Strontium (Sr) is a bone seeking trace element that closely parallels calcium metabolism. At the present, there is no available
long-term biological indicator for assessing the human Sr nutritional status. In this article, we have presented a novel
concept on how to assess the human strontium nutritional status by studying its frequency distribution in the hair and
whole blood. In this prospective, observational, cross-sectional, and exploratory epidemiological study, we analyzed hair
Sr (SrH) in 311 apparently healthy adult Croatians (123 men, 188 women); among them, whole blood strontium (SrWB)
was detected in 142 women and 89 men.
Hair and WB samples were analyzed for strontium by the inductively coupled mass plasma spectrometry (ICP MS). The
natural frequency distribution of hair strontium obeyed the power law so that the data were analyzed by fitting the logistic
bioassay sigmoid curve (ogive) of the median derivatives.
Women have accumulated more SrH than men (median men 0.867 µg·g-1 vs. median women 3.120 µg·g-1). The normal
physiological response range covered by the linear part of the sigmoid curve was 0.418 - 2.950 µg·g-1 for men and 0.846
- 7.260 µg·g-1 for women. Values below that linear range were considered to denote low Sr nutritional status, whereas
values above that range would indicate excessive dietary strontium exposure. The long term biological indicator of hair
strontium (SrH) is incommensurable with that of the short term biological indicator of the whole blood strontium (SrWB).
On the average, women have about three times more strontium in their hair than men, regardless of the age. Analysis of
the hair strontium frequency distribution is a valuable long term biological indicator in assessing the population strontium
nutritional status.
Strontium is an osteotrophic (bone-seeking) trace element
that is normally present in our diet and our bodies. The
pioneers of trace element analysis considered strontium to be
an essential trace element for humans , but the conclusive evidence
on strontium essentiality for humans has yet to be provided . Strontium was in the limelight in the 50’s and 60’s
of the last century when it was discovered that the metabolism
of strontium was closely related to the metabolism of calcium
in bone tissue. Indeed, 99% of typical body burden
of 320 mg Sr is found in the bone. The atmospheric fallout
of fission products after nuclear testing included a long-living
bone seeker of 90Sr which has a physical half-life of ~ 27 y anda biological T/2 ~ 10 y. Radioactive 90Sr is a powerful beta
radiation source and, when lodged in the bones, would act as
a strong radio-toxic carcinogen. Moreover, strontium, like
calcium, could be transferred from mother to fetus/newborn
via the mother’s milk and get deposed in their mineralized tissue
with possibly deleterious consequences. Later on,
the interest in strontium was renewed when Skoryna demonstrated
the pharmacological effect of both the stable and
89Sr radiopharmaceutical isotope Metasteron® to alleviate
the pain of mammary and prostate carcinoma bone metastases. Today, the most recent research has shown that
strontium ranelate [Protelos®, Osseor®] acts as an effective
nutritive agent, capable of slowing down mineral bone loss
due to old age. Indeed, these strontium compounds are preventing
and delaying the onset and progression of osteoporosis,
including both femur and vertebral osteoporosis.
How much such a treatment can affect the strontium body
burden and the metabolism of other trace elements in the
skeleton remains to be elucidated. Since strontium is not as
yet recognized to be an essential trace element, there are no
recommended dietary allowances (RDA’s) for strontium, and
there is also no available long term biological indicator tissue
for assessing the strontium nutritional status of the body; the
US Environmental Protection Agency has derived an oral recommended
dose for strontium of 0.6 mg per kg body weight
per day .
Today, hair trace element analysis is accepted as a long-term
biological indicator for assessing trace element nutritional
status and the level of their environmental exposure.
The aim of this study was to demonstrate how strontium hair
analysis (SrH) may serve as a long term biological indicator tissue
for assessing the strontium nutritional status of the human
body by analyzing hair strontium frequency distribution
properties with a median derivative method. Thus far, we have
shown that our innovative approach yielded a reliable assessment
of the nutritional status of the essential trace elements
iodine and selenium, and in evaluating the exposure to the
non-essential elements of silver and aluminium. The
observed data on hair strontium analysis were compared with
that for whole blood strontium (SrWB), i.e., a common short
term biological indicator tissue for the assessment of numerous
bioelements and other different clinical parameters.
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