אז יש לי פה איזה מחקר קטן שמאוד מעניין אותי לדעת מה קורה סביב זה והאנגלית שלי בסדר אבל לא ממש מושלמת ככה שאולי אם מישהו יוכל לעזור לי אני מאוד אשמח!
נושא המחקר הוא עצם האינטרקציה בין מגנזיום וסידן והשפעת הספיגה של שני החומרים הללו.
אם אין לכם כוח לקרוא וזה לא מעניין אותכם אז אני מבין, ולא צריך להעלות השמצות למיניהן.
פשוט מי שלא בא לו אז אני לא מכריח אף אחד אלא רק מבקש את עזרתכם.
תודה רבה למי שעוזר.
נלקח מפה: http://jn.nutrition.org/cgi/reprint/121/1/13.pdf
עמ' 18 (העמודים רשומים על החלק העליון השמאלי של הדפים)
וזה נלקח מPubmed
CALCIUM AND
MAGNESIUM INTERACTIONS
In humans, several laboratories have reported that
increasing Ca in the diet significantly depresses Mg
absorption (49, 50). Normal et al. (50) fed healthy hu
mans a low (300 mg/d) or a high (2000 mg/d) Ca diet for
4 wk and perfused jejunal and ileal segments in vivo
with solutions that contained no Ca and 5 mmol/L
MgCli. They found a significant decrease in Mg absorp
tion in the ileum of subjects fed the high Ca diet.
Spencer et al (51), however, fed diets containing 200-
2000 mg Ca/d for 29 to 43 d and saw no significant effect
on fecal Mg. Leichsenring et al. (52) also observed no
correlation between fecal Ca and fecal Mg when Ca was
increased from 300 to 1200 mg/d in the diet of healthy
women.
Increasing Mg in the diet has been reported to signif
icantly decrease fecal Ca in humans (47,52,53). Brannan
et al. (18), however, found in an intestinal perfusion
study that increasing the concentration of Mg in the
lumen decreased Ca absorption in the jejunum. Direct
intestinal perfusion with various concentrations of sol
uble Mg or Ca salts in an isolated segment, however,
may not reflect what is actually occurring in vivo.
Ammann et al. (54) found significant absorption of 45Ca
when the 45Ca was injected directly into the colon of
rats. After an oral dose of 45Ca,however, net 45Caabsorp
tion in the colon was negligible. The data suggest that
Ca arriving in the colon from the small intestine is
unavailable for absorption because of binding of Ca to
complexing agents found in the intestine, such as oxalate or fatty acids. It is possible that Mg also binds to
these complexing agents. The question is therefore
raised whether interactions between Ca and Mg that are
observed in isolated segments actually reflect what is
occurring in the intact animal.
Moreover, the differences in methodology between
studies makes it difficult to compare many of the
human studies and to conclude whether there is any
interaction between Ca and Mg in the intestine. Differ
ent levels of Ca and Mg were given, often within the
same study. In some studies healthy subjects were used;
in others the participants had a variety of diseases. Age
and previous Ca and Mg intakes, both known to signif
icantly affect Ca and Mg absorption, also differed be
tween studies.
Although there are conflicting results in studies with
humans (18, 49, 51, 52), all but one study (53) in rats
have demonstrated that net absorption of Mg in vivo is
depressed by a high Ca intake (10, 21, 54-61). The
mechanism by which Ca and Mg interact, however, has
not been well-defined. Several possible mechanisms
have been proposed. These include competition for a
common carrier system (55), a Ca-induced change in
membrane permeability to Mg (52), and modulation of
a specific Mg carrier by Ca (2).
A number of studies in animals, using a variety of in
vivo and in vitro techniques, have indicated that there
is direct competition between Ca and Mg for intestinal
transport (21, 27, 55, 62). Behar (21), using an in vitro
technique, reported that increasing the Ca concentra
tion from 2 to 4 mmol/L in the incubation medium
significantly reduced Mg transport in rat ileum at all Mg
concentrations studied (Fig. 7, 8).
