and is very safe to use. Zinc Picolinate is the best absorbed and most likely to improve blood levels of Zinc over a longer period (other forms of Zinc stay in the body for less than 24 hours).

Food Sources: Oysters, beans, lentils, nuts, seeds, tofu and beef.

Vitamin D

Vitamin D is arguably one of the most important vitamins our bodies need and is very different to the other vitamins, in that it is actually a steroid hormone. It is essential for immune system function and health, for example affecting the activity and number of white blood cells. Vitamin D deficiency, which many people suffer from, can negatively affect immune function. As a ‘master’ hormone, it affects the actions of other hormones in the body. Increased vitamin D blood levels have been seen to improve outcomes from COVID-19 infection. Sublingual intake (oral drops or spray) work well.

Food Sources: Fatty fish, eggs, fortified milk and plant milk products, cheese, tofu and mushrooms.

NAC (N-Acetyl Cysteine)

N-acetyl cysteine (NAC) is a supplement form of cysteine, a semi-essential amino acid, which plays a very important role in antioxidant production, helping protect the body’s cells against damage. It also helps to replenish glutathione, the ‘master antioxidant’ that is naturally produced by the body.

Food Sources: Cysteine can be found in foods with high levels of protein such as chicken, turkey, yogurt, cheese, eggs, sunflower seeds and legumes.

Glutathione (GSH)

This antioxidant is produced naturally in the body’s cells. It helps reduce oxidative stress which will help the body fight against factors that can cause damage to cells. It is known as the ‘master antioxidant’ as it can ‘recycle’ other antioxidants, such as vitamin C, E, etc. Glutathione also ‘fine-tunes’ the immune response to infection, acting as a modulator and inhibitor of inflammation, including that of the lungs.

Food Sources: Broccoli, cauliflower, brussels sprouts, garlic and onions, eggs, nuts, legumes, lean protein, such as fish, and chicken.

Coenzyme Q10 (CoQ10)

CoQ10 is a compound that is naturally produced in the body which helps energise your cells. CoQ10 has a wide range of health benefits such as improving heart function by increasing ATP production and limiting oxidative damage. For Long COVID it seems to help improve energy levels but not necessarily reduce heart palpitations. 

Food Sources: Organ meats (heart, liver and kidney), pork, beef, chicken, fatty fish, spinach, cauliflower, broccoli, oranges, strawberries, soybeans, lentils and peanuts, sesame seeds and pistachio nuts.

Magnesium (Citrate or Bisglycinate)

Arguably the most important essential mineral, magnesium plays a very important part in contributing towards both your brain and body health. For example, magnesium has anti-inflammatory benefits, can help lower blood pressure, improve heart health, help with energy creation, protein formation, muscle movements, bowel movements and it is good for lowering tension and provides nervous system regulation. Also, taking magnesium with other supplements and medications help them to work better. For many with Long COVID who experience constipation, magnesium is a convenient solution.

Food Sources: Pumpkin seeds, spinach, swiss chard, dark chocolate, black beans, quinoa, halibut, almonds, cashews, mackerel, avocado, and salmon.

Fish Oil

Fish oil is one of the most popular types of food supplements as it has many health benefits as a result of being very high in omega-3. The main omega-3s in fish oil are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) which are good for both heart and brain health - especially for those with brain disorders or heart conditions. EPA and DHA also give rise to newly discovered ‘resolvins’ which are anti-inflammatory. However, the patient and practitioner feedback we’ve collated indicates that taking significant levels of fish oil supplements for up to 30 days did not significantly reduce any particular Long COVID symptoms. There is however some evidence that taking fish oil supplements can lower the risk of testing positive for SARS-CoV-2.


Melatonin is a naturally produced hormone that plays a large part in regulating your sleep-wake cycle. Melatonin can be increased by improving levels of tryptophan, an amino acid that can be found in many foods and supplements. By improving melatonin levels you can improve your sleep cycle. (Please note that melatonin supplements cannot be sold in the UK due to Department of Health regulations, however, you can get this nutrient with a prescription from your doctor). Despite being initially very popular in various patient-led groups at the end of 2020 for Long COVID, our understanding is that beyond improving the onset and depth of sleep, it does not appear to directly address Long COVID issues such as breathlessness, fatigue or heart palpitations. 

Food Sources: There are a variety of foods that research has shown can help increase melatonin levels naturally, such as tart cherries (or cherry juice), goji berries, eggs, milk, oily fish, and nuts (pistachios and almonds in particular).


