From the Guidelines
Vitamin D supplements should not be considered anabolic agents as their primary function is to regulate calcium and phosphorus absorption and maintain proper bone structure, rather than directly building muscle tissue. When examining the effects of vitamin D on musculoskeletal health, a study published in Autoimmunity Reviews 1 highlights the importance of vitamin D in maintaining bone density and quality, as well as its role in increasing muscle strength, which reduces the risk of falling in older individuals. Key points to consider include:
- The impact of vitamin D on bone density and muscle strength, which contributes to a reduced risk of fractures in the elderly
- A meta-analysis demonstrating that high doses of vitamin D (482-770 IU/day or 12.0-19.25 μg/day) can reduce non-vertebral fractures by 20% and hip fractures by 18%, but only when achieving 25(OH)D levels of at least 30 to 40 ng/ml
- The supportive role of vitamin D in muscle function and strength, particularly in correcting deficiencies, as shown in a meta-analysis of 8 double-blind RCTs that found a 13% reduction in falling risk among vitamin D supplemented individuals While vitamin D may have some indirect benefits for muscle function, particularly in individuals with deficiencies, its anabolic effects are not comparable to those of true anabolic compounds like anabolic steroids or testosterone. In the context of real-life clinical medicine, prioritizing morbidity, mortality, and quality of life, the use of vitamin D supplements should focus on maintaining adequate vitamin D status for overall health support, rather than relying on them as anabolic agents for muscle building.
From the Research
Definition and Role of Vitamin D
- Vitamin D is unique among vitamins, as it can be synthesized endogenously through ultraviolet B (UVB) exposure, and its structure is similar to that of a steroid 2.
- Vitamin D has been found to have a role in various enzymatic, metabolic, physiological, and pathophysiological processes related to many organs and systems in the human body 3.
Vitamin D and Athletic Performance
- There is growing evidence to suggest that many athletes are Vitamin D deficient, especially in the winter months, which may impair muscle function and reduce regenerative capacity 2.
- Vitamin D supplementation has been shown to improve vitamin D status and can positively affect skeletal muscles, but its effect on athletic performance is still unclear 4, 5.
- Some studies have found that vitamin D deficiency may cause deficits in strength and lead to fatty degeneration of type II muscle fibers, which can negatively correlate with physical performance 5.
Anabolic Agents
- Anabolic agents are substances that promote muscle growth and repair, but there is limited evidence to suggest that vitamin D supplements have anabolic effects 4, 5.
- Vitamin D may interact with extra-skeletal tissues such as muscle to modulate recovery from damaging exercise, but its role as an anabolic agent is not well established 6.
- Further studies are necessary to fully characterize the underlying mechanisms of vitamin D action in human skeletal muscle tissue and to understand how these actions impact athletic performance in athletes 5.