Vitamin B12 Is Quietly Running Your Brain
Why B12 matters more as you age, what actually happens when you run low, and what to do about it Monday morning.
Rachel & Drew · 2:37
Transcript
Drew, I want to talk about something that's apparently running my brain without my permission.
B12. Tiny vitamin, enormous job. And most people don't notice it's missing until things have already gone sideways.
Okay so what is it actually doing up there?
Two big things. First, it builds myelin — that's the fatty insulation wrapped around every nerve fiber in your body. No myelin, nerve signals get scrambled. Think frayed electrical wire.
So literally the wiring in my brain needs this stuff.
Every single wire. Second thing — B12 breaks down homocysteine, which is a compound your body makes naturally. Sounds harmless. At high levels it's basically acid for your blood vessels and brain tissue.
That sounds horrifying. Why does this get worse with age?
Your stomach makes less of something called intrinsic factor — a protein that physically grabs B12 in your gut and escorts it into your bloodstream. Less intrinsic factor, less B12 absorbed, even if you're eating steak every night.
So the food isn't the problem, the bouncer stopped letting it in.
Exactly. And certain medications make it worse — metformin for diabetes, proton pump inhibitors for heartburn. Hugely common in older adults.
Okay so what can people actually do? Starting Monday.
Food first — clams, oysters, salmon, eggs, dairy. Clams are genuinely absurd, B12-wise. Like, comically high.
So I just need to become a clam person.
Or supplement. The research suggests methylcobalamin or cyanocobalamin, both work. If absorption is the issue, sublingual tablets — dissolve under your tongue — or injections bypass the gut entirely.
Should people get tested?
Yes, a standard blood test. If you're over 50, vegetarian, or on metformin or a PPI, ask your doctor. Deficiency is treatable, but nerve damage from long-term deficiency can be slow to reverse.
One thing to walk away with?
Get the blood test. Seriously. It's cheap, it's easy, and B12 deficiency is one of the most fixable things on the list of reasons your brain might slow down.