 Dietary ergothionine is known to cross the blood-brain barrier since it can be found in human cerebrospinal fluid and post-mortem brain samples. Perhaps this is why I study in Singapore. I found that those who consume more than two servings of mushrooms a week had less than half the odds of suffering from mild cognitive impairment compared to less than once a week. And I study more than 10,000 Japanese elders found that three or more times a week mushroom eaters had a significantly lower risk of developing dementia over a period of about six years. With cross-sectional studies correlating mushroom consumption with better brain function, researchers decided to put it to the test using lion's mane mushroom, which is especially popular in traditional Chinese medicine, randomized double-blind placebo-controlled trials on people with normal cognitive function, on people with mild cognitive impairment, and on those with early stage Alzheimer's disease did find small cognitive or functional improvements after months of a third to a full teaspoon of powdered lion's mane mushroom a day compared to placebo.