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In this post I’m going to talk about evidence-based herbal and nutraceutical strategies to improve your resilience to viral exposure, particularly to COVID-19 should you be exposed.
If you do a Google search on antiviral herbs you’ll find a lot out there. Much of the research has been done on viruses like influenza, rhinovirus and herpesviruses, but viruses of the coronavirus family aren’t as well-studied. For that reason I’m focusing first on herbs that have shown the most activity against viruses that look like COVID-19 and that have the most robust research supporting their use, then I’ll move on to other antivirals that haven’t been studied in the coronavirus family, but that have demonstrated broad-spectrum action against many other virus types. I’ll share some of the more compelling research with you, as well.
When a virus infects your body, the fight that goes down on a cellular level is a little bit like the opposing team’s play during a football game — you’re playing defense and the virus is playing offense. There are two general strategies in antiviral pharmacology, then: Weaken viral offense (this is how many HIV drugs work, for example), or strengthen your defense (by which I mean your immune response).
Most antiviral drugs on the market work by interfering with key offensive plays in the virus playbook: viral replication, viral attachment and internalization into a cell, and viral shedding. Most drugs were designed to work for one specific virus. On the other hand, most of the botanicals and nutraceuticals that have been studied work at least in part by strengthening your immune system’s defensive line, and most of the compounds I’ll talk about do both — they improve your defense and hinder the virus’ offense. For this reason almost all of these herbs have two-for-one action and can improve your resilience to invasion from many different kinds of pathogens, not just one. And now that I’ve reached the end of my knowledge of sports, let’s talk about science…
I use all of the supplements I’ll mention below in clinical practice, so I’ll give you some of my favorite brand recommendations as well (*I don’t work for any of these companies, I just like their stuff). Although everything I’ll mention is generally safe and well-tolerated, please check-in with your doctor before starting anything new. I don’t recommend any of the following in pregnancy.
Licorice is an antiviral, anti-inflammatory and an adaptogen and has been used in traditional Chinese medicine for literal centuries. The main compound shown to have antiviral activity is called Glycyrrhizin, but there are several other active substances in licorice that have been studied for their antiviral properties as well, making whole-root extracts a good choice.
My favorite study of all the research that I went through to prepare for this post was a 2003 study published in The Lancet (a big-deal medical journal). It was an in-vitro study that showed licorice root extract to be effective against SARS-related coronavirus. There have also been several robust studies in HIV, Respiratory Syncytial Virus, and herpes viruses, but its effect on a virus of the coronavirus family stood out to me the most.
I also like licorice because it’s an adaptogen and can support blood pressure and cortisol levels, both of which can drop in a severe viral infection. That being said, if you have high blood pressure you should use caution when taking licorice – monitor your blood pressure and talk to your doctor about it.
A good dose is 150-300 mg daily. I really like the licorice root extract from Orthomolecular (it’s a medical supplement company, so you have to get it from a practitioner).
Astragalus is my OG fave antiviral herb – both for preventing and speeding recovery from upper respiratory infections. It has a long history of use in traditional Chinese Medicine and was colloquially termed “the Long Life Root.” My friend Sam told me about it in med school and I’ve been using and recommending it ever since.
Astragalus has been well-studied in humans and animals, and there’s strong evidence for it’s efficacy as an anti-inflammatory, antioxidant and antiviral. A 2009 study showed that astragalus inhibited the secretion of viral particles from Hepatitis B more effectively than a pharmaceutical called Lamivudine. A 2016 study showed that Astragalus reduced inflammation-mediated cellular damage caused by exposure to a bacterial cell wall component called lipopolysaccharide.
My favorite way to take Astragalus is to make a tea from the loose roots. I keep a lot of dried astragalus root around and as soon as I feel myself getting sick I boil a handful or two in water for more than five minutes. I like to put some ginger slices and dried elderberries in there for extra antiviral action, too. I also like Herb Pharm’s liquid extract and Vital Nutrient’s capsules.
Beta-Glucans are natural biologically active compounds known to be “immunomodulators” or “biological response modifiers”. They are found in the cell walls of several organisms and in high concentrations in mushrooms like Maitake, Shiitake, Reishi, Agaricus, and Chaga.
The biological effects of beta-glucans are well established, including improvement of anti-infectious immunity, inhibition of cancer growth, reduction of stress, and reduction of cholesterol level. They promote the activity of T cells and macrophages, two crucial players of the immune system, which provide the first line of defense against foreign invaders, remove cellular debris and speed recovery of damaged tissue.
