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?
Snapshot
- May improve muscle strength and physical performance
- May reduce the risk of falls in the elderly (insufficient evidence)
- 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.
Does Supplementation Improve Physical Performance?
Clinical evidence suggests that vitamin D plays a role in muscle metabolism and function [1].
However, the benefits of supplementation for improving physical performance are uncertain. There is insufficient evidence to rate the effectiveness and safety of vitamin D for this use.
Supplementation has been suggseted to improve muscle strength, balance, and physical performance in some studies. It also appeared to reduce falls in adolescents, the elderly, and chronic kidney disease patients–but the evidence is inconclusive [2, 3, 4].
In one study, supplementation reduced the risk of falls by more than 20%. However, other studies found no benefit. Some scientists have suggested that supplementation might only be useful in older people who are deficient [5].
Tissue-based studies hypothesize 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].
Insufficiency has also been associated with increased fat infiltration in the muscles of healthy young women. Higher fat infiltration worsens muscle strength and overall fitness [7].
Other studies suggest that vitamin D might also improve athletic performance in vitamin D-deficient athletes, but further trials are needed. 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 & Heart Health
Snapshot
- Deficiency may increase the risk of heart disease
- Supplementation may help prevent heart failure
- Supplementation likely doesn’t protect against heart disease or high blood pressure
- Getting enough vitamin D through sun exposure 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 Likely Not Beneficial for Preventing Heart Disease
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].
Adequate Sun Exposure Likely 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.
Supplementation May Improve 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].
Does Vitamin D Improve Metabolic Health?
Snapshot
- 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].
Supplementation May Decrease the Risk of Type 2 Diabetes (if deficient)
Studies show that supplementation with vitamin D has the potential to restore insulin secretion, in specific cases [49, 42, 50, 51].
However, findings have been mixed. Evidence suggests that supplementation might only be beneficial in people at risk of type 2 diabetes who are deficient in vitamin D.
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].
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].
Read More:
- What is Vitamin D? Health Benefits & Dosage
- Can Vitamin D3 Help Prevent Infections?
- Can Vitamin D Help Protect Against Inflammation & Autoimmunity?
- Can Vitamin D Reduce the Likelihood of Cancer?
- Vitamin D Benefits for Brain Health & Sleep
- How Vitamin D Improves Bone & Kidney Health
- Is Vitamin D Safe for Fertility, Pregnancy & Breastfeeding?
- Does Vitamin D Improve Hair & Skin Health?
- Vitamin D: Dosage, Sources, Deficiency, Toxicity
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.