Taurine is an amino acid that occurs naturally in the body. It provides a variety of important health benefits, such as supporting the healthy function of your brain, eyes, heart and muscles. It is also known to help the brain and body relax and can improve the quality of sleep. Another important function of taurine is the detoxification of xenobiotics (defined as any foreign substances or exogenous chemicals which the body does not recognize, such as drugs or pollutants), it can also protect the liver. Taurine is often associated with the energy drink Redbull, despite not being a stimulant at all. There are also various urban myths that it is produced from bulls, which are not true.

Food Sources: The best food sources of taurine are meat, fish and dairy. If you are vegetarian/vegan, some plant-based foods do contain added taurine, although you may also want to consider taking food supplements containing taurine in order to receive sufficient quantities.

Vitamin K2

Studies have shown that vitamin K2 has anti-inflammatory effects. It also has antioxidant properties, thus protecting cellular membranes from damage. Taking vitamin K2 also helps protect against high levels of calcium in the blood if taking larger doses of vitamin D over a longer period. Hence, vitamin K2 is often combined with vitamin D3 or D2.

Food Sources: Sauerkraut, dairy products (especially hard cheeses), liver, beef, pork, egg yolks, chicken, and fatty fish (such as salmon).

Vitamin C

Vitamin C is vital for immune health. It increases the production of white blood cells that fight off infections and may reduce the duration of cold symptoms. Whilst it does not appear to directly alleviate Long COVID symptoms dramatically, many patient groups have indicated they felt an improvement in overall health with additional vitamin C supplementation. 

Food Sources: Fruit and veg: oranges, strawberries, bell peppers, broccoli, brussels sprouts, cauliflower, spinach, asparagus, kiwi fruit, citrus fruit, watercress and pineapple.


Selenium is an essential mineral that plays a significant role in bodily processes, such as metabolism and thyroid function, and is well recognised for its antioxidant and anti-inflammatory effects. It is an important cofactor for the production of glutathione which is very helpful for reducing lung inflammation. 

Food Sources: Pork, beef, turkey, chicken, fish, shellfish, eggs, wholegrains, and dairy products, including milk and yogurt. Some beans and nuts, especially Brazil nuts, also contain selenium.

Vitamin A

Beta carotene is converted into vitamin A, which is essential for a good immune system. Examples include imprinting T and B cells with gut-homing specificity and array T cells and IgA+ into intestinal tissues. It also supports the intestinal immune response, thus supporting the gut barrier. It helps antibodies respond to foreign substances and toxins and acts as an anti-inflammatory agent. It also regulates the number and function of NK cells. 

Food Sources: Cheese, eggs, oily fish, fortified low-fat spreads, milk and yoghurt, liver and liver products such as liver pâté. Sources for beta-carotene are yellow, red and green (leafy) vegetables, such as spinach, carrots, sweet potatoes and red peppers. Also yellow fruit, such as mango, papaya and apricots.

Vitamin E

Vitamin E is a highly effective nutrient known to modulate immune function. Supplementing vitamin E has been shown to enhance the function of the immune system and reduce the risk of infection. Examples of functionality include; protecting cell membranes from damage caused by free radicals and supporting the integrity of epithelial barriers, maintaining or enhancing NK cell cytotoxic activity and hindering the chain reaction induced by free radicals, protecting cells against harm.

Food Sources: Nuts and seeds, wheatgerm (found in cereals and cereal products), and plant oils such as soya, corn and olive oil.


Polyphenols are micronutrients which are thought to improve or help treat digestion issues, weight management difficulties, diabetes, neurodegenerative disease, and cardiovascular diseases. A large number of scientific publications suggest immunomodulatory and anti-inflammatory properties of these compounds as well as expression and activity of enzymes involved in the generation of nitric oxide (NO).

Food Sources: Cloves, cocoa powder and dark chocolate, highbush blueberries, blackberries, strawberries, raspberries, black currants, plums, sweet cherries, apples, beans, hazelnuts, walnuts, almonds, pecans, artichokes, chicory, red onions, spinach, and soy.

Epigallocatechin gallate (EGCG)

EGCG is a type of plant-based compound called catechin with various health benefits, such as reducing inflammation, helping weight loss, and preventing heart and brain disease. It has also been shown to have antibacterial and antiviral effects against pathogenic viruses. 

