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15 Science-Based Benefits of Vitamin D

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 often called “the sunshine
vitamin.”

Young Woman Outside on a Cold Day Turning Her Face Towards the Sun

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% of the US 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% 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

Tuna Fish in a Can

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% 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% 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% 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% 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

Heart and Stethoscope

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% 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

Fresh Shrimp on a Stone Chopping Board

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% lower risk of developing bladder cancer.
Higher vitamin D levels may also reduce the risk of dying from
the disease (38, 39).

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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

Grilled Salmon

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%
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%
(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

Shiitake Mushrooms on a Chopping Board

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% (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

Two Salmon Fillets

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
.

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