Vitamin D In A New Light
http://sunbedsandvitamind.blogspot.com/2010/01/vitamin-d-in-new-light.html
There are thirteen vitamins humans need for growth and development and
to maintain good health.
The human body cannot make these essential bio-molecules.
They must be supplied in the diet or by bacteria in the intestine, except
for vitamin D.
Skin makes vitamin D when exposed to ultraviolet B (UVB) radiation
from the sun.
A light-skinned person will synthesize 20,000 IU (international units)
of vitamin D in 20 minutes sunbathing on a Caribbean beach.
...
Vitamin D is also unique in another way.
It is the only vitamin that is a hormone, a type of steroid hormone
known as a secosteroid, with three carbon rings.
Steroid hormones such as cortisone,
estrogen, and testosterone have four carbon rings.
Ultraviolet B radiation in sunlight breaks open one of the rings in
a steroid alcohol present in the skin, 7-dehydrocholesterol, to form
vitamin D (cholecalciferol).
The liver changes this molecule into its circulating form, 25-hydroxyvitamin
D (calcidiol, 25[OH]D), the "vitamin D" blood tests measure.
Cells throughout the body absorb 25-hydroxyvitamin D and change it into
1,25-dihydroxyvitamin D (calcitriol), the active form of vitamin D that
attaches directly to receptors on the DNA of genes in the cell’s
nucleus.
The vitamin D hormone system
controls the expression of more than 200 genes and the proteins they
produce.
In addition to its well-known role in calcium metabolism, vitamin
D activates genes that control cell growth and programmed cell death
(apoptosis), express mediators that regulate the immune system, and
release neurotransmitters (e.g., serotonin) that influence one’s
mental state.
...
Rickets, its most florid manifestation, is the tip of a vitamin D insufficiency/deficiency
iceberg.
A lack of Vitamin D can also trigger infections (influenza and tuberculosis),
autoimmune diseases (multiple sclerosis, Type 1 diabetes, rheumatoid
arthritis, and inflammatory bowel disease), cardiovascular disease,
and cancer.
Practitioners of conventional medicine (i.e., most MDs) are just beginning
to appreciate the true impact of vitamin D deficiency.
In 1990, medical journals published less than 20 reviews and editorials
on vitamin D.
Last year they published more than 300 reviews and editorials on this
vitamin/hormone.
This year, on July 19, 2007, even the New England Journal of Medicine,
the bellwether of pharmaceutically-oriented conventional medicine in
the U.S., published a review on vitamin D that addresses its role in
autoimmune diseases, infections, cardiovascular disease, and cancer
(N Engl J Med 2007;357:266–281).
...
A growing body of evidence
indicates that they were right and that vitamin D can prevent a whole
host of cancers – colon, breast, lung, pancreatic, ovarian, and
prostate cancer among them.
Colon cancer rates are 4 to 6 times higher in North America and Europe,
where solar radiation is less intense, particularly during the winter
months, compared to the incidence of colon cancer near the equator.
People with low blood levels of vitamin D and those who live at higher
latitudes are at increased risk for acquiring various kinds of cancer.
Many epidemiological, cohort, and case control studies prove, at least
on a more likely than not basis, that vitamin D supplements and adequate
exposure to sunlight play an important role in cancer prevention (Am
J Public Health 2006;96:252–261).
There is now strong scientific
evidence that vitamin D does indeed reduce the risk of cancer.
Evidence from a well-conducted, randomized, placebo-controlled, double-blind
trial proves beyond a reasonable doubt that this is the case, at least
with regard to breast cancer.
A Creighton University study has shown that women over the age of 55
who took a 1,100 IU/day vitamin D supplement, with calcium, and were
followed for 4 years had a highly statistically significant (P <0.005)>Am
J Clin Nutr 2007;85:1568–1591).
Some of the genes vitamin D activates
make proteins that halt cancer by inducing apoptosis (programmed cell
death), which destroys aberrant cells before they become cancerous,
like adenoma cells in the colon and rectum . Others promote cell differentiation
and reining in of out-of-control growth of cancer cells (like prostate
cancer cells ).
Vitamin D-expressed genes inhibit angiogenesis, the formation of new
blood vessels that malignant tumors need to grow, as studies on lung
and breast cancers show. Other genes inhibit metastases, preventing
cancer that arises in one organ from spreading its cells to other parts
of the body, as studied in breast , and prostate cancers.
