White button mushrooms: an immunological weapon with a safety catch
Button mushrooms activate the immune system and make immune cells more aggressive. An aggressive immune system is useful if there are pathogens or cancer cells in the body, but not if you are healthy. In this case an overactive immune system results in constant low-grade infections - with all sorts of consequences. So can a diet containing lots of white button mushrooms be a bad thing for healthy people? According to immunologists at Pennsylvania State University, the answer is no. They discovered that the mushrooms only make the immune system more aggressive if there is a good reason to do so.
In vitro study
In 2009 the researchers published a series of experiments in which they unravelled the effects of ordinary mushrooms on the immune system. They started by extracting immune cells from the bone marrow of mice, and exposed these to a mushroom extract [WB], lipopolysaccharide [LPS] or both [WB+LPS]. Lipopolysaccharides are toxic. They are found in the membrane of dangerous bacteria and therefore stimulate the immune system.
The mushroom extract had no effect on the immune cells; lipopolysaccharides boosted the secretion of interleukin-1-beta, a substance that encourages immune cells to attack a source of infection. Mushrooms strengthen this response.
If immune cells become active anywhere in the body, the production of interleukin-10 also rises. This substance prevents the immune system from becoming too zealous. The mushroom extract inhibited interleukin-10.
The researchers gave mice dextran sulphate sodium for a couple of days, a substance with approximately the same characteristics as lipopolysaccharides.
If the mice were also given food that contained mushrooms [WB], the mice started to produce more of the inflammatory proteins interleukin-1-beta and TNF-alpha - and less interleukin 10.
The amount of mushrooms in the mice's feed corresponded with the amount of mushrooms in the diet of people who consume lots of mushrooms.
"Consuming mushrooms in the diet had an effect on immune function, but that effect is evident only when the immune system is challenged," wrote the researchers.
"The change in the immune response induced by whole mushrooms is consistent with a potentially important improvement in cancer surveillance and anti-microbial killing while increasing inflammation - and perhaps autoimmunity."
BMC Immunol. 2009 Feb 20;10:12.
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