Food Sources: Green tea, cranberries, strawberries, blackberries, kiwis, cherries, pears, peaches, apples, avocados, pecans, pistachios, and hazelnuts.


Quercetin is a plant pigment which has antiviral, antioxidant and anti-inflammatory effects, and it can help reduce platelet aggregation (reduce clotting) and lipid peroxidation, control blood sugar, and may help prevent heart disease. 

Food Sources: Apples, honey, raspberries, onions, red grapes, cherries, citrus fruits, and green leafy vegetables.

L. Acidophilus

Lactobacillus acidophilus is a live culture which builds up your gut health, thus supporting the immune system. Good gut health (ie. the ‘microbiome’) is generally closely connected with good immune health.

L. acidophilus is well known and studied and is very safe to consume. It can inhibit the growth of pathogenic bacteria, in terms of reducing allergies and reducing the effects of colds and influenza-like symptoms. For those with MCAS (Mast Cell Activation Syndrome) L. acidophilus has been found from patient-led groups to NOT be a histamine-producing strain (it is a 'histamine neutral strain') and therefore should be fine for anyone with histamine issues to take.

Food Sources: Manufacturers add L. acidophilus to yogurt and many other dairy products, check the label to see if it contains the words, “live culture” or “active”. It also occurs naturally in a range of fermented and pickled foods, including kombucha, some cottage cheese, kefir, sauerkraut, miso, and tempeh.


Prebiotics have been defined as “non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or the activity of one or a limited number of bacterial species already resident in the colon, and thus attempting to improve host health”. Intake of prebiotics can significantly influence colonic microbiota by increasing the number of specific bacteria and thus changing the composition of the microbiota. Nondigestible oligosaccharides in general, and fructooligosaccharides (FOS) in particular, are prebiotics. 

Food Sources: chicory root, garlic, onion, asparagus, banana, artichoke, leeks. Other examples of prebiotics are; polyphenols (such as Quercetin and EGCG), barley, oats, apples, cocoa, konjac, and seaweed.

Astragalus Root

Astragalus is a herb that has been used in TCM (Traditional Chinese Medicine) for centuries. It has many purported health benefits, including antiviral, immune modulation, anti-inflammatory and antiallergic properties. Within the TCM framework, astragalus is used to treat a wide variety of ailments, such as fatigue, allergies, the common cold, heart disease and diabetes.

Ginger Root

Ginger belongs to the Zingiberaceae family, and it’s closely related to turmeric, cardamom, and galangal. Ginger has a very long history of use in various forms of traditional and alternative medicine, with gingerol being the main bioactive compound in ginger. Ginger exerts (in vitro) antioxidative, antitumorigenic and immunomodulatory effects and is an effective antimicrobial and antiviral agent.

Interestingly for Long COVID, ginger has antiviral activity specifically against human respiratory tract cell lines. Ginger also has antioxidant and anti-inflammatory compounds and can help reduce nausea and some forms of pain.

Liquorice Root

Liquorice root, which is considered one of the world’s oldest herbal remedies, comes from the root of the liquorice plant (Glycyrrhiza glabra). Historical sources for the use of Glycyrrhiza species include ancient manuscripts from China, India and Greece. They all mention its use for symptoms of viral respiratory tract infections and hepatitis. In TCM (Traditional Chinese Medicine), liquorice is rarely prescribed by itself, it is almost always given to the patient with an adjunct, for example paired with astragalus.

Liquorice contains many substances that can be helpful for Long COVID, as they have immunomodulatory, antiallergic, antiviral, antimicrobial and anti-inflammatory activities. As an example, a letter to ‘The Lancet’ from Prof J Cinatl PhD, of the Institute of Medical Virology, Frankfurt University Medical School, indicated that “of all the compounds, glycyrrhizin was the most active in inhibiting replication of the SARS-associated virus”. Additionally, in vivo, glycyrrhizin downregulated inflammation in human lung cell lines. 

Vitamin B3 - Niacin (nicotinic acid, nicotinamide / niacinamide)

There are various forms of Niacin available and it can get confusing knowing the differences between them. The main form used by many Long COVID patients is Vitamin B3 - Niacin (nicotinic acid), which is also identified as being the “flushing kind” as it causes flushing (reddening) of the face and upper body. For some it can also cause tingling, burning, or itching of skin and chills and/or upset stomach. 

