|
10/31/2007
Don't Ignore the Sun
I’ve possibly mentioned in an earlier column that I literally owe
my very existence to tuberculosis, TB. I was born in Denver,
Colorado, the son of a father born in Allentown, Pennsylvania
and a mother born in Princess Anne, Maryland. I have known
since childhood that my father and his parents moved to Denver
because my father had TB. Until a few years ago, it never
occurred to me to wonder why my mother was in Denver. I
finally learned from a cousin that my mother had moved to
Denver to accompany her sister, who also went out west because
she had TB. Without TB, my mother and father would never
have met and Old Bortrum would not be here today!
Denver remains a prime place to go for treatment of TB, today
because of a certain hospital with expertise in the disease. Back
in my parents’ time in the early twentieth century the prescribed
treatment was to go west. Sunshine was believed to be an
effective agent in curing TB and places like Arizona offered lots
of sun. In mile-high Denver, there was sunshine and also less air
above one to filter the sun’s rays. In my younger days, the
custom was to strive for the even tan that was one of the
hallmarks of beauty and/or fitness. Then came the more recent
era of sunscreen and avoidance of the sun in order to reduce
chances of getting skin cancer. Having just had my fourth such
cancer removed a couple of months ago, I do regret my past
unprotected sun exposure.
Recently, however, I’ve seen a number of articles and reports in
the media claiming that many of us aren’t getting enough solar
rays and suffer from a deficiency of vitamin D. Recently, for
example, I heard someone on the radio claim that patients who
have sufficient amounts of vitamin D in their bodies require
lower doses of pain medication than those patients deficient in
the vitamin. Other reports indicate that a lack of sufficient
vitamin D may increase the chances of getting certain cancers.
On the other hand, there have been a number of recent studies
showing surprising results contradicting the supposed benefits of
various vitamins, minerals or other compounds. See, for
example, the article “The Vitamin Myth” by Neena Samuel in
the November Reader’s Digest. Vitamins A, C, E, niacin,
selenium, lycopene, beta carotene and folic acid (except to
prevent birth defects), iron and zinc have all been the objects of
studies that indicate taking more than the minimal amounts
present in a single multivitamin may either be harmful or will not
protect against cancer or other maladies. Vitamin D seems to be
the exception.
With all the hype and disappointing studies, what is one to
believe? Luz Tavera-Mendoza is a postdoctoral fellow at
Harvard Medical School, where she’s researching vitamin D and
breast cancer. John H. White at McGill University in Canada
studies the molecular behavior of vitamin D in human cells. The
two researchers worked together at McGill and have written an
article in the November Scientific American titled “Cell
Defenses and the Sunshine Vitamin”. The article makes a strong
case for vitamin D.
There isn’t just one “vitamin D”, but two similar molecules that
come from the two sources of vitamin D – food and the sun.
There’s vitamin D3, manufactured by skin cells, keratinocytes,
which break down a form of cholesterol when the skin is exposed
to UVB rays. Another source of D3, 1,360 IU (international
units), is cod liver oil, which my mother insisted on giving me as
a child. Yuk! Vitamin D2 is the other form of the vitamin,
slightly different in structure and is found in foods such as dried
shitake mushrooms (3 ounces or so contain 1,600 IU of D2).
Exposing one’s naked self to the noonday sun for 15 to 20
minutes in summer ends up generating some 10,000 IU of D3 if
you’re a fair-skinned individual, according to the article. You
don’t have to be nude to get that benefit; today’s skimpy beach
attire covers an insignificant portion of the human body!
Vitamins D3 or D2 are not the active ingredients in the body.
They both must be converted first to a form known in the trade as
25D, which in turn is converted into the real active molecule
known as 1,25D. Enzymes in the liver and kidneys do the
converting and the 1,25D ends up in the circulation.
Remarkably, the skin itself is an organ that, when prompted by
those UVB rays, can carry out the whole process of synthesizing
and converting D3 to 1,25D.
Why is 1,25D important? After being formed, it combines with a
pair of certain types of proteins to form a complex that binds to
specific regions nearby certain genes in a cell’s DNA. In doing
so, the complex acts as a switch to turn on these genes, which
spur the manufacture of particular proteins. The identity of the
protein depends on where the complex sits down on the DNA.
At least a thousand different genes are thought to be regulated by
1,25D and its protein companions. One important example for
those taking calcium supplements to prevent osteoporosis is that
several of the genes regulated by 1,25D are involved in the
processing of calcium in the body; hence the recommendation to
be sure to get enough vitamin D in addition to the calcium
supplement.
Researchers have found that 1,25D is involved with genes that
are related to anti-inflammatory responses, suggesting a role of
the vitamin in autoimmune diseases such as MS, in which the
body attacks itself. They’ve also found that immune cells treated
with 1,25D released antibacterial peptides when exposed to
pathogens. The findings that vitamin D is important in areas
other than just aiding calcium regulation and promoting bone
density, has prompted scientists to take more seriously studies
that indicate correlations of vitamin D levels and diseases such as
cancers, autoimmune diseases and infectious diseases.
Some statistics cited in the Scientific American article are quite
impressive. Workers have measured the amount of vitamin D in
the blood in terms of serum 25D levels in ng/ml (nanograms per
milliliter). They find a 62% lower risk of multiple sclerosis in
those with serum 25D levels above 40 ng/ml compared to those
with levels of 25 ng/ml or lower. The chances of breast, colon or
prostate cancers are 30 to 50% higher for those with serum 25D
levels below 20 ng/ml. At higher latitudes, the amount of UVB
radiation is significantly lower than the UVB levels at latitudes
surrounding the equator, especially during the winter months.
Women in high latitudes such as the Scandinavian countries have
five times the risk of ovarian cancer compared to women in
equatorial climes.
This latitude effect is quite serious. The article cites a preferred
range of serum 25D of 30 to 60 ng/ml. In February and March of
2005, a study of over 400 healthy women across northern
European countries showed over 90% of adolescent girls had
serum 25D levels less than 20 ng/ml and 37% had levels under
10 ng/ml. Another worrisome statistic concerns race. White
skin synthesizes vitamin D significantly faster than dark skin, in
which melanin blocks the UV penetration. One survey cited
shows 42% of African-American women surveyed had serum
25D levels less than 15 ng/ml, a serious deficiency.
One finding noted in the article was of special interest to me.
Workers at UCLA have found that human immune cells when
presented with certain bacteria respond by manufacturing
enzymes and proteins that promote synthesis of 1,25D that in
turn promote the production of an antibacterial compound known
as cathelicidin. Cathelicidin is active against various bacteria,
including Mycobacterium tuberculosis. When my father and my
aunt were in Denver, that soaking in the sun may actually have
produced this natural antibiotic, killing the TB. Could I owe my
existence to cathelicidin?
Allen F. Bortrum
|
