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Vitamin D

(Calciferol)
What is Vitamin D and what does it do?
Vitamin D is a nutrient you
need for good health. It helps your body absorb calcium,
one of the main building blocks for strong bones. Together with
calcium, Vitamin D helps protect you from developing osteoporosis,
a disease that thins and weakens the bones and makes them more
likely to break. Your body needs Vitamin D for other functions too.
Your muscles need it to move, and your nerves need
it to carry messages between your brain and your body. Your immune
system needs Vitamin D to fight off invading bacteria and viruses.
How much Vitamin D do I need?
The
amount of Vitamin D you need each day depends on your age.
Average
daily recommended amounts are listed below in micrograms (mcg)
and International
Units (IU).
Life Stage |
RDA |
Birth to 12 months |
10 mcg (400 IU) |
Children 1–13 years |
15 mcg (600 IU) |
Teens 14–18 years |
15 mcg (600 IU) |
Adults 19–50 years |
15 mcg (600 IU) |
Adults 51-70 years |
15 mcg (600 IU) |
Adults 71 years and older |
20 mcg (800 IU) |
Pregnant teens and women |
15 mcg (600 IU) |
Breastfeeding teens and women |
15 mcg (600 IU) |
What foods provide Vitamin D?
Very
few foods naturally contain Vitamin D. Fortified foods
provide most of the Vitamin D in the diets of people in the United
States. Check the Nutrition Facts label for
the amount of Vitamin D in a food or beverage.
- Almost all of the U.S. milk
supply is fortified with about 3 mcg (120 IU) Vitamin D per cup.
Many plant-based alternatives such as soy milk,
almond milk, and oat milk are similarly fortified, but foods
made from milk, like cheese and ice cream, are usually not
fortified.
- Vitamin D is added to many breakfast cereals and to some
brands of orange juice, yogurt, margarine, and other food
products.
- Fatty fish (like trout, salmon,
tuna, and mackerel) and fish liver oils
are among the best natural sources of Vitamin D.
- Beef liver, egg yolks, and cheese
have small amounts of Vitamin D.
- Mushrooms provide a little
Vitamin D. Some mushrooms have been exposed to ultraviolet
light to increase their Vitamin D content.
Can I get Vitamin D from the sun?
Your
body makes Vitamin D when your bare skin is exposed to the sun. Most
people get at least some Vitamin D this way. However, clouds, smog,
old age, and having dark-colored skin reduce the amount of Vitamin D
your skin makes. Also, your skin does not make Vitamin D from
sunlight through a window.
Ultraviolet radiation from sunshine can cause skin
cancer, so it’s important to limit how much time you spend in
the sun. Although sunscreen limits
Vitamin D production, health experts recommend using sunscreen with
a sun protection factor (SPF)
of 15 or more when you’re out in the sun for more than a few
minutes.
What kinds of
Vitamin D dietary supplements are available?
Vitamin D is found in multiVitamin/mineral supplements. It is also
available in dietary
supplements containing only Vitamin D or Vitamin D combined with
a few other nutrients. The two forms of Vitamin D in supplements are
D2 (ergocalciferol) and D3 (cholecalciferol). Both forms increase
Vitamin D in your blood, but D3 might raise it higher and for longer
than D2. Because Vitamin D is fat soluble, it is best absorbed when
taken with a meal or snack that includes some fat.
Am I getting enough
Vitamin D?
Because you get Vitamin D from food, sunshine, and dietary
supplements, one way to know if you’re getting enough is a blood
test that measures the amount of Vitamin D in your blood. In the
blood, a form of Vitamin D known as 25-hydroxyVitamin D is measured
in either nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL).
One nmol/L is equal to 0.4 ng/mL. So, for example, 50 nmol/L is the
same as 20 ng/mL.
- Levels of 50 nmol/L (20 ng/mL) or
above are adequate for most people for bone and overall health.
- Levels below 30 nmol/L (12 ng/mL)
are too low and might weaken your bones and affect your health.
- Levels above 125 nmol/L (50 ng/mL)
are too high and might cause health problems.
In
the United States, most people have adequate blood levels of Vitamin
D. However, almost one out of four people have Vitamin D blood
levels that are too low or inadequate for bone and overall health.
Some
people are more likely than others to have trouble getting enough
Vitamin D:
-
Breastfed infants. Breast
milk alone does not provide infants with an adequate amount of
Vitamin D. Breastfed infants should be given a supplement of 10
mcg (400 IU) of Vitamin D each day.
