Several large studies have found that older adults who eat mushrooms more often tend to do better on measures of memory and thinking. These findings are widely quoted, sometimes in support of mushroom supplements. This article looks at three of the main studies, what they measured, and what kind of conclusion each can bear.
What a population study is
A population study, also called an observational or epidemiological study, doesn’t give anyone anything. Researchers record what people already eat and how their health turns out, then look for patterns. There are two main designs. A cross-sectional study takes a single snapshot, measuring diet and health at the same moment. A cohort study records diet first and then follows people for years to see what happens. Cohort studies are the stronger of the two, because the diet was recorded before the outcome occurred.
The studies, one by one
Zhang et al., 2017 (Japan). The Ohsaki Cohort 2006 Study followed 13,230 people aged 65 and over in Ohsaki City, north-eastern Japan, for an average of 5.7 years. Over that time 8.7% developed dementia. Compared with people who ate mushrooms less than once a week, those who ate them three or more times a week had a 19% lower rate of dementia (hazard ratio 0.81, 95% confidence interval 0.69 to 0.95) after adjusting for other factors. For those eating mushrooms once or twice a week the difference was small and not statistically significant (0.95, 0.81 to 1.10). The link remained when the researchers left out people who developed dementia in the first two years.
This is the strongest of the three, being large and forward-looking. The researchers themselves listed its limits: dementia was identified from long-term care insurance records and not from clinical diagnosis, mushroom intake was asked about only once at the start, and the types of mushroom eaten were not recorded.
Feng et al., 2019 (Singapore). This study used data from 663 people aged 60 and over in the Diet and Healthy Aging study. Those who ate more than two portions of mushrooms a week had lower odds of mild cognitive impairment than those who ate them less than once a week (odds ratio 0.43, 95% confidence interval 0.23 to 0.78). The mushrooms were common culinary types, including oyster, shiitake and white button mushrooms.
This was a cross-sectional study. Diet and cognition were measured at the same time, so it can’t tell us which came first. Some news coverage described it as a six-year study that followed people over time. The data were collected over six years, but each person was assessed once. The team has a long-standing research interest in ergothioneine, a compound found in mushrooms, and suggested it as a possible explanation. See Ergothioneine Explained.
Ba et al., 2022 (USA). Using the US National Health and Nutrition Examination Survey for 2011 to 2014, this study looked at 2,840 adults aged 60 and over. Higher mushroom intake was associated with better scores on some of the cognitive tests used. It was also cross-sectional, and intake was estimated from what people recalled eating over two separate days.
Why a link is not a cause
- Confounding. People who eat mushrooms several times a week may also eat more vegetables, cook more at home, be better off or be more active. Researchers adjust for the factors they measured, but can’t adjust for those they didn’t.
- Reverse causation. Early cognitive decline can change what people shop for, cook and eat, sometimes years before a diagnosis. Lower mushroom intake could be a result as well as a possible cause. The Ohsaki study’s two-year exclusion reduces this problem but doesn’t remove it.
- Measuring diet is hard. Food questionnaires rely on memory and honest estimates of portion size, and a single questionnaire can’t capture changes over the years.
- Culture and cuisine. Two of the three studies come from East and South-East Asia, where mushrooms are a routine part of the diet. Findings may not carry over to places where they are eaten differently.
See Correlation, Mechanism and Causation in Mushroom Research.
Food is not a supplement
All three studies are about mushrooms eaten as food, in portions of tens or hundreds of grams, as part of whole meals. None involved extracts, powders, capsules or tinctures, and none looked at Lion’s Mane, Reishi, Cordyceps or chaga specifically. Using them to support a claim about a supplement is a step the studies don’t take. The only way to test whether mushrooms themselves make a difference is a randomised trial, and the trials that exist are small. See Lion’s Mane Research: What Does the Evidence Actually Show?
What we can reasonably conclude
Across three countries, older adults who ate mushrooms more often had better cognitive outcomes on average. That pattern is consistent enough to justify further research, and it fits with general advice to eat a varied diet with plenty of vegetables. It does not show that mushrooms prevent dementia, and it tells us nothing about mushroom supplements. No health claims are authorised for mushrooms and cognition in the UK.
What remains uncertain
- Whether mushrooms themselves are responsible, or something else about the people who eat them.
- Which mushrooms, in what amounts, and prepared how.
- Whether any particular compound, such as ergothioneine, plays a part.
What better evidence would look like
More cohort studies that measure diet repeatedly, record the types of mushroom eaten and confirm diagnoses clinically, followed by long randomised trials of a defined mushroom food or compound.
Our approach
We make tinctures, not food, and we don’t use studies of mushrooms in the diet to suggest what our products might do. We describe them by what they are and how they’re made. For the wider picture, see Understanding Mushroom Science: A Beginner’s Guide.
References
- Zhang S, Tomata Y, Sugiyama K, Sugawara Y, Tsuji I. Mushroom consumption and incident dementia in elderly Japanese: the Ohsaki Cohort 2006 Study. Journal of the American Geriatrics Society. 2017;65(7):1462–1469.
- Feng L, Cheah IK, Ng MM, et al. The association between mushroom consumption and mild cognitive impairment: a community-based cross-sectional study in Singapore. Journal of Alzheimer’s Disease. 2019;68(1):197–203.
- Ba DM, Gao X, Al-Shaar L, et al. Mushroom intake and cognitive performance among US older adults: the National Health and Nutrition Examination Survey, 2011–2014. British Journal of Nutrition. 2022;128(11):2241–2248.
Study titles are reproduced as published and are not claims made by Spore & Bloom.
