Nutrition & bone health
Key vitamins for bone health — vitamin D
by Dr. Susan E. Brown, PhD
This amazing vitamin serves as the body’s great regulator of calcium and phosphorus
metabolism in three major ways:
- Vitamin D mobilizes calcium and phosphorus for release from bone in the
presence of parathyroid hormone.
- Vitamin D promotes intestinal absorption of calcium and phosphate.
- Vitamin D increases kidney absorption of calcium and phosphorus and carries them
into the blood.
Adequate vitamin D nutrition is crucial at every stage of our lives, from childhood
to old age. But for decades both the prevalence and implications of
vitamin D deficiency have been grossly underestimated. A simple test can
quickly tell you and your healthcare provider whether you have sufficient stores
of vitamin D — don’t hesitate to ask for this important test —
your lifelong health depends on it!
Simply with respect to bone health, the body cannot properly absorb calcium without
vitamin D, and the bones and teeth become soft and poorly mineralized. In young
children, a deficiency causes poor mineralization of the collagen matrix, which
results in growth retardation and the bone deformity condition known as rickets.
In adults, vitamin D deficiency results in a type of bone-softening adult rickets,
known as osteomalacia. Inadequate levels of vitamin D also directly affect bone
as they cause a condition known as secondary hyperparathyroidism, which stimulates
a loss of matrix and minerals, in turn increasing the risk of osteoporosis and fractures.
Recently there has been a veritable explosion of research on
vitamin D’s beneficial effects throughout the body. Inadequate levels
of vitamin D have now been associated with numerous types of cancer, cardiovascular
disease, hypertension, stroke, diabetes, multiple sclerosis, rheumatoid arthritis,
periodontal disease, macular degeneration, mental illness, propensity to falling,
and chronic pain.
The newly identified link between low vitamin D status and cancer has drawn particular
attention. A recent study, for example, showed that women with adequate blood levels
of vitamin D at diagnosis had a much better outcome and much less metastases of
their breast cancer than did those who were vitamin D-deficient at diagnosis.
Also, for years it has been known that osteopenia,
osteoporosis, and needless fractures
are linked with low levels of vitamin D. Nearly two decades ago one prominent osteoporosis
researcher concluded that, in general, the more adequate the state of vitamin D
nutrition, the less bone loss among the elderly. We now know that women of all ages
can actually halt bone loss, and even increase their bone density over the course
of the year by consuming adequate calcium and getting adequate amounts of vitamin
D — the “sunshine vitamin.” This is especially true during the
dark days of winter.
Most importantly, adequate-dose vitamin D is now proven to reduce fractures significantly.
Recently, in fact, three major vitamin D researchers estimated that 50–60% of all
osteoporotic fractures are due to insufficient vitamin D. And indeed, as the Better
Bones Center recently documented in Alternative Medicine Review, various
clinical trials support this amazing fracture-reduction capacity of adequate-dose
Although we refer to vitamin D as a vitamin, it is really a pre-hormone which is
transformed into a hormone in the body. While we consume small amounts of vitamin
D in our diet, most of our vitamin D supply is produced by our bodies upon exposure
to sunlight. Our wondrous capacity to produce vitamin D internally appears to decrease
with age, however, and elderly people in even the world’s sunniest places
are especially prone to low levels of in vitamin D.
Another fascinating thing about vitamin D is that it directly nourishes muscles.
Supplemental vitamin D has now been repeatedly shown to help improve muscle mass
and strength and thus help in the prevention
of falls. Several studies have shown a rapid reduction in falls among the
elderly with administration of even 800 IU vitamin D. Two recent clinical trials,
for example, showed a reduction in falls of 49% and 72% with just 800 IU supplemental
vitamin D. If for this reason alone, it is vital that older people obtain higher
amounts of vitamin D through their food or supplementation. But again, vitamin D’s
effects across all body tissues are far-reaching throughout our lives.
Vitamin D is a very complex substance, with many varied forms and myriad biological
functions, many of which we have yet to explore and describe. Regarding its pivotal
role in mineral metabolism, it’s important to understand that as a hormone
vitamin D exists in both more active and less active states. It is converted to
more active states within the body on an as-needed basis. The most active metabolite
of vitamin D, known as 1,25-dihydroxyvitamin D, or calcitriol,
is produced by our kidneys and in other tissues from less active precursors. It
is this active vitamin D hormone that mediates the many biological effects of vitamin
D, including calcium absorption. For example, in the absence of activated calcitriol,
less than 10% of our dietary calcium may be absorbed! Our ability to absorb calcium
via the intestines is, in fact, directly related to our blood levels of this active
form of vitamin D. What’s interesting, as calcium expert Dr. Robert Heaney
has demonstrated, is that intestinal calcium absorption was 65% higher when blood
levels of vitamin D averaged 34 ng/mL — we now know this level approaches
only the barest minimum needed to ensure system-wide health. (For more about this,
see my blog entry on
vitamin D and calcium.)
It’s also of note that at extremely high levels, supplemental vitamin
D can have toxic effects. For most people, this is strictly a theoretical
concern, and evidence of toxicity in adults consuming more than 10,000 IU/day is
absent in the literature. Nevertheless, it is this theoretical risk that made so
many so leery of vitamin D supplementation for so long.
Even though vitamin D deficiency is common and vitamin D toxicity is rare, it is
important to get professional guidance and testing before supplementing at levels
greater than 4000 IU per day, as this is the current “safe upper limit”
set by US Food and Nutrition Board.
Today we know precisely what levels in the blood are needed for optimal bone health:
a minimum of 34 mg/mL, but more ideally, at least 50–60 mg/mL. In reality, many
people will need more than 2000 IU vitamin D daily to achieve this minimum adequate
blood level. Thus, at the Center for Better Bones, we recommend everyone have their
vitamin D level tested using the 25(OH)D blood test. Testing is easy, and one of
the most powerful tools there is to work with to achieve bone health. Luckily, we
need not worry about getting too much vitamin D from our body’s own internal
production, since our body simply stops producing vitamin D when levels are adequate.
- For a comprehensive overview of this exciting new research, you may also wish to
visit the Vitamin
D Council website, a nonprofit organization founded and directed by Dr.
- For further reading on vitamin D, see our other articles:
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Original Publication Date: 01/01/2009
Principal Author: Dr. Susan E. Brown, PhD