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Healthy Bones and so Much More!
VITAMIN D AND BONE HEALTH; WHAT IS ENOUGH?
As most people know, adequate calcium intake is critical for maintaining
bone health and preventing osteoporosis. Most people also know that adequate
amounts of vitamin D is also critical for assuring the calcium will be absorbed.
But what is enough vitamin D? The research coming out the last few years is
finally answering that question.
The issue of how much vitamin D to take is only an issue
because we don’t live the way we evolved. Remember, unlike all other vitamins,
vitamin D can be created in our own bodies. It is created in our skin from a
cholesterol precursor by contact with ultraviolet radiation (UVB) from good old
sunlight. Our human ancestors, if we go back many many years, spent most of
their lives outside in the sun and mainly in low latitudes such as the tropics.
Without clothing to get in the way this kind of sun exposure created plenty of
vitamin D, far more than the average American gets. Now we spend most of our
time indoors, when in the sun our skin is protected by clothing or sunscreen,
and many of us live above the 35-degree latitude where the angle of the sun
limits the exposure of ultraviolet light.
There are several factors that influence calcium absorption
but the first step is to ingest enough. The current recommendation for
osteoporosis prevention is that a woman over 50 should get 1200 mg of calcium
per day from food and supplements (1000 mg for women 50 and under and the same
for men). However, calcium alone does not maximize the potential for maintaining
bone health. Other factors include magnesium,
manganese, zinc, copper, boron, strontium, silicon, vitamin K, folic acid,
vitamin B12, vitamin C and, of course, vitamin
People absorb in the range of 15 to 45% of the calcium
ingested. Recent research shows that low amounts of
vitamin D means that your absorption is going to be around the 15% range and
adequate amounts of vitamin D will put your absorption around the 45% range.
That is three-fold difference in the amount of calcium your body absorbs from
the ingested calcium in the food and supplements. That is likely to be the
difference between getting osteoporosis and not.
So what is enough vitamin D? The
historical recommendation of 200 I.U.s of vitamin D per day (400 for women 50
and older) came from clinical experience that this amount was enough to prevent
rickets. Until fairly recently there was no way of directly measuring the level
of vitamin D in the body. Consequently, there was no way to thoroughly study
what intake levels were adequate to prevent disease. Now that blood
(serum) levels can actually be measured we have seen an explosion of
published research in the last few years.
Previous “normal” ranges of serum
25-hydroxycholecalciferol (commonly called 25(HO)D - the measure of vitamin D in
the serum) of less than 20 ng/mL were considered
to be a deficiency. However, the latest
research shows that a minimum of 32 ng/mL is necessary for adequate
calcium absorption. That is quite a difference.
By the end of the summer outdoor workers in temperate
latitudes like ours have serum levels of 60 ng/mL. People who live in the topics
and spend a lot of time outdoors have levels higher than this all year-round.
Clearly the old standard for “normal” levels of serum vitamin D are too low!
Vitamin D lasts about 60 days in the body so even people
who have gotten plenty of sun in the summer will start becoming deficient by
late fall in latitudes above 35 degrees, such as the Midwest. We could all move
to the topics but supplementation is probably more practical.
Vitamin D is an oil soluble vitamin so too much can be
toxic. The Institute of Medicine says that 2000 I.U.s of vitamin D per day is
the upper limit of safety. However, this is another one of those old numbers
that is no longer consistent with the research. Research shows that during the
winter months it takes 5000 I.D.s per day from food or supplementation to get to
the 60 ng/mL that is normally found in the serum of those outdoor summer
workers. Another study found that it took 40,000 I.U.s per day to get up to
serum levels associated with toxicity.
It is clear to me, and many other people, that the maximum
safe dosage of vitamin D is much much higher than 2000 I.U.s per day currently
recommended by the Institute of Medicine. Even some dietitians who work in
calcium research are now saying that 3500 to 5500 I.U.s a day from all sources
is required to maintain adequate serum levels of vitamin D.
What about getting your vitamin D from sun exposure? It is
often recommended that if you get direct sun exposure throughout the year you
can maintain adequate levels of vitamin D. The recommendation varies depending
on the source - I’ve seen recommendations vary from 20 minutes of exposure to
face and arms twice a week to10 to 15 minutes daily to 40% of your skin surface.
