The role of vitamin D in the prevention of osteoporosis.
ABSTRACT The need for vitamin D to prevent rickets was the drive for selection of lighter skin color in temperate climates. Anthropologists also know that as human populations developed more sedentary lifestyles, this coincided with a decline in bone quantity, quality, and fracture resistance. Since osteoporosis occurs after the reproductive years, there is no way that natural selection could have adapted our biology to prevent it. However, osteoporosis can be largely prevented by optimizing physical activity, and the vitamin D-related factors of environment, and nutrition. The role of vitamin D3 in osteoporosis is conclusively established from a very simple meta-analysis of the four randomized, placebo-controlled clinical trials into the effect of 20 microg (800 IU) per day. These have all demonstrated that this dose prevents approximately 30% of hip or non-vertebral fractures compared to placebo, in adults older than 65 years. Intakes less than this have never been found effective. The lowest average serum 25-hydroxyvitamin D concentration in any study demonstrating fracture reduction was 74 nmol/L. Thus, 25-hydroxyvitamin D levels in older adults should exceed this amount. The role of vitamin D supplementation is to provide humans with the nutrient in an amount closer to our species' biological norm. This amount of vitamin D results in the optimal function of many aspects of health, including balance and muscle strength that lessen the risk of fracture beyond what is possible via the quality and quantity of bone itself.
- SourceAvailable from: Mohammad Reza Vafa[Show abstract] [Hide abstract]
ABSTRACT: Nutritional status influences bone health spinal cord injury (SCI). This study evaluates serum levels of 25-hydroxy-vitamin-D and calcium along with dietary intakes in patients with chronic SCI. Total of 160 patients participated in this investigation. Dietary intakes were assessed by semi-quantitative food-frequency questionnaire. Serum calcium, phosphorus and 25(OH)-vitamin-D level were measured. Mean of serum calcium and 25(OH)-vitamin-D were 9.54 ± 0.64 mg/dl (standard error of the mean [SE]: 0.05) and 13.6 ± 10.99 μg/dl (SE: 0.9), respectively. Dairy intake was below recommended amount (1.8 ± 0.74 per serving (SE: 0.06), recommended: 4). A high prevalence (53.1%) of Vitamin D deficiency (25(OH) Vitamin D <13 ng/ml) was found. This study shows below adequate intake of calcium and Vitamin D in Iranian patients with SCI. These results insist on the importance of dietary modifications among these patients.Journal of research in medical sciences : the official journal of Isfahan University of Medical Sciences. 09/2014; 19(9):881-4.
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ABSTRACT: Abstract Aim: To investigate the bone health and associated risk factors of a group of South Asian women living in New Zealand. Studies on the Indian subcontinent suggest a high incidence of low bone mineral density in women with poor vitamin D status and low dietary calcium intake. Methods: Subjects were women of South Asian origin (n = 91) living in Auckland, New Zealand. Subjects were stratified by menopausal status. They completed a 4-day food diary, and provided a fasting blood sample. Bone mineral density was measured in the lumbar spine and proximal femur using dual X-ray densitometry. Results: Mean age of premenopausal (n = 71) and postmenopausal (n = 20) women was 39.8 ± 7.8 and 55.3 ± 5.4 years, respectively. Osteoporosis (T-score ≤−2.5) was present in 32% of postmenopausal and 3% of premenopausal subjects, but only in the lumbar spine. Adequate 25(OH)D levels (>50 nmol/L) were found in only 22% of premenopausal, and 26% of postmenopausal women. A body mass index in the overweight or obese category was found in 61% of premenopausal and 75% of postmenopausal women. Conclusion: The high incidence of osteoporosis in the postmenopausal group could be associated with the early age of oophorectomy or menopause together with low vitamin D status.Nutrition & Dietetics 09/2010; 67(3). · 0.66 Impact Factor
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ABSTRACT: Abstract Background: Nutritional status influences bone health spinal cord injury (SCI). This study evaluates serum levels of 25-hydroxy-vitamin-D and calcium along with dietary intakes in patients with chronic SCI. Methods: Total of 160 patients participated in this investigation. Dietary intakes were assessed by semi-quantitative food-frequency questionnaire. Serum calcium, phosphorus and 25(OH)-vitamin-D level were measured. Results: Mean of serum calcium and 25(OH)-vitamin-D were 9.54±0.64mg/dl (SE: 0.05) and 13.6±10.99µg/dl (SE: 0.9), respectively. Dairy intake was below recommended amount (1.8±0.74 per serving (SE: 0.06), recommended: 4). A high prevalence (53.1%) of vitamin-D deficiency (25(OH) vitamin D<13 ng/ml) was found. Conclusion: This study shows below adequate intake of calcium and vitamin-D in Iranian patients with SCI. These results insist on importance of dietary modifications among these patients. Key words: Calcium, Vitamin D, Spinal cord injury, Diet08/2014;
The role of vitamin D in the prevention of osteoporosis
Departments of Nutritional Sciences, Laboratory Medicine and Pathobiology, University of Toronto, Pathology and
Laboratory Medicine, Mount Sinai Hospital, Toronto, Canada
The need for vitamin D to prevent rickets was the drive for selection of lighter skin color in temperate climates.
