Summary
Shawn Stevenson delivers a comprehensive masterclass on vitamin D, explaining that it is actually a group of fat-soluble steroid hormones rather than a conventional vitamin. He breaks down how approximately 90% of vitamin D comes from UVB sunlight interaction with the skin, while only about 10% comes from food. The episode covers vitamin D's role in sex hormone production, cancer prevention, immune function, and its connection to COVID-19 outcomes. Stevenson discusses how UVB light triggers vitamin D synthesis through 7-dehydrocholesterol in the skin, and why supplementation alone may not replicate the full spectrum of benefits from natural sun-derived vitamin D. He emphasizes that UVB lamps can serve as an alternative source for people who cannot get adequate sun exposure.
Key Points
- Vitamin D is a group of fat-soluble steroid hormones, not a conventional vitamin, and 90% comes from UVB sunlight interaction with the skin
- UVB light triggers vitamin D synthesis through 7-dehydrocholesterol in the skin, a process that supplementation cannot fully replicate
- Vitamin D sufficiency is linked to significantly reduced mortality from COVID-19 and lower risk of autoimmunity and cancer
- The vitamin D receptor is found in virtually every tissue in the body, influencing over 1,000 genes
- UVB lamps can serve as an alternative vitamin D source for people in northern latitudes or those unable to get adequate sun
- Vitamin D plays a critical role in testosterone and estrogen production, with deficiency linked to lower sex hormone levels
- Sunscreen blocks UVB light and therefore prevents vitamin D synthesis, contributing to widespread deficiency
Key Moments
Vitamin D is a steroid hormone produced by UVB light
Stevenson explains that vitamin D is actually a group of fat-soluble steroid hormones primarily produced in the skin in response to UVB radiation, with about 90% coming from sunlight and only 10% from food.
"Here in this episode, we're gonna be diving into a masterclass on vitamin D. It's one of the most well-researched, remarkable nutrients that's ever been discovered. Now let's kick things off and talk about what is vitamin D in the first place. Well, vitamin D is a group of fat-soluble steroid hormones. So it's not even a vitamin in the conventional sense. It functions as a steroid and does many other processes in the body related to hormones that we're going to talk about soon. But first and foremost, it's a group of fat-soluble steroid hormones. Now, vitamin D is primarily produced in the skin in response to UVB radiation from sunlight. And of course, we know that it can be absorbed through the food that we eat, which we're getting about on average 10% of our vitamin D is coming from food and upwards of 90% is going to be coming from interacting with sunlight. That's kind of the natural turn of things and evolution of things. If we're talking about humans living in a natural setting, that would be about the ratio. So the question is, how does your body actually turn sunlight into usable vitamin D? I'm glad you asked. The first thing is this incredible interaction that takes place from UVB rays from the sun hitting our skin and interacting with a compound in our skin called 7-dihydrocholesterol. That's right. It's a form of cholesterol embedded in our epidermis that UVB rays from the sun interacts with, and it converts it into something called cholecalciferol, also known as vitamin D3. Now, hold up. This isn't where the story ends because D3 is not the usable form of vitamin D, all right? This is just where the story begins, all right?"
UVB light triggers vitamin D synthesis through skin cholesterol
Stevenson details how UVB radiation converts 7-dehydrocholesterol in the skin into pre-vitamin D3, a process that supplementation cannot fully replicate because natural sunlight triggers a cascade of additional beneficial metabolites.
"Here in this episode, we're gonna be diving into a masterclass on vitamin D. It's one of the most well-researched, remarkable nutrients that's ever been discovered. Now let's kick things off and talk about what is vitamin D in the first place. Well, vitamin D is a group of fat-soluble steroid hormones. So it's not even a vitamin in the conventional sense. It functions as a steroid and does many other processes in the body related to hormones that we're going to talk about soon. But first and foremost, it's a group of fat-soluble steroid hormones. Now, vitamin D is primarily produced in the skin in response to UVB radiation from sunlight. And of course, we know that it can be absorbed through the food that we eat, which we're getting about on average 10% of our vitamin D is coming from food and upwards of 90% is going to be coming from interacting with sunlight. That's kind of the natural turn of things and evolution of things. If we're talking about humans living in a natural setting, that would be about the ratio. So the question is, how does your body actually turn sunlight into usable vitamin D? I'm glad you asked. The first thing is this incredible interaction that takes place from UVB rays from the sun hitting our skin and interacting with a compound in our skin called 7-dihydrocholesterol. That's right. It's a form of cholesterol embedded in our epidermis that UVB rays from the sun interacts with, and it converts it into something called cholecalciferol, also known as vitamin D3. Now, hold up. This isn't where the story ends because D3 is not the usable form of vitamin D, all right? This is just where the story begins, all right?"
Vitamin D receptor controls over 1000 genes across the body
Stevenson explains that the vitamin D receptor is found in virtually every tissue in the body and influences over 1,000 genes, making vitamin D deficiency a systemic health issue affecting everything from immunity to hormones.
"But from there, it's going to move through the bloodstream to your amazing liver, where your liver is now going to convert that D3 into another compound. And this compound is called 25-hydroxyvitamin D. 25-hydroxyvitamin D, also known as 25-hydroxycholacalciferol, right? Long-term's bottom line is now we're getting closer to the usable form of vitamin D. And actually, this is what most doctors will test for if we're looking for vitamin D deficiencies, is this interaction with vitamin D and then this conversion taking place with the liver. But still, this is not the usable form of vitamin D in the body. It has to take another step. And this is where it's getting transported to the kidney. So it's hitting the bloodstream again, going to the kidneys. And once 25-hydroxyvitamin D reaches the kidneys, it's getting converted into its final form, which is 125-dihydroxycholacalciferol, aka 125-dihydroxyvitamin D. And this final compound in the name that we need to know it by is calcitriol. This is the real vitamin D. Would the real slim, shady vitamin D please stand up? He probably needs some vitamin D. All right, calcitriol."
