AUTHORITY NUTRITION

Mushrooms: Good or Bad?

Written by Audur Benediktsdottir, MS on September 23, 2017

Mushrooms have been consumed for thousands of years for both culinary and medicinal purposes.

In cooking, they add a savory taste to dishes and can be used as a substitute for meat.

But while mushrooms add extra taste, some believe they offer little to no nutritional value.

Furthermore, poisonous varieties have given them a bad reputation.

This article looks at the health benefits and potential risks of eating mushrooms.

Mushrooms

Mushrooms are often considered plants, but they actually have their own kingdom: Fungi.

Mushrooms are the fleshy fruiting body of fungi and typically have a cap resembling an umbrella on a stalk.

They are both commercially grown and found in the wild, growing above and below ground.

Thousands of types exist, but only a small portion of them is edible.

The most well-known types include white mushrooms (portobello), shiitake and chanterelle.

Mushrooms are used like vegetables and can be eaten raw or cooked, although their flavor usually intensifies with cooking.

They are often used as a substitute for meat, as they give a rich and meaty texture and flavor to dishes.

They can be bought fresh, dried or canned. Some types are also used as dietary supplements to improve health.

Summary: Mushrooms are the fruiting body of fungi, found both in the wild and grown commercially. Many types exist, but not all are edible.

Called the “food of the gods” by the Romans, mushrooms contain few calories but are rich in protein, fiber and several vitamins and minerals.

Amounts vary between types, but they are generally rich in potassium, B vitamins and selenium. All are low in fat.

A 3.5-ounce (100-gram) serving of raw white mushrooms contains (1):

  • Calories: 22
  • Carbs: 3 grams
  • Fiber: 1 gram
  • Protein: 3 grams
  • Fat: 0.3 grams
  • Potassium: 9% of the RDI
  • Selenium: 13% of the RDI
  • Riboflavin: 24% of the RDI
  • Niacin: 18% of the RDI

Interestingly, cooking releases more of their nutrients, with cooked white mushrooms containing higher levels of most nutrients (2).

Different varieties may contain higher or lower levels of nutrients. One example is cooked shiitake mushrooms, which contain 45% of the RDI for copper in a 3.5-ounce (100-gram) serving (3).

In addition, mushrooms contain antioxidants, phenols and polysaccharides. The content of these compounds may vary depending on many factors, such as cultivation, storage conditions, processing and cooking (4).

Summary: Mushrooms are low in calories but rich in protein, potassium, vitamin B and selenium. Nutrient amounts vary across different types.

Mushrooms have been used in traditional Chinese medicine for hundreds of years to improve health. For example, shiitakes have long been thought to cure the common cold (5, 6).

There seems to be some truth to this, as studies have shown that mushroom extract, especially from shiitakes, may help fight viruses. They enhance resistance against infections from viruses, as well as from bacteria and fungi (6, 7).

Beta-glucans, which are polysaccharides found in mushrooms, may be responsible for this effect, as they have been shown to strengthen the immune system. Shiitake and oyster mushrooms contain the highest levels of beta-glucans (8, 9).

Many studies have focused on mushroom extract, rather than whole mushrooms. However, a study on dried shiitake mushrooms showed promising results.

In this study, 52 people consumed one or two dried mushrooms a day for one month. At the end of the study, the participants showed improvements in immune function, as well as reduced inflammation (10).

Summary: Mushrooms, especially shiitake extract, may offer protection against various viruses and bacteria. Dried shiitake may also improve immune function.

In Asian countries, beta-glucans from mushrooms have long been used in the treatment of cancer (11).

Results from animal and test-tube studies indicate that mushroom extract might decrease the likelihood of tumor growth (11, 12).

While beta-glucans do not kill tumor cells, they might enhance defense against further tumor growth by activating cells in the immune system (11, 12, 13).

However, their effects may not be the same in humans.

Human studies indicate that beta-glucans, including lentinan, may have a slightly positive effect on survival when used alongside chemotherapy. Lentinan is one of the main beta-glucans in shiitakes (14).

A meta-analysis examining five studies in 650 patients showed that when lentinan was added to chemotherapy, the survival rates of those with stomach cancer increased (15).

Yet, the patients who received lentinan with chemotherapy only lived 25 days longer, on average, than those who only received chemotherapy.

When taken as a supplement, beta-glucans from mushrooms have also been used to counteract the side effects of chemotherapy and radiation therapy, such as nausea (16).

All research on the effects of mushrooms on cancer treatment has been focused on mushroom extract, either as supplements or injections, not on eating whole mushrooms.

Therefore, it is hard to say whether they might play a similar role in fighting cancer when consumed as part of the diet.

Summary: Mushroom extract has been shown to reduce tumor growth in animal and test-tube studies. Patients undergoing chemotherapy could benefit from supplementing with mushrooms.

Mushrooms contain several substances that may help lower your cholesterol. This includes beta-glucans, eritadenine and chitosan.

One study in people with diabetes showed that eating oyster mushrooms for 14 days reduced total cholesterol and triglycerides. What’s more, blood glucose and blood pressure decreased as well (17).

Mushrooms also contain a variety of potent antioxidants, including phenols and polysaccharides, which are known to help reduce inflammation and oxidative stress. Oyster mushrooms seem to have the highest antioxidant content (18, 19, 20).

One study in individuals with high blood fats showed increased antioxidant activity after consuming powdered extract from oyster mushrooms for six weeks (21).

While studies have shown that mushroom extract is good for your health, eating mushrooms as part of a healthy diet may also have several health benefits.

In one study, obese people were assigned to one of two diets for a year. One diet included meat, while the other used mushrooms to substitute for meat three times a week (22).

The results showed that by replacing meat with white mushrooms, “good” HDL cholesterol increased by 8%, while blood triglyceride levels were reduced by 15%. Participants also experienced a reduction in blood pressure.

Individuals on the mushroom diet even lost 3.6% of their weight during the study, while the meat group only lost 1.1%. They also experienced satiety while still being satisfied with the taste.

Mushrooms may help reduce salt in meat-based dishes, too. In fact, adding crimini or white mushrooms to a beef taco blend enhanced the flavor of the reduced-salt version of the tacos (23).

Besides being useful for reducing salt intake, this indicates that mushrooms can be a healthy substitute for meat, without compromising taste or flavor.

Summary: Compounds in mushrooms may lower cholesterol and reduce inflammation. They also have antioxidant abilities that could benefit your health.

Just like humans, mushrooms produce vitamin D when exposed to sunlight.

In fact, they are the only food of non-animal origin that may contain substantial amounts of vitamin D (18).

Wild mushrooms contain a considerable amount, as they are exposed to sunlight. The amount they contain depends on climate and latitude (6, 24).

Exposing them to ultraviolet light before or after harvesting also causes them to produce vitamin D (25).

Eating vitamin D-enriched mushrooms could improve your vitamin D status.

One study had participants eat white mushrooms that had been enhanced with vitamin D for five weeks. Doing so had positive effects on vitamin D status that were similar to a vitamin D supplement (26).

Summary: Wild mushrooms contain vitamin D, while cultivated varieties produce vitamin D when exposed to ultraviolet light.

Not all mushrooms are safe to eat. Many wild varieties contain toxic substances and are therefore poisonous.

Eating toxic mushrooms can cause abdominal pain, vomiting, fatigue and hallucinations. It can even be fatal (27).

Some wild toxic types closely resemble edible varieties. This includes the deadly mushroom Amanita phalloides, also known as the death cap.

Amanita phalloides is responsible for most of the deaths related to mushroom consumption (28).

If you want to explore wild mushrooms, be sure you have had sufficient training to identify which ones are safe to eat.

To be safe, it is best to buy them from your local store or market.

Summary: Some mushrooms are toxic and can cause severe symptoms or even death. Sufficient training is necessary in order to identify which are safe to eat.

Mushrooms easily absorb both good and bad compounds from the soil in which they grow. This includes the element arsenic, which can cause several health problems and increase the risk of certain diseases like cancer when ingested over the long-term (29).

Arsenic is naturally present in soil, but levels vary between areas. Wild mushrooms contain higher arsenic levels than cultivated ones, with the highest levels in those found near industrial areas, such as mining and smelting areas (30, 31).

Be sure to avoid wild mushrooms found near polluted areas.

Cultivated mushrooms contain less arsenic, as the growing conditions can be controlled (32, 33, 34).

In one study, only a single sample of 12 store-bought mushrooms exceeded the Chinese guidelines for arsenic. China is the only country that sets limits for arsenic in mushrooms (34).

While store-bought mushrooms may contain arsenic, it is found in small amounts and should not be a concern, as they are not usually consumed on a daily basis.

When it comes to arsenic contamination, rice is more of a problem than mushrooms. That’s because rice and rice products are more commonly consumed, and their levels of arsenic are sometimes relatively high (35, 36).

Summary: Arsenic may be present in mushrooms. Wild varieties near industrial areas contain the highest amounts.

Mushrooms are a healthy food that's rich in protein, fiber and several vitamins and minerals.

In fact, eating mushrooms and consuming mushroom extract may have health benefits.

In particular, mushroom extract has been proven to improve immune function and heart health and may also help fight cancer.

However, keep in mind that some wild mushrooms are poisonous, while others may contain high levels of the harmful chemical arsenic.

Make sure to avoid wild mushrooms, especially those found near industrial areas, if you do not know how to identify them.

Apart from this, it’s safe to include them in your diet.

Mushrooms are very low in calories and add a great taste to dishes.

An evidence-based nutrition article from our experts at Authority Nutrition.

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