The other kind of Niacin is the “non-flushing” kind, known as Vitamin B3 - Niacin (nicotinamide or niacinamide). This form works in a different way and does not cause flushing. However, many in the Long COVID patient community prefer the flushing kind as that was the form recommended by Dr Wentzel in the blog post by Alexandrov (see references below for link).

Reishi Mushroom

Medicinal mushrooms can have immune-enhancing properties. In particular, the reishi mushroom contains molecules that can increase the activity of a type of white blood cell called natural killer cells which fight infections in the body. Reishi mushrooms also exhibit antiviral, antibacterial properties, and interestingly are able to regulate the immune system as required. For example allergic reactions and autoimmune disease call for a down-regulation of the immune system. 

Alpha Lipoic Acid (ALA)

ALA is an extremely powerful antioxidant, and it protects your body’s cells against damage. It is a special compound in that it helps recycle glutathione, the “master antioxidant” that is naturally produced by the body.

Food Sources: Red meats, organ meats (liver, heart, kidney, etc.), broccoli, spinach, tomatoes, Brussels sprouts, potatoes, green peas, and rice bran.

Vitamin B2 (Riboflavin)

B vitamins aid in the conversion of food into energy. In addition, vitamin B2 (also known as riboflavin) has a key role in maintaining many aspects of your health. For instance, it has been shown to host resistance to bacterial infections. B2 is also an important cofactor for glutathione production in the body.

Food Sources: Milk, eggs, fortified breakfast cereals, oats, cooked beef, mushrooms, plain fat-free yoghurt, and rice.


Copper is an essential mineral that plays an important role in the making of red blood cells and maintaining nerve cells, healthy bones, and blood vessels. In the immune system it has a role in functions of macrophages, neutrophils and monocytes and enhances NK cell activity. It also contributes to iron absorption.

Food Sources: Oysters and other shellfish, whole grains, beans, potatoes, yeast, dark leafy greens, cocoa, dried fruits, black pepper, organ meats (such as kidneys and liver), and nuts (such as cashews and almonds).


Manganese is needed for the activity of a range of enzymatic proteins including glutamine synthase and arginase. Such enzymes are expressed ubiquitously in immune cells. Experimental animal studies suggest that even marginal manganese deficiencies could limit immunological function. 

Food Sources: Tea, bread, nuts, cereals, and green vegetables (such as peas and runner beans).

Piper Nigrum Extract (PNE)

PNE has been reported to have antioxidant, anti-bacterial, anti-mutagenic, anti-diabetic, and anti-inflammatory properties. Dietary piperine has been reported to stimulate digestive enzymes of the pancreas, reduce gastrointestinal transit, protect against oxidative damage by neutralising free radicals and reduce lipid peroxidation. It is an important bioactive compound that has been found to improve the bioavailability of certain nutrients, phytochemicals, and certain therapeutic drugs when co-administered. It is often included with supplements to increase bioavailability. 

Food Sources: Black Pepper.


Curcumin is a yellow-pigment substance and component of turmeric (Curcuma longa), which was identified more than a century ago. It is a natural anti-inflammatory agent that has been used for treating medical conditions for many years.

It has been suggested that curcumin could provide protection against the adverse vascular effects of the proinflammatory response and provide a novel strategy to prevent cytokine-induced endothelial dysfunction. There is also a growing body of evidence that curcumin provides endothelial protective effects.

Food Sources: Turmeric (the raw turmeric spice contains around 3% curcumin, compared to 95% curcumin in extracts).


Iron is an essential mineral. It is crucial for red blood cell formation and oxygen transport and is essential for differentiation and growth of epithelial tissue (epithelial cells line both internal surfaces and external surfaces of the body). It is also a component of enzymes critical for functioning of immune cells and is involved in regulation of cytokine production and action.

Food Sources: Lean beef, oysters, chicken, turkey, beans and lentils, tofu, baked potatoes, cashews, dark green leafy vegetables such as spinach, fortified breakfast cereals, whole-grain and enriched breads.

Vitamin B6

Vitamin B6 has antioxidant and anti-inflammatory properties. It plays a role in modulating your immunity and also helps maintain a healthy sleep cycle as it is involved in producing melatonin (the sleep-promoting hormone). A deficiency in vitamin B6 can result in the decreased production of antibodies, which fight infections. B6 also maintains or enhances NK cell cytotoxic activity, and helps to regulate inflammation (higher levels of the active form result in lower rates of inflammation).

