Seniors who ate more than 300 grams of cooked mushrooms a week were half as likely to have mild cognitive impairment
Mild cognitive impairment (MCI) is the stage between the cognitive decline of normal ageing and the more serious decline of dementia.
Seniors afflicted with MCI often display some form of memory loss or forgetfulness and may also show deficit on other cognitive function such as language, attention and visuospatial abilities.
However, the changes can be subtle. People with MCI are still able to carry out normal daily activities as they do not experience disabling cognitive deficits which is characteristic of Alzheimer鈥檚 and other forms of dementia.
Seniors who consume more than two standard portions of mushrooms weekly may have 50 per cent reduced odds of having MCI, according to a study by researchers from the Department of Psychological Medicine and Department of Biochemistry at the Yong Loo Lin School of Medicine at the National University of Singapore (NUS).
The six-year study collected data from more than 600 Chinese seniors over the age of 60 living in Singapore.
A portion was defined as three quarters of a cup of cooked mushrooms with an average weight of around 150 grams. Two portions would be equivalent to approximately half a plate.
The study used neuropsychological tests to determine if seniors had poorer performance than other people of the same age and education background.
The six commonly consumed mushrooms in Singapore referenced in the study were golden, oyster, shiitake and white button mushrooms, as well as dried and canned mushrooms. However, it is likely that other mushrooms not referenced would also have beneficial effects.
The researchers believe the reason for the reduced prevalence of MCI in mushroom eaters may be down to a specific compound found in almost all varieties, called ergothioneine (ET).
ET is a unique antioxidant and anti-inflammatory which humans are unable to synthesise on their own.
An earlier study by the team on elderly Singaporeans revealed that plasma levels of ET in participants with MCI were significantly lower than age-matched healthy individuals. The work, which was published in Biochemical and Biophysical Research Communications in 2016, led to the belief that a deficiency in ET may be a risk factor for neurodegeneration, and increasing ET intake through mushroom consumption might possibly promote cognitive health.
Other compounds contained within mushrooms may also be advantageous for decreasing the risk of cognitive decline.
Certain hericenones, erinacines, scabronines and dictyophorines may promote the synthesis of nerve growth factors. Bioactive compounds in mushrooms may also protect the brain from neurodegeneration by inhibiting production of beta amyloid and phosphorylated tau, and acetylcholinesterase.
While the portion sizes in this study acted as a guideline, it was shown that even one small portion of mushrooms a week may still be beneficial to reduce chances of MCI.
The results were published in the Journal of Alzheimer鈥檚 Disease.
The potential next stage of research for the team is to perform a randomised controlled trial with the pure compound of ET and other plant-based ingredients, such as L-theanine and catechins from tea leaves, to determine the efficacy of such phytonutrients in delaying cognitive decline.
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