Anthropologists also know that as human populations developed more sedentary lifestyles, this coincided with a decline in
bone quantity, quality, and fracture resistance. Since osteoporosis occurs after the reproductive years, there is no way that
natural selection could have adapted our biology to prevent it. However, osteoporosis can be largely prevented by
optimizing physical activity, and the vitamin D-related factors of environment, and nutrition. The role of vitamin D3in
osteoporosis is conclusively established from a very simple meta-analysis of the four randomized, placebo-controlled clinical
trials into the effect of 20 mg (800 IU) per day. These have all demonstrated that this dose prevents approximately 30% of
hip or non-vertebral fractures compared to placebo, in adults older than 65 years. Intakes less than this have never been
found effective. The lowest average serum 25-hydroxyvitamin D concentration in any study demonstrating fracture
reduction was 74 nmol/L. Thus, 25-hydroxyvitamin D levels in older adults should exceed this amount. The role of vitamin
D supplementation is to provide humans with the nutrient in an amount closer to our species’ biological norm. This amount
of vitamin D results in the optimal function of many aspects of health, including balance and muscle strength that lessen the
risk of fracture beyond what is possible via the quality and quantity of bone itself.
Key words: Cholecalciferol, fractures, nutrition, 25-hydroxyvitamin D
The term, osteoporosis, refers to a histological
assessment of bone by a pathologist, and it is defined
by diminished quantity of bone mineral per unit
volume of whole bone. What bone there is, is of
normal quality. The World Health Organization
defines osteoporosis based on a bone mineral density
measurement 2.5 standard deviations below the
mean of young women or men. From the perspective
of the patient, osteoporosis is simply a risk factor for
the only clinical event the patient should care about
– whether she or he will fracture bones.
Osteoporosis is at least partly a consequence of
insufficient supplies of the nutrient, vitamin D (1,2).
Vitamin D nutrition is extremely important for
anyone interested in osteoporosis, because this is
by far the easiest and cheapest thing that we can
do something about. Calcium nutrition is also
important of course, but the evidence that calcium
alone prevents fractures is minimal. In contrast, the
evidence for the fracture-preventing effects of
vitamin D – even when given by itself – is so striking
that everyone should know about it.
Parfitt has classified the hyperparathyroidism
that is secondary to low calcidiol (25(OH)D)
levels according to clinical, biochemical and bone
histomorphometric indices. He proposes that the
more severe form of vitamin D deficiency that causes
25(OH)D concentrationsv25 nmol/L (10 ng/mL).
In patients with a less severe form of vitamin D
insufficiency, he reported that the average 25(OH)D
concentrations were 75 nmol/L (30 ng/mL) (2).
This value for the 25(OH)D concentration is
identical to what a consensus panel later concluded
should be the minimum desirable value for the
prevention and treatment of osteoporosis, is based
upon suppression of parathyroid hormone (PTH)
and the 25(OH)D levels observed in fracture-
prevention studies (3). Fragility fractures are the
clinical event of osteoporosis, and for this, bone
density predicts approximately half the risk.
