The stage between the cognitive decline of normal ageing and the more serious decline of dementia is referred to as mild cognitive impairment (MCI). Symptoms primarily include memory loss or forgetfulness, as well as a decline of other cognitive functions such as language, attention span, and visuospatial abilities. It is not a drastically serious condition, but unpleasant and inconvenient nonetheless.
Seniors afflicted with MCI often display very subtle changes. They do not experience disabling cognitive deficits that affect everyday life activities, which is characteristic of Alzheimer’s and other forms of dementia. Assistant Professor Lei Feng, who is from the NUS Department of Psychological Medicine, and the lead author of this work, explained:
“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 educational 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).”
Fortunately, there may be a very easy way to prevent MCI from happening in the first place – eating mushrooms. A recent study conducted by a team 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) revealed that eating more than two servings of mushrooms per week reduces the risk of having MCI by 50%. Although, even one small portion of mushrooms a week may still be beneficial to reduce the chances of MCI.
Lei Feng said:
“This correlation is surprising and encouraging. It seems that a commonly available single ingredient could have a dramatic effect on cognitive decline.”
How many mushrooms is a portion? Three-quarters of a cup of cooked mushrooms with an average weight of around 150 grams. Visually speaking, two portions would be about half a plate.
The Study
- It went on for a period of 6 years, from 2011 to 2017.
- Six commonly consumed mushrooms in Singapore were referenced in the study – golden, oyster, shiitake and white button mushrooms, as well as dried and canned mushrooms. However, they believe that it is highly likely that other mushrooms not referenced would also have beneficial effects.
- They collected data from more than 600 Chinese seniors over the age of 60 living in Singapore.
- Extensive interviews and tests were conducted with the senior citizens to determine an accurate diagnosis.
- The interview took into account demographic information, medical history, psychological factors, and dietary habits.
- Testing involved a nurse measuring blood pressure, weight, height, handgrip, and walking speed. In addition, the participants also did a simple screen test on cognition, depression, and anxiety.
- Then, a two-hour standard neuropsychological assessment was performed, along with a dementia rating.
The overall results of all these tests combined were discussed in depth with expert psychiatrists involved in the study to get a diagnostic consensus. - The research was carried out with support from the Life Sciences Institute and the Mind Science Centre at NUS, as well as the Singapore Ministry of Health’s National Medical Research Council.
The Results
- After the six years of gathering information through tests and interviews, the team found that seniors who ate more than 300 grams of cooked mushrooms a week were half as likely to have mild cognitive impairment.
- The results were published online in the Journal of Alzheimer’s Disease on 12 March 2019.
Their Theory
The reason for the reduced prevalence of MCI in mushroom eaters may be due to one specific compound found in almost all varieties. Dr. Irwin Cheah, Senior Research Fellow at the NUS Department of Biochemistry, said:
“We’re very interested in a compound called ergothioneine (ET). ET is a unique antioxidant and anti-inflammatory which humans are unable to synthesize on their own. But it can be obtained from dietary sources, one of the main ones being mushrooms.”
The team had done a study, previous to this one, on elderly Singaporeans which revealed that plasma levels of ET in participants with MCI were significantly lower than age-matched healthy individuals. It was this study that lead them to believe that an increase in ET intake through mushroom consumption might possibly promote cognitive health. This earlier research was published in the journal Biochemical and Biophysical Research Communications in 2016.
They also list other potentially beneficial compounds in the university press release:
“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.”
What’s Next?
The next study (phase 3 of the research) will be to perform a randomized 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. What they are ultimately hoping to identify are other dietary factors that could be associated with healthy brain ageing and reduced risk of age-related conditions in the future.