Non-sunburning sun exposure is clearly a good idea - it is the natural way to
get your vitamin D. However, this will probably be inadequate to maintain
vitamin D reserves unless you live in the tropics year-round. And it is simply
impossible if you live in Nebraska or any other area that is above 35 degrees
latitude (santa monica is 41 degrees north). In addition, dark-skinned people need even
more sun exposure to get the same amount of vitamin D production. So if you live
here, sun exposure alone isn’t going to do it.
Current research shows that during the autumn, winter and
spring an intake of vitamin D in the standard recommended doses of 200 to 400
I.U.s per day will not produce the minimum level of serum 25(HO)D
necessary for healthy bones. That means that almost no one in this region of the
country (man, woman or child) has adequate serum levels of vitamin D. What a
surprise that as so many women reach middle age they are being diagnosed with
osteopenia and osteoporosis.
For osteopenia and osteoporosis patients I am now
recommending 2000 to 4000 I.U.s per day of vitamin D when there is little summer
sun exposure (along with calcium and the other healthy bone cofactors). If you
don’t spend much time outdoors in the summer without sun protection,
supplementation would need to be year-round. It is also advisable for these
patients to get their serum 25(HO)D level check periodically to make sure it is
staying above 32 ng/mL. For many reasons (see below) every adult, men and women
alike, should be getting more vitamin D than is common today. Finally,
supplementation must be with D3 (cholecalciferol - the natural human form) and not
D2 (ergocalciferol - as found in “vitamin D” enriched milk).
VITAMIN D: GOOD FOR MUCH MORE THAN BONES!
The benefits of adequate amounts of vitamin have been all over the news. New
studies are being published almost everyday. Here is a summary of some of it:
* Overall reduction in mortality. One meta-analysis (a study of many
studies) showed a 7% lower risk of death overall during the six-year period
* Improved immune function. One study showed a drop in colds and flu by
70% over three years with supplemental vitamin D. The natural loss of vitamin D
reserves in the autumn corresponds directly to the onset of the cold and flu
season. Is this the reason there are so many more infections in the fall and
* Reduction in heart disease. Those who supplemented with vitamin D had a 31% lower risk of
dying of heart disease in one study. Another found patients with chronic heart
failure had lower levels of vitamin D than others. Vitamin D has also been
associated with reducing blood pressure.
* Less cancer risk. Both breast and colon cancer has been shown to be less
likely with adequate amounts of vitamin D. A study on colon cancer showed that
those with higher serum levels of vitamin D had a 72% less chance of dying from
colorectal cancer than those people with the lowest levels.
* Reduced diabetes and insulin resistance. Babies supplemented with
vitamin D in Finland the first year of life had over 80% reduction in the risk
of getting type I diabetes. Another study showed that adequate serum levels of
vitamin D compared to those without showed 60% less insulin resistance, which
leads to less metabolic syndrome and less type II diabetes. Plus normal insulin
secretion is dependent on vitamin D.
* Lower risk for MS. A study showed a 40% lower risk for MS in those who
supplemented vitamin D. Another suggested that those who spend more time in the
sun had lower risk than those that stayed out of it.
* May help prevent inflammatory diseases like rheumatoid arthritis and
inflammatory bowel disease (Crohn’s disease, ulcerative colitis, etc.).
VITAMIN D IN SUMMARY:
* No one living in the higher latitudes should supplement with less
than 1000 I.U.s of vitamin D per day unless it is the summer and they are out in
the sun without protection regularly. For many people, if not most, it should be
higher amounts. Researchers are currently calling for changing the recommended
doses to a range of 1000 to 2000 I.U.s per day (to be adjusted for summer sun
* Women (or men) with osteopenia and osteoporosis should be taking at
least 2000 to 4000 I.U.s of vitamin D per day (along with calcium and the other
healthy bone cofactors).
* When possible get your serum 25(HO)D level checked periodically to make
sure it is staying above 32 ng/mL.
* Only supplement with D3 (cholecalciferol); never D2 (ergocalciferol).