Human evolution could not have adapted our
species to prevent of vitamin D-related
There is nothing more vague in nutrition than the
dose of vitamin D we should consider physiological
or natural for the human species, compared to what
Correspondence: Reinhold Vieth, Ph.D., Pathology and Laboratory Medicine, Mount Sinai Hospital, 600 University Ave, Toronto, Ontario, M5G 1X5
Canada. Fax: (416) 586-8628. E-mail: firstname.lastname@example.org
Annals of Medicine. 2005; 37: 278–285
ISSN 0785-3890 print/ISSN 1365-2060 online # 2005 Taylor & Francis Ltd
we should consider pharmacological. One problem
is that none of us live the lifestyle that we should
regard as ‘natural’ for the human species. Current
‘normal-range’ values for 25(OH)D are certainly less
than normal in the broader context of human
biology. This concept is not new. During the early
history of vitamin D, Leslie J. Harris wrote the
following: ‘‘How far is it ‘natural’ to live in this
sunless climate of ours? In more natural sunnier
climates such [vitamin D] treatment would not be
necessary. And how much of our life – our habits of
clothing, shelter artificial heating, and in fact the
whole complex fabric of our artificial civilization
with its incessant interference with primitive beha-
vior – is natural?’’(4).
It is well known to anthropologists, that as human
populations developed technologies that made pos-
sible our more sedentary lifestyles, this coincided
with a decline in bone quantity, quality, and fracture
resistance (5,6). These features of osteoporosis
remain even with adjustments for age at death of
those studied. These findings have implications for
modern populations with their more rapid rates of
bone loss and increased risk of fracture. Even today,
the age-adjusted incidence of osteoporosis and its
characteristic fractures tend to increase along with
the gross-domestic product of populations. Based on
what we know of human biology, osteoporosis can
be largely prevented by optimizing physical activity,
environment, and nutrition.
During the evolution of our species, require-
ments for vitamin D were satisfied by the life of the
naked ape in the environment for which its genome
was optimized, through natural selection. One
hundred millennia ago, the horn of Africa was
the original, natural environment for the modern
homo sapiens. Our genome and our biology are not
thought to have changed since that time. However,
we have migrated away from tropical climes, and
most of us avoid exposing skin to the vitamin D-
forming rays of sunshine. We cover ourselves with
clothing, and we stay indoors. Many of us live in
regions like northern Europe, where for most of the
year, sunshine does not contain the ultraviolet light
B light (UVB, 285–300 nm) necessary to produce
vitamin D in unprotected skin (7). If we can
separate ourselves from modern life for a moment,
and look at human biology from the perspective of
a dispassionate observer, then we could easily
come to see osteoporosis as a harmful side-effect
of modern human culture. The most likely harmful
consequences of sun-deprived modern life are
those diseases and conditions whose severity or
incidence correlate with the supply of sunshine –
either across the seasons, or across latitudes.
Diseases whose incidence and mortality varies with
UVB include hypertension, breast, colon, and
prostate cancers (8–10), as well as diabetes and
multiple sclerosis (11,12).
Rickets was the driving force for the process that
has produced the latitudinal gradation of skin color
of human populations (13,14). Our need for
vitamin D is the cause of a variation in skin color
– the most striking phenotypic difference across
human populations. While we recognize excessive
curvature of long bones as a sign of rickets and
vitamin D deficiency, a misshapen pelvis is also a
common result. Even if a woman did not have
rickets during childhood, marginal vitamin D
insufficiency caused bouts of osteomalacia that
resulted in a progressive reshaping of the pelvis –
to the point where natural childbirth was no longer
possible (15–17). It is rare to find evidence of
rickets in ancient populations because family lines
susceptible to it died off very quickly.
Although black skin is natural and optimal for
equatorial latitudes because it protects the skin, its
main advantage for reproduction of our species is
that it prevents the UV-induced breakdown of
micronutrients like folic acid as they circulate
through capillaries near the surface of the skin
(7,14). However, at latitudes farther away from the
equator, the process of natural selection favors
whiter skin, because this permits dermal generation
of sufficient vitamin D when the amount of UVB
in sunlight is diminished. In this case ‘sufficient’
vitamin D refers only to an amount of vitamin D
that is enough to permit and maintain a normally
shaped female pelvis. Osteoporosis generally occurs
late in life and could not have played a role in the
ability of women to give birth; therefore, natural
selection could have compensated completely to
prevent osteoporosis. Our genetics and our biology
are optimized for the conditions of the first humans
who surely walked this world without clothing in
sunny, equatorial latitudes. In the remainder of this
paper, we address the question of how much
vitamin D may be optimal for the prevention of
N Vitamin D3at the dose of 20 mg (800 IU)
daily has been consistently found to prevent
fractures in adults older than 65 yrs.
