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Vitamin D
The one health benefit that sunlight has on
human skin is the production of vitamin D.
Unfortunately, the ultraviolet rays that stimulate vitamin D
production (UVB rays) are the same ones that
cause skin cancer and premature aging.
There isn't very much vitamin D in the
typical American's diet. Some is
present in oily fish (e.g., salmon, mackerel,
sardines) milk, and fortified cereal or orange
juice, but dietary sources alone are usually not
sufficient for a healthy blood level without the
addition of substantial sun exposure or a
vitamin supplement.
Vitamin D deficiency can cause rickets in
children, and osteoporosis in adults. An
increased risk of other ills, such as cancer of
the colon, breast, or prostate, as well as
multiple sclerosis and type 1 diabetes might be
linked to vitamin D deficiency. More
research is needed before all of these
associations can be considered certain but in
the meantime it seems reasonable for everyone to
take prudent measures to maintain an adequate
blood level of vitamin D.
During summer months, particularly in the southern
latitudes, some individuals acquire enough
sun exposure to achieve an adequate vitamin D
level. However, while sun exposure is an
effective source of vitamin D, it can
simultaneously increase the risk of skin cancer.
When sunscreen is applied to the
skin, it not only reduces sun damage, but unfortunately it also blocks vitamin
D production.
Darkly pigmented skin, advanced age, and low UV index
(e.g., winter months in northern latitudes) are
some of the factors that decrease the amount of
vitamin D produced by the skin in response to
sun exposure. Because of the dual impact
of the sun's UV rays (skin cancer induction and
vitamin D production) those with the lightest
skin pigment are at the highest risk of
sun damage resulting in skin cancer, while people
with darker skin pigment are at lower risk of
skin cancer but higher risk for
vitamin D deficiency.
Some
authorities recommend routine limited or
"sensible" sun
exposure for vitamin D. However, too many variables affect the amount of
exposure time needed (e.g., season, time of day,
weather conditions, skin color, age) making it
impossible to give a simple recommendation such
as
"[X] minutes of sun per day" that
would be assured to provide sufficient vitamin D
for all people. This introduces the risk that
people will unintentionally over-expose (fall
asleep while sunning) and increase their risk of
skin cancer in the process. Sun Safety for Kids agrees with the
American Academy of Dermatology: “Vitamin D from
food and dietary supplements offers the same
benefits — without the danger of UV exposure —
as vitamin D obtained from the sun1.”
The amount of Vitamin D in food or
in a supplement is commonly listed in International
Units (IU). Evidence is still emerging to
determine the ideal safe and effective amount of
vitamin D that people should get. At present, the National Institutes of Health2
maintains that, unlike other vitamins, there is
insufficient scientific information to establish
a Recommended Dietary Allowance (RDA) for
vitamin D. However, they list Adequate
Intake (AI) amounts as follows: 200 IU
from birth to age 50, 400 IU for ages 51-70, and
600 IU beyond age 70. Based on
recent research, many experts now believe that the
average healthy adult should ingest a total of 800 to
1,000 IU daily to maintain an adequate level of vitamin D.
In June, 2007, the Canadian Cancer Society3
recommended that adults who do not get much sun
should take a daily 1,000 IU vitamin D
supplement.
Vitamin D supplements are most effective if
taken with food. But,
Beware! Vitamin D can be toxic in high doses. The NIH lists 2,000 IU per day as
the upper limit
for safety.
The directors of Sun Safety for Kids believe
that optimum health will be achieved if people
practice careful sun
protection year round and compensate by
ingesting a sufficient daily
amount of vitamin D. Until more
evidence is available, a total daily
intake in the range of 800 to 1,000 IU is reasonable for healthy
sun-safe adults.
Vitamin D for
Children
A 2008
report4
from the American Academy of Pediatrics (AAP)states,
"The new recommended daily intake of vitamin D
is 400 IU/day for all infants, children,
and adolescents beginning in the first few days
of life." This is the same amount of
vitamin D that is contained in one teaspoon of
cod liver oil, a treatment that was proven safe
and effective at preventing rickets by routine
use in children over a period of several
decades.
The recommendation applies to all children
except those who consume at least one quart of
vitamin D-fortified formula or milk per day.
The AAP recognizes that, "Given the dietary
practices of many children and adolescents, a
dietary intake of 400 IU of vitamin D is
difficult to achieve. Thus, for older
children and adolescents, a daily multivitamin
or vitamin D-only preparation containing 400 IU
of vitamin D would be warranted."
Regarding sun exposure, the report states,
"Although the AAP encourages physical activity
and time spent outdoors, children's activities
that minimize sunlight exposure are preferred,
and when outdoors, protective clothing as well
as sunscreens should be used. In following
these guidelines, vitamin D supplements during
infancy, childhood, and adolescence are
necessary."
"Children and adolescents at increased risk
of developing rickets and vitamin D deficiency,
including those with... ...decreased sunlight
exposure... ...may require even higher doses
than 400 IU/day of vitamin D," according to the
AAP. However, because vitamin D can be
toxic in high doses parents should consult their
child's pediatrician before increasing the
amount of supplementation above 400 IU per day.
The doctor can assess the child's vitamin D
status with a simple blood test and then could
advise an appropriate adjustment to the daily
supplement amount if indicated.
The AAP's recommendations are aimed primarily
at preventing rickets or poor bone
mineralization. Further refinement of the
AAP's recommendation might be forthcoming as
additional benefits of vitamin D are discovered
and confirmed. Perhaps it will be revealed
that a different amount is necessary to provide
optimum health for not only the bones but other
systems as well. However, more study is
needed before that can be determined.
Ask to Be Tested
A simple blood test called "25-hydroxy
vitamin D" measures circulating vitamin D and
provides a fair assessment of one's level.
Periodically checking this test helps to assure
that vitamin D sufficiency is being maintained.
Leading experts suggest that blood levels in the
range of 30 to 60 ng/ml are preferred. Levels
tend to fluctuate with the seasons (lower in
winter/higher in summer) due to incidental sun
exposure. Bearing this in mind, blood test
results will aid your doctor in determining the
amount of vitamin D supplementation that is
indicated (in winter or year-round) in order to
maintain an optimum level.
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1
http://www.aad.org/ (type “vitamin D” into
the search site dialog box)
2
http://ods.od.nih.gov/factsheets/vitamind.asp
3
http://www.cancer.ca/ccs/internet/mediareleaselist/
0,3208,3172_1613121606_1997621989_langId-en,00.html
4
http://www.aap.org/new/VitaminDreport.pdf
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