The implications of vitamin D

The research supporting the widespread systemic benefits of adequate vitamin D has only increased in recent years. Researchers are now considering vitamin D more of a hormone than a simple vitamin. 

Unfortunately, as of the mid-2000’s, over 40% of the US population was deficient in vitamin D. Further, populations with more melanin (skin pigmentation) are at an increased risk for vitamin D deficiency. In the same mid-2000’s study, over 80% of African Americans and over 60% of hispanic populations were deemed vitamin D deficient. [1-9]

Indoor lifestyles, stay-at-home orders, and increased sunscreen use are all factors that are expected to lead to increased prevalence of vitamin D deficiency in modern populations. Therefore, the previously mentioned statistics could be much higher today.  

How does vitamin D deficiency affect longevity and performance training? 

Deficient vitamin D levels have been shown to significantly impact health in both short- and long-term studies. Long-term findings associated with vitamin D deficiencies include increased risk of cardiovascular disease, arthritis, diabetes, intestinal cancer, and osteoporosis. [3, 6] 

Short-term studies have shown that deficient vitamin D levels can lead to “muscle weakness, bone pain, and fragility fractures” [7].  

One specific role of vitamin D includes the proliferation, hypertrophy, and regeneration of skeletal muscle through IGF-1. IGF-1 is a potent anabolic signaling protein influenced through the vitamin D receptor cascade. 

Further evidence for vitamin D’s influence over muscle function is its role in calcium absorption and subsequent muscle performance. In studies examining vitamin D plus calcium supplementation (like the combination found in our D1 Mass Stack), researchers found improvements in knee flexion, knee extension, and grip strength [3]. In vivo studies have also shown that by depleting vitamin D receptor binding, muscle groups were 20% smaller than those found in unregulated and functional vitamin D binding sites. [1,2,3]

How does vitamin D affect immunity? 

Deficient levels of vitamin D have been shown to increase susceptibility to infection and are further associated with increased autoimmunity. Vitamin D has been “used” to treat infections throughout history (as seen with tuberculosis patients prescribed sunlight and cod liver oil), but recent studies have highlighted the significance of vitamin D and protection against infection. When using vitamin D in a double-blind, placebo-controlled study to evaluate influenza susceptibility, researchers found vitamin D groups were 42% less likely to develop flu. 

In the last year, researchers have found that those deficient in vitamin D had a relative risk of a positive COVID-19 test that was 1.77 times higher than individuals in the sufficient vitamin D group. [10]

As these and other studies have shown, sufficient vitamin D supports a healthy immune system. Therefore, vitamin D3 should be a mainstay component of your supplementing routine. [5] 

What’s the best vitamin D amount for you? 

The optimal dose of vitamin D depends on several factors. Specifically, you should be aware of:

  1. How much time you spend outside
  2. What time of day you go outside 
  3. How many high-vitamin D2/vitamin D3 foods you consume
  4. Your body fat percentage (vitamin D is fat-soluble and high body fat will decrease available levels)
  5. How tan you are/your skin pigmentation

A standard recommendation for ensuring you don’t become deficient in serum vitamin D levels is 15-25 minutes of direct midday sunlight across as much surface area as possible [8]. Some recommendations suggest at least 40% of skin surface area must be exposed to reach sufficient vitamin D levels naturally. 

Supplementation with vitamin D3 is regarded as a strong and safe way to ensure you are in the optimal window of 40-60 ng/ml. Aiming between 1,000 and 4,000 IUs of vitamin D3 will allow you to raise serum levels of vitamin D, though you should consult with your healthcare provider to see how your lifestyle habits shape your current levels.

It is important to keep in mind the vitamin D toxicity levels shown in many studies, which is reached with doses higher than 10,000 IU. [1,2,4] 

When you use D1 Lab’s stack, you’ll get 2,000 IU of third-party tested vitamin D3, along with calcium, key minerals, and 4 other clinically-tested doses of key supplements for peak performance. 



  1. Ogan, Dana, Kelly Pritchett. Vitamin D and the Athlete: Risks, Recommendations, and Benefits. Nutrients. 2013.
  2. Holick, M F. Vitamin D and Bone Health. The Journal of Nutrition. 1996.
  3. Hamilton, Bruce. Vitamin D and Athletic Performance: The Potential Role of Muscle. Asian Journal of Sports Medicine. 2011. 
  4. Patrick, Rhonda. The Nuances of Vitamin D--and How to Get Enough of It. Goop Wellness. 2020.
  5. Aranow, Cynthia. Vitamin D and the Immune System. Journal of Investigative Medicine. 2012. 
  6. Haimi, Motti; Richard Kremer. Vitamin D deficiency/insufficiency from childhood to adulthood: Insights from a sunny country. World Journal of Clinical Pediatrics. 2017. 
  7. Pfotenhauer, Kim M.; Jay H. Shubrook. Vitamin D Deficiency, Its Role in Health and Disease, and Current Supplementation Recommendations. The Journal of the American Osteopathic Association. 2017. 
  8. Sakamoto, Rosario Rose. Sunlight in Vitamin D Deficiency: Clinical Implications. The Journal for Nurse Practitioners. 2019.
  9. Parva NR, Tadepalli S, Singh P, et al. Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population (2011-2012). Cureus. 2018;10(6):e2741. Published 2018 Jun 5. doi:10.7759/cureus.2741
  10. Meltzer DO, Best TJ, Zhang H, Vokes T, Arora V, Solway J. Association of Vitamin D Status and Other Clinical Characteristics With COVID-19 Test Results. JAMA Netw Open. 2020;3(9):e2019722. doi:10.1001/jamanetworkopen.2020.19722