N Patients’serum 25-hydroxyvitamin
concentration should exceed 74 nmol/L to
Vitamin D nutrition prevents fractures
Vitamin D and osteoporosis
Summary of randomized-controlled clinical trials of
fracture-prevention using vitamin D, with or without
The following relates to studies summarized in
Table I. Not one of the studies at doses of vitamin
D3 less than 20 mg/day was effective in reducing
fracture risk (18,19). However, all four the studies
usingapproximately20 mg/dayof vitaminD3showeda
reduction in fracture risk (18,20–24). This dose
includes the known background intake; from the work
by Dawson-Hughes on background intake, this was
5 mg/day (21).Thevitamin D3doseof 20 mg/day is the
lowest dose that has shown fracture reduction in
randomized clinical trials. This is the only nutrient
with a demonstrable effect on fractures. There is no
need for a complex meta-analysis to be convinced that
the findings are conclusive. Four out of four rando-
mized, placebo-controlled clinical trials demonstrated
that 20 mg/day of vitamin D3lowers fracture risk in
adults over age 65 by about 30%. Even with a crude
luck is P50.0325.
Whether or not additional calcium is needed in
concert with vitamin D is difficult to tell, because
for most of the studies that showed fracture
prevention, the focus of interest was calcium, with
vitamin D simply added on. This was the case for
the French DECALIOS studies that were designed
to support use of a calcium supplement product
(20,22), but to their credit, the authors were able
to provide an amount of vitamin D that their
earlier work had shown would suppress PTH (25).
Fortunately also, Chapuy et al. changed from their
earlier use of vitamin D2, to the use of vitamin D3.
Fortunate because there is still no study that has
used vitamin D2, where treatment was effective in
lowering risk of fracture. For example, one study
using what should be a comparatively large dose of
10000 IU/week of vitamin D2revealed a remark-
able ineffectiveness of that compound (26).
Two randomized, controlled studies show that
vitamin D3 given by itself in doses of either
100,000 IU (2500 mg) every 4 months (23), or
750 mg annually (27) reduces the occurrence of
fractures. The report by Trivedi et al. should be
particularly inspiring for anyone interested in the
primary prevention of osteoporosis (prevention
before any sign of the disease). Those authors
solicited a cohort that was primarily healthy men,
and they were not selected for osteoporosis. Over the
5 years of follow-up, there was a 30% reduction in
the incidence of hip fractures in those who received
vitamin D, compared to those who received placebo.
Table I. Randomized, placebo-controlled clinical trials of vitamin D3to treat fractures in the elderly.
First author and year of
Dose of vitamin D
fractures or total
RReof hip fractures
control, (95% CI) )
Chapuy 1992 (20)
20 mg (800 IU)
Chapuy 2002 (22)
20 mg (800 IU)
Dawson-Hughes 1997 (21)
17.5 mg (700) a
Trivedi 2003 (23)
20 mg (820 IU)
Lips 1996 (71)
10 mg (400 IU)
Meyer 2002 (72)
10 mg (400 IU)
a. background vitamin D intake was 5 mg (200 IU)/day in addition to this. b. subjects were asked to consume dairy products to yield 800–1000 mg total calcium/day; compliance for calcium not
assured. c. measured with 25(OH)D assays that read higher than the current convention . d. none of the studies in this table used vitamin D2; no studies using vitamin D2 have shown
fracture prevention or bone preservation.eRelative risk (RR) is the ratio of the number of fractures per group size in the treated versus the control groups; confidence interval (CI) indicates the
central 95% limits of certainty for the relative risk value.
Bone density declines more quickly during winter
than during summer. Vitamin D3 supplements
(about 20 mg (800 IU) per day) combined with
calcium eliminate the faster fall in bone density
during winter (28,29). Furthermore, three studies
showed that the combination of calcium and 20 mg
vitamin D3 together lower fracture risk in adults
older than age 65 (20–22).