Work by other investigators with rats, however, indi
cates that the interaction between Ca and Mg is not
always predictable. In the everted gut sac, Hendrix et al.
(19) found that Ca and Mg are taken up preferentially in
different portions of the intestine and that their interac
tion varied throughout the intestine. Specifically, Ca
inhibited Mg transport in the ileum but not the duode
num, whereas Mg inhibited Ca transport primarily in
the duodenum. Aldor and Moore (9) concluded that Mg
transport was depressed by increases in luminal Ca from
0 to 1 or 5 mmol/L in the colon, but not in the small
intestine. O'Donnell and Smith (61) investigated the
interaction of Ca and Mg by studying short-term uptake
in rat duodenal mucosa. Mg significantly inhibited the
time-dependent uptake of Ca, but Ca did not signifi
cantly reduce uptake of Mg. Petith and Schedi (56),
however, found that Ca absorption from the cecum and
colon was depressed in Mg-deficient rats as compared to
controls, but Ca deficiency had no effect on Mg absorp
tion.
More recently, Karbach and Ewe (45) reported that
increasing the Ca concentration from 1.25 to 10 mmol/L
in in vivo intestinal perfusate has no effect on Mg
absorption in the colon of rats. Likewise, increasing the Ussing system, however, they found that Mg had a
significant effect on net Ca absorption. Specifically in
creasing the Mg concentration to 1.25 mmol/L de
creased the mucosal-to-serosal flux of Ca by 50% and
abolished net Ca absorption. The effect was due to a
depression of the voltage-dependent component, that is,
the paracellular pathway. Increasing the Ca concentra
tion from 0.125 to 5 mmol/L had no effect on Mg
transport. This study does not rule out that Ca at lower
concentrations may significantly alter Mg absorption.
Much of the evidence for intestinal interactions be
tween Ca and Mg has come from studies in which
transport of one nutrient was studied in the absence of
dietary intake of the other nutrient (21, 55, 56). This
approach does not represent the situation of an animal
consuming a normal diet. The deficient animals are
often sick, and changes that alter cell permeability may
occur. Indeed, Krawitt (57) found that whereas Mg-deficient
animals absorbed more Ca than rats fed ad libitum,
they absorbed the same amount of Ca as pair-fed con
trols. Another problem in interpreting these studies is
that absorption of Ca and Mg was studied primarily in
isolated segments rather than in the intact animal.
The results of the studies discussed previously do not
exclude an adaptive effect of Ca upon Mg transport in
the intestine. Ca may indirectly affect Mg absorption
through changes in serum concentrations of Ca-regulating
hormones. Alterations in serum Ca concentration
are known to affect not only 1,25-dihydroxycholecalciferol
but also parathyroid hormone (PTH). Al
though the effect of 1,25-dihydroxycholecalciferol on
Mg absorption is not fully elucidated (see earlier discus
sion), PTH increases absorption of Mg in both humans
and animals (1-5). The precise manner by which PTH
affects Mg absorption, however, is uncertain. Although
the involvement of 1,25-dihydroxycholecalciferol and
PTH in mediating interactions between Ca and Mg in
the intestine cannot be ruled out, these hormones are
probably more important in the long-term adaptation to
dietary Ca and Mg levels rather than in mediating shortterm
fluctuations. In addition, the in vitro evidence does
suggest that there is interaction between Ca and Mg in
the intestine independent of these hormones.
It has also been postulated that Ca may indirectly
affect Mg absorption through changes in membrane
permeability. Intestinal membrane permeability is sen
sitive to alterations in luminal Ca and Mg concentra
tions (63-65). Investigators have found that depletion of
either luminal Mg or Ca increases tight junction perme
ability and thereby increases diffusion through the paracellular
pathway (66, 67). While depletion of Ca and Mg
in the lumen is an extreme state, one can postulate that
physiologic changes in the concentration of Ca or Mg in
the lumen might also influence diffusion through the
paracellular pathway and may be important in the reg
ulation of cation transport through this pathway. Fur
ther investigation will be required to test this hypothesis and to determine its importance in shortand
long-term regulation of Ca and Mg transport.
