When it comes to COVID-19, there seem to be a lot more questions than answers. But as we continue to learn about the pathophysiology of the virus, more research is coming out about how to combat and/or prevent it.
Researchers from an August 2020 study published in Science of the Total Environment are the first to look at beta-glucans, types of soluble fiber, and how they may be able to protect you from SARS-CoV-2, the virus that causes COVID-19.1
One of the major complications of COVID-19 is pneumonia, which is also accompanied by rapid replication of the virus. During this rapid replication, your immune system releases pro-inflammatory cytokines that lead to an overreaction of the immune response called cytokine storm. Cytokine storm can lead to lung injury, acute respiratory distress syndrome (ARDS) and death.
In this study, researchers took beta-glucans extract from a form of shiitake mushroom called Lentinus edodes and combined it with a lung injury model in vitro.
They found that beta-glucans reduced interleukin 1 beta and interleukin-6, two cytokines that can trigger the cytokine storm that causes ARDS in severe COVID-19 cases. The beta-glucans also reduced oxidative stress and activated immune substances called macrophages that destroy potential invaders like viruses.
According to other studies, beta-glucans also enhance the cell activity and function of natural killer (NK) cells,2 a type of white blood cell that plays a critical role in your innate immune system and acts as the first line of defense against viruses.3 Research shows NK cell count and function decrease considerably with COVID-19 infection, especially in those who become critically ill.4,5
Based on this information, researchers suggest that boosting innate immunity through things like beta-glucan supplementation may help mitigate COVID-19 infection and potentially flatten the curve.6
Beta-Glucans May Help Prevent Colds and the Flu
The research on beta-glucans and COVID-19 is promising, but since the virus is still new, there are only a limited number of studies available at this time. However, a number of studies have confirmed that beta-glucans offer powerful protection against other viral infections, such as the common cold and flu, which can result in similar immune responses. For example:
- A 2013 study found that taking 900 mg of beta-glucans in the form of brewer's yeast for 16 weeks reduced the rate of cold infections by 25% and eased symptoms in those who got ill by 15%.7
- Marathon runners who took 250 mg of beta-glucans containing brewer's yeast for 28 days following a marathon were 37% less likely to contract a cold or flu symptoms compared to those taking a placebo.8
- People who took 250 mg of beta-glucans per day for 90 days reported 43 fewer days with symptoms of upper respiratory tract infection compared to those taking a placebo.9
- A 2015 animal study found feeding mice beta-glucans for two weeks "significantly reduced the effects of influenza infection in total mortality."10 According to the authors, "these effects are caused by stimulation of both cellular and humoral immune reaction resulting in lower viral load."
Other Health Benefits of Beta-Glucans
In addition to helping combat COVID-19 and other viral illnesses, beta-glucans also come with a number of other health benefits, including the following:
• Improved insulin resistance — Beta-glucans have been shown to reduce post-meal glucose and insulin responses, improve insulin sensitivity in diabetic and nondiabetic individuals, and help with glycemic control.11 Although other types of soluble fiber have this effect as well, when compared to the others, smaller amounts of beta-glucans are required to achieve the same results.
• Improved microbial diversity in the gut — Beta-glucans may help promote the growth of beneficial bacteria in your gut by acting like a prebiotic. In one study, beta-glucans improved the growth rate of Lactobacillus plantarum in the gut in both unstressed and stressed conditions.
Perhaps most importantly, beta-glucans were able to protect the probiotics from gastrointestinal stress caused by low pH, bile salts and digestive enzymes, increasing their survival rate as they traveled through the digestive system.12
• Cancer prevention — Beta-glucans have been used as a cancer treatment in Japan since 1980.13 According to a 2007 report in Medicina, beta-glucans can prevent oncogenesis — the process in which healthy cells become cancer cells — by protecting against carcinogens that damage cellular DNA.
The report notes that beta-glucans have also shown to inhibit tumor growth by activating macrophages and NK cells. Beta-glucans also help reduce inflammation associated with cancer and fight against metastasis, cancer recurrence and tumor drug resistance.14
• Reduced appetite and weight loss — In a 2018 animal study in PLOS One, researchers divided mice into two groups. One group was fed a high-fat diet with beta-glucans, while the other was fed a high-fat diet with cellulose, another high-fiber carbohydrate, for 12 weeks.
