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DIETARY IRON POSITIVELY INFLUENCES
BONE MINERAL DENSITY IN POST MENOPAUSAL WOMEN ON
HORMONE REPLACEMENT THERAPY
J Nutr 2005 April;135(4):863-9
Maurer J, et al.
The associations of dietary intakes of iron and calcium
on change in bone mineral density (BMD) were examined over
1 year in healthy nonsmoking postmenopausal women (mean age
55.6 ± 4.6 years) stratified by hormone replacement
therapy (HRT) use (HRT, n = 116; no HRT, n = 112). BMD was
measured using dual-energy X-ray absorptiometry at
baseline and 1 year. Mean nutrient intakes were assessed
using 8-d diet records. All women received 800 mg/d of
supplemental elemental calcium. Regression analyses examined
the effects of iron and calcium intakes on BMD
change adjusting for years past menopause, baseline BMD,
weight change, exercise, and energy intake. The
interaction of iron with calcium on BMD change was assessed
using tertiles of iron and calcium intake and estimated
marginal mean change in BMD. Iron was associated with
greater positive BMD change at the trochanter and Ward’s
triangle in women using HRT. Calcium was associated with BMD
change at the trochanter and femur neck for women
not using HRT. In women using HRT in the lowest tertile of
calcium intake, change in femur neck BMD increased
linearly as iron intake increased. In women not using HRT,
BMD increased in the women in the highest tertile of
calcium intake. The researchers conclude that HRT use
appears to influence the associations of iron and calcium on
change in BMD.
THE IMPORTANCE OF MAGNESIUM STATUS IN
THE PATHOPHYSIOLOGY OF MITRAL VALVE PROLAPSE
[IN PROCESS CITATION]
Magnes Res 2005 Mar;18(1):35-52
Bobkowski W; Nowak A; Durlack J.
Idiopathic mitral valve prolapse
(IMVP) refers to the systolic displacement of one or both
mitral leaflets into the left
atrium, with or without mitral regurgitation. It is one of
the most common forms of cardiac abnormalities among
young people, especially in women. IMVP usually appears to
be a benign condition and even capable of recovery. In
a minority of cases IMVP may predispose to complications.
IMVP appears to be one form or aspect of latent tetany
due to magnesium deficit (MDLT). The prevalence, latent
nature, and symptomatology of these two conditions appear
to be strictly similar. Primary magnesium (Mg) deficit may
result from Mg deficiency (insufficient Mg intake) and Mg
depletion (excessive urinary Mg loss). Constitutional
factors (e.g. HLA-B35, type-A behavior pattern) should be
considered in the etiology of Mg deficit (MD). MD may cause
abnormal fibrosis, abnormalities in collagen synthesis
as well as in the myocardium, capable of inducing mitral
apparatus dyskinesia. MD is a part of a picture of metabolic
abnormalities, alteration of immune and autonomic nervous
systems, cardiac arrhythmias and thromboembolic
phenomena in IMVP. Laboratory evaluation must involve plasma
Mg, erythrocyte Mg, calcemia, calciuria, and daily
magnesuria. Normal plasma Mg concentration does not rule out
the diagnosis of primary chronic MD. The diagnosis
of MD requires the oral Mg load test. Correction of
symptomatology by this oral physiological Mg load (5
mg/kg/day)
is the best proof that it was due to Mg deficiency. Mg
therapy is essential and specific for IMVP. In the majority
of
cases MD is due to Mg depletion and the oral Mg
supplementation must be combined with Mg-sparing diuretics
or
physiological doses of vitamin D. Partial “Mg analogues”
(beta-blockers, verapamil, phenytoin) may prove to be
useful in some cases.
CALCIUM AND VITAMIN D INTAKE AND RISK
OF INCIDENT PREMENSTRUAL SYNDROME
Arch Intern Med 2005 Jun 13;165(11):1246-52
Bertone-Johnson ER, et al.
Premenstrual syndrome (PMS)
is one of the most common disorders of premenopausal
women. Studies suggest that
blood calcium and vitamin D levels are lower in women
with PMS and that calcium supplementation may reduce
symptom severity, but it is unknown whether these
nutrients may prevent the initial development of PMS.
