Your brain is a garden. And most people are letting weeds take over while their hippocampus quietly shrinks year after year.
In this clip from The Human Upgrade, Dave Asprey sits down with Dr. Majid Fotuhi, a neuroscientist and neurologist trained at Johns Hopkins and Harvard, for a conversation that completely reframes how we think about brain aging.
Dr. Fotuhi’s core argument is simple and a little startling: your hippocampus, the thumb-sized memory center sitting in the middle of your brain, is not fixed. It can grow four, five, six millimeters larger with the right inputs. And the larger it is, the lower your Alzheimer’s risk. He published a paper in Nature identifying a dozen modifiable factors that either grow or shrink this structure. The number one driver is physical fitness.
Things get interesting when Dave brings up vegan diets and brain size, then backs it up with data from his Unlimited Life concierge practice. Vegan clients consistently show lower endurance, depleted minerals and fatty acids, and measurably worse brain function compared to vegetarians. Dr. Fotuhi zeroes in on B12 as the critical variable and shares a case from his Johns Hopkins residency where a young woman was admitted to a psych unit for behavioral problems that turned out to be severe B12 deficiency. Her doctors never checked.
Dave closes with a broader point about lab reference ranges, and why the hard cutoff between normal and abnormal is actively keeping patients sick while their doctors tell them everything looks fine.
You’ll Learn:
Why your hippocampus can physically grow or shrink based on lifestyle and the dozen factors that control it
How fitness is the single strongest predictor of hippocampal size, telomere length, and longevity
The clinical data behind why vegan diets may compromise brain function through mineral and fatty acid depletion
Why normal B12 levels on a standard lab test can still mean your brain is starving
How outdated lab reference ranges are keeping patients sick while doctors tell them they’re fine
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