Older adults who consume more than two servings of mushrooms each week may reduce their risk of mild cognitive impairment (MCI) by 50 percent, according to a new 6-year study conducted by researchers from Yong Loo Lin School of Medicine at the National University of Singapore (NUS).
“This correlation is surprising and encouraging. It seems that a commonly available single ingredient could have a dramatic effect on cognitive decline,” said Assistant Professor Lei Feng, who is from the NUS department of psychological medicine, and the lead author of this work.
The study used six types of mushrooms commonly consumed in Singapore: golden, oyster, shiitake and white button mushrooms, as well as dried and canned mushrooms. However, researchers believe it is likely that other mushrooms would also have beneficial effects.
A serving was defined as three quarters of a cup of cooked mushrooms with an average weight of around 150 grams. Two servings would be equivalent to about half a plate. While the portion sizes act as a guideline, the study found that even one small serving of mushrooms a week may still help reduce chances of MCI.
MCI falls between the typical cognitive decline seen in normal aging and the more serious decline of dementia. Older adults with MCI often exhibit some form of memory loss or forgetfulness and may also show declines in other types of cognitive function such as language, attention and visuospatial abilities.
These changes can be subtle, as they do not reflect the disabling cognitive deficits that can impact everyday life activities, which are characteristic of Alzheimer’s and other forms of dementia.
The research, which was conducted from 2011 to 2017, collected data from more than 600 Chinese seniors over the age of 60 living in Singapore. The findings are published online in the Journal of Alzheimer’s Disease.
“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,” Feng said.
As such, the researchers conducted extensive interviews which took into account demographic information, medical history, psychological factors, and dietary habits. A nurse measured blood pressure, weight, height, hand grip, and walking speed. The participants also completed a simple screen test on cognition, depression and anxiety.
Finally, a two-hour standard neuropsychological evaluation was performed, along with a dementia rating. The overall results of these tests were discussed in depth with psychiatrists to come to a diagnostic consensus.
The researchers believe the reason for the reduced prevalence of MCI in mushroom eaters may come down to a specific compound found in almost all varieties. “We’re very interested in a compound called ergothioneine (ET),” said Dr. Irwin Cheah, Senior Research Fellow at the NUS Department of Biochemistry.
“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.”
A previous 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 findings led to the belief that an ET deficiency may be a risk factor for neurodegeneration, and increasing ET intake through mushroom consumption might possibly promote cognitive health.
The next step is to conduct 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 potential of such phytonutrients in delaying cognitive decline.
Source: National University of Singapore