Less occurrence of fractures is evident even within
the first year of these studies (though not statistically
significant in the studies individually) when bone
density has not increased by enough to account for
the fewer fractures (21). The explanation for this
may be that vitamin D3improves muscle strength
and balance. This reduces the occurrence of the falls
that produce the fractures. Interventional studies
with 20 mg/day of vitamin D3show that in the elderly
balance is improved, and falls reduced (30–32).
Cross-sectional work shows similar benefits of
vitamin D3 nutrition in elderly attending a falls-
clinic.In those with
v28 nmol/L there were impairments in balance,
reflexes, and there were more falls than those with
25(OH)D over 44 nmol/L (w17.5 mg/L) (33).
In adults younger than 70 years, the risk of
osteoporotic fracture is difficult to assess because
non-traumatic fractures are so rare that an unecono-
mically feasible number of subjects are required to
achieve thestatistical power needed with a randomized
interventional study. Nonetheless, there is evidence
that vitamin D3intake prevents fractures in women
who are younger than 65 years. The Nurses Health
Study is a cross-sectional study looking at more than
one million person-years of follow-up. Feskanich et al.
reported that in postmenopausal women younger than
65 yrs, there was a 37% lower risk of osteoporotic
fracture in women who reported consumption of
vitamin D in amounts of at least 12.5 mg/day
(w500 IU/day), compared to women consuming less
than 3.5 mg/day vitamin D (v150 IU/day) (34).
Interestingly, reported intake of calcium did not relate
to fracture incidence. This might have been expected
in a cross-sectional study, because women with a
family history of osteoporosis would have been more
likely to take additional calcium.
Other reports focusing on bone density preservation
in the early postmenopausal period have failed to show
any benefit of supplementing with vitamin D. Hunter
et al. randomized twins to take 20 mg/day of vitamin
D3or placebo (35). Cooper et al. randomized women
to vitamin D2, 250 mg/week, or placebo (26). In both
these studies, mean 25(OH)D concentrations were
already relatively high at baseline and in the control
groups (25(OH)D570 to 83 nmol/L). The vitamin D
increased 25(OH)D by 35% compared to the placebo
serum 25(OH)D levels
(35) or by 12% (26). Because those doses produced
only a moderate change in 25(OH)D, it is not
surprising that the findings were negative. The study
by Hunter suggests that when 25(OH)D concentra-
for osteoporosis prevention may be reaching an
asymptote. However, the appearance of an asymptote
may simply reflect a lack of statistical power, because
very few adults have 25(OH)D levels higher than
Data derived from large cross-sectional cohorts can
produce very impressive statistical power to support a
concept. Data from The National Health and
Nutrition Examination Survey (NHANES ) from the
U S A show that bone density correlates positively with
25(OH)D concentrations as these rise toward and
beyond 100 nmol/L for white women (36).
Concentrations of 25(OH)D have only modest
effects on bone turnover markers. Devine et al. failed
to detect changes in bone markers when 10 mg/day
of vitamin D3was given to elderly women (37). A
larger, cross-sectional study showed that higher
25(OH)D concentrations correlated with lower
urinary excretions of hydroxyproline, pyridinoline,
deoxy-pyridinoline, and lower plasma alkaline phos-
phatase and PTH concentrations (38). In a cross-
section of younger, healthy adults, bone markers are
higher in the winter season (39). Likewise, the
elderly show wintertime increases in bone turnover
markers (40). Winter is also the season of greater
loss of bone mineral density (40), and vitamin D
supplementation can overcome this (41). In a
randomized controlled trial, vitamin D supplemen-
tation of elderly women insufficient in vitamin D
resulted in lower bone turnover markers than with
calcium supplementation alone (31). The data
available on bone markers indicate that 25(OH)D
concentrations greater than 60 to 80 nmol/L may be
approaching an asymptote in terms of bone per se,
because there is no evidence of further suppression
of bone turnover if initial 25(OH)D concentrations
already exceed 60 nmol/L.
Several reports show that active absorption of
calcium through the gut correlates with 25(OH)D
concentrations (31,37,42,43). This relationship does
not appear to reach a plateau, so that an ‘optimal’
25(OH)D concentration cannot be determined
based on calcium absorption. What it does suggest,
is that the dietary requirement for calcium may be
lower with higher 25(OH)D concentrations.
