A shared property of all mushrooms is said to be immune-modulation: research has been investigating their potential to help balance our natural defense against diseases for many decades.

In particular water-soluble beta-glucans have triggered the interest of scientists: in the EU several health-claims based on beta-glucans have been ratified in the past years by the EFSA. Beta-glucans are supporting a well-balanced immune function and might help to create an good balance between the good and the bad types of cholesterol. Reishi is a mushroom with significant levels of beta-glucan.

Reishi also contains so-called 'proteoglycans' which are beta-glucans linked to a peptide. Similar to the PSP and PSK fractions in Turkey Tail these compounds show a high level of bioactivity.

Given that our immune system is the core of our health this is very important - allergies, infections, auto-immune diseases and many old-age problems are all immune related. Also see our dedicated article about the immune system.

Two terms are worth mentioning here: adaptogenic (helping our body to adapt to the never-ending assaults on our health) and BRM (a natural Biological Response Modifier - helps to normalize the body's natural defense mechanisms without any side effects). These terms are keywords when describing these particular mushrooms. They do not cure or heal, but they help the body to perform at its best.

The beta-glucan fractions are the most important compounds for immune support.

Polysaccharide-bound proteins (glycoproteins / proteo-glycans, comparable to the PSK and PSP fractions in Coriolus versicolor) from Reishi showed inhibitory effects on Herpes Simplex Virus type 1 (HSV-1), Herpes Simplex Virus type 2 (HSV-2), and Vesicular Stomatitis Virus (VSV - New Jersey strain) in a lab test. Using the plaque reduction method, a significant inhibitory effect was seen at doses that showed no cytotoxicity.

A dried hot water extract of Reishi taken orally was used as the sole treatment for postherpetic (varicella zoster virus) neuralgia in 4 elderly patients. This treatment was reported to dramatically decrease pain and promote the healing of lesions without any toxicity, even at very high doses. This is very promising and will hopefully lead to more research in this field.

The anti-microbial combination of Reishi with four commonly used antibiotics resulted in an additive or synergistic effect in most, but not all, instances, with apparent antagonism against cefazolin and ampicillin effects on Proteus vulgaris (known to cause urinary tract infections and wound infections).

There are indications that mushroom extracts that are rich in beta-glucans can be benificial for diabetics. In several controlled animal studies the oral administration of hot water extracted Reishi was found to lower serum glucose levels. The first effects were seen after one week. The extract markedly reduced levels of phosphoenol-pyruvate carboxykinase (PEPCK).

Serum insulin levels increased (when compared to the nontreated diabetic group) and glucose levels decreased in a dose-dependent way. Levels of non-enzymic and enzymic anti-oxidants increased and lipid peroxidation levels decreased. Therefore, in addition to its glycemic modulation, treatment with this hot water extract appeared to help to decrease oxidative stress.

There are a few human trials with similar positive results. Overall, the data from several studies suggests that taking a Reishi extract supports modulating blood glucose levels. However, these studies were performed mostly with animals. More support from well-planned human clinical studies is needed with and without combination with conventional medicines to be able to make more definitive claims.

Triterpenes are mainly responsible for the hepato-protective effects, but some studies also show polysaccharide/beta-glucan extracts to be benificial. A dual extract, again, would therefore be the best choice, because it guarantees both triterpenes and beta-glucans.

Reishi extracts were also found to support the healing of ulcers; up to 56%, depending on the dosage. The Helicobacter Pylori, the bacteria that causes e.g. peptic ulcers and gastritis (and might also be involved in the development of stomach cancers) was inhibited in its growth by a Reishi extract.

As far as we know all research in this field has been performed with animals or in the lab, though. No controlled trials with humans exist as far as we know. Research was performed with ethanol and/or hot water extracts, which were administered orally.

In SE-Asia Reishi extracts are popular supplements, taken by cancer patients along with conventional therapies, to reduce the side effects of those therapies (including the negative effects on the immune-function, which can lead to secondary infections and indirectly can increase the chances of metastasis). The chemo-preventive activities of the mushroom on prostate cancer were demonstrated by a triterpenoid-rich extract of Reishi that suppressed the ventral prostate growth induced by testosterone. Reishi is said to have relatively strong anti-androgenic effects, limiting the production of DHT. This is very positive for those with prostate cancer but can cause loss of libido as well.

Reishi appears to have a positive effect in inflammatory breast-cancer, but should not be used in hormone-related breast cancers - there are contradicting results.

However, whether the anti-tumor effect of Reishi is a direct one or is mediated via the immune system is still unclear. The research results with humans seem to indicate that the anti-tumor effects are a side effect of Reishi's effects on the immune system. Much more research with human volunteers is needed - the majority of research so far was in vivo and in vitro.

Some people taking high dosages of 1.5 - 9 grams per day reported one or more of the following side effects: temporary sleepiness, thirst, rashes, bloating, frequent urination and diarrhea. Taking the extract together with vitamin C seemed to improve many of the side effects. Lowering the dosage also helped.

These reports do not give details about the quality and properties of the extracts that were consumed; and taking into account the poor quality level of most Reishi products (see this 2017 report) it is not unlikely that at least some of these side effects might be related to that, so this appears not to be a direct cause for alarm.

As said, the anti-microbial combination of Reishi with four commonly used antibiotics resulted in an additive or synergistic effect in most, but not all, instances. Reishi appears to cause cefazolin and ampicillin to be less effective against Proteus vulgaris (known to cause urinary tract infections and wound infections).

Reishi extracts rich in triterpenes are very powerful; these might not be the best choice for everybody.

Reishi with a high level of triterpenes should not be used in hormone-related breast cancers - there are contradicting results, so it is best to stay on the safe side. The anti-androgenic effects of Reishi can suppress libido.

Because Reishi has immune-balancing properties, it should not be used together with immune-suppressants, like those prescribed after a transplant. The blood sugar lowering effects can cause fatigue in those that are highly susceptible. In general these people are also very susceptible to e.g. caffeine and alcohol, or are diabetic. Taking the extract together with a sugar-containing liquid can neutralise this effect.

Rare side effects are: not sleeping well, bad, vivid dreams, feelings of anxiety, feeling mentally numb/clouded or having a sense of heightened mental activity. These effects are most likely caused by a genetic anomaly, like overreacting to specific triterpenes, such as lanostan. Just like with Cordyceps some people experience effects that are exactly the opposite of what usually happens. This is personal and due to genetic wiring.

Lanostan triggers the function of the adrenal glands, which are responsible for adrenaline/nor-adrenaline production. If you’re very sensitive to this you can experience hyper-activity which can make you feel anxious, etc. If you experience daily stress on top of that, this will also push the production of adrenaline/noradrenaline in your body, potentially causing anxiety.

Reishi Primo contains a relatively high level of triterpenes; if you experience these side effects it might be better to look for a different mushroom extract or to choose a hot-water-extracted-only Reishi extract, which contains no triterpenes.