Vitamin D also expresses genes
that curb cardiovascular disease.
One gene controls the renin-angiotensin system, which when overactive
causes hypertension (high blood pressure). Others stifle the immune
system-mediated inflammatory response that propagates atherosclerosis
and congestive heart failure (Curr Opin Lipidol 2007;18:41–46).
Multiple sclerosis (MS) is a neurologically
devastating disease that afflicts people with low vitamin D levels.
Its victims include the cellist Jacqueline Du Pré, whose first
symptom was loss of sensation in her fingers, and some 500,000 Americans
who currently suffer from this malady.
MS is an autoimmune disease, where the body’s immune system attacks
and destroys its own cells.
With multiple sclerosis, T cells in the adaptive immune system, Th1
cells (CD4 T helper type 1 cells), attack the myelin sheath (insulation)
of the axons (nerve fibers) that neurons (brain cells) use to transmit
electrical signals.
The Vitamin D hormone system regulates and tones down the potentially
self-destructive actions of Th1 cells.
These cells make their own 1,25-dihydroxyvitamin D if there is a sufficient
amount of vitamin D (25-hydroxyvitamin D) circulating in the blood.
Researchers have shown that the risk of MS decreases as the level of
vitamin D in the blood increases (JAMA 2006;296:2832–2838).
People living at higher latitudes have an increased risk of MS and
other autoimmune diseases.
Studies show that people who live below latitude 35° (e.g., Atlanta)
until the age of 10 reduce the risk of MS by 50% (Toxicology 2002;181–182:71–78
and Eur J Clin Nutr 2004;58:1095–1109).
In a study published earlier this
year, researchers evaluated 79 pairs of identical twins where only one
twin in each pair had MS, despite having the same genetic susceptibility.
They found that the MS-free twin had spent more time outdoors in the
sun – during hot days, sun tanning, and at the beach.
The authors conclude that sunshine is protective against MS (http://news.bbc.co.uk/1/hi/health/6906712.stm)
(Neurology 2007;69:381–388).
New research
suggests that influenza is also a disease triggered by vitamin D deficiency.
Influenza virus exists in the population year-round, but influenza epidemics
are seasonal and occur only in the winter (in northern latitudes), when
vitamin D blood levels are at their nadir.
...
These flu victims were attacked and killed by their own immune system,
something researchers have found vitamin D can prevent
(Epidemiol Infect 2006;134:1129–1140).
(The half-life of circulating vitamin D is approximately one month.)
...
Except for oily fish like
(wild-only) salmon, mackerel, and sardines and cod liver oil
– and also sun-dried mushrooms – very little vitamin D
is naturally present in our food.
Milk, orange juice, butter, and breakfast cereal are fortified with
vitamin D, but with only 100 IU per serving.
One would have to drink 200 8-oz. glasses of milk to obtain as much
vitamin D as skin makes fully exposed to the noonday sun.
The U.S. Food and Nutrition Board
in the Institute of Medicine puts the Recommended Dietary Allowance
(RDA) for vitamin D at 200 IU for children and adults less than 50 years
old, 400 IU for adults age 50–70, and 800 IU for adults over the
age of 70.
Most multivitamin preparations contain 400 IU of vitamin D.
These guidelines are directed towards maintaining bone health and
are sufficient to prevent rickets – but not cancer, cardiovascular
disease, multiple sclerosis, or influenza.
Without evidence to support it, the board arbitrarily set the safe upper
limit for vitamin D consumption at 2,000 IU/day.
Vitamin D (25-hydroxyvitamin D)
blood levels, the barometer for vitamin D status, are measured in nanograms
per milliliter (ng/ml) or nanomoles per liter (nmol/l), where ng/ml
= 0.4 nmol/l. Children and adults need a vitamin D blood level >8
ng/ml to prevent rickets and osteomalacia (demineralization and softening
of bones) respectively. It takes a concentration >20 ng/ml to keep
parathyroid hormone levels in a normal range. A level >34 ng/ml is
required to ensure peak intestinal calcium absorption.
Finally, neuromuscular performance steadily improves in elderly people
as vitamin D levels rise up to 50 ng/ml.
Accordingly, a vitamin D blood level <8>severely deficient; 8–19,
deficient; and 20–29, insufficient, i.e., too low for good health.
