Fan-shaped and orange to reddish brown in color, reishi mushrooms (Ganoderma lucidum for us science geeks) are a rare find in nature, and were typically reserved for royalty when they were first used in Asian cultures thousands of years ago. Today, they're grown commercially and sold in a variety of formats, including tea, tinctures, capsules, and even hot cocoa, beauty products, and energy bars. And no, you won't find them hanging out in the produce aisle of Whole Foods—while reishi mushrooms can be eaten fresh, their woody texture and bitter taste aren't very palatable.

So why are they suddenly everywhere? "Reishi mushrooms are great for stimulating the immune system and liver function, producing an anti-inflammatory effect in the body,  and have even been shown to reduce tumor growth," says Rachel Gargiulo, RD, a certified nutrition consultant at Nourishing Journey in Columbia, MD.

Indeed, reishi mushrooms exhibit a full array of the qualities that make medicinal 'shrooms so buzzy—they're adaptogenic stress-soothers and high in antioxidants, which is why they've long been a staple of Eastern medicine. No wonder everyone in the wellness world seems to be hailing this king right now.

Photo: Getty Images/Ryan McVay

While reishi mushrooms are generally safe for most people to experiment with, they can cause some side effects—digestive and otherwise—so you should consult with your doctor before taking them. (That goes double if you're pregnant, breast feeding, about to have surgery, or have any type of blood disorder or high/low blood pressure.)

Once your MD gives you the all-clear, however, there are lots of ways that reishi 'shrooms can potentially enhance your health. Below are 10 reishi mushroom benefits that have been uncovered by scientists—although it's important to note that many of these studies weren't conducted on humans (or if they were, the sample size was very small), and more research needs to happen before these theories are definitively proven.

Historically, reishi mushrooms have been used as an immune system enhancer—they're even used in Asian cultures as an immunostimulant for patients with HIV and cancer. The beta glucans (complex sugars) in the mushroom are believed to stimulate the immune system to prevent infection.

Reishi mushrooms are adaptogens, plants that help the body combat stress. In one study of 132 patients suffering from neurasthenia (a condition characterized by physical and mental exhaustion), consumption of a compound found in reishi mushrooms was shown to improve aches, pains, and feelings of irritability.

What's more, a new study conducted by a group of researchers from Penn State College of Medicine took data from the National Health and Nutrition Examination Survey, collected from more than 24,000 U.S. adults from 2005 to 2016, and looked at two days of dietary recall to assess how often participants were consuming mushrooms. The authors then compared that frequency with reported levels of depression. Researchers found that participants who reported eating moderate-to-high levels of mushrooms over the course of the two days had lower odds of depression, as compared to those who ate low or no amounts of mushrooms. Their findings confirmed their hypothesis that people who eat mushrooms have a lower risk of depression, due to their high levels of vitamin B-12, antioxidants, and anti-inflammatory components. "Mushrooms are the highest dietary source of the amino acid ergothioneine—an anti-inflammatory agent which cannot be synthesized by humans," said lead researcher Djibril Ba. Inflammation has been linked to depression, as well as a host of other chronic illnesses. Building on previous small clinical trials that have shown reductions in both depression and anxiety among regular mushroom consumers, the research is very promising for those seeking nutritional solutions for preventing and treating mood disorders.

Baking a batch of these stress-busting reishi mushroom muffins rich in chocolate and adaptogens is guaranteed to boost your mood:

Numerous studies have been done on reishi mushrooms' effect on cancer cells. The results have been intriguing—one small study in the Journal of Oncology found that tumors shrunk in three cancer patients that were taking reishi mushrooms. Researchers believe beta glucans in the mushrooms may prevent new blood vessel growth, which is key as cancer cells need a steady blood supply to grow. The triterpenes (AKA essential oils) in the mushrooms may also inhibit the development and metastasis of tumors. Additional research indicates that the mushrooms could alleviate chemotherapy-induced nausea and improve the efficacy of radiation therapy.

That said, if you're currently undergoing cancer treatment, be sure to check in with your doctor before adding reishi mushrooms to your routine, as they may interact with your protocol.

Compounds in reishi mushrooms may help keep high blood pressure at bay, according to a rat study carried out in 2014. But again, if you’re currently taking blood pressure medication, consult with your doctor before taking reishi mushrooms—the combination could lower your BP to dangerous levels.

Research done on animals indicates that reishi mushrooms may be therapeutic for neurodegenerative disorders such as Alzheimer’s disease and may also be able to protect the brain from seizures. Further research still needs to be done to confirm this, however.

Some studies have shown that reishi mushrooms may have antihistamine effects and can improve the body’s oxygen supply, which is key to those suffering from chronic and allergic asthma.

Both triterpenes and beta glucans may reduce total cholesterol and LDL—commonly referred to as "bad cholesterol."

Reishi mushrooms were found to decrease blood sugar in one small double-blind, placebo-controlled study—possibly by inhibiting an enzyme that produces glucose. Plus, after seeing noticeably reduced kidney stress and lower blood-sugar levels in test subjects, a different group of researchers concluded that reishi mushrooms may prevent or halt kidney complications in type 2 diabetes patients.

Reishi mushroom spores were found to promote liver cell regeneration in mice, improving the organ’s ability to shuttle toxins out of the body. A healthy liver can also be critical to supporting other health benefits mentioned above, including managing blood sugar and allergies.

Despite the fact that their other nickname is "the mushroom of immortality," reishi mushrooms won't, in fact, make you live forever. But they do have antioxidant properties that can reduce the risk of disease and premature aging—and we can never have too many foods like that in our diets, right?

Possible side effects or allergic reactions to reishi include dry mouth, itchy mouth or throat, digestive distress, or bloody stools. If you experience any of these effects, it's best to steer clear of reishi mushrooms in the future. If you are taking any medications, talk to your doctor before taking reishi—just to be safe.

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