Research from a Singapore-based study has suggested that mild cognitive impairment could be prevented in people over the age of 60 by simply eating mushrooms more than twice a week.
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The National University of Singapore (NUS) carried out the cross-sectional study with support from the Life Sciences Institute and the Mind Science Centre at NUS, and the National Medical Research Council from the Singapore Ministry of Health. Assistant professor Lei Feng from the National University of Singapore’s department of psychological medicine led the study.
The study was based on data collected on the diets of 663 Chinese people over the age of 60. Their diet and lifestyles were tracked over a period of six years from 2011 to 2017.
A portion of mushrooms was defined as having an average weight of approximately 150 grams, with two portions being equal to half a plate. The mushrooms included in the study were golden, oyster, shiitake, white button mushrooms, and dried and canned mushrooms, as these are commonly consumed varities in Singapore.
Other mushroom varieties that were not included in the study may also harness the same benefits as the types included in the study.
The results, which have been published in the Journal of Alzheimer’s Disease, showed that consuming over two portions of cooked mushrooms a week decreased the risk of mild cognitive impairment by 50 percent, when compared with individuals who ate fewer than one portion a week.
Although the study emphasizes the effects of two or more portions of mushrooms per week, results also showed that one small portion per week could still contribute to decreasing the chances of mild cognitive impairment in advanced ages.
Mild cognitive impairment is defined as the stage between normal, age-related cognitive decline and the significant decline caused by dementia. Mild cognitive decline is characterized by memory loss or forgetfulness, and it may also present difficulties with language, attention, and visuospatial functions.
The effects of mild cognitive impairment do not manifest as clearly as those of dementia as they do not affect a person’s ability to carry out everyday activities as severely. Feng explains how the study accounted for this difference, saying:
People with MCI are still able to carry out their normal daily activities. So, what we had to determine in this study is whether these seniors had poorer performance on standard neuropsychologist tests than other people of the same age and education background.
Neuropsychological tests are specifically designed tasks that can measure various aspects of a person’s cognitive abilities. In fact, some of the tests we used in this study are adopted from commonly used IQ test battery, the Wechsler Adult Intelligence Scale (WAIS).”
Lei Feng, Lead Author
To make accurate diagnoses, the researchers carried out detailed interviews and tests. On the type of information gathered in these interviews, Feng said:
“The interview takes into account demographic information, medical history, psychological factors, and dietary habits. A nurse will measure blood pressure, weight, height, handgrip, and walking speed. They will also do a simple screen test on cognition, depression, anxiety.”
The study reports that the association between higher mushroom consumption and reduced risk of cognitive decline was “independent of age, gender, education, cigarette smoking, alcohol consumption, hypertension, diabetes, heart disease, stroke, and physical activities.”
Feng said the correlation found in the study was “surprising and encouraging,” adding, “It seems that a commonly available single ingredient could have a dramatic effect on cognitive decline.”
A previous study found that levels of this particular, single ingredient, called ergothioneine (ET), in the plasma of people with MCI were notably lower than healthy people of the same age.
It was this study that fuelled the belief that ET deficiency may contribute to neurodegeneration, and that consuming foods rich in ET, like mushrooms, may help to combat the effects of this particular deficiency.
The ET compound is common to all types of mushrooms studied. Dr. Irwin Cheah, Senior Research Fellow at the NUS Department of Biochemistry explains:
We’re very interested in a compound called ergothioneine (ET). […] ET is a unique antioxidant and anti-inflammatory which humans are unable to synthesise on their own. But it can be obtained from dietary sources, one of the main ones being mushrooms.”
Dr. Irwin Cheah
However, Feng acknowledges that it is not mushrooms alone that can contribute to better cognitive function in older people.
“[…] We are talking about a combination of many factors – tea, green leafy vegetables, nuts and fish are also beneficial,” he explains.
Additionally, some hericenones, erinacines, scabronines, and dictyophorines may be responsible for encouraging nerve growth factors. The bioactive compounds of mushrooms may also be responsible for reducing the risk of cognitive decline by inhibiting beta amyloid production, phosphorylated tau, and acetylcholinesterase.
Dr. James Pickett, head of research at Alzheimer’s Society agrees that there is more to better later-life cognitive health than the number of portions of mushrooms a person eats per week. He expands on the issue, saying:
“There are lots of factors that contribute to the development of dementia and it’s estimated that up to a third of cases could be prevented by changes in lifestyle, including diet.
“Dementia is one of the top 10 causes of death, but people can take action to reduce their risk, so it’s important that we base our advice on consistent evidence that’s built up over multiple studies, and don’t get carried away with the findings of any one single study.”
“So while eating a diet full of fruit and vegetables, including mushrooms, is a great starting point, our best advice is to also cut down on sugar and salt, be physically active, drink in moderation and avoid smoking.”
In the future, Feng and his research team aim to find other dietary factors that help keep the brain healthy in later life and lower the incidence of age-related neurodegeneration.
Randomized trials with the pure ET compound and different plant-based ingredients including L-theanine and catechins from tea leaves could be carried out in the future to prove the efficacy of plant-based chemical compounds in reducing the risk of neurodegeneration, and definitively prove conclusions made about their causal relationship.
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