Food Sources: Pork, chicken, turkey, fish, bread, wholegrain cereals, such as oatmeal, brown rice, eggs, vegetables, soya beans, peanuts, milk, potatoes, and some fortified breakfast cereals.

Vitamin B9 - Folate (Folic Acid)

Vitamin B9 has a crucial effect on the immune response, so inadequate levels of this vitamin can have a dramatic effect on your immune system. Vitamin B9 is required for the survival of regulatory T cells, which play a central role in the immune system and is important for antibody production and metabolism.

Food Sources: Broccoli, brussels sprouts, liver (but avoid this during pregnancy), leafy green vegetables, such as cabbage and spinach, peas, chickpeas, and breakfast cereals fortified with folic acid.

Vitamin B12

Vitamin B12 has an important role in the production of white blood cells, which are essential for the proper functioning of the immune system, and is important for antibody production and metabolism, via folate (Vitamin B9) mechanism.

Food Sources: Meat, salmon, cod, milk, cheese, eggs, and some fortified breakfast cereals.

Choline Bitartrate

Adequate levels of choline are associated with a normal, healthy relationship between the immune system and the inflammatory response. Choline is required to make certain phospholipids, which are essential components of all membranes and it has also been shown to support normal liver function. Given the fact that certain viruses replicate in the liver, coupled with the fact that choline shortfalls could result in liver dysfunction, choline could have an important role to play in COVID-19 and Long COVID patients. 

Much attention has been given to the effect of supplemental choline upon brain function, i.e., enhancement of acetylcholine synthesis, which can in some cases improve ‘brain fog’ (diminished cognitive function) symptoms. 

Food Sources: Beef liver, chicken liver, eggs, cod, salmon, cauliflower, broccoli, and soybean oil.

Ashwagandha Root

Ashwagandha (Withania Somnifera) is an adaptogenic herb that has been shown to reduce inflammation. It supports the activity of immune cells that fight infection and help you stay healthy, whilst also supporting a positive mood as a result of it’s anti-anxiety functions. Ashwagandha is a herb traditionally used in Indian Ayurvedic medicine and is known as a “rejuvenator” and used as a Rasayana (tonic). It has been reported to facilitate energy levels, mitochondrial health and exert anxiolytic (reducing anxiety) and anti-inflammatory effects.


Bromelain is an proteolytic enzyme, extracted from pineapples that has been found to possess many health-improving properties, such as anti-inflammatory, antithrombotic, fibrinolytic and immunomodulatory effects, in addition to being a wound healing and circulatory improvement agent. In particular, proteolytic enzymes help break down and digest protein.  

Food Sources: Pineapple.

Cinnamon Extract

Cinnamon is a spice extracted from cinnamon tree (Cinnamomum) bark and has been used for its culinary and medicinal properties since ancient times. A review of ethnobotanical and pharmacological properties of Cinnamomum reported that its plant extract appeared to possess antiviral, antibacterial, anti-inflammatory and immunomodulatory properties, amongst others. 

Animal and lab studies show it may reduce blood sugar spikes, increase insulin sensitivity and improve metabolic markers associated with insulin resistance. Cassia cinnamon contains higher levels of coumarin (whose derivatives are blood thinners such as warfarin) compared to Ceylon cinnamon.

Phosphatidylserine (PS) & Phosphatidylcholine (PC)

Phosphatidylserine is a fatty substance produced in the body that covers and protects every cell (membrane) in the body. Some with Long COVID found that PS helped with their brain function and energy levels. However, some complained of increased fatigue on the first day of taking PS. Another option is phosphatidylcholine which has the benefit of providing liver support via the addition of choline.

Food Sources: The main food source of phosphatidylserine is soy, and it can also be found in white beans, egg yolks, chicken liver, and beef liver. It is however difficult to absorb from food sources, which is why you may wish to consider taking it in supplement form. Phosphatidylcholine is available from foods such as eggs, red meat, and whole grains.


Creatine is a natural substance that plays an important role by increasing energy production in the mitochondria, by virtue of influencing adenosine triphosphate (ATP) buffering. It is possibly the most popular supplement used in athletics and has been shown to be beneficial in disease-induced muscle atrophy, improving rehabilitation. (Note: creatine can also cause water retention, which may also lead to temporary weight gain).

Food Sources: Animal products like meat, fish and eggs.