The history of vitamin D intake recommendations
highlights how hard it is to establish an appropriate
Vitamin D nutrition prevents fractures
dose before the nature of a compound is understood
teaspoonful of cod liver oil has been a folk remedy
whose purpose it was to help infants thrive. This
typically less than 400 IU of vitamin D3. The 375 IU
(9 mg) of vitamin D3contained in that teaspoon (44)
was confirmed only recently as being appropriate for
infants (45–47). Compared to the adult, vitamin D
nutrition in the infant and child has been well
characterized. Until it became clear in the past two
of adults, there was no thought directed at how much
vitamin D3(cholecalciferol) now recommended for
prevention or treatment of osteoporosis (48) was
originally selected because it was easy to double the
10 mg/day dose present in formulations of vitamin D2
(ergocalciferol). In the 1980s, Chapuy and Meunier
found that 20 mg/day of ergocalciferol produced a
statistical suppression of PTH in the elderly, but half
that dose had no significant effect (25). When they
carried out their fracture-prevention studies later, the
group changed the form of vitamin D used in their
studies. This was because of a report by Tjellesen,
suggesting that vitamin D3was more effective than
vitamin D2(49). The change was fortuitous, because
subsequent studies using vitamin D2(26) have not
matched the efficacy reported with vitamin D3.
The fact that 20 mg/d of vitamin D3 prevents
fractures is not proof that this is the optimal dose for
osteoporosis. This is only the lowest dose that
consistently shows a statistically significant response.
Because vitamin D is regarded as only a nutrient and
freely available, there has never been a commercial
incentive to optimize the dose. It could be argued
that the commercial incentive is actually to under-
dose with vitamin D in clinical trials, to make
proprietary products look better. There are no
studies of osteoporosis prevention at a vitamin D
dose beyond the 20 mg/day. Knowledge of the dose-
response curve for vitamin D and osteoporosis is
very limited (Figure 1).
The responsiveness to vitamin D administration,
based on the nmol/L increase in 25(OH)D per mg of
vitamin D consumed per day, increases with: 1)
lower vitamin D dosage; 2) lower initial 25(OH)D
concentration; 3) longer duration of supplementa-
tion; and 4) lower body mass. The conventional way
to improve vitamin D nutritional status has been to
give vitamin D3or vitamin D2(ergocalciferol). Until
recently, availability of 25(OH)D was another
option (50), but the product has been discontinued
by Organon (NJ, USA). The company’s disconti-
nuation of 25(OH)D may have made sense, because
the objective of increasing plasma 25(OH)D con-
centrations can be almost as easily achieved by
providing enough vitamin D3.
Hormonal 1,25(OH)2D is not an alternative to
nutritional vitamin D
For most of the 20th century, there was no debate,
that vitamin D was a nutrient. It was known as ‘the
sunshine vitamin’. Confusion arose when it was
realized that the active form of the vitamin D
molecule was 1,25(OH)2D (calcitriol), which is a
hormone in the true sense of the word. Official
nutrition reports in both North America (51) and
Europe (52) now describe nutritional vitamin D as
perhaps more suitably referred to as a ‘hormone’
than a nutrient. However, vitamin D is no more a
hormone than is cholesterol, because vitamin D is
only the raw material needed for synthesis of
calcitriol. The purpose of supplementing with
vitamin D is to optimize the natural functions of
the endocrine/paracrine systems that require it.
There are many studies looking into the use of the
hormone, calcitriol, and analogs of it in the prevention
and treatmentof osteoporosis. Byfar thebest review of
this is by Papadimitropoulos et al. who found no
evidence that calcitriol and its analogs offer any benefit
over the use of plain, simple, safe and cheap vitamin
D3(53). Based on some reviews that focus on studies
involving high doses of calcitriol compared to studies
using pediatric doses of vitamin D3, some have
suggested that calcitriol or its analogs might be better
under some conditions (54,55). If osteoporosis occurs
because the vitamin D system is somehow deficient or
defective, it makes little sense to resort to the use of the
Figure 1. Relative dose-response effects of vitamin D intake on
prevention of bone disease and possible toxicity. Since it is
unlikely that any dose of vitamin D can entirely prevent or cure
osteoporosis, the osteoporosis dose-response curve does not reach
100%. However, doses essential for preventing osteoporosis are
higher than those needed to prevent rickets and osteomalacia, and
they are far lower than anything that might be implicated as
harmful. To convert from the more contemporary units in this
figure, to the traditional IU for vitamin D, multiply by 40 (i.e.
