By Alina Petre
Vitamin D is a fat-soluble vitamin that is essential for optimal health.
Only a handful of foods contain significant amounts of this vitamin. These include fatty fish, organ meats, certain mushrooms and fortified foods.
However, unlike other vitamins that you can only get through your diet, vitamin D can also be made by your body when your skin is exposed to the sun.
For this reason, vitamin D is technically considered a hormone.
The limited availability of vitamin D in the human diet, combined with most people’s insufficient sun exposure, may explain why up to 41.6 percent of the U.S. population has deficient blood levels (1).
Interestingly, having adequate blood levels of this vitamin can provide many important health benefits.
This article lists 15 science-based benefits linked to vitamin D.
1. Improves Bone Health
Vitamin D plays an important role in the health of your bones.
That’s because it increases the absorption of calcium and phosphorus from your diet—two nutrients important for bone health.
Studies show that individuals with low blood levels tend to suffer from more bone loss (2).
In addition, research shows that individuals taking vitamin D supplements may benefit from a 23–33 percent lower risk of bone fractures (3, 4).
Moreover, recent studies report that taking vitamin D supplements may help improve fracture healing, especially in people with low levels. However, more studies are needed to support these results (5).
Most experts recommend that individuals with blood values under 12 ng/ml (25 nmol/l) should consider taking a vitamin D supplement that provides at least 20–25 mcg (800–1,000 IU) each day (2).
However, some insist that this recommendation is too low and propose that people take higher dosages in order to maintain blood vitamin D levels above 30 ng/ml (75 nmol/l) (6, 7, 8, 9).
In any case, all experts agree that elderly individuals, who have an elevated risk of falls and fractures, should supplement at the higher end of the recommendation (2).
Bottom Line: Vitamin D helps increase the absorption of minerals that are important for bone health. Higher levels may also reduce the risk of fractures, limit bone loss and improve recovery from fractures.
2. Reduces Diabetes Risk
Diabetes is a disorder in which your body cannot process carbs normally. Several types of diabetes exist, but type 1 and type 2 diabetes are the most common.
Type 1 diabetes is an autoimmune disease generally diagnosed during childhood or adolescence, whereas type 2 diabetes usually occurs later in life and is related to lifestyle.
Interestingly, vitamin D may help reduce the risk of both types of diabetes.
Type 1 Diabetes in Children
Type 1 diabetes is a genetic autoimmune disease that destroys the insulin-producing beta cells in the pancreas.
For this reason, type 1 diabetics must inject insulin several times per day to ensure their blood sugar stays at a healthy level (10).
Although type 1 diabetes has a large genetic component, certain environmental factors—perhaps including low vitamin D intake—may act together to promote the disease.
For instance, studies show that infants and toddlers who take vitamin D supplements may have a 29–88 percent lower risk of developing type 1 diabetes than infants given no supplements (11, 12).
The recommended daily allowance is 10 mcg (400 IU) vitamin D for infants 0–12 months and 15 mcg (600 IU) for most children and adults (13).
However, many argue that these recommendations are too low, with one study observing that only daily doses of 50 mcg (2,000 IU) and above successfully reduced the risk of developing type 1 diabetes (14).
That said, few studies have so far investigated the link between vitamin D and type 1 diabetes. More research is needed before strong conclusions can be made.
Type 2 Diabetes in Children, Teenagers and Adults
Type 2 diabetes is a disease that develops over time. It can happen if your pancreas stops producing enough insulin or if your body develops a resistance to insulin—or both (15).
Interestingly, vitamin D levels may play a role in the development of type 2 diabetes (16, 17, 18, 19).
Experts believe that vitamin D may protect against type 2 diabetes by reducing insulin resistance, increasing insulin sensitivity and enhancing the function of the cells responsible for producing insulin (17, 20, 21).
In fact, two recent reviews report that people with low blood vitamin D levels may have up to a 55 percent higher risk of developing type 2 diabetes (22, 23).
What’s more, adults who consumed at least 12.5 mcg (500 IU) of vitamin D per day appeared to benefit from a 13 percent lower risk of developing type 2 diabetes than those who regularly consumed less than 5 mcg (200 IU) per day (23).
Similar results were also reported in vitamin-D-deficient children and teenagers with insulin resistance (24).