ושוב תודה!
נושא המחקר הוא עצם האינטרקציה בין מגנזיום וסידן והשפעת הספיגה של שני החומרים הללו.
אם אין לכם כוח לקרוא וזה לא מעניין אותכם אז אני מבין, ולא צריך להעלות השמצות למיניהן.
פשוט מי שלא בא לו אז אני לא מכריח אף אחד אלא רק מבקש את עזרתכם.
תודה רבה למי שעוזר.
נלקח מפה: http://jn.nutrition.org/cgi/reprint/121/1/13.pdf
עמ' 18 (העמודים רשומים על החלק העליון השמאלי של הדפים)
וזה נלקח מPubmed
CALCIUM AND
MAGNESIUM INTERACTIONS
In humans, several laboratories have reported that
increasing Ca in the diet significantly depresses Mg
absorption (49, 50). Normal et al. (50) fed healthy hu
mans a low (300 mg/d) or a high (2000 mg/d) Ca diet for
4 wk and perfused jejunal and ileal segments in vivo
with solutions that contained no Ca and 5 mmol/L
MgCli. They found a significant decrease in Mg absorp
tion in the ileum of subjects fed the high Ca diet.
Spencer et al (51), however, fed diets containing 200-
2000 mg Ca/d for 29 to 43 d and saw no significant effect
on fecal Mg. Leichsenring et al. (52) also observed no
correlation between fecal Ca and fecal Mg when Ca was
increased from 300 to 1200 mg/d in the diet of healthy
women.
Increasing Mg in the diet has been reported to signif
icantly decrease fecal Ca in humans (47,52,53). Brannan
et al. (18), however, found in an intestinal perfusion
study that increasing the concentration of Mg in the
lumen decreased Ca absorption in the jejunum. Direct
intestinal perfusion with various concentrations of sol
uble Mg or Ca salts in an isolated segment, however,
may not reflect what is actually occurring in vivo.
Ammann et al. (54) found significant absorption of 45Ca
when the 45Ca was injected directly into the colon of
rats. After an oral dose of 45Ca,however, net 45Caabsorp
tion in the colon was negligible. The data suggest that
Ca arriving in the colon from the small intestine is
unavailable for absorption because of binding of Ca to
complexing agents found in the intestine, such as oxalate or fatty acids. It is possible that Mg also binds to
these complexing agents. The question is therefore
raised whether interactions between Ca and Mg that are
observed in isolated segments actually reflect what is
occurring in the intact animal.
Moreover, the differences in methodology between
studies makes it difficult to compare many of the
human studies and to conclude whether there is any
interaction between Ca and Mg in the intestine. Differ
ent levels of Ca and Mg were given, often within the
same study. In some studies healthy subjects were used;
in others the participants had a variety of diseases. Age
and previous Ca and Mg intakes, both known to signif
icantly affect Ca and Mg absorption, also differed be
tween studies.
Although there are conflicting results in studies with
humans (18, 49, 51, 52), all but one study (53) in rats
have demonstrated that net absorption of Mg in vivo is
depressed by a high Ca intake (10, 21, 54-61). The
mechanism by which Ca and Mg interact, however, has
not been well-defined. Several possible mechanisms
have been proposed. These include competition for a
common carrier system (55), a Ca-induced change in
membrane permeability to Mg (52), and modulation of
a specific Mg carrier by Ca (2).