-
Older adults. As you
age, your skin’s ability to make Vitamin D when exposed to
sunlight declines.
-
People who seldom expose
their skin to sunshine because they do not go outside or
because they keep their body and head covered. Sunscreen also
limits the amount of Vitamin D your skin produces.
-
People with dark skin. The
darker your skin, the less Vitamin D you make from sunlight
exposure.
-
People with conditions that
limit fat absorption, such as Crohn’s
disease, celiac
disease, or ulcerative
colitis. This is because the Vitamin D you consume is
absorbed in the gut along with fat, so if your body has trouble
absorbing fat, it will also have trouble absorbing Vitamin D.
-
People with Obesity or who
have undergone gastric bypass
surgery. They may need more Vitamin D than other people.
What are the symptoms of Vitamin D deficiency?
Severe lack of Vitamin D in children causes rickets.
Symptoms of rickets
include:
- Incorrect growth patterns due to bowed or bent bones.
- Muscle weakness.
- Bone pain.
- Deformities in joints.
This is very rare. Children with a mild Vitamin deficiency may just have
weak, sore and/or painful
muscles.
Lack of Vitamin D isn’t quite as obvious in adults.
Symptoms
might include:
- Fatigue.
- Bone pain.
- Muscle weakness, muscle aches or muscle
cramps.
- Mood changes, like depression.
However, you may have no signs or symptoms of Vitamin D deficiency.
What causes Vitamin D deficiency?
In general, the two main causes of Vitamin D deficiency are:
- Not getting enough Vitamin D in your diet and/or through sunlight.
- Your body isn’t properly absorbing or using Vitamin D.
There are several specific causes of Vitamin D deficiency, including:
- Certain medical conditions.
- Weight loss-surgeries.
- Certain medications.
Several different biological and environmental factors can also put you
at a greater risk of developing Vitamin D deficiency, such as older age
and the amount of melanin (pigment) in your skin.
Medical conditions that can cause Vitamin D deficiency
Medical conditions that can cause Vitamin D deficiency include:
-
Cystic fibrosis, Crohn's
disease and celiac
disease: These conditions can prevent your intestines
from adequately absorbing enough Vitamin D through supplements,
especially if the condition is untreated.
-
Obesity: A body mass index greater than 30 is
associated with lower Vitamin D levels. Fat cells keep Vitamin D
isolated so that it’s not released. Obesity often requires taking
larger doses of Vitamin D supplements to reach and maintain normal
levels.
-
Kidney disease and liver
disease: These conditions reduce the amount of certain
enzymes (hepatic enzyme 25–hydroxylase from your liver and
1-alpha-hydroxylase from your kidneys) your body needs to change
Vitamin D to a form it can use. A lack of either of these enzymes
leads to an inadequate level of active Vitamin D in your body.
What are some effects of
Vitamin D on health?
Scientists are studying Vitamin D to better understand how it affects
health. Here are several examples of what this research has shown.
Bone health and osteoporosis
Long-term shortages of Vitamin D and calcium cause your bones to
become fragile and
break more easily. This condition is called osteoporosis. Millions
of older women and men have osteoporosis or are at risk of
developing this condition. Muscles are also important for healthy
bones because they help maintain balance and prevent falls.
A shortage of Vitamin D may lead to weak, painful muscles.
Getting recommended amounts of Vitamin D and calcium from foods (and
supplements, if needed) will help maintain healthy bones and prevent
osteoporosis. Taking Vitamin D and calcium supplements slightly
increases bone strength in older adults, but it’s not clear whether
they reduce the risk of falling or breaking a bone. Cancer
Vitamin D does not seem to reduce the risk of developing cancer of
the breast, colon,
rectum, or lung.
It is not clear whether Vitamin D affects the risk of prostate
cancer or chance of surviving this cancer. Very high blood
levels of Vitamin D may even increase the risk of pancreatic
cancer.
