Today, I want to zoom in on one piece almost nobody in the functional or allopathic world talks about enough:
Can vitamin D supplements actually lower your natural melatonin?
It sounds impossible, right?
Yet a human study found that melatonin dropped in as little as 90 days on a "completely normal" dose of vitamin D.
This doesn’t mean vitamin D is “bad", but it does mean that the conversation has been way too simplistic.....and potentially explains why so many people take vitamin D all winter and still feel:
• wired but tired
• depleted
• moody
• inflamed
• or just “off”
Because winter biology isn’t only about vitamin D.
It’s about your body shifting into a melatonin-dominant repair season - and what happens when that shift gets disrupted.
Keep reading to learn more about the study & read my deep dive analysis
Why the "vitamin D in winter" conversation tends to be overly simplistic
I was genuinely surprised when I came across this study, because until now I hadn’t seen solid evidence that exogenous vitamin D could directly influence endogenous hormone production.
There have been hints in the literature - which I’ve written about before - but this was the first study that felt truly compelling.
If you want the full breakdown, including the mechanisms, the limitations, and what this means for winter biology, you can read the deep dive here.
I also recorded a 47-minute solo episode earlier this week on the lesser-known downsides of vitamin D supplementation. The full episode premieres on December 24, but you can get a 20 minute preview here or by clicking on the photo above.
In the episode I delve into the complexities of vitamin D and melatonin, particularly during the winter months. I discuss the natural decline of vitamin D levels in winter, the critical role of melatonin, and how modern lifestyles disrupt these hormonal balances.
And before you label me 100% "anti vitamin D" - at the 29 minute mark - I do delve into specific situations where a short term - supervised protocol could be helpful - as well as what labs someone might want to get beyond the standard serum D3.
