It’s well-known that vitamin D is great for the bones, but can it also strengthen the muscles and rev up metabolism? Continue reading to discover what the latest research says about its effects on fitness and cardiovascular and metabolic health.

Vitamin D for Fitness: Does it Help?


  • May improve muscle strength and physical performance
  • Likely reduces the risk of falls in the elderly
  • Improves performance in athletes who are deficient
  • Deficiency has been linked with sport injuries

The body naturally makes vitamin D when exposed to sunlight. Getting regular, moderate sun exposure is a safe way to maintain normal vitamin D levels during the summer months.

Vitamin D is also found in certain foods, such as fatty fish like salmon and sardines. Additionally, many vitamin D supplements are available on the market.

Taken at the recommended doses, vitamin D supplements are considered safe. However, taking too much can be harmful. Vitamin D supplements may also interact with prescription medications. Remember to talk to your doctor before supplementing.

Vitamin D might help maintain good fitness and heart and metabolic health. People who don’t get enough of this vitamin through sunlight and food are at risk of deficiency.

Supplementation Improves Physical Performance

Clinical evidence suggests that vitamin D plays a role in muscle metabolism and function [1].

Supplementation has been shown to improve muscle strength, balance, and physical performance. Additionally, it reduces falls in adolescents, the elderly, and chronic kidney disease patients [2, 3, 4].

In one study, supplementation reduced the risk of falls by more than 20% [5].

Tissue-based studies suggest that vitamin D may increase muscle strength by reversing the atrophy of type II muscle fibers, which may lead to fewer falls and hip fractures [6].

What’s more, an insufficiency of this vitamin is associated with increased fat infiltration in the muscles of healthy young women. Higher fat infiltration worsens muscle strength and overall fitness [7].

Vitamin D might also improve athletic performance in vitamin D-deficient athletes. Deficiency appears to be correlated with increased risk of illness and injury among athletes, especially in regards to stress fractures [8, 9, 10].

Vitamin D may help strengthen muscles, improve fitness, and reduce the risk of falls in the elderly. Deficiency might make athletes more prone to injuries, according to some studies.

Vitamin D & Heart Health


  • Deficiency may increase the risk of heart disease
  • Supplementation may help protect the heart and blood vessels
  • Getting enough vitamin D may help maintain normal blood pressure

Deficiency May Increase Cardiovascular Disease Risk

Vitamin D deficiency has been associated with increased risk of cardiovascular disease (including high blood pressure, heart attacks, peripheral arterial disease, and stroke) in several studies [11, 12, 13].

According to cell-based research, vitamin D receptor (and 1α-hydroxylase) are present in the heart and blood vessels, suggesting they play a role in maintaining heart health [14, 15, 16].

Studies including more than 1,800 patients found an increased risk of high blood pressure in those with vitamin D level <50 nmol/L compared to those >75 nmol/L [17].

Supplementation May Protect the Heart & Blood Vessels

One study showed that vitamin D supplementation or UVB irradiation may lower blood pressure, improve blood pressure control, and regress heart enlargement. Similarly, deficiency causes hardening of the arteries (atherosclerosis) and blood vessel dysfunction, which predispose people to cardiovascular disease [18, 19, 20].

Several studies found that low levels of vitamin D and decreased exposure to sunlight are associated with an increased risk of heart disease [21, 22, 23].

In vitamin D-deficient elderly women, a combination of vitamin D and calcium reduced systolic blood pressure by 9% more (by 13 mmHg) than calcium alone [24].

However, some studies did not find benefits to vitamin supplementation.

Daily supplementation with 800 IU vitamin D for 12 weeks did not impact blood pressure, renin and fat concentrations, which are markers of heart disease [25].

Similarly, studies conducted in women and the elderly demonstrated no effect of vitamin D supplementation on blood pressure [26, 27].

In another study of healthy postmenopausal women, vitamin D (400 IU/day or 1,000 IU/day) did not reduce heart disease risk, given over one year [28].

Though studies linked vitamin D deficiency with heart disease, supplementation might not have a protective effect. Additional studies are needed.

Sun Exposure Reduces Blood Pressure

Scientists have associated skin exposure to UVB radiation with lower blood pressure [29].

Additional studies confirmed that blood pressure is affected by variations in skin color, geographic region, and season [29].

In fact, UVB therapy was able to significantly reduce blood after 6 weeks in one study [30].

How does sunlight-derived vitamin D achieve this effect?

According to cell-based studies, it decreases the activity of the renin-angiotensin system, which otherwise works to constrict blood vessels. Some blood-pressure-lowering medications act on this system as well.

