Summary

• Mushrooms are one of the highest antioxidant foods on the market. 
• Studies in both humans and animals indicate that mushrooms stimulate the immune system. 
• Mushrooms are particularly high in one unique antioxidant called ergothioneine. As ergothioneine has a specific protein transporter in the blood it must very important to human health. 
• A serve of mushrooms provides about a quarter of an adult’s requirements of selenium, an antioxidant mineral.

Many of the potential therapeutic effects of mushrooms and mushroom components on a variety of diseases appear to be directly or indirectly mediated by enhancing natural immunity of the host via effects on natural killer (NK) cells, macrophages, via balance of T cells and their cytokine production, and via the activation of Mitogen Activated Protein Kinase (MAPK) pathways.

CSIRO Mushrooms & Health Report 2014

Immune system

The 2014 CSIRO Mushrooms and Health report includes many types of mushrooms, however studies show that white button mushrooms play their role by enhancing the action of Natural Killer Cells and other immune responses in mice (Wu 2007; Xu 2013). Other reports have shown that mushroom extracts given to mice decreased inflammation, assist gut bacteria to resolve infection, and increased the anti-cancer immune response (Yu 2009; Kuvibidila 2010, Varshney 2013).

Since then researchers at the University of Western Sydney have shown that mushrooms increase the production of salivary IgA in healthy humans, an indicator of IgA levels at other mucosal sites such as the intestinal and respiratory tract (Jeong 2012a). In a follow-up study they identified two mushroom polysaccharides that inhibit breast cancer cell growth, possibly through enhanced macrophage function (Jeong 2012b). See our fact sheet on cancer for more details.

Antioxidants in mushrooms

For a long time, scientists have appreciated the antioxidant effect of fresh produce such as vegetables and fruit. Eating plenty of high anti-oxidant foods seems to protect you from future disease. Mushrooms are a rich source of antioxidants, as confirmed by laboratory analysis. In one study of 30 common vegetables, mushrooms were placed in the top 5 highest antioxidant levels when compared to vegetables (Pellegrini 2003; Savoie 2008). 

Ergothioneine

Mushrooms are also very high in the powerful antioxidant ergothioneine, in amounts similar to that found in animal foods (Ey 2007). Ergothioneine is found in very few vegetables or fruit. Ergothioneine appears to protect blood cells, especially monocytes and red blood cells that transport nutrients and oxygen to body cells (Martin 2010). It also protects your artery lining from atherosclerosis (fatty deposits).

Ergothioneine is not produced by the body. It can only be obtained through your diet. With low levels of ergothioneine, the oxidation (damage) of DNA and proteins can begin. It has been suggested that ergothioneine should be classified as a vitamin because it is so important to human health (Paul 2010). Ergothioneine levels do not decrease with cooking, so you get your ergothioneine through both raw and cooked mushrooms.

In 2005, scientists were surprised to find an ergothioneine transporter protein in the blood (Gründemann 2005; Gründemann 2012). Transporter proteins only exist in the blood if they have a specific role. For example, haemoglobin is a transporter protein for carrying oxygen to cells. To find one for ergothioneine again suggests that it is an essential compound for our health and that humans have long evolved as mushroom eaters.

Antioxidants are natural compounds in food that help neutralise the free radicals produced by the body. Free radicals are also quite natural, although they tend to cause damage to all parts of the body over time, hence speeding up the ageing process. For example, free radicals can damage the DNA found in the nuclei of body cells. When DNA becomes damaged, then antioxidants within the body work to correct the damage before it becomes a cancerous cell. 

The evidence is strongly in favour that regularly dining on mushrooms is good for your health and immunity.