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Lichtenstein A
292 Rev Assoc Med Bras 2015; 61(4):291-292
For believers, the justification is that meta-analyzes
are based on studies with vitamin D supplementation us-
ing various doses and duration. They believe that we would
have to give high doses for a long time to achieve the ef-
fect. For skeptics, it is a matter of reverse bias, that is, pa-
tients are ill and, therefore, have low levels of vitamin D,
it not being the cause of the event studied.
Vitamin D dosage adds flavor to the discussion: if
there is a high probability of having low pre-test levels,
why should we measure it? It is known that 70% of the
US population has levels below normal.
For the American Society of Endocrinologists, vita-
min D levels should “only” be measured in risk groups
(chronic use of medication [anticonvulsants, corticoste-
roids, antiretrovirals and antifungal], pregnant women
and infants, African-Americans and Hispanics, obese and
elderly individuals with a history of falls and non-trau-
matic fractures, osteoporosis, malabsorption and granu-
lomatous diseases. It also recommends that dosage for
cases of rickets, chronic kidney disease, and liver disease.9
Which means most people).
For the United States Preventive Service Task Force
(USPSTF, one of the main advisors for health promotion),
supplementation would help prevent falls in the elderly,
and this should be done indiscriminately, without serum
measurements.10
What to do when the levels are below normal is also
controversial.
First, cutoff values for serum 25(OH)D3 have not been
defined for incidence or prevalence of health problems
in population groups. They were calculated from the sim-
ple correlation with serum concentrations of parathyroid
hormone (PTH). In other words, levels of 25(OH)D3 be-
low 20 ng/mL (divider between insufficiency and vitamin
D deficiency, according to most of the criteria adopted)11
trigger elevation of PTH levels above the established as
normal (intermediate outcome), but do not necessarily
represent higher risks of appearance of non-bone disease
(final outcome). In addition, there is a wide variation in
seasons and latitude of the study population. Thus, it is
very difficult to know the normal level of vitamin D3. The
question is: normal values, when and where?
Thus, the natural tendency, but not necessarily right,
is to correct an altered level, which would result in over-
treatment.
In the midst of such fascinating scenario, some paths
can be traced. Observational studies are no longer neces-
sary, but a large prospective study to define the levels of
vitamin D3/parathyroid hormone before the outcome,
then correct them and re-evaluate the outcome.
For the management of a patient, there is no reason
to measure vitamin D3 levels if the intention is to sup-
plement it. Use it in reasonable doses, no more than 2000
UI/day, always keeping in mind the implications of in-
dustrializing sunbathing.
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