The
researchers conducted a case-control study nested within
the prospective Nurses’ Health Study II cohort.
Participants were a subset of women aged 27 to 44 years
and free from PMS at baseline in 1991, including 1057
women who
developed PMS over 10 years of follow-up and 1968 women
reporting no diagnosis of PMS and no or minimal
menstrual symptoms. Intake of calcium and vitamin D was
measured in 1991, 1995, and 1999 by a food frequency
questionnaire. After adjustment for age, parity, smoking
status, and other risk factors, women in the highest
quintile of
total vitamin D intake (median, 706 IU/d) had a relative
risk of 0.59 compared with those in the lowest quintile
(median, 112 IU/d). The intake of calcium from food
sources was also inversely related to PMS; compared with
women with a low intake (median, 529 mg/d), participants
with the highest intake (median, 1283 mg/d) had a
relative
risk of 0.70. The intake of skim or low-fat milk was
also associated with a lower risk. A high intake of
calcium and
vitamin D may reduce the risk of PMS. Large-scale
clinical trials addressing this issue are warranted.
Given that
calcium and vitamin D may also reduce the risk of
osteoporosis and some cancers, clinicians may consider
recommending these nutrients even for younger women.
CALCIUM SUPPLEMENTATION INCRASES
STATURE AND BONE MINERAL MASS OF 16 TO 18 YEAR OLD
BOYS
J Clin Endocrinol Metab 2005 Jun;90(6):3153-61
Prentice A, et al.
The effect of calcium carbonate
supplementation on bone growth and mineral accretion was
studied in 143 boys aged
16-18 years, randomized to 1000 mg Ca/d or a matching
placebo for 13 months. Anthropometry and dual-energy xray
absorptiometry of the whole body, lumbar spine, hip, and
forearm were performed before, during, and after the
intervention. The intervention resulted in greater bone
mineral content (BMC) of the whole body (+1.3%), lumbar
spine (+2.5%), and hip (total +2.3%, neck +2.4%,
intertrochanter +2.7%). This was associated with greater
height
(+0.4%, equivalent to 7 mm), lean mass (+1.3%), and lumbar
spine bone area (+1.5%). The increases in BMC
diminished after size adjustment, suggesting that the
intervention effect was mediated through an effect on
growth.
The BMC response at the intertrochanter was greater in
subjects with high physical activity (+4.4%). There were no
other significant interactions with physical activity,
plasma testosterone, calcium intake, or tablet compliance.
The
researchers concluded that calcium carbonate supplementation
of adolescent boys increased skeletal growth, resulting
in greater stature and bone mineral acquisition. Follow-up
studies will determine whether this reflects a change in the
tempo of growth or an effect on skeletal size that persists
into adulthood.
INTERACTIVE EFFECTS OF IRON AND ZINC
ON BIOCHEMICAL AND FUNCTIONAL OUTCOMES IN
SUPPLEMENTATION TRIALS
Am J Clin Nutr 2005;82:5-12
Fischer-Walker C, et al.
Iron and zinc are essential micronutrients for human
health. Deficiencies in these 2 nutrients remain a global
problem,
especially among women and children in developing countries.
Supplementation with iron and zinc as single
micronutrients enhances distinct and unique biochemical and
functional outcomes. These micronutrients have the
potential to interact when given together; thus, it is
important to assess the biochemical and functional evidence
from
clinical trials before supplementation policies are
established. The researchers reviewed randomized trials that
assessed the effects of iron and zinc supplementation on
iron and zinc status. On the basis of this review, zinc
supplementation alone does not appear to have a clinically
important negative effect on iron status. However, when
zinc is given with iron, iron indicators do not improve as
greatly as when iron is given alone. In most of the studies,
iron supplementation did not affect the biochemical status
of zinc, but the data are not clear regarding morbidity
outcomes. Although some trials have shown that joint iron
and zinc supplementation has less of an effect on
biochemical or functional outcomes than does supplementation
with either mineral alone, there is no strong evidence to
discourage joint supplementation. Supplementation programs
that provide iron and zinc together are an efficient way
to provide both micronutrients, provided the benefits of
individual supplementation are not lost. Further research is
needed before health policies on joint supplementation
programs can be established.
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