Dr. Rhonda Patrick

That is because we actually make vitamin D in our skin upon exposure from UV radiation from the sun.

So anything that blocks out UVB radiation is also going to block out the ability to produce vitamin D3 in our skin.

That includes sunscreen.

It also includes skin pigmentation.

So melanin, this is the...

Darker pigmentation that serves as a natural sunscreen.

That also blunts the body's ability to make vitamin D3 from UVB radiation.

Age.

As you get older, your body is less efficient and effective at producing vitamin D3 from sun exposure.

In fact, a 70-year-old makes four times less vitamin D from the sun than a 20-year-old.

Where you live.

So living in a northern latitude...

Many months of the year, actually, there's no UVB radiation even reaching the atmosphere.

So people that are living in more northern latitude areas are not able to make vitamin D3 in their skin from the sun for many, many months out of the year.

So that also really affects the ability to make vitamin D. And then also just body fat.

So vitamin D is actually a fat-soluble vitamin.

And it's stored in fat.

And so the more body fat that you have, that means the less vitamin D3 is bioavailable to be released into the bloodstream, where that it undergoes further metabolic conversion to the steroid hormone, which is actually what's regulating all these genes, many of them in the brain.

I mean, there are many, many, many what are called observational studies that are looking at a correlation between low vitamin D levels and dementia risk.

Many different studies have found this same association.