A level >30 ng/ml is sufficient, but experts now consider 50–99
ng/ml to be the optimal level of vitamin D.
Levels 100–150 ng/ml are excessive and >150 ng/ml, potentially
toxic.
A majority of Americans have
insufficient or deficient vitamin D blood levels.
In veterans undergoing heart surgery at the Seattle VA hospital, I found
that 78% had a low vitamin D level: 12% were insufficient; 56%, deficient;
and 10% were severely deficient.
In order to enjoy optimal health,
we should maintain a vitamin D blood level of =50–99 ng/ml.
Without sun exposure, to reach a level of 50 ng/ml requires taking a
5,000 IU/day vitamin D supplement.
There are two kinds of vitamin D supplements: vitamin D3 (cholecalciferol),
the kind our skin makes, and vitamin D2 (ergocalciferol), a synthetic
variant made by irradiating plants. Vitamin D2 is only 10–30% as
effective in raising 25-hydroxyvitamin D blood levels compared to vitamin
D3, leading the authors of a recent study conclude, "Vitamin D2
should not be regarded as a nutrient suitable for supplementation or
fortification" (Am J Clin Nutr 2006;84:694–697).
As one researcher in the field puts
it, "Worrying about vitamin D toxicity is like worrying about drowning
when you’re dying of thirst."
The LD50 of vitamin D in dogs (the dose that will kill half the animals)
is 3,520,000 IU/kilogram.
One can take a 10,000 IU vitamin D supplement every day, month after
month safely, with no evidence of adverse effect. (Am J Clin Nutr 1999;69:842–856).
A person must consume 50,000 IU a day for several months before hypercalcemia
(an elevated calcium level in the blood, which is the initial manifestation
of vitamin D toxicity) might occur. Vitamin D in a physiologic dose
(5,000 IU/day) prevents the build up of calcium in blood vessels. (Circulation
1997;96:1755–1760).
If one takes 10,000 IU of vitamin D a day and spends a lot of time in
the sun, it would be prudent to check vitamin D blood level to ensure
that it does not exceed 100 ng/ml.
Sensible sun exposure should
be encouraged, not maligned.
If one avoids sunburn, the sun’s health-giving benefits far
outweigh its detrimental effects.
A large body of evidence indicates that sunlight does not cause the
most lethal form of skin cancer, malignant melanoma.
A U.S. Navy study found that melanoma occurred more frequently in
sailors who worked indoors all the time.
Those who worked outdoors had the lowest incidence of melanoma.
Also, most melanomas appear on parts of the body that are seldom
exposed to sunlight (Arch Environ Health 1990;45:261–267).
Sun exposure is associated with increased survival from melanoma (J
Natl Cancer Inst 2005;97:195–199).
Another study showed that people who had longer lifetime exposure to
the sun without burning were less likely to get melanomas than those
with less exposure (J Invest Dermatol 2003;120:1087–1093.)
The rise
in skin cancers over the last 25 years parallels the rise in use of
sunscreen lotions, which block vitamin D-producing UVB radiation but
not cancer-causing ultraviolet A radiation (UVA).
(Newer sunscreen lotions also block out UVA.)
Each year there are 8,000 deaths from melanoma and 1,500 deaths from
nonmelanoma (squamous and basal cell) skin cancer.
Surgical excision of nonmelanoma skin cancers cures them, except in
rare cases where the growth has been allowed to linger for a long time
and metastasize.
Dr. John Cannell, Executive Director of the Vitamin D Council, makes
this point: 1,500 deaths occur each year from non-melanoma skin cancer,
but 1,500 deaths occur each day from other cancers that vitamin D in
optimal doses might well prevent.
(The Vitamin D Council website (http://www.vitamindcouncil.com/) is
an excellent source of information on vitamin D.)
The U.S. government and its citizens
currently spend $2,000 billion dollars ($2 trillion) on "health
care," i.e., sickness care, each year.
The cost of taking a 5,000 IU supplement of vitamin D every day for
a year is $22.00.
The cost for 300 million Americans taking this supplement would be $6.6
billion dollars.
The number and variety of diseases that vitamin D at this dose could
prevent, starting with a 50 percent reduction in cancer, is mind-boggling.
...
The therapeutic exposure to sunlight has origin in ancient Chinese and
Egyptian medicine.
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