In vitamin D-sufficient hypertensive rats, oral vitamin D decreased blood pressure precisely by suppressing the renin-angiotensin system [18, 31].

Sun exposure has many benefits beyond vitamin D, which may explain why some studies found greater benefits to sun exposure than to vitamin D supplements. Large-scale studies will hopefully soon clarify how the effects of vitamin D supplements differ from sun exposure since both have the potential to increase vitamin D blood levels.

Several studies have linked sun exposure, which increases vitamin D levels, to lower blood pressure. Limited evidence suggests that UVB therapy might also reduce blood pressure, though larger studies are needed.

Supplementation Improves Heart Health in PCOS

Women with polycystic ovary syndrome (PCOS) tend to have low vitamin D blood levels. Vitamin D supplementation might improve sugar balance and menstrual frequency in PCOS women (32, 33, 34, 35, 36).

What’s more, women with PCOS are at an increased risk of cardiovascular disease. Limited research suggests that low-dose vitamin D may help as an add-on for women who suffer from both PCOS and cardiovascular disease [37].

Women with PCOS are at a higher risk of heart disease. Small-scale studies suggest low-dose vitamin D might reduce their risk when added on to standard care.

Does Vitamin D Improve Metabolic Health?


  • Deficiency may impair insulin production and sugar control
  • People with type 2 diabetes are commonly deficient
  • Supplementation may help prevent type 2 diabetes (limited evidence)
  • Normal vitamin D levels may reduce the risk of obesity and metabolic syndrome

Deficiency May Impair Sugar Control

Vitamin D plays a role in insulin production and secretion from pancreatic cells [38].

Several studies suggest deficiency leads to impaired glucose and insulin secretion, which, in turn, may increase the risk of type 1 and type 2 diabetes [39, 40, 41, 42, 43, 44, 45].

Studies have demonstrated that blood vitamin D concentrations are lower in patients with type 2 diabetes [46, 47, 48].

Vitamin D helps the pancreas produce insulin, which controls sugar levels. Deficiency may impair this process and is common in people with type 2 diabetes.

Supplementation May Decrease the Risk of Type 2 Diabetes

Studies show that supplementation with vitamin D has the potential to restore insulin secretion, in specific cases [49, 42, 50, 51].

In the Women’s Health Study, an intake of 511 IU/day of vitamin D or more was associated with a lower risk of type 2 diabetes [52].

Vitamin D might have a role in delaying the progression to diabetes in adults at high risk of type 2 diabetes. In one study, supplementation was associated with good functioning of pancreatic cells. It also reduced the rise of Hb A1C (a marker of blood sugar levels over several months) over time [53, 53].

Limited studies suggest vitamin D supplementation might lower the risk of type 2 diabetes, but the available evidence is far from conclusive.

Healthy Levels May Prevent Obesity & Metabolic Syndrome

According to some researchers, being overweight or obese is associated with decreased blood concentrations of vitamin D [54, 55].

There may be a genetic component to this. Evidence suggests that people with a genetically higher body mass index (BMI) tend to have lower vitamin D status [56].

Additionally, lower blood levels are associated with higher waist circumference and percentage of total body fat in children, adolescents, and adults [57, 58, 59, 60, 61].

Obese people need higher vitamin doses than lean individuals to achieve the same vitamin D concentrations in the blood [62, 63, 64].

12-week supplementation with 25 μg of vitamin D in overweight and obese women decreased body fat mass by 7% but did not affect body weight and waist circumference [65].

Obese African Americans are at particularly high risk for this vitamin deficiency. Physicians should consider routine supplementation or screening of these patients for low vitamin D levels [66].

Lastly, vitamin D deficiency may be a risk factor for metabolic syndrome [67, 68, 69].

On the other hand, higher blood levels of vitamin D were associated with a decrease metabolic syndrome features–high blood pressure, high triglycerides, and low HDL cholesterol–in postmenopausal women [70].

Several studies found a link between low vitamin D levels and obesity. Higher blood levels might prevent people from obesity and metabolic syndrome, limited studies suggest.

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Aside from its well-known benefits for bone health, vitamin D may be equally important for physical, metabolic, and heart health.

Research studies have linked vitamin D deficiency with muscle loss and fractures, type 2 diabetes, obesity, and heart disease. It’s not certain whether low vitamin D status can directly cause these conditions. However, strong evidence confirms that maintaining healthy blood vitamin D levels through sun exposure and diet is beneficial.

On the other hand, mixed results were seen with vitamin D supplementation. Weak evidence supports it for people who are deficient, particularly the elderly and athletes, but more studies are needed.

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