Shiitake mushrooms are Asia’s tasty ‘superfood’ and traditional remedy. People use them to boost their immunity, longevity, liver health, and more. Modern science confirms their immune-stimulating effects but brings up notable limitations. Read on to learn the potential benefits of shiitake and how to add them to your diet.
What are Shiitake Mushrooms?
Synonyms: sawtooth oak mushroom, black forest mushroom, oakwood mushroom, golden oak mushroom.
Asia’s Tasty Superfood
Chinese and Japanese people have praised this tasty “superfood” for ages, both as a culinary ingredient and a traditional remedy. They still have the biggest share in worldwide production, but more and more growers in the US produce shiitake [1].
Shiitake is the second most popular edible mushroom in the world, available in various forms as a food or supplement.
Did you know? The US authorities didn’t allow the cultivation of shiitake mushrooms before the 80s. Supposedly, they feared that the mushrooms would “escape” into wild forests and harm the trees.
Traditional & Modern Uses
Shiitake is one of the pearls of traditional Chinese medicine. Other eastern countries, such as Japan, Korea, and Russa, have also used it as a natural remedy for ages. Folks mostly take it to boost immunity, longevity, circulation, and liver health [2].
This mushroom is popular in modern medicine, alike. Scientists are researching its potential to combat HIV/AIDS, heart disease, cancer, chronic infections, and more. People also use it as a mouth rinse to maintain oral health [3, 4].
What does the available evidence say about the traditional & modern uses of shiitake? How should we take it, and is it safe for everyone? Let’s find out.
Snapshot
PROPONENTS:
- Boost immunity
- May support heart health
- May improve oral health
- May support cancer treatment
- Have antimicrobial effects
SKEPTICS:
- Not well researched in humans
- May cause skin irritation
- May interact with immunosuppressants
- Supplements have unknown potency and purity
Active Compounds
Shiitake mushrooms are rich in bioactive compounds such as polysaccharides, sterols, and terpenoids. They stimulate the immune response, have antioxidant and anti-inflammatory effects, and more. The amount of these compounds depends on the growth and storage conditions [2].
Lentinan is a type of beta-glucan with immune-boosting, anti-cancer, and anti-microbial properties. Ergothioneine, a sulfurous amino acid, combats inflammation and oxidative stress [5, 6, 7, 8].
Spores (mycelia) of shiitake mushrooms are rich in anti-inflammatory molecules that protect the liver [9].
Shiitake Mushrooms Nutrition & Calories
Shiitakes are a low-calorie food rich in fiber, vitamins, and minerals. Four dried mushrooms (15 g) contain [10]:
Macronutrients and Calories
- Calories: 44
- Carbs: 11 g
- Protein: 1.5 g
- Fiber: 2 g
Vitamins and Minerals
- Riboflavin (B2): 0.19 mg (15% DV)
- Niacin (B3): 2.12 mg (13% DV)
- Pantothenic acid (B5): 3.12 mg (66% DV)
- Copper (Cu): 0.77 mg (86% DV)
- Selenium (Se): 6.9 mcg (13% DV)
- Zinc (Zn): 1.15 mg (10% DV)
- Vitamin D: variable
They’re an excellent source of fiber, copper, selenium, and vitamin B5, among others.
Mushrooms are the only plant-based source of vitamin D, but its content depends on UV/sunlight exposure during growth. UV-enhanced shiitake provides a decent amount of vitamin D, which is crucial for immunity, bone health, and more [11, 12].
That said, mushrooms contain vitamin D2 (ergocalciferol), which our bodies can’t use as well as vitamin D3 (cholecalciferol) [13, 14].
Shiitake mushrooms contain zinc, vitamin D, and all essential amino acids, which makes them a great food choice for vegans and vegetarians.
Health Benefits of Shiitake Mushrooms
Insufficient Evidence for:
The following potential benefits are only supported by low-quality clinical studies and preclinical research. There is insufficient evidence to support the use of shiitake for any of the below-listed conditions. Speak with your doctor before supplementing.
1) Immune System Support
For ages, people have used medicinal mushrooms, including shiitake, to boost their immunity. Shiitake contains lentinan and other beta-glucans that support our defense mechanisms [5, 15].
In a study of 52 volunteers, consuming 5 or 10g of shiitake (L. edodes) [16]:
- 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 [17, 18].
Besides beta-glucans, they are rich in other types of fiber that act as prebiotics and nurture our gut microbiome [19, 20].
Shiitake provides zinc and copper, the two minerals crucial for robust immunity [21, 22].
2) Heart Health
Shiitake has a range of heart-friendly components, including sterols, beta-glucans, and eritadenine. They can protect blood vessels from inflammation and lower cholesterol levels [23, 24, 25, 26].
As a side benefit, these mushrooms are high in dietary fiber and low in sodium and fat [10].
In multiple studies on rats and mice, supplementation with shiitake and its components was able to [27, 28, 29, 30]:
- Reduce cholesterol, triglycerides, and blood pressure
- Improve weight control
- Protect the blood vessels from atherosclerosis
3) Oral Health
Gum Inflammation
Gum inflammation or gingivitis occurs due to the buildup of bacteria on the gums. If untreated, it can lead to a more severe condition known as periodontitis [31].
In two lab models, shiitake mushroom extract prevented the growth of harmful bacteria that cause gum inflammation. Unlike a popular mouthwash ingredient, chlorhexidine, it didn’t harm the beneficial bacteria [32, 33].
Tooth Plaque and Decay
Tooth plaque or caries is the first step toward tooth decay. It forms as a consequence of bacterial infections (Streptococcus mutans) that impair the pH value and other protective factors [34].
According to a review of preclinical studies, shiitake may prevent tooth plaque formation by protecting the enamel surface and inhibiting harmful microbes such as S. mutans [35].