Clinical trials suggest that while Vitamin D supplements (with
or without calcium) may not affect your risk of getting cancer, they
might slightly reduce your risk of dying from this disease. More
research is needed to better understand the role that Vitamin D
plays in cancer prevention and
cancer-related death. Heart disease
Vitamin D is important for a healthy heart and blood
vessels and for normal blood pressure. Some studies show that
Vitamin D supplements might help reduce blood cholesterol levels
and high
blood pressure—two of the main risk
factors for heart disease. Other studies show no benefits. If
you are overweight or
have obesity, taking Vitamin D at doses above
20 mcg (800 IU) per day plus calcium might actually raise your blood
pressure. Overall, clinical trials find that Vitamin D supplements
do not reduce the risk of developing heart disease or dying from it,
even if you have low blood levels of the Vitamin. Depression
Vitamin D is needed for your brain to function properly. Some
studies have found links between low blood levels of Vitamin D and
an increased risk of depression. However, clinical trials show that
taking Vitamin D supplements does not prevent or ease symptoms of
depression. Multiple sclerosis
People who live near the equator have more sun exposure and higher
Vitamin D levels. They also rarely develop multiple sclerosis (MS),
a disease that affects the nerves that carry messages from the brain
to the rest of the body. Many studies find a link between low blood
Vitamin D levels and the risk of developing MS. However, scientists
have not actually studied whether Vitamin D supplements can prevent
MS. In people who have MS, clinical trials show that taking Vitamin
D supplements does not keep symptoms from getting worse or coming
back. Type 2 diabetes
Vitamin D helps your body regulate blood
sugar levels. However, clinical trials in people with and
without diabetes show
that supplemental Vitamin D does not improve blood sugar levels, insulin
resistance, or hemoglobin A1c
levels (the average level of blood sugar over the past 3 months).
Other studies show that Vitamin D supplements don’t stop most people
with prediabetes from developing diabetes. Weight loss
Taking Vitamin D supplements or eating foods that are rich in
Vitamin D does not help you lose weight. Cognitive health
Research shows that people with low levels of Vitamin D
in the blood are less able to think and learn, called
cognitive decline. But more studies are needed to find out
whether Vitamin D supplements may help.
Bone conditions passed through families, called inherited
conditions
Vitamin D supplements can be used to help treat inherited
conditions that happen when the body can't take in or use
Vitamin D. One such condition is familial hypophosphatemia.
Osteomalacia
Vitamin D supplements treat adults with extreme Vitamin D
deficiency that results in this softening of the bones.
Psoriasis
Vitamin D treats plaque-type psoriasis in some people.
Vitamin D or a cream that has a form of Vitamin D called
calcipotriene can be used on the skin.
Rickets
Not having enough Vitamin D in the body can cause this
rare condition that weakens bones in children. Taking a
Vitamin D supplement can prevent and treat the condition.
Can
Vitamin D be harmful?
Yes,
getting too much Vitamin D can be harmful. Very high levels of
Vitamin D in your blood (greater than 375 nmol/L or 150 ng/mL) can
cause nausea,
vomiting, muscle weakness, confusion, pain, loss of appetite,
dehydration, excessive urination and thirst, and kidney
stones. Extremely high levels of Vitamin D can cause kidney
failure, irregular heartbeat, and even death. High levels of
Vitamin D are almost always caused by consuming excessive amounts of
Vitamin D from dietary supplements. You cannot get too much Vitamin
D from sunshine because your skin limits the amount of Vitamin D it
makes.
The
daily upper
limits for Vitamin D include intakes from all sources—food,
beverages, and supplements—and are listed below in micrograms (mcg)
and IU. However, your health care provider might recommend doses
above these upper limits for a period of time to treat a Vitamin D
deficiency.
Ages |
Upper Limit
(per day) |
Birth to 6 months |
25 mcg (1,000 IU) |
Infants 7–12 months |
38 mcg (1,500 IU) |
Children 1–3 years |
63 mcg (2,500 IU) |
Children 4–8 years |
75 mcg (3,000 IU) |
Children 9–18 years |
100 mcg (4,000 IU) |
Adults |
100 mcg (4,000 IU) |
Pregnant teens and women |
100 mcg (4,000 IU) |
Breastfeeding teens and women |
100 mcg (4,000 IU) |
Safety and side effects
Taken in typical doses, Vitamin D is thought to be mainly
safe.
But taking too much Vitamin D in the form of supplements can
be harmful and even deadly. Taking more than 4,000 IU a day
of Vitamin D might cause:
- Upset stomach and vomiting.
- Weight loss and not wanting to eat.
- Muscle weakness.
- Not being able to think clearly or quickly.
- Heart rhythm issues.
- Kidney stones and kidney damage.
Interactions with Medications or Supplements?
