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. As it turns out, the Greeks recognised the vitamin D/muscle connection long before the science was well understood.

Though vitamin D’s contributions to bone health are far more researched, the sunshine vitamin’s involvement in muscle health is just as important. Evidence suggests that vitamin D plays a vital role in many skeletal muscle activities, including early development, mass, function, and metabolism.

Vitamin D Health Benefits

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.

If you think vitamin D isn’t a top priority for your musculoskeletal health because you aren’t a pro athlete, think again:

Skeletal muscle accounts for approximately 35% of total body mass in females and 42% in males, making it an important factor in overall body composition, metabolism, and physical function.

Sufficient vitamin D levels are a must for healthy muscles, no matter how you’re using them.

Support Muscle Function

According to nutrition musculoskeletal scientist Christian Wright, Ph.D., vitamin D modulates a number of cellular pathways and functions that maintain muscle health—such as skeletal muscle differentiation (i.e. dividing cells decide to become muscle cells), growth, and even regeneration. “Having adequate levels of vitamin D is essential for optimising the benefits of vitamin D on muscle,” says Wright.

The research supports his insight, demonstrating vitamin D’s ability to improve muscle function when given to those deficient in vitamin D.

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.

Maintain Healthy Muscle Mass and Overall Body Composition

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 study 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) along with regular physical activity.

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

Nutrition scientist Ashley Jordan Ferira, Ph.D., RDN, says 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 explains Ferira. “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.”

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 this essential vitamin.

How Does Vitamin D Aid Skeletal Muscle Metabolism?

What is skeletal muscle metabolism exactly? Well, it’s a highly co-ordinated process involving the 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, 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.

Wright explains, “Increasing vitamin D concentrations is shown to increase mitochondrial biogenesis, oxygen consumption, and phosphate uptake, all the while decreasing oxidative stress.”

In other words, vitamin D aids metabolic activities in skeletal muscle and supports the overall health of muscle cells, making it a powerful teammate for us and our daily movement and overall health.

The Bottom Line

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 makes the vitamin D/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. Whether you’re training for the Olympics, trying to master a yoga inversion, or simply looking to support day-to-day activities, consider vitamin D supplementation – your muscles will thank you!*