Singapore University

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) has found that seniors who consume more than two standard servings of mushrooms each week are 50 percent less likely to have mild cognitive impairment (MCI).

A serving was defined as three quarters cup of cooked mushrooms with an average weight of about 150 grams. Two servings equate to about half a plate. While portion sizes serve as a guideline, it has been shown that even a small portion of mushrooms per week can still be beneficial in reducing the likelihood of MCI.

“This correlation is surprising and encouraging. It appears that a widely available single ingredient can have a dramatic effect on cognitive decline,” said assistant professor Lei Feng, of the NUS Department of Psychological Medicine, and the lead author of this work.

The six-year study, which was conducted from 2011 to 2017, collected data from more than 600 Chinese seniors over the age of 60 living in Singapore. The research was conducted with support from the Life Sciences Institute and Mind Science Center of NUS, as well as the National Medical Research Council of the Ministry of Singapore. The results were published online in the Journal of Alzheimer's Disease on March 12, 2019.

Determination of MCI in Seniors

MCI is usually thought of as the stage between the cognitive decline of normal aging and the more severe decline of dementia. Seniors suffering from MCI often exhibit some form of memory loss or forgetfulness and may also be deficient in other cognitive functions such as language, attention and visuospatial skills. However, the changes may be subtle, as they do not experience cognitive impairments that affect daily activities, which is characteristic of Alzheimer's disease and other forms of dementia.

“People with MCI are still able to go about their normal daily activities. What we needed to determine in this study is whether these seniors perform worse on standard neuropsychologist tests than other people of the same age and background,” explains Asst Prof. Feng. “Neuropsychological tests are specifically designed tasks that can measure different aspects of a person's cognitive abilities. In fact, some of the tests we used in this study come from the widely used IQ test battery, the Wechsler Adult Intelligence Scale (WAIS). †

As such, the researchers conducted extensive interviews and tests with the elderly in order to get an accurate diagnosis. “The interview takes into account demographic information, medical history, psychological factors and dietary habits. A nurse measures blood pressure, weight, height, handgrip and walking speed. They will also do a simple screen test on cognition, depression, anxiety,” said Asst Prof Feng.

Following this, a standard two-hour neuropsychological assessment was performed, along with an assessment of dementia. The overall results of these tests were discussed in depth with expert psychiatrists involved in the study to arrive at a diagnostic consensus.

Mushrooms and Cognitive Impairments

Six commonly consumed mushrooms in Singapore were named in the study. These are: golden enoki, oyster mushroom, shiitake and white mushrooms, as well as dried and canned mushrooms. However, it is likely that other mushrooms that are not referenced would also have beneficial effects.

The researchers believe that the reason for the reduced prevalence of MCI in mushroom eaters may be due to a specific compound found in nearly all varieties. “We are very interested in a compound called ergothioneine (ET),” said Dr. Irwin Cheah, Senior Research Fellow in the NUS Department of Biochemistry. “ET is a unique antioxidant and anti-inflammatory that humans cannot synthesize on their own. But it can be obtained from dietary sources, one of the main ones being mushrooms. †

A previous study by the team on elderly Singaporeans showed that plasma levels of ET in participants with MCI were significantly lower than in healthy peers. The work, published in 2016 in the journal Biochemical and Biophysical Research Communications, led to the belief that a deficiency in ET may be a risk factor for neurodegeneration, and increased ET intake from mushroom consumption may potentially promote cognitive health.

Other compounds in mushrooms may also be beneficial in reducing the risk of cognitive decline. Certain hericenones, erinacins, scabronins and dictyophorins can promote the synthesis of nerve growth factors. Bioactive compounds in mushrooms may also protect the brain from neurodegeneration by inhibiting the production of beta-amyloid and phosphorylated tau and acetylcholinesterase.

Next steps

The possible next phase of research for the team is to conduct a randomized, controlled trial using the pure compound of ET and other botanicals, such as L-theanine and tea leaf catechins, to determine the efficacy of such phytonutrients in slowing cognitive decline. . Such interventional studies will lead to a more robust conclusion about the causal relationship. In addition, Asst Prof Feng and his team also hope to identify other dietary factors that may be associated with healthy brain aging and a reduced risk of age-related disorders in the future.