Osteoporosis and the subsequent risk of
bone fracture are characterized by enhanced bone fragility, resulting in an
increased risk of fracture, and it is usually defined as a reduction in bone
mineral density (BMD). These disorders account for a significant burden of
morbidity and mortality worldwide and have become a major public health problem.
In women with
postmenopausal osteoporosis, estrogen deficiency enhances the sensitivity to
parathyroid hormone (PTH), leading to an increase in bone resorption. This
results in elevated concentrations of calcium (Ca) in the blood. High blood Ca levels then prevent the release of parathyroid
hormone (PTH), and, this, in turn, suppresses the production of 1,25-(OH)2 D3,
which can promote Ca absorption in the intestine. Ultimately, the reduced
absorption of Ca causes a decrease in bone mineral density (BMD). So it is critical to
maintain blood Ca levels in the normal range.
Citric acid is mainly responsible for the acidic flavor of lemons.
Recent studies have demonstrated that this organic acid acts as a chelating
agent and promotes the absorption of minerals such as Ca and iron. The aim of the
present study was to elucidate how bone metabolism and bone mineral density are
affected by the consumption of a lemon juice containing calcium (Ca)-enriched
beverage.
The efficacy of
this investigational product was evaluated in postmenopausal women during five
months of continuous intake (intervention). This was a randomized, controlled
trial. Eighty-three subjects were assigned to three groups. Using a
double-blind format, the first two groups received a Ca-supplemented
lemon-juice (lemon) beverage (LECA) or a Ca-unsupplemented lemon-juice (lemon)
beverage (LE). The third group (control) received no intervention. Each subject
in the LECA and LE groups consumed one bottle (290 mL) of their assigned
investigational product every day for five consecutive months.
After five months
of intervention, the gain in bone mineral density at the lumbar spine was
significantly larger in the LECA and LE groups than in the control group. In
the femur, subjects in the LECA group gained significantly more bone mineral
density than the control subjects. The largest gain in bone mineral density at
the lumbar spine was observed in the LECA group. As for the concentrations of
the bone resorption marker tartrate-resistant acid phosphatase 5b (TRACP-5b),
subjects in the LECA group had significantly lower values than those in the
control group. Similarly, when compared with the LE and control groups, a
significant decrease was detected in the LECA group in the concentrations of
the bone formation markers, bone alkaline phosphatase (BAP) and osteocalcin
(OC).
In conclusion, in
postmenopausal women, continuous consumption of Ca-supplemented lemon beverages
improved Ca absorption and inhibited bone resorption. The suppression of bone
resorption likely blocked bone formation mediated by the proliferation and
differentiation of osteoblasts, resulting in the attenuation of high-turnover
bone metabolism. The present results
also suggest that citric acid in lemons enhances the absorption of dietary Ca. It’s
expected that such beverages will have an efficacy in preventing osteoporosis
in the future.
Article by Hiromi
Ikeda, et al, from Japan.
Full access: http://mrw.so/4quGds
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