Yes,
Vitamin D supplements may interact with
some medicines. Here are several examples:
-
Aluminum. Taking Vitamin D and phosphate
binders that have aluminum might cause harmful levels of
aluminum in people with kidney failure. Phosphate
binders treat high blood levels of phosphate in people
with longtime kidney disease.
-
Anticonvulsants. The anticonvulsant medicines
phenobarbital (Sezaby) and phenytoin (Dilantin, Phenytek)
break down more Vitamin D. This lessens how well the
body can take in calcium.
-
Atorvastatin (Lipitor). Statin medications
reduce cholesterol synthesis. Because endogenous Vitamin
D is derived from cholesterol, statins may also reduce
Vitamin D synthesis [170]. In addition, high intakes of
Vitamin D, especially from supplements, might reduce the
potency of atorvastatin (Lipitor), lovastatin (Altoprev
and Mevacor), and simvastatin (FloLipid and Zocor),
because these statins and Vitamin D appear to compete
for the same metabolizing enzyme
-
Calcipotriene (Dovonex, Sorilux). Don't take
Vitamin D with this psoriasis medicine. Mixing the two
might raise the risk of having too much calcium in the
blood, called hypercalcemia.
-
Cholestyramine (Prevalite, Locholest). Taking
Vitamin D with this cholesterol-lowering medicine can
lower how much Vitamin D the body takes in.
-
Cytochrome P450 3A4 substrates, also called CYP3A4
substrates. Use Vitamin D with care if you take
a medicine affected by these enzymes. One such medicine
is the cholesterol-lowering medicine lovastatin (Altoprev).
-
Digoxin (Lanoxin). Don't take high doses of
Vitamin D with this heart medicine. High doses of
Vitamin D can cause too much calcium in the blood,
called hypercalcemia. Hypercalcemia raises the risk of
fatal heart conditions with digoxin.
-
Diltiazem (Cardizem, Tiazac, others). Don't
take high doses of Vitamin D with this blood pressure
medicine. High doses of Vitamin D can cause too much
calcium in the blood, called hypercalcemia.
Hypercalcemia may keep the medicine from working as it
should.
-
Orlistat (Xenical, Alli). The weight-loss drug,
together with a reduced-fat diet, can reduce the
absorption of Vitamin D from food and supplements,
leading to lower 25(OH)D levels
-
Thiazide diuretics. Thiazide diuretics (e.g.,
Hygroton, Lozol, and Microzide) decrease urinary calcium
excretion. The combination of these diuretics with
Vitamin D supplements (which increase intestinal calcium
absorption) might lead to hypercalcemia, especially
among older adults and individuals with compromised
renal function or hyperparathyroidism.
-
Steroids. Corticosteroid medications, such as
prednisone (Deltasone, Rayos, and Sterapred), are often
prescribed to reduce inflammation. These medications can
reduce calcium absorption and impair Vitamin D
metabolism [174-176]. In the NHANES 2001–2006 survey,
25(OH)D deficiency (less than 25 nmol/L [10 ng/mL]) was
more than twice as common among children and adults who
reported oral steroid use (11%) than in nonusers
-
Stimulant laxatives. Long-term use of high
doses of stimulant laxatives can lessen how much Vitamin
D and calcium the body takes in.
-
Verapamil (Verelan). Taking high doses of
Vitamin D with this blood pressure medicine can cause
too much calcium in the blood, called hypercalcemia.
High doses of Vitamin D also might keep verapamil from
working as well.
Tell
your doctor, pharmacist,
and other health care providers about any dietary supplements and prescription or
over-the-counter medicines you take. They can tell you if the
dietary supplements might interact with your medicines. They can
also explain whether the medicines you take might interfere with how
your body absorbs or uses other nutrients.
Vitamin D and healthful eating
People
should get most of their nutrients from food and beverages, according to
the federal government’s Dietary Guidelines for Americans. Foods contain
Vitamins, minerals, dietary
fiber, and other components that benefit health. In some cases,
fortified foods and dietary supplements are useful when it is not
possible otherwise to meet needs for one or more nutrients (for example,
during specific life stages such as pregnancy). For more information
about building a healthy dietary pattern.
One Final Note..
Vitamin D is an important Vitamin your body needs to be healthy. If
you have risk factors for developing Vitamin D deficiency or are
experiencing symptoms, be sure to contact your healthcare provider
to get a blood test to check your levels.
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