Top Health Benefits of Vitamin D

Although it’s best known for its role in bone health, vitamin D does so much more, ranging from mood and muscle strength to cardiovascular health and cognition. 

In this article, we’ll explore the top evidence-based health benefits of vitamin D, including what happens if you don’t get enough of it.

9 Health Benefits of Vitamin D

Although vitamin D’s classic function is its effects on the skeletal system, it also has anti-inflammatory and immune-regulating properties that can benefit our bones, muscles, brain, lungs, heart, gut, kidneys, and immune system.

Bone Health

Vitamin D first became known for its bone-related benefits when it was discovered as a cure for rickets (while vitamin D deficiency was found to be its cause).

The disease of rickets causes bowed legs and stunted growth because vitamin D helps your body absorb calcium, which induces proper bone mineralization. 

In adults, insufficient vitamin D can cause a loss of bone mineral density, bone fractures, osteomalacia (softening of bones), and eventual osteoporosis if untreated. 

Research with postmenopausal women has found that each 10 ng/mL decrease in blood vitamin D levels is linked to a 33% increased risk of hip fracture.

However, supplementation trials have not consistently shown beneficial effects from taking vitamin D. 

For example, a meta-analysis published in the Lancet combined data from 23 studies with over 4,000 people (primarily women). The researchers concluded that only six of the studies significantly and positively affected bone mineral density and only at the femoral neck (at the top of the thigh bone).

Researchers aren’t entirely sure why clinical trials don’t always produce benefits of taking vitamin D. Some theories are inadequate supplement doses, not enough people in the studies being low in vitamin D, studies being too short, or people having poor absorption of the vitamin D supplement.

Muscle Strength

Vitamin D affects muscle health, as specific vitamin D receptors have been found in skeletal muscle tissue, and vitamin D deficiencies are linked to an increased risk of sarcopenia (muscle wasting) with age. 

In a meta-analysis of eight randomized controlled trials, vitamin D supplements in doses of 700-1,000 IU per day reduced the risk of falling among older adults by 19%, which is largely based on muscle strength. Lower doses (200-600 IUs) did not produce any benefit. 

Adults who achieved healthy blood vitamin D levels (60 nmol/L or more) also had a 23% reduced risk of falls. While falling doesn’t sound so bad when you’re young, older adults who fall may never fully recover, increasing the risk of fractures, immobility, loss of independence, and even mortality. 

Plus, a systematic review of 30 studies concluded that vitamin D supplementation significantly increased muscle strength (but not muscle mass or power), especially in people with low vitamin D levels to begin with and those over the age of 65.However, like with bone strength, not all studies have found that vitamin D improves muscle health—in fact, some research even shows a negative effect.

Mental Health

Sunshine or light therapy has been used to treat depression or mood disorders for centuries, which is likely due, in part, to increased vitamin D levels. 

Some potential mechanisms behind vitamin D’s impact on mood include:

• An increased expression of vitamin D receptors in areas of the brain known to play a role in mood regulation, including the limbic system, cerebellum, and cortex. 
• Modulation of the link between depression and inflammation. 
• Anti-inflammatory effects that may be neuroprotective and positively impact mood.

In one meta-analysis, researchers found that people who took supplemental vitamin D had significant improvements in their depressive symptoms that were comparable to anti-depressant medication.

Notably, these results were only from high-quality trials, meaning the researchers excluded poorly designed studies with low methodological quality. When they analyzed low-quality studies, the results were either null or negative, emphasizing how poorly designed studies can affect supplementation trials—which may be why so many other trials do not find benefits.

Respiratory Health

Having adequate vitamin D levels is associated with a reduced risk of several respiratory illnesses, including tuberculosis, influenza, and upper respiratory tract infections. 

In a meta-analysis analyzing data from almost 11,000 participants, people who took vitamin D supplements had a 19% reduced risk of acute respiratory tract infections, with the most significant benefits in vitamin D deficient people. One theory behind vitamin D’s link to respiratory health is that it increases the production of antimicrobial peptides, which fight against respiratory pathogens and help regulate local immune and inflammatory responses.

Heart Health

Vitamin D may benefit cardiovascular health by suppressing foam cell formation. Foam cells are pro-inflammatory, cholesterol-containing macrophage cells that increase fatty deposits on blood vessel walls, contributing to heart disease. 

Research has also shown that vitamin D plays a role in cholesterol and blood pressure regulation, glucose metabolism, and insulin sensitivity, all of which are important markers of heart health. 

In a large study of over 41,000 adults, vitamin D deficiency was linked to an increased risk of coronary artery disease, heart failure, stroke, and heart attack. In addition, people with the lowest vitamin D levels were most likely to have other cardiometabolic-related conditions or symptoms, including a higher prevalence of diabetes, hypertension, hyperlipidemia, and peripheral vascular disease. Another study of over 21,000 older adults found that vitamin D supplements (a monthly dose of 60,000 IUs for 5 years) slightly reduced the incidence of major cardiovascular events, particularly heart attacks.

Cognitive Function

Low vitamin D levels have also been associated with cognitive impairment and dementia. 

The link between vitamin D and cognition is similar to that between vitamin D and mood. Vitamin D reduces neuroinflammation and provides neuroprotective activity.

Research suggests that vitamin D promotes the production of neurotrophic factors such as nerve growth factor (NGF), which, as the name suggests, regulates the growth and maintenance of neurons. While observational studies and meta-analyses have consistently shown lower vitamin D levels in people with Alzheimer’s disease and other forms of cognitive impairment, supplementation trials have produced mixed results.

Gut Health

With its anti-inflammatory and immunomodulatory properties, vitamin D may support a healthy gut. 

Vitamin D increases the production of antimicrobial peptides and improves the innate immune response in the gut, which can help to reduce dysbiosis and support a healthy gut microbiome. It may also support gut integrity by strengthening the tight junctions in the epithelial lining of the gut, which is linked to reduced intestinal permeability. Plus, vitamin D deficiency is associated with an increased risk of inflammatory bowel disease (Crohn’s disease and ulcerative colitis) and improvements in symptoms related to IBD.

Kidney Health

Vitamin D deficiency is linked to decreased kidney function, and people with chronic kidney disease have been shown to have altered vitamin D metabolism. 

This is because the kidneys convert the inactive form of vitamin D into the active form, which can further decrease vitamin D levels in people with chronic kidney disease. 

Immune System Health

Vitamin D plays a role in both innate and adaptive immune responses.

Briefly, the innate immune system is the first line of defense against invading bacteria or pathogens. In contrast, the adaptive immune system is more specialized, targeting specific invaders and adapting to previous infections.

Vitamin D facilitates innate immunity by enhancing the production of the molecule cathelicidin (one of those antimicrobial peptides mentioned previously) and defensive immune cells, as well as strengthening the physical barrier function of epithelial cells.

It also modulates the adaptive immune system by supporting the differentiation of naive T cells into immune-benefiting regulatory T cells and reducing the secretion of pro-inflammatory cytokines.

Because of these immunomodulatory effects, vitamin D has been studied for its role in reducing the incidence of or controlling the symptoms of certain autoimmune diseases, including rheumatoid arthritis, lupus, psoriasis, and multiple sclerosis. Notably, an extensive study of almost 26,000 people found that vitamin D supplements (2,000 IUs per day for five years) reduced the rate of developing any autoimmune disease by 22%.

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