Vitamin D
What is vitamin D?
Vitamin D is a fat soluble vitamin that your body needs to absorb calcium.
It also plays an important role in maintaining muscle strength. Vitamin
D deficiency is associated with reduced calcium absorption, bone loss,
reduced muscle strength, and increased risk of fractures.
What are the sources of vitamin D?
Sunlight is the major source of vitamin D for many populations but
sun exposure is a risk factor for skin cancer. It is important to know
that even without sun exposure, you can get vitamin D from
some foods and supplements.
Why is vitamin D called the "sunshine vitamin" ?
Vitamin D is often referred to as the "sunshine vitamin". That is
because the human body has the potential to make vitamin D from casual
sun exposure of short duration. However, sun exposure can put an individual
at risk for skin cancer, cataracts, and premature aging.
According to the American Academy of Dermatology, vitamin D from food
and dietary supplements offer the same benefits as vitamin D from the
sun- without the danger of UV exposure- as vitamin D obtained
from the sun. For more information, click on the American Academy of
Dermatology Vitamin D Fact Sheet:
http://www.aad.org/media/background/factsheets/fact_vitamind.htm
For quick tips for sun protection, take the American Cancer Society's
Sun Safety Quiz:
What foods and supplements contain vitamin D?
There are only a few naturally occurring food sources of vitamin D,
such as fatty fish. Some foods are fortified with vitamin D. It
is important to know that the type of vitamin D added to fortified
foods varies. Vitamin D3 (cholecalciferol) is preferred since it is
4 to 9 times more bioactive than vitamin D2 (ergocalciferol). Vitamin
D3 is found in animal products or made from the ultraviolet irradiation
of lanolin. Vitamin D2 is more common in vegetarian food sources and
manufactured through the ultraviolet irradiation of yeast. Foods fortified
with vitamin D3 include cow's milk, some yogurts, vitamin D fortified
orange juice, some breakfast cereals and some breakfast bars.
Vitamin D3 can also be obtained from multivitamins (most contain 400
IU), in combination with some calcium supplements, or alone as a separate
vitamin D3 supplement. It is important to read nutrition fact labels
of supplements to determine the source of vitamin D since vitamin
D3 is preferable. Since the vegetarian source of vitamin D is vitamin
D2, individuals who follow vegan diets (strict vegetarian
diets that exclude all animal products and by-products) should to speak
to their healthcare provider to find out more about their vitamin
D needs.
What are the sources of vitamin D?
There is currently limited information about the vitamin
D content of foods. The average vitamin D content of some foods
has been measured. Vitamin D content is stated in international
units (IU).
The amount of vitamin D that is found in food varies depending on the
feed given to animal sources of vitamin D, the brand purchased, as well
as the amount of vitamin D added to fortified foods. For example, milk
is fortified with 100 IU of vitamin D3 per 8-ounce cup. Most dairy products
including yogurts and cheeses have not traditionally been made with fortified
milk. However, recently a few dairy products and other foods have
been manufactured with vitamin D3 added. It is important to read
food labels for vitamin
D content.
It's sensible to avoid sources of vitamin D that are high in retinol.
Vitamin D and vitamin
A are both fat-soluble vitamins that may be present in some
of the same foods or supplements. Cod liver oil, for example, contains
high amounts of both vitamin D and a type of vitamin A called
retinol.
A large study found that postmenopausal women who consumed very
high intakes of retinol (from food sources such as cod liver oil and liver,
from certain multivitamins or from vitamin A supplements) appeared
to have an increased risk of hip fractures. However, there was
no association between high intakes of another type of vitamin A, called
beta-carotene and the risk of hip fracture. Beta-carotene is found
in a wide variety of yellow and orange-colored fruits and vegetables,
as well as green leafy vegetables.
A large population study also found an association between high
intakes of retinol from supplements and hip fracture but reported no
association between retinol from cod liver oil or other food sources
and fracture risk. Although further investigation is needed to
study the relationship between retinol from various sources and fracture
risk, it is sensible to avoid foods and supplemental sources of vitamin
D that are high in retinol. This includes the avoidance of cod
liver oil and vitamin D supplements that have vitamin A added.
How much vitamin D do I need?
According to The National Osteoporosis Foundation, experts recommend
that adults under age 50 consume a daily intake of 400 to 800 international
units (IU) of vitamin D. People age 50 and older need between
800 and 1000 IU. Some people will need even more.Your doctor or medical
professional may recommend more Vitamin D than recommended for the
general population, if you are at high risk for vitamin D deficiency
or if you have been diagnosed with low serum vitamin D levels.
What populations are at higher risk for vitamin D deficiency?
The following populations are at higher risk for vitamin D
deficiency than the general population:
- Older individuals who consume diets low in vitamin D and
do not take supplements containing vitamin D
- Individuals who take total sun precautions, consume diets low in
vitamin D and do not take a supplement containing vitamin D
- Homebound individuals who get little sun exposure, consume diets
low in vitamin D and do not take a supplement containing vitamin
D
- Individuals with malabsorption syndromes who are not able to absorb
dietary vitamin D (examples include: some people with Crohn's disease
or celiac disease)
- Individuals with liver or kidney diseases who may be less able
to process vitamin D
- Individuals taking certain medications that interfere with
vitamin D metabolism (Some of these medications include steroids
taken for more than 3 months, certain medications used to control
seizures such as dilantin or phenobarbitol and cholestryamine
used to lower the cholesterol level)
What should I do if I am at high risk for vitamin D deficiency?
If you happen to be at high risk for vitamin D deficiency, it does
not mean that you actually have vitamin D deficiency. Only your doctor
or medical professional can make that determination. If you think that
you may be at risk for vitamin D deficiency, it is important to speak
to their doctor or medical professional. If your doctor or medical
professional feels that it is necessary, he or she may recommend a
blood test to check your vitamin D level.
There is evidence that the intake of 800 IU/day of vitamin D (or
more) along with adequate calcium may reduce the risk for falls
(by increasing muscle strength) and reduce the risk for fracture in
postmenopausal women and seniors. We know that as adults age, the need
for vitamin D increases, however older adults are often not not meeting
the recommended intake for vitamin D. In order for seniors to get enough
vitamin D, a supplement if often required. It is a good idea for all
adults to speak to their medical professional about their individual recommendations
for vitamin D.
Can too much vitamin D be harmful?
Since vitamin D can be stored in your body, it has been presumed that
too much may be harmful. However, toxicity is rarely seen. It
is important to follow the advice of your doctor or medical professional
and not to exceed 2000 IU/day of vitamin D from diet and/or supplements
without a prescription.
|
Vitamin
D Sources
