Mushrooms are actually the visible fruiting bodies of fungi, the mycelium (branching vegetative system consisting of hyphae) of which is mostly hidden underground or in decaying vegetable matter. Mushrooms are nutritionally interesting because they are an important source of nutrients for a large proportion of the World’s population, particularly in certain Asian countries including Japan. Edible mushrooms that have become popular in the West include maitake, shiitake, reishi, button, oyster and chestnut. Of course not all mushrooms are edible and some like Amanita phalloides (the Death Cap Mushroom) are actually highly poisonous. However, as more is learnt about mushrooms and their effects on human metabolism, it is becoming clear that many edible mushrooms possess immune stimulating effect in mammals that may explain many of their associated health effects. These medicinal mushrooms have been extensively studied in cell culture, animal and human studies for their ability to cause immunological changes.
For example in one study1, researchers investigated the immunomodulatory effects of white button mushrooms in mice. Mice were fed a diet containing either 0, 2 or 5 % (of weight) white button mushrooms for 4 weeks before being vaccinated for Salmonella. The mice were then infected with Salmonella typhimurium. Salmonella was chosen because it is a common food borne pathogen and white button mushrooms were chosen because they are a commonly consumed mushroom in the West. As expected the immunisation increase animal survival, and amongst the immunised mice those receiving 2 % white button mushrooms had the highest survival rates. Consumption of the mushrooms caused an increase in production of Salmonella specific immunoglobulin G1 and faecal immunoglobulin A, as well as enhanced T helper cell responses. The white button mushrooms also increased interferon-γ, tumour necrosis factor-α, interleukin 17A and increased numbers of active dendritic cells in the spleens of the mice.
These results suggest that white button mushrooms may possess many of the immune modulatory effects of other more studies varieties. In particular maitake (Grifola frondosa), reishi (Ganoderma lucidum) and shiitake (Lentinus edodes) have been extensively studied. Medicinal effects of these mushrooms appear to be varied and due to slightly different phytochemical profiles. For example, the immune modulatory effects of shiitake mushrooms may be due to their polysaccharide components, whereas the benefits of maitake mushrooms may be due to their beta-glucan components. One polysaccharide in shiitake mushrooms is called lentinan, and studies suggest that it has anti-cancer effects, although it may have to be injected for this purpose as it is poorly absorbed. Shiitake mushrooms also contain a component called eritadenine, that has been shown to lower plasma cholesterol levels. The beta-glucans in maitake mushrooms are believed to bind to receptors of white blood cells and enhance their activity.
Dr Robert Barrington’s Nutritional Recommendation: White button mushrooms therefore appear to have the ability to cause an enhanced adaptive immune response in mice. Based on other studies involving humans and rodents, it is possible that similar effects may be seen in human subjects. The ability of medicinal mushrooms to modulate the immune system explains their anti-cancer, anti-viral, anti-bacterial, anti-parasitic and anti-inflammatory effects. The polysaccharide and beta-glucan components of mushrooms may be responsible for these immune modulatory effect and in this regard reishi, shiitake and maitake mushrooms have been most extensively studied. However, many mushrooms contain similar phytochemicals to these studied varieties and it might be that more commonly eaten mushrooms such as white button mushrooms are also able to offer similar immune modulatory effects when regularly consumed. Because the effects of medicinal mushrooms appear to vary between varieties, and many mushrooms appear to have these beneficial effects, it is prudent to incorporate a wide variety of mushrooms into the diet to benefits from their differing modes of action.
RdB