In another study, type 2 diabetics given 1,250 mcg (50,000 IU) vitamin D per week had a 5–21 percent decrease in fasting blood sugar levels and insulin resistance over the two-month study period, compared to controls (25).
It’s important to mention that not all reviews agree on the protective effects of taking vitamin D supplements (26, 27, 28).
Although it is possible that not all type 2 diabetics benefit from taking vitamin D supplements, it seems particularly beneficial to those with poor blood sugar control (26).
Bottom Line: Adequate vitamin D levels may help reduce the risk of developing both type 1 and type 2 diabetes. In certain cases, vitamin D supplements may also help improve blood sugar control in type 2 diabetics.
3. Could Improve Heart Health
Vitamin D may help improve the health of your heart and reduce the likelihood of heart attacks.
In one study, men with blood levels below 15 ng/ml (37 nmol/l) were twice as likely to get a heart attack as those with levels of 30 ng/ml (75 nmol/l) or higher (29).
In another study, the likelihood of developing heart disease was 153 percent higher for people with blood vitamin D levels below 15 ng/ml (37 nmol/l) (30).
The highest risk was seen in individuals with low vitamin D levels who also had high blood pressure (30).
That said, although low blood vitamin D levels are often linked to an increased risk of heart disease, many studies fail to find a decreased risk from taking vitamin D supplements (31, 32, 33, 34).
Experts speculate that other factors linked to a good vitamin D status may be at play, such as time spent outdoors or a preference for vitamin-D-fortified beverages instead of soft drinks (35).
Thus, although taking vitamin D supplements may be beneficial for other reasons, increasing your levels through lifestyle choices still seems to be the best strategy against heart disease.
Bottom Line: Individuals with a good vitamin D status have a lower risk of developing heart disease. However, taking supplements doesn’t seem to have an effect.
4. May Lower Your Risk of Certain Cancers
Maintaining adequate vitamin D levels may have some benefits for preventing cancer.
In fact, various studies suggest that individuals with higher levels have a lower risk of certain types of cancer (36, 37).
Two recent reviews report that those with adequate levels may have up to a 25 percent lower risk of developing bladder cancer. Higher vitamin D levels may also reduce the risk of dying from the disease (38, 39).
Similarly, several other studies show that maintaining higher blood vitamin D levels may reduce the risk of developing colorectal cancer (40, 41, 42, 43).
In addition, some studies report that vitamin D may play a role in slowing down the progression of cancer. That said, it remains unclear whether taking vitamin D supplements provides any anti-cancer benefits (44).
In fact, several studies failed to find protective effects against cancer after participants took vitamin D supplements, despite having increased blood levels (45, 46, 47, 48, 49).
In sum, more studies are needed to determine cause and effect, as well as the true value of taking vitamin D supplements as an anti-cancer strategy.
Until then, it may be wise to focus on maintaining adequate vitamin D levels through lifestyle choices that are known to reduce the risk of cancer. For instance, through a healthy diet and regular physical activity—preferably outdoors.
Bottom Line: Vitamin D may play a role in cancer prevention. However, more studies are needed to determine its exact role.
5. May Reduce the Risk of Premature Death
Vitamin D may help you live a longer life.
Indeed, several studies describe a remarkably consistent link between blood vitamin D levels and the risk of dying prematurely (50, 51).
For instance, a Cochrane review looked at 50 randomized controlled studies—the gold standard in scientific research.
It found that people taking vitamin D supplements had a 6 percent lower risk of premature death (52).
Therefore, those getting enough vitamin D through the sun, their diet or supplements may be adding a few extra years to their lives.
Bottom Line: Maintaining good vitamin D levels may slightly reduce your risk of dying prematurely.
6. Diminishes Symptoms of Depression
Researchers are now discovering that vitamin D may also have an effect on depression.
The vitamin’s exact role in the development of depression is not fully understood. One theory suggests it increases the amount of serotonin in the brain, which is a known contributor to feelings of well-being and happiness (53, 54).
Accordingly, a recent review reports that low vitamin D levels may increase the likelihood of depression by up to 131 percent (55).
However, research to date hasn’t provided clear evidence that vitamin D supplements are effective at treating or preventing depression (54, 55, 56, 57).
