How Optimizing Your Vitamin D Status Promotes Muscle Health & Function*

In ancient Greece, rooms with prime sun exposure were recommended to strengthen muscles, and Olympians were told to train outside in the sunshine for optimal performance. No, they weren't just trying to look tan in their togas—as it turns out, the Greeks recognized the vitamin D/muscle connection long before the science was well understood. 

Vitamin D receptors (VDR) have been found in skeletal muscle (aka the muscles on your bones that help you move), suggesting vitamin D plays a crucial role in the maintenance of muscle form and function.*

The research supports his insight, demonstrating vitamin D's ability to improve muscle function when given to those deficient in vitamin D (i.e., correct the deficiency).* With vitamin D deficiency and insufficiency affecting 29% and 41% of U.S. adults2, respectively, a significant portion of the U.S. population can benefit from the muscle health benefits that healthy levels of vitamin D support.* 

Beyond its direct impact on muscle health, vitamin D also helps maintain calcium homeostasis.* This vitamin-mineral partnership is crucial to muscle contraction—i.e., the tightening, shortening, or lengthening of muscles to accomplish a physical activity.

The total amount of skeletal, cardiac, and smooth muscles in your body make up your muscle mass, and sufficient vitamin D throughout life is required to maintain a healthy percentage.*

Higher muscle mass is related to a number of health benefits—including slowing down muscle loss with age, improving metabolism, and even longevity.* Indeed, older adults with more muscle mass were found to live longer than those with less in a 2014 clinical study3 published in the American Journal of Medicine.

Maintaining healthy muscle mass isn't as easy as adding some vitamin D to your diet (which rarely provides enough of the essential fat-soluble vitamin to affect your vitamin D status and health in a meaningful way). While a vitamin D supplement is a no-brainer for achieving and maintaining vitamin D sufficiency throughout life, your muscle mass will also benefit from an overall nutrient-dense dietary pattern (with a particular focus on high-quality and adequate protein) and regular physical activity, too.*

Additionally, there are many facets of body composition (the percentage of fat, bone, and yes, muscle) unique to each individual that affects the amount of vitamin D needed. 

Nutrition scientist and vice president of scientific affairs at mbg Ashley Jordan Ferira, Ph.D., RDN, previously shared that, "Adiposity, or the amount of body fat one has, is one key facet of body composition (as are lean mass and bone density). Research has repeatedly demonstrated that fat tissue is inversely correlated with vitamin D status (i.e., higher adiposity, lower vitamin D levels)."

The reasons for this are varied and "involve perturbations in storage, dilution, and complex feedback loops," explains Ferira. She goes on to say, "One major factor is that fat tissue has a tendency to store fat-soluble compounds like vitamin D, making less of this essential nutrient available to circulate and be activated to support our cells, tissues, and organs throughout the body."*

Additionally, according to Wright, there appears to be little to no additional benefit of vitamin D on muscle mass once sufficiency status is achieved. "Overall, vitamin D does not help increase muscle mass if circulating levels of 25-hydroxyvitamin D are at or above recommendations," says Wright. But as Ferira jokes, "That would be an excellent problem to have since 93%-plus of Americans aren't even eating their way to 400 IU of vitamin D3 a day."

What does this mean for us? Well, evidence suggests that muscle mass is greatly improved by vitamin D supplementation for those deficient or insufficient in the essential vitamin (again, 29% and 41% of American adults2, respectively), so a significant number of the U.S. population can benefit from adding some vitamin D to their supplement routine.* 

Wait, hold up—what is skeletal muscle metabolism, exactly? Well, it's a highly coordinated process involving communication between immune and muscle cells.

Skeletal muscle metabolism largely depends on mitochondrial oxidative capacity, and, according to Wright, vitamin D has been shown to influence factors of energy metabolism such as mitochondrial density and function.*

Increasing the size and number of your mitochondria, aka the powerhouse of the cell (thanks, high school biology class), helps the mitochondria convert energy (aka from the foods we eat throughout the day) into ATP, which is the primary carrier of energy in cells for all of their reactions and hard work. This process, called mitochondrial biogenesis, allows your muscles to work harder for longer.

Vitamin D is a critical nutritional player in our muscle health, not only when we exercise but for daily physical activity and functions as well.* The widespread prevalence of vitamin D nutritional inadequacy in the United States makes the vitamin D and muscle connection a vital topic of discovery, and while the research is ongoing, it's clear that sufficient vitamin D levels contribute to musculoskeletal health and function.* 

Because it's practically impossible to restore vitamin D levels from food and sunshine alone, vitamin D supplementation is also an important consideration when trying to achieve optimal muscle health.*

We rounded up the best high quality, research backed vitamin D supplements here, but for our top pick, look no further than, mindbodygreen's own vitamin D3 potency+. In addition to providing an effective level of vitamin D3 (5,000 IU) from sustainable organic algae, our vitamin D is optimized with built-in absorption technology to support your muscle, bone, immune, and whole-body health.*