Beta-glucans have been well-studied for respiratory issues. A 2012 study showed beta-glucan supplements reduced upper respiratory symptoms and improved the mood state in psychologically stressed women. A 2015 study found that beta-glucans improved mucosal immunity in children with chronic respiratory issues.
Another 2015 study found that feeding Influenza infected mice with a beta-glucan mixture from mushrooms for 2 weeks resulted in stimulation of both cellular and humoral immune response, resulting in lower viral load, reduced viral effect and reduced total mortality.
I generally give beta-glucans in blends of immune-enhancing herbs, at doses around 300 mg twice per day, but you can go nuts on mushroom extracts since they’re food-based and very well-tolerated. I really like Four Sigmatic’s line of mushroom extracts for daily maintenance therapy.
Larch Arabinogalactan is a large molecule polysaccharide and soluble fiber, mainly derived from North American larch trees. Arabinogalactan stimulates Natural Killer cells – these guys are the special forces of the immune system, attacking virus-infected cells, cancer cells and other bad guys with military precision. Arabinogalactan has been shown to increase the production of short-chain fatty acids – the primary fuel source of beneficial bacteria found in the gut.
A 2013 clinical study in humans demonstrated that larch arabinogalactan increased defense against the common cold. Larch arabinogalactan decreased the incidence of cold infections by 23% and a reduction in severity of symptoms in those infected. This study stood out to me because some of the viruses that cause the common cold are of the Coronavirus family.
I tend to use larch arabinogalactan in immune blends, but I’ve seen ResistAid brand showing up in several studies if you want to get it by itself. Doses from 1.5 – 4.5 grams per day have been used in studies, with the most powerful effects from the higher doses. It’s very safe and well-tolerated, so I wouldn’t be concerned about taking more. It also shows up in several soluble fiber supplement blends.
Echinacea is an herb of the sunflower family that has been used for centuries in Native American medicine for its anti-inflammatory and antiviral properties. A large body of research demonstrates Echinacea’s ability to activate multiple aspects of immune function and its benefit for respiratory issues.
A double-blinded, placebo-controlled trial published in New England Journal of Medicine in 2005 showed that Echinacea was effective for treating the common cold caused by rhinovirus, and several studies have shown similar effects in other other upper respiratory infections. It was shown to inactivate bird flu and swine flu viruses in a 2009 study.
There are negative studies out there on the efficacy of Echinacea which is probably mostly due to differences in preparations of the supplements (there are several different species that are used in supplemental blends), but it’s worth a mention.
Take 300-500 mg up to three times daily. Preparations of Echinacea vary greatly in quality, so get a medical-grade supplement. I like Vital Nutrients brand.
Zinc is a mineral that has been well studied in the common cold, HIV, hepatitis C and as a general stimulator of viral immunity. A subset of common colds are caused by viruses of the coronavirus family, and the broad range of viruses studied makes Zinc applicable here.
Clinical trial data support the value of zinc in reducing the duration and severity of symptoms of the common cold when administered within 24 hours of the onset of common cold symptoms. The studies are numerous and mixed, but several good review articles can give you an overview of the copious studies on Zinc as an antiviral. Zinc both improves host response and impairs viral entry into the cell.
I prefer the Zinc Citrate form. I give 30 – 60 mg daily for acute viral illness and 15 – 30 mg daily for general immune support. I rarely give Zinc for longer than 8 weeks because it can cause imbalances with Copper. Take it with food if you get easily nauseated.
Selenium, like Zinc, is an immune-supporting mineral, and deficiency is associated with decreased immune function. Selenium is also necessary for glutathione production. The research on Selenium is extensive, so I’d recommend a review article or eBook if you want to read more about it.
If you’re going to take a supplement I recommend selenomethionine at 100 – 150 mcg per day. Another great way to get selenium is Brazil nuts. Two per day should do it. Long term selenium supplementation has been associated with higher rates of prostate cancer in men, so have your doctor follow your levels, favor food sources and only take it for a few months at a time.
N-acetylcysteine, or NAC is a potent antioxidant and a precursor to the detox molecule glutathione, which is found in abundance in the lungs and liver. It’s a relatively old drug and we use it for two very different things in the hospital setting: We nebulize it and give it as an inhaled mist for acute respiratory conditions for its powerful ability to dissolve mucus, and we give it in IV form for Tylenol overdose for its antioxidant capacity and help with liver detox.