Interestingly, it may depend on the severity of symptoms.
For example, vitamin D supplements seem most effective at reducing symptoms in individuals with strong symptoms of depression, but less effective in those with moderate or light symptoms (58).
However, more studies are needed to support these effects and determine what supplement recommendations are most effective.
Bottom Line: Vitamin D may help prevent or reduce symptoms of depression, particularly in individuals with strong symptoms.
7. Increases Muscle Strength
Recent studies show a link between vitamin D, muscle growth and strength, in both adults and the elderly.
A recent review looked at the effects of vitamin D on athletic and non-athletic adults.
It found that those given vitamin D supplements increased their upper and lower body strength slightly more than those given no supplements (59).
Similarly, several studies examined how vitamin D affects muscle strength, the risk of falls and frailty in the elderly. A large majority found that supplementing led to better increases in muscle strength and fewer falls than a placebo (60, 61).
Daily doses of 20–25 mcg (800–1,000 IU) seem sufficient to cause improvements in elderly people. The benefits appear to be strongest in individuals with low vitamin D levels to begin with (60).
Studies performed on younger individuals report using vitamin D dosages up to eight times as high. Thus, it is possible that stronger dosages may be required to see any increases in muscle strength in younger individuals (59).
However, more studies are needed before definitive recommendations can be made.
Bottom Line: Maintaining good levels of vitamin D may help increase muscle strength. It may also reduce the risk of falls and frailty in the elderly.
8. May Help Prevent and Treat Multiple Sclerosis
Multiple sclerosis (MS) is an autoimmune disease that involves the brain, spinal cord and optic nerves of the eyes.
Certain studies suggest that adequate blood vitamin D levels may help lower the risk of MS by up to 62 percent (62, 63).
Individuals with MS who are able to maintain high vitamin D levels may slow down the progression of their disease (64, 65).
However, only a limited number of studies have been done in this population (66).
Bottom Line: Vitamin D may help lower MS risk and slow its progression. However, more studies are needed.
9–15. Other Benefits
Over the past decade, vitamin D has become an especially popular topic of scientific research.
For this reason, new studies investigating the benefits of vitamin D are continuously popping up in a wide variety of areas. Some potential extra benefits include:
1. Fewer asthma attacks: Daily doses of 7.5–30 mcg (300–1,200 IU) may decrease the likelihood of asthma attacks in school-aged children (67, 68).
2. Prevention of the common cold: Taking vitamin D supplements may help reduce the risk of upper respiratory tract infections (URTI) (69, 70).
3. Improved recovery from surgery: Adequate blood levels may help enhance recovery following surgery (71).
4. Reduction of chronic pain: Adequate vitamin D levels may help decrease pain in some, but not all, individuals suffering from chronic pain (72, 73, 74, 75).
5. Promotion of healthy births: Taking vitamin D supplements during pregnancy may help increase the length and weight of babies at birth (76).
6. Protection against Parkinson’s disease: Higher blood levels may reduce the risk of developing Parkinson’s (77, 78).
7. Reduction in age-related mental decline: Adequate blood levels may reduce the risk of mental decline among the elderly (79).
It’s important to note that research on the benefits listed above is generally sparse.
In addition, the way some studies were designed makes it impossible to determine whether low vitamin D levels actually cause the adverse effects.
Bottom Line: Adequate vitamin D levels are linked to a variety of health benefits. However, more studies are needed to confirm these benefits.
Take Home Message
Vitamin D plays several important roles in the body.
Thus, maintaining adequate levels—whether through food, sun exposure or supplements—is very important for optimal health.
It’s actually quite common for people to be deficient without knowing it. For this reason, it’s generally a good idea to get your vitamin D levels checked by a doctor.
Here are the 8 most common symptoms of vitamin D deficiency.
Those who are deficient and unable to increase sun exposure should strongly consider taking a supplement, preferably with the D3 form of the vitamin.
Dosage recommendations can vary from person to person. Discuss this with your doctor or dietitian.
Those who choose to increase their vitamin D levels from the sun should make sure to avoid excessive exposure, which can lead to sunburns.
If you’re interested in learning more about vitamin D, make sure to check out this detailed guide: Vitamin D 101—A Detailed Beginner’s Guide.
Reposted with permission from our media associate Authority Nutrition.