10 mg510 mcg5400 IU).
relatively potent and more likely toxic hormone,
calcitriol, to prevent osteoporosis. The fact never
mentioned by those who advocate use of calcitriol for
osteoporosis, is that rickets and osteomalacia usually
exist despite normal – and often elevated – serum
concentrations of calcitriol (56–59). Increases in
vitamin D supply will not increase calcitriol levels
unless the depletion of 25(OH)D is virtually absolute
(60–63). As kidney function deteriorates, its endocrine
capability also declines. A low serum calcitriol level is
more often a measure of impaired renal function than
poor nutrition (63,64). The effect that aging has on
calcitriol levels and on PTH can be overcome by
raising the 25(OH)D concentration (15,65). If osteo-
porosis is to be prevented, there is no role for calcitriol
or its analogs which, at best, might be considered as an
unproven alternative to vitamin D nutrition in the
treatment of active osteoporosis. These agents must be
used under the care of the physician and do not have a
role in prevention of osteoporosis.
Conclusions and commentary
In 1997, when the Food and Nutrition Board last
reviewed this nutrient, there was no evidence that
intakes of vitamin D below 20 mg (800 IU)/day would
have any measurable health effect in adults. All data
available at the time showed that to lower risk of
(20,21,66). Based on the study of Chapuy et al. alone,
a British report had determined only from the costs of
treating fractures, that there was justification to
supplement all women in British nursing homes with
vitamin D3(67). Little has resulted from any of this.
The final recommendations of the Food and Nutrition
Board established values for vitamin D intakes that
were 15 mg (600 IU)/day for those over age 70 years,
and recommendations for younger adults were even
lower (51). The Food and Nutrition Board openly
admitted that there was no evidence that these intakes
would do anything (68). Since that 1997 report, all of
the new evidence that vitamin D has an effect on bone
density, fractures, or muscle function confirms that
adults require at least 20 mg/day of vitamin D in the
(22,23,31,69). Recently, new products have become
available that combine daily, two-pill doses of calcium
and vitamin D3 in the amounts of 1000–1200 mg
calcium and 800 IU vitamin D3that have consistently
shown fracture prevention.
In relation to the question of what the optimal
25(OH)D concentration may be for prevention of
osteoporosis, current evidence points to a serum level
of 70–80 nmol/L as the minimum concentration to
aim for. However, the dose-response curve for this
toconsume 20 mg/day
nutrient has been explored only part of the way. The
physiological range extends to 25(OH)D concentra-
tions higher than 200 nmol/L for humans. The
pharmacological range for 25(OH)D concentrations
beyond that has not been touched on in any context
pertinent to osteoporosis. It cannot be assumed that
anything higher than a ‘normal’ concentration of
25(OH)D is harmful. Further health benefits cannot
be ruled out for 25(OH)D concentrations in the
pharmacological range. This field deserves more
clinical research, because the cost of vitamin D is
trivial compared to its potential benefits.
The evidence from randomized controlled clinical
trials summarized in Table I is so convincing that it
changes the ethical background for future research in
the field of osteoporosis. We cannot continue to
offer the control group only 10 mg (400 IU)/day –
this amounts to a homeopathic dose of vitamin D.
Ethical considerations demand that we treat patients
in any control group according to the best knowl-
edge to date (70). However, to evaluate doses of
vitamin D3beyond 20 mg (800 IU)/day will prob-
ably require studies in which a daily dose of 20 mg is
given to the control group, against which any higher
dose must be shown to be superior. This kind
research will be far more demanding than what has
been done in the past because the greatest step in
efficacy has almost certainly been achieved with
800 IU/day. Studies addressing the issue of an
optimal dose of vitamin D3 will require greater
numbers of participants than the studies published
to date. Although doses of vitamin D3higher than
20 mg/day probably will offer additional benefits for
osteoporosis, further research is faced with the need
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