Dr. Rhonda Patrick

However, serotonin does not cross the blood-brain barrier.

So tryptophan has to get into your brain, and then you have to convert it to serotonin in your brain.

Well, the enzyme that does that in your brain is called tryptophan hydroxylase 2, and it's activated by vitamin D.

But most people, I mean, this is regulating our immune cell, immune system.

It's regulating our blood pressure, you know, all that water retention, you know, I mean, bone, of course, homeostasis, 5%, more than 5%.

I mean, I can't tell you like so much.

So vitamin D3 is a good way to supplement with it.

Vitamin D2 would be a plant source.

You often find it fortified in like foods like milk.

Yeah.

Vitamin D is naturally to some degree in fatty fish, but you're not going to correct a deficiency with eating fish for your vitamin D.

you're either going to correct it with sun exposure, being in the right area, having the right amount of sun and being the right age.

Because as you get old, you become very inefficient at making vitamin D3 in your skin.

There've been a lot of these Mendelian randomization studies.

So these are studies where scientists will look at people that have these common variations of a gene that's a little more than 1% of the population.

So it's not a random mutation.

It's actually found in a

sizable percent of the population.

A lot of times they'll look at genes that are also involved in SNPs that basically make the conversion of either vitamin D precursor into D3 or D3 into 25-hydroxyvitamin D or into the active steroid hormone, which is 125-hydroxyvitamin D.

So you're not looking at vitamin D levels at all.