In a study of 65 volunteers, a mouthwash with shiitake extract suppressed the harmful bacteria but was inferior to a standard mouth rinse in reducing tooth plaque [36].
4) Cancer Treatment Support
The findings discussed below stem from preliminary clinical and preclinical research. They should guide further investigation but shouldn’t be interpreted as supportive of the anti-cancer effects until more research is done. Shiitake mushroom extracts are not proven to prevent or treat cancer.
Lentinan and other polysaccharides from shiitake mushrooms can stimulate the immune response and suppress the growth of cancer cells [37, 38, 39, 40].
When added to standard treatment, the extract of shiitake mycelia improved the quality of life and immune function in 47 patients with breast cancer [41].
Two smaller studies without placebo controls observed the same results in cancer patients receiving hormonal and immunotherapy [42, 43].
A review of clinical and animal studies confirmed that shiitake extract could boost the effectiveness of standard treatment, immune response, and quality of life in surgically treated cancer patients. That said, the authors emphasized significant limitations such as [44]:
- Potential conflicts of interest
- Inadequate sample size
- Poor study quality
In 61 patients with prostate cancer, shiitake mushroom extract wasn’t able to prevent disease progression, as measured by PSA levels [45].
Doctors in China and Japan use lentinan from shiitake to enhance standard cancer treatment and reduce the side effects. Different clinical trials have documented its ability to improve immune function, survival, and quality of life in patients with advanced cancer [46, 47, 48, 49, 50].
Animal and Cell Research (Lacking Evidence)
No clinical evidence supports the use of shiitake for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts but should not be interpreted as supportive of any health benefit.
Antimicrobial Activity
Bacteria and Yeasts
In test tubes, the extract of shiitake mushrooms (Lentinula edodes) was able to inhibit up to 85% of tested bacteria and 50% of yeasts and molds. It was particularly effective against gram-positive bacteria and food contaminants [51, 52, 53, 54].
Two studies found it equally potent as antibiotics (ciprofloxacin) and standard antifungal agents [52, 53].
HIV
Two shiitake components, lentin and lentinan, inhibited HIV growth and replication, and increased the effectiveness of an antiviral drug Zidovudine (AZT) [55, 56].
It’s important to note that antimicrobial effects in test tubes often don’t translate to living organisms.
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.
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 [57]:
- Influenza B (in humans) [58]
- Hepatitis C (in humans) [59]
- Human Papillomavirus (in humans and mice) [60]
- Influenza A (H1N1) (in mice) [61, 62]
- Avian influenza virus (H5N1, in mice) [62]
- West Nile encephalitis (in mice) [63]
Another shiitake extract (Lentinus edodes mycelia or LEM) reduced the growth of the influenza A virus and increased survival rates in infected mice [64].
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 [65, 66].
Limitations and Caveats
Despite the promising health effects of shiitake, it’s important to note that most of them lack solid clinical evidence. Additionally, studies often use extracts and purified components in the doses that people can’t achieve by eating mushrooms or taking supplements.
More research is needed to uncover the therapeutic potentials of shiitake mushrooms.
Shiitake Mushrooms Side Effects & Safety
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 [67, 68, 69].
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 [70, 71, 72].
According to rare clinical reports, shiitake mushrooms may cause or worsen a blood disorder called eosinophilia. People with this condition should talk to their doctor before consuming shiitake [68].
In the amounts present in food, shiitake mushrooms are likely safe for all populations. Children and pregnant women should avoid taking supplements due to the lack of safety data.
Drug Interactions
Components from shiitake mushrooms have immune-boosting effects and may thus reduce the effectiveness of corticosteroids and other immunosuppressants [5, 15].
For the same reason, people with autoimmune conditions shouldn’t use it before consulting their doctor.
How to Use Shiitake Mushrooms
Diet: How to Cook and Prepare Shiitake?
You can cook with both fresh and dry shiitake. They have a distinct “umami” flavor, described as savory or meat-like, which makes them a great meat substitute. Shiitake blend well into omelets, soups, stir-fries, and many more dishes.
When buying fresh mushrooms, look for the ones with thick, whole caps. Avoid those looking slimy or wrinkled. Remove their stems when cooking as they usually remain tough. If cooking with dry mushrooms, soak them in warm water for 30-60 mins first.
Can you Eat Shiitake Raw?
The risk of shiitake dermatitis is much higher when consuming the mushrooms raw, so that wouldn’t be a good idea. Saute them lightly to improve their taste and digestibility while preserving the nutritional value [73].
Supplements
Besides dried shiitake, different supplement forms are available. The most common ones include:
- Powder
- Dry extract
- Liquid extract (tincture)
Dry extracts can be 10x more concentrated, meaning that 1g of extract replaces 10g of powder. However, most products are not standardized and thus have unknown potency [74].
Conventionally grown shiitake can contain traces of pesticides. It may be a good idea to opt for certified organic products instead [75].
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 [16].
Takeaway
Shiitake is an edible mushroom from East Asia, praised for its nutritional and healing properties. Folks have been using it for ages to improve their immunity, longevity, and liver health.
Modern research reveals their potential to boost the immune response, heart health, and oral health, but there’s insufficient evidence to back up any of these uses. Despite its potential to inhibit certain respiratory viruses, there’s no evidence that shiitake can help with the new coronavirus.
The most common side effect is so-called shiitake dermatitis, but cooking the mushrooms greatly reduces the risk. People with eosinophilia and autoimmune conditions should consult their doctors before consuming shiitake, while pregnant women should avoid medicinal amounts.
Both fresh and dried mushrooms blend well into various dishes and give unique, meaty flavor. When it comes to shiitake supplements, there are liquid extracts, dry extracts, and powders available. Speak with a healthcare professional before supplementing.
