Nutrient Notes
Vitamin A, Obesity, and Gastric Bypass
Surgery
What is vitamin A?
Vitamin A is actually not a single nutrient,
but a family of vitamins. Vitamin A is
one of four vitamins that are carried
into the body with fat, and are called
fat-soluble for that reason. The preformed
active form of vitamin A is found in
animal foods such as eggs and liver,
as well as in some fortified foods or
supplements. Most fat free milk and dried
nonfat milk solids sold in the US are
fortified with vitamin A to replace the
vitamin A lost when the fat is removed.
Many breakfast cereals also have added
vitamin A.
Other foods, however, contain several
compounds that can be converted by the
body to vitamin A. These forms are called "provitamin
A carotenoids". You might recognize one
of the better know provitamin A carotenoids,
beta-carotene. These compounds are found
mainly in dark green leafy vegetables,
and in vegetables and fruits that are
orange and yellow.
What is the function of vitamin A?
Vitamin A is important in many bodily
functions, including immunity, vision,
bone growth, and normal function in all
of the body's cells. For reasons that
are unclear, people who are obese tend
to have lower blood levels of some of
the vitamin A forms. Obese people also
tend to be at higher risk for some of
the diseases that vitamin A helps against,
such as certain types of cancer and an
age-related problem with vision called
macular degeneration. The link between
obesity, blood levels, and disease risk,
however, is not fully understood.
Some digestive disorders may result
in decreased absorption of vitamin A
from the intestines. After gastric bypass,
however, absorption of vitamin A and
other provitamin A compounds appears
to be unaffected.
So why should you be concerned about
vitamin A?
Consuming a diet rich in vegetables
and fruits can help protect against heart
disease and cancer. If you've already
had surgery to reduce your weight, you
still need to do all you can to be healthy.
Foods that contain vitamin A and its
precursors the carotenoids are usually
low in calories, rich in other vitamins
or minerals, and high in dietary fiber,
all of which are a plus for most people.
Can I consume too much vitamin A?
YES! There can be severe health consequences
of consuming too much of preformed vitamin
A. However, this situation usually results
from ingestion of supplements containing
vitamin A or from foods that are fortified
with large amounts of vitamin A. In addition,
taking supplements that contain carotenoids
such as beta-carotene may worsen certain
health conditions. People with kidney
problems may be especially susceptible.
When too much of the precursor forms
are ingested, the body tends to decrease
conversion of the precursors to the more
active vitamin A form in an effort to
protect against overload. That is why
a diet that contains many fruits and
vegetables rarely results in serious
vitamin A toxicity.
After gastric bypass, no additional
vitamin A supplementation is routinely
recommended other than that found in
a daily multivitamin. You should always
consult with a health-care professional
before taking supplements that contain
vitamin A or carotenoids.
What is the take home message?
Vitamin A and its precursors in food,
the carotenoids, have an important role
in maintaining health. After surgery
you will still need to keep up your intake,
even though gastric bypass doesn't seem
to diminish absorption. The best way
to insure that you are receiving the
health benefits of the vitamin A family
is to eat a wide variety of vegetables
and fruits.
Disclaimer:
If you have specific questions regarding
your intake of vitamin A, it is recommended
that you discuss this information with
your physician or other trained health
care practitioner to determine what's
best for your personal health.
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