Shiitake mushrooms are Asia’s tasty ‘superfood’ and traditional remedy, praised for immune-boosting effects. People are curious about natural products that might protect them against the new coronavirus — is shiitake one of them? Read on to find out.
This post is for informational purposes only. The current coronavirus outbreak is an ongoing event, and details may change as new information comes to light. No effective or FDA-approved products are yet available to treat or prevent COVID-19 infection.
Shiitake Mushrooms and Immunity
Shiitake is an edible mushroom from East Asia, praised for its nutritional and healing properties. It’s one of the pearls of traditional Chinese medicine. Folks mostly take it to boost immunity, longevity, circulation, and liver health [1, 2].
For ages, people have used medicinal mushrooms to enhance the immune response. Shiitake contains lentinan and other beta-glucans that support our defense mechanisms [3, 4].
In a study of 52 volunteers, consuming 5 or 10g of shiitake (L. edodes) [5]:
- Enhanced the activity of white blood cells
- Improved gut immunity
- Reduced inflammation (CRP levels)
Research on mice has confirmed the potential of shiitake mushrooms to support gut health and reverse age-related decline in the immune response [6, 7].
Besides beta-glucans, they are rich in other types of fiber that act as prebiotics and nurture our gut microbiome [8, 9].
Shiitake provides zinc and copper, the two minerals crucial for robust immunity [10, 11].
Scientists haven’t yet tested shiitake mushrooms against the new coronavirus (SARS-CoV-2 or COVID-19). A standardized mixture of polysaccharides from shiitake mushroom (AHCC) activated immune cells in humans and animals with viral infections such as [12]:
- Influenza B (in humans) [13]
- Hepatitis C (in humans) [14]
- Human Papillomavirus (in humans and mice) [15]
- Influenza A (H1N1) (in mice) [16, 17]
- Avian influenza virus (H5N1, in mice) [17]
- West Nile encephalitis (in mice) [18]
Another shiitake extract (Lentinus edodes mycelia or LEM) reduced the growth of the influenza A virus and increased survival rates in infected mice [19].
Influenza viruses cause flu, which can have similar respiratory complications as COVID-19 infection. However, the effects observed on these strains don’t imply the therapeutic potential of shiitake against the new coronavirus [20, 21].
Dosage & Safety Precautions
Side Effects
The most common side effect that usually occurs from consuming raw or undercooked shiitake is “shiitake dermatitis” — a characteristic skin irritation sometimes followed by fever and digestive issues [22, 23, 24].
The first signs appear 24 hours upon consumption and may be worsened by sun exposure. In most cases, cooking removes its potential to cause reactions [25, 26, 27].
Dosage
Because the FDA hasn’t approved shiitake supplements for any condition, there is no official dose. Users and supplement manufacturers have established unofficial doses based on trial and error.
When using shiitake as a food, a standard portion is 15g dried mushrooms (4 pieces). That would equal about 150g of raw mushrooms.
There are no official doses for shiitake supplements, but manufacturers suggest using 1-2g of dry extract daily (10-20g powdered mushrooms) or 1-2 ml of liquid extract (20-40 drops).
In healthy volunteers, 5-10g of shiitake daily was sufficient to enhance their immunity [5].
Takeaway
Shiitake is an edible mushroom from East Asia, praised for its nutritional and immune-enhancing properties. Studies have confirmed its potential to boost the immune response to various infections and cancer.
Shiitake may inhibit certain respiratory viruses that have similar complications such as the new coronavirus. However, no studies have examined the effects of shiitake on the new coronavirus.
There’s no available evidence to support their use for COVID-19 infection treatment or prevention. While researchers work to identify potential treatments, the best protective measures you can take are social distancing, hand washing, and avoiding touching your face.
The most common side effect of shiitake mushrooms is so-called shiitake dermatitis, but cooking the mushrooms greatly reduces the risk. Supplements are available as liquid extracts, dry extracts, and powders. Speak with a healthcare professional before supplementing.