After the test period, the mice given the beta-glucans had significantly less weight gain and fat mass compared to the cellulose group. They also had increased production of short-chain fatty acids, especially butyrate, and higher secretions of the gut hormones peptide YY and GLP-1, which help reduce appetite and improve insulin sensitivity.15
You can find beta-glucans in supplemental form, but, as always, it’s best to get this type of fiber from whole food sources16 such as mushrooms (Reishi, Shiitake, Maitake), baker’s yeast or seaweed. Certain grains such as oats, barley, sorghum, rye and rice also contain it.
Other Nutrients That Help Boost Immunity
While beta-glucans are important immunomodulators, there are several other nutrients that boost immunity too, including:
• Vitamin C — Vitamin C is a potent antioxidant and one of the most powerful nutrients involved in both the innate and adaptive immune system. The vitamin protects against oxidative stress, helps kill microbes and supports the epithelial barrier of your skin, which keeps pathogens from entering your body. Vitamin C also helps clear white blood cells from infection sites and helps decrease potential tissue damage.17
In one 2020 study published in Pulmonology, researchers looked at whether high-dose vitamin C administered intravenously could help treat critically ill COVID-19 patients.18 Fifty-four patients were divided into two groups. One group was given 12 grams of vitamin C every 12 hours for seven days and the other group was given a placebo.
Patients in the high-dose vitamin C group had lower levels of interleukin-6, a pro-inflammatory cytokine that’s one of the underlying contributors to cytokine storm, and saw a significant reduction in 28-day mortality.
As a general rule, I don't recommend high doses of vitamin C unless it's in liposomal form. I also don't recommend long-term or chronic high-dose vitamin C supplementation as this may cause nutritional imbalances. For example, taking large doses of vitamin C (ascorbic acid) on a regular basis lowers your level of copper, so if you are already deficient in copper and take high doses of vitamin C, you can actually compromise your immune system.
• Vitamin D — Vitamin D, which is produced in your skin in response to sun exposure, is a steroid hormone with powerful antimicrobial activity capable of fighting bacteria, viruses and fungi. The evidence is clear that the lower your vitamin D level, the higher your risk of contracting a cold or the flu.19
One scientific review confirmed vitamin D supplementation boosts immunity and cuts rates of cold and flu.20 The researchers believe vitamin D offers protection by increasing antimicrobial peptides in your lungs, and that "[t]his may be one reason why colds and flus are most common in the winter, when sunlight exposure (and therefore the body's natural vitamin D production) is at its lowest …”21
According to a 2020 report in The Lancet Diabetes & Endocrinology, vitamin D has been used to prevent or treat acute respiratory infections since the 1930s.22 Recently, similarities between the risk factors of vitamin D deficiency and risk factors for severe COVID-19 infection have led researchers to look at whether vitamin D supplementation could be beneficial for preventing or treating the novel virus.
In one Indonesian study, researchers found that the majority of severe COVID-19 cases with inadequate vitamin D levels or vitamin D inadequacy died, leading them to conclude that vitamin D status is strongly correlated with COVID-19 mortality.23
In another study published in Aging Clinical and Experimental Research, British researchers analyzed data from 20 different European countries, comparing rates of COVID-19 and mortality rates against the population’s average vitamin D level.24
They found countries like Spain and Italy that reported higher death rates also had higher levels of vitamin D deficiency in the population. Conversely, countries with lower rates of COVID-19 and mortality, like Sweden and Norway, also had lower rates of vitamin D deficiency.
• Zinc — Zinc affects several different parts of your immune system. The nutrient is critical for normal development and function of neutrophils, NK cells and macrophages. Zinc also functions as an antioxidant and helps prevent damage from free radicals during inflammation associated with viral illness.25
Zinc has also been shown to inhibit viral replication of RNA-dependent viruses, which include COVID-19, rhinoviruses (which cause common colds) and influenza. Because of this, researchers from a 2020 report in Medical Hypotheses state that it’s likely that zinc may be beneficial for preventing and treating COVID-19.26
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