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) 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 affect 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 adults, respectively), so a significant number of the U.S. population can benefit from adding some vitamin D to their supplement routine.*
Of course, managing to squeak just above the cutoff for vitamin D insufficiency (30 ng/ml) is not the goal to aim for but a boundary to avoid. (More on vitamin D levels to achieve for lifelong health here.)