A number of studies in animals, using a variety of in
vivo and in vitro techniques, have indicated that there
is direct competition between Ca and Mg for intestinal
transport (21, 27, 55, 62). Behar (21), using an in vitro
technique, reported that increasing the Ca concentra
tion from 2 to 4 mmol/L in the incubation medium
significantly reduced Mg transport in rat ileum at all Mg
concentrations studied (Fig. 7, 8).
Work by other investigators with rats, however, indi
cates that the interaction between Ca and Mg is not
always predictable. In the everted gut sac, Hendrix et al.
(19) found that Ca and Mg are taken up preferentially in
different portions of the intestine and that their interac
tion varied throughout the intestine. Specifically, Ca
inhibited Mg transport in the ileum but not the duode
num, whereas Mg inhibited Ca transport primarily in
the duodenum. Aldor and Moore (9) concluded that Mg
transport was depressed by increases in luminal Ca from
0 to 1 or 5 mmol/L in the colon, but not in the small
intestine. O'Donnell and Smith (61) investigated the
interaction of Ca and Mg by studying short-term uptake
in rat duodenal mucosa. Mg significantly inhibited the
time-dependent uptake of Ca, but Ca did not signifi
cantly reduce uptake of Mg. Petith and Schedi (56),
however, found that Ca absorption from the cecum and
colon was depressed in Mg-deficient rats as compared to
controls, but Ca deficiency had no effect on Mg absorp
tion.
More recently, Karbach and Ewe (45) reported that
increasing the Ca concentration from 1.25 to 10 mmol/L
in in vivo intestinal perfusate has no effect on Mg
absorption in the colon of rats. Likewise, increasing the Ussing system, however, they found that Mg had a
significant effect on net Ca absorption. Specifically in
creasing the Mg concentration to 1.25 mmol/L de
creased the mucosal-to-serosal flux of Ca by 50% and
abolished net Ca absorption. The effect was due to a
depression of the voltage-dependent component, that is,
the paracellular pathway. Increasing the Ca concentra
tion from 0.125 to 5 mmol/L had no effect on Mg
transport. This study does not rule out that Ca at lower
concentrations may significantly alter Mg absorption.
Much of the evidence for intestinal interactions be
tween Ca and Mg has come from studies in which
transport of one nutrient was studied in the absence of
dietary intake of the other nutrient (21, 55, 56). This
approach does not represent the situation of an animal
consuming a normal diet. The deficient animals are
often sick, and changes that alter cell permeability may
occur. Indeed, Krawitt (57) found that whereas Mg-deficient
animals absorbed more Ca than rats fed ad libitum,
they absorbed the same amount of Ca as pair-fed con
trols. Another problem in interpreting these studies is
that absorption of Ca and Mg was studied primarily in
isolated segments rather than in the intact animal.
The results of the studies discussed previously do not
exclude an adaptive effect of Ca upon Mg transport in
the intestine. Ca may indirectly affect Mg absorption
through changes in serum concentrations of Ca-regulating
hormones. Alterations in serum Ca concentration
are known to affect not only 1,25-dihydroxycholecalciferol
but also parathyroid hormone (PTH). Al
though the effect of 1,25-dihydroxycholecalciferol on
Mg absorption is not fully elucidated (see earlier discus
sion), PTH increases absorption of Mg in both humans
and animals (1-5). The precise manner by which PTH
affects Mg absorption, however, is uncertain. Although
the involvement of 1,25-dihydroxycholecalciferol and
PTH in mediating interactions between Ca and Mg in
the intestine cannot be ruled out, these hormones are
probably more important in the long-term adaptation to
dietary Ca and Mg levels rather than in mediating shortterm
fluctuations. In addition, the in vitro evidence does
suggest that there is interaction between Ca and Mg in
the intestine independent of these hormones.
It has also been postulated that Ca may indirectly
affect Mg absorption through changes in membrane
permeability. Intestinal membrane permeability is sen
sitive to alterations in luminal Ca and Mg concentra
tions (63-65). Investigators have found that depletion of
either luminal Mg or Ca increