Mushrooms are a popular food that offer many potential health benefits. They are low in calories and rich in nutrients like B vitamins, selenium and potassium. Some research shows that mushrooms may help fight cancer and boost immunity due to their antioxidant content. However, some people wonder if it’s possible to eat too many mushrooms and experience adverse effects.
Nutritional Profile of Mushrooms
Most types of mushrooms are low in calories and fat and high in fiber. For example, one cup (70-80 grams) of raw white button mushrooms contains just 21 calories and 0.3 grams of fat. They also provide 2 grams of fiber, making up 8% of the Daily Value (DV).
Mushrooms are a good source of several micronutrients as well:
- Selenium: 27% of the DV
- Riboflavin: 23% of the DV
- Niacin: 15% of the DV
- Phosphorus: 12% of the DV
- Copper: 12% of the DV
- Potassium: 9% of the DV
They also contain antioxidants like ergothioneine and glutathione, which help neutralize harmful free radicals to prevent oxidative damage and chronic disease.
Potential Health Benefits
Some research shows that increased mushroom consumption may be associated with several potential health benefits.
May Help Fight Cancer
Mushrooms contain antioxidants like ergothioneine, which may help prevent and fight cancer. Test-tube and animal studies show extracts from mushrooms like maitake, crimini and portobello have anticancer effects and may block tumor growth.
One observational study in over 63,000 Chinese women found that higher mushroom intake was associated with a lower risk of breast cancer.
However, human studies are limited, and more research is needed to determine the cancer-fighting effects of mushrooms and their extracts.
Could Boost Immunity
Mushrooms contain antioxidants like selenium, glutathione and ergothioneine. These antioxidants help neutralize harmful free radicals to protect your cells against oxidative damage.
Test-tube studies note that mushroom antioxidants boost the activity of natural killer cells and increase immune response. This could partly explain why some research shows a link between higher mushroom intake and enhanced immunity.
One study found that giving mice maitake mushroom extract increased their immune response to the influenza (flu) virus. Another study in men showed that turkey tail mushroom extract helped improve immune function and reduced fatigue.
May Support Blood Sugar Control
Adding mushrooms to your diet may benefit blood sugar control. This is likely due to their high fiber content, ability to improve insulin sensitivity and potential to reduce glucose production in the liver.
One 16-week study gave overweight adults maitake mushroom extract. It led to reductions in insulin levels by 35% and fasting blood sugar levels by 10%.
However, human studies are limited. More high-quality research is needed to confirm the beneficial effects of mushrooms on blood sugar control.
Side Effects and Downsides
For most people, eating mushrooms is safe and healthy. Yet, they may have some downsides:
May Not Be Good for Everyone
Some people may need to avoid or limit mushroom intake, including:
- Those with mushroom allergies. Allergic reactions can cause skin inflammation, nausea, vomiting, wheezing and anaphylaxis.
- People taking anticoagulants. Mushrooms contain vitamin K, which plays a key role in blood clotting. High vitamin K intake could reduce the effectiveness of blood-thinning medications like warfarin.
- Pregnant women. Some types of mushrooms contain agaritine, which may stimulate cell mutations and tumor growth. More research is needed on mushroom intake during pregnancy.
Can Absorb Toxins
Mushrooms can absorb toxins, heavy metals and pesticides from soil, air and water. To minimize exposure, it’s best to purchase organic varieties, wash mushrooms thoroughly and avoid wild mushrooms unless harvested by an expert.
Mushrooms contain naturally occurring purines. Those with gout or kidney stones may want to limit intake since purines can form uric acid kidney stones.
However, research on mushroom intake and gout risk is limited and conflicting.
Provide Very Little Protein
Protein intake is important for health, muscle mass and weight management. Though mushrooms contain some protein, the amounts are quite small.
For example, a cup (70–80 grams) of chopped white mushrooms contains just 2.9 grams of protein.
To meet your daily protein needs, you will likely need to pair mushrooms with other protein-rich foods like meat, seafood, legumes, nuts or seeds.
Unlike fruits and vegetables, there are no official recommendations for how many mushrooms you should eat per day or week to obtain health benefits while preventing adverse side effects.
According to existing research, the following daily intake levels may be beneficial:
- 1–2 cups per day for cancer prevention
- About 1 cup per day for immune health
- 3.5 ounces (100 grams) per day for blood sugar control
It’s best to include a variety of mushrooms in your diet, such as shiitake, maitake and oyster mushrooms. Try adding them to soups, salads, stir-fries and sautés.
Additionally, you can take mushroom supplements like cordyceps, lion’s mane, turkey tail and maitake to potentially enhance immunity and fight disease.
Can You Eat Too Many?
Research on maximum intake levels is limited. However, eating very large amounts could have some adverse effects, especially in susceptible populations.
Potential risks of eating too many mushrooms may include:
- Nutrient imbalances. Eating mushrooms in very high amounts could potentially lead to overexposure to some micronutrients like copper and selenium.
- High purine intake. Large servings provide greater amounts of purines, which could trigger gout flares in those susceptible.
- Toxin exposure. Mushrooms absorb toxins from their environment. Higher intakes may increase exposure to toxic pesticides, heavy metals or other contaminants.
- Drug interactions. Large doses provide high levels of vitamin K1, which could interfere with blood thinners.
However, this depends on the type and serving size of mushrooms, as well as the health of the individual consuming them.
How Many Is Too Many?
An average serving size of mushrooms is around 1 cup (70–80 grams). Consuming over 10 cups (700–800 grams) per day could potentially lead to adverse effects in some people.
However, most people eat nowhere near this amount. The average intake among mushroom consumers in the United States is just over 1 cup per week.
Unless you have an underlying health condition, eating 2–4 servings of mushrooms per day is likely safe for most individuals.
Yet, there isn’t enough research to determine a definite maximum amount for the general population. Those with concerns may want to limit intake to 2 cups (140–160 grams) per day.
Risks in Children
There are no official recommendations for mushroom intake in children. However, they may be more susceptible to adverse effects due to their small size.
Potential long-term risks are unknown as well. Due to their developing bodies, children may be especially vulnerable to toxins like heavy metals, pesticides and agaritine.
For safety, it’s best to limit intake to 1–2 child-sized servings per week. Make sure to wash mushrooms well, avoid wild varieties and choose organic when possible.
During Pregnancy and Breastfeeding
Due to limited research, it’s unclear how much is safe during pregnancy. Exposure to agaritine and other carcinogens may stimulate cell mutations and tumor growth in developing fetuses.
For this reason, pregnant women should avoid or limit mushroom consumption to 2–3 servings per week. Focus on thoroughly washed, organic varieties whenever possible.
While nursing, babies may be exposed to small amounts of toxins through breast milk if their mothers eat mushrooms. Intake of 2–3 servings weekly is unlikely to cause harm but optimal intake is unknown.
For People with Diabetes
Mushrooms may improve insulin resistance and blood sugar control. However, human studies are limited and results are mixed.
The fiber, vitamins, minerals and antioxidants in mushrooms make them a healthy choice for people with diabetes. Yet, it’s unclear if they directly reduce diabetes risk or blood sugar levels.
Individuals with diabetes can include mushrooms as part of a balanced, healthy diet. Aim for 2–4 servings per week as part of a diet high in vegetables, fiber and lean protein.
For Those Taking Blood Thinners
Mushrooms are high in vitamin K, which is essential for proper blood clotting. Consuming large amounts could interfere with the effectiveness and safety of blood-thinning medications like warfarin.
People taking blood thinners like warfarin should keep intake consistent by incorporating 1–2 servings of mushrooms per week. This helps maintain steady vitamin K levels. Avoid sudden increases in mushroom intake.
With Gout or Kidney Stones
Purines in mushrooms may increase uric acid production and formation of kidney stones in those susceptible. However, research on mushroom intake and gout is inconsistent.
Limiting high-purine foods may help prevent recurring gout attacks and kidney stones. People prone to these conditions may want to keep mushroom consumption to 2–3 times per week.
What About Mushroom Powder or Extract?
Mushroom supplements like powders, capsules and liquid extracts are increasing in popularity due to their purported health benefits.
These provide concentrated doses of the bioactive compounds in mushrooms and don’t contain pesticides and toxins that fresh mushrooms might. Yet, optimal intake remains unknown.
For therapeutic effects, studies use dosages ranging from 1–3 grams per day of mushroom powder or 150–2,500 mg per day of extract. These supplement forms seem to be safe for most adults in the short term.
However, the long-term safety is unknown. As with whole mushrooms, those taking blood thinners or medications should exercise caution.
The Bottom Line
Mushrooms offer important nutrients and have been associated with health benefits. These include enhanced immunity, improved blood sugar control, anticancer effects and protection against heart disease.
For most people, eating 2–4 servings of mushrooms daily is likely safe. This provides around 1–2 cups of chopped mushrooms per day.
Higher intakes, especially in excess of 5 servings per day, may cause adverse effects in some individuals — especially if mushrooms are not washed properly.
Those with specific health conditions like gout or kidney problems may also want to limit intake. Additionally, the maximum safe intake level for children and pregnant women is unknown.
In general, adding a few servings of mushrooms to your diet each week is a simple way to take advantage of their unique health benefits.