#009 Rhonda Answers the Most Popular Questions About Vitamin D

Rhonda Patrick (0:00)

Hello, guys and gals. In this episode of the FoundMyFitness Podcast, I address some of the most popular questions regarding vitamin D, including, how do I decide how much vitamin D I should supplement with? Can you get too much vitamin D? Is there a difference in vitamin D made from the sun versus a supplement? And what form of vitamin D is more bioavailable and absorbed better?

But before we dig in, disclaimer. Please keep in mind that the information in this podcast is not intended as medical advice. It is for informational purposes only, and run it by your physician if applicable. Also in this podcast, I refer generally to some gene polymorphisms, which change the conversion and function of vitamin D. To learn more about these gene polymorphisms, you can sign up for my newsletter at foundmyfitness.com, and you'll be notified when I release a new tool on my website, hopefully very soon, that can help you understand some of your raw 23andMe data, allowing you to explore information that ties to your unique genotype, and may tell you about your own individual metabolic idiosyncrasies. The newsletter is also your gateway to podcast notes and in-depth articles I simply do not share anywhere else online. The sign up form can be found at foundmyfitness.com.

Finally, this episode of the FoundMyFitness podcast is sponsored by people like you. So if you like it or otherwise find the information in it valuable, please consider signing up to contribute $5 per month, which is right about the cost of a latte these days. My goal in a nutshell, if I can achieve my next funding milestone, is to ramp up the frequency of my podcast and videos by getting a little bit of production help and possibly even take a year to distill down as much information as I can into a book. Sounds like worthy goals, right? Great. So you can find out more about this on my website, or you can head right over to my crowdfunding page at Patreon, patreon.com/foundmyfitness. Now, on to the podcast, starting with the most frequent question I receive about vitamin D, which is how do I decide how much vitamin D to supplement with? Unfortunately, I don't have a simple answer for this question because there are many factors that regulate vitamin D levels in the body. For this reason, I think it is very difficult to have a one size fits all recommended daily intake. I can, however, give you a guideline and explain the reasons for this. Vitamin D gets converted into a steroid hormone. You actually make it in the skin from UVB radiation from the sun. But there are many factors that can interfere with this process. Since UVB light from the sun is the primary source of vitamin D, anything that blocks UVB light also inhibits the ability of the skin to produce vitamin D. Things that directly block the efficiency of this process include sunscreen, which filters out UVB radiation, melanin, which is the dark skin pigmentation that acts as a natural sunscreen, living in a northern latitude such as the northern US and Europe, because during the fall and winter months, UVB radiation does not make its way into the atmosphere in these northern regions. Even in a completely ideal situation for vitamin D synthesis, age also has a profound effect on your skin's ability to produce vitamin D, such that a 70-year-old produces only about 25% of the vitamin D from the same amount of sun exposure that they would if they were formally 20 years old. All other factors aside. So the vitamin D we can make in our skin from the sun clearly has many factors regulating that alone. In addition, the amount of body fat also plays a role, though not by affecting synthesis. Vitamin D is a fat-soluble vitamin. This means a higher body fat composition impairs the bioavailability of vitamin D because the fat itself acts as a sink, preventing the vitamin D from being readily released into the bloodstream where it makes its way onto the liver and then the kidneys to be converted into the active vitamin D hormonal form.

There are also gene polymorphisms, which are variations in the sequence of DNA of a gene that alter the function of that gene in genes that convert vitamin D3 into the more bioactive forms. These gene polymorphisms affect the way vitamin D3 is converted into the precursor to the active hormone, form of vitamin D, which is the major circulating form of vitamin D that is measured in blood to indicate a person's vitamin D levels, and it's called 25-hydroxy vitamin D. So to circle back to the question, how do I decide how much vitamin D to supplement with, we must first look at what is considered to be an adequate level of vitamin D.