A 1997 study published in European Respiratory Journal found that of subjects who became infected with Influenza, only 25% of those supplementing with NAC became symptomatic, compared to 79% percent in the placebo group. That’s a fancy way of saying that if you do have the bad luck to contract COVID-19 or another upper respiratory virus, NAC may help keep your symptoms mild or non-existent, and could prevent bronchitis-causing bacteria from taking up residence in the mucus in your respiratory tract.
You can get NAC in supplement form, and the NOW Foods brand is inexpensive and good. I dose it frequently due to its short halflife, 300 mg three times per day should be sufficient, but in acute illness I’d give higher doses, up to a gram three times daily. I’m careful not to give this supplement for longer than several months, because it has the potential to dissolve the necessary mucus in GI tract.
European Elderberry is a common home remedy for upper respiratory infections and in vitro studies have demonstrated antiviral, antibacterial, immunomodulatory, anti-inflammatory, antioxidant and antidiabetic properties. One small, randomized clinical trial found that taking elderberry extract orally significantly reduced symptoms of influenza A and B.
The effects are probably due to the high concentration of flavonoids found in Sambucus. Elderberry flavonoids were observed binding to viral particles of H1N1 (swine flu) and preventing its spread in a 2009 in vitro study.
Sambucus syrup is one of my top care-package items for friends who just came down with a cold. You can find it at most natural food markets. I also like to buy dried elderberries and keep them around for my astragalus brew.
Adequate vitamin D levels are crucial for host immunity. A 2010 study in Nature Immunology showed that the activation of immune cell learning (yes, they learn!) was dependent on vitamin D.
My favorite source of vitamin D is sunlight (30 minutes three times per week should do the trick) and pasture-raised egg yolks, but a close second is High Vitamin Cod Liver Oil. My longtime fave is Rosita brand. Have your doctor check your levels to keep them between 35 ang 60 ng/mL.
This might surprise you, but the research on Linus Pauling’s favorite old cold remedy is actually mixed, with most studies showing a modest effect on duration and severity of infection or no effect at all. This is probably an effect of variability and study design and poor absorption of most forms of the vitamin. This review article summarizes the results of several studies in Table 4.
Despite the mixed information, I’m still convinced by the positive evidence for vitamin C as an adjunct to an antiviral regimen, but make sure to take it in as absorbable a form as you can get. I prefer liposomal form at 500 mg to 1 gram per day.
The above are my top hitters, but if you just can’t get enough keep your eyes out for these herbs and compounds as well:
Transfer Factors are probably the most powerful antiviral intervention in this whole post, but I’m putting them in this section because they’re only made by one company, which only sells to doctors. Nevertheless, you should keep an eye out for them. They are small molecules that are native to the immune system and taking Transfer Factors from an animal that has been exposed to a disease is a way to passively transfer that animal’s learned immunity to you.
Derived from lauric acid, a component of coconut oil. Monolaurin is antiviral, antibacterial, anti-fungal AND anti-parasitic. If you’re one of my patients and you’ve had microbial issues, I’ve probably given you monolaurin. I generally give 600 mg twice or three times per day. Lauricidin is a great brand.
Mostly studied in cancer for its ability to increase Natural Killer cells (the Special Forces of the immune system), IP-6 also promotes metal chelation to prevent buildup of minerals that can weaken the immune system. Take it in a blend or alone up to several grams per day.
Antiviral and a literal chill-pill, Lemon Balm is most commonly used for relieving stress and anxiety. Take 300-1200 mg daily in tea or capsules, or 40-60 drops of tincture 1 to 3 times daily. I love Herb Pharm brand for any tincture.
Supports your immune system and mucus membranes, especially your lungs. I’d recommend against taking Beta-carotene. Instead try to get Vitamin A in its fat Soluble form. A great way is High Vitamin Cod Liver Oil. Rosita is my favorite brand.
An antiviral with a history of use for depression. Take 300-600 mg/day of products standardized to 0.3% hypericin and/or 3-5% hyperforin.
The microbiome colonizes the interface between our immune system and the outside world. A healthy immune system isn’t possible without a healthy microbiome. I recommend a broad-spectrum, medical-grade probiotic to anyone who’s concerned with immune health. The organisms I choose differ case-by-case, but some of my favorites are spore-based probiotics.
