“In the winter months, when the sun’s rays are not intense enough to generate sufficient vitamin D production (this is the case for three to five months per year for locations in North American—you know it’s downtime for D when you can’t get a tan even with prolonged sun exposure), supplements and safe-designated artificial tanning implements can be useful or even essential if you are at high risk for deficiency.
If you have an indoor-dominant lifestyle or even a hint of aforementioned risk factors, you should regularly test your blood for vitamin D. (Make sure it’s for ’25-vitamin D’ or ‘serum 25(OH)D.’ You can order this test directly from an online provider like direct labs.com. or, if you are getting a routine checkup, insist they include vitamin D in your blood panels. (Unfortunately, it’s often not included.)”
For more on vitamin D sources, deficiency, testing and recommended levels, see The New Primal Blueprint or check out past articles on MDA.
About the Author
Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.