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Research Desk

Research Desk: No. 8 [Vitamin D Recommendation Update]

From the Research Desk

Being at the forefront of human performance means staying up-to-date with the most recent research in the field. It also means revising protocols when the literature calls for changes.

We recently came across two 2025 studies examining vitamin D supplementation protocols, which made us take a deeper look at our current vitamin D recommendation. 

Today, The Research Desk changes a few things up and dives into two studies that convinced us to amend our current vitamin D protocol recommendation. 

Articles: Newbury 2025, Kralova 2025 

PMID:40219027, 39740917

Vitality Take 

The first looked at supplementing protocols in elite swimmers. Within three years of implementing a standardized vitamin D supplementation protocol of 4,000 IU daily, 93% of tested swimmers demonstrated sufficient levels or better (from 35% in the starting year). Most notably, after one year of implementation, vitamin D deficiency was completely removed from this cohort. 

The second study examined vitamin D concentrations after a slew of various dosing protocols during the winter months. Researchers found that supplementing with 4,000 IU led to a more significant increase in serum vitamin D concentrations than lower dosing protocols and was more effective at maintaining optimal vitamin D levels that support broader benefits.  

Both of these studies call to attention that vitamin D levels suffer significantly during the winter months. This can have rippling effects across the multiple systems that are influenced by vitamin D concentrations. Together, these drastic and consistent changes in vitamin D statuses in the winter months prompted the re-examination and revision of the current Vitality recommendation. 

Vitality Application 

Vitamin D is a foundational component of physiology. A 2013 review in Nutrients clearly illustrates its importance. It plays a crucial role in calcium absorption and bone health. The article goes on to call out its part in other physiological processes such as gene response signaling, protein and hormone synthesis, immune response, cellular maintenance, and muscle function

Undoubtedly, vitamin D concentrations are  paramount when it comes to optimized performance and must be maintained year-round. 

Considering its importance and our recent findings demonstrating potential seasonal changes, Vitality has revised its vitamin D supplementation protocol recommendation to include an amendment to optimally support vitamin D concentrations during the winter months. 

New Recommendation: Supplement with at least 2,000 IU of vitamin D daily during the spring, summer, and fall months. Increase supplementation to at least 4,000 IU during the winter months. 

Explore the Vitality Encyclopedia to learn more about these topics.