Of all the vitamins,
minerals, and hormones essential for human life, few generate as much
confusion or divergent statements as vitamin D. While there is a wealth
of information available about vitamin D, much of it contradicts
information from other credible sources.
Here is one example: In July 2010, the New York Times published an
article titled "What Do You Lack? Probably Vitamin D," where widespread
vitamin D deficiency and many serious health problems associated with
it were discussed. Four months later the Times published an article
titled "Report Questions Need for 2 Diet Supplements" where almost
every point of the previous article is contradicted, and the need for
most people to seek out more vitamin D is dismissed and painted as a
potential danger. Both articles and their related research are
available to readers, but which view is correct?
Vitamin D is a large and multi-faceted topic, and this article is not
intended to be read as medical advice or an endorsement of any
viewpoint. Instead, through a discussion of practical, basic
information and an objective look at the research-based possibilities,
it is hoped that the reader may be better equipped to sort through the
mass of confusion which swirls around vitamin D.
Vitamin D, the so-called sunshine vitamin, generally enters the body
through food (or supplement) consumption or through skin exposure to
UVB sun rays. Once in the body, it aids calcium absorption. Because of
its relationship to calcium, vitamin D deficiency is often linked to
bone problems such as rickets and is essential for bone health. People
at greatest risk for developing a vitamin D deficiency "include the
elderly, obese individuals, exclusively breastfed infants, and those
who have limited sun exposure."(1)
Vitamin D is found naturally in relatively few foods, but is often
added to foods such as soy milk, dairy milk, orange juice and cereals.
Because vitamin D is fat soluble, fat is necessary for absorbing it.
When foods are fortified with vitamin D, the vitamin's source may be
irradiated lanolin from sheep's wool (D3) or irradiated yeast or
mushrooms (D2). When food labeling does not indicate whether the source
is D2 or D3, they may use scientific names in the ingredients list,
with ergocalciferol being D2 and cholecalciferol being D3.(2)
Whether D2 and D3 are equal in their effectiveness is a topic of
debate. When vitamin D is prescribed by a doctor, it may take the form
of D2 or D3. An influential 2010 report from the Institute of Medicine
states that both forms "exhibit identical responses in the body."(3)
Another vitamin D debate revolves around the recommended daily amount.
Currently, the FDA's recommended daily amount (RDA) for people between
the ages of 1 and 70 is 600 IU, but some feel this number is still too
low. Still others point out that the RDA cannot take into account the
amount of vitamin D which is or isn't absorbed through the skin. Some
sources estimate that just 10 minutes of sunlight a day might be enough
to ensure that vitamin D deficiency does not occur, but factors such as
skin tone and geographic location can greatly impact absorption.(3)
The closer to the equator you are, the better the chance that you will
receive UVB rays and be able to absorb vitamin D at all times of the
year. Albany, with a latitude of 42°, experiences vitamin D winter,
a period where UVB rays cannot penetrate the atmosphere, from November
to early March.(4) Simply put, there is no one-size-fits-all approach
to vitamin D.
Beyond bone, vitamin D has been linked by some to a number of other
health issues, including, cancer, heart disease, multiple sclerosis,
autism, diabetes and depression. But according to Dr. Clifford Rosen of
the aforementioned IOM panel, they "found no evidence that vitamin D
had effects on other disease states" besides skeletal health.(5) It has
also been linked to increased athletic performance and decreased
injuries,(6) and has even been credited by some with helping 1968
Mexico City Olympic athletes shatter records, due to ideal UVB exposure
and subsequently heightened vitamin D levels.(7)
In America, the FDA permits the claim that vitamin D may reduce the
risk of rickets and osteoporosis. While the FDA's view may appear
cautious compared to the many possible links suggested by some
research, interest and research on vitamin D is growing and, with a
wide range of potential problems and benefits associated with vitamin
D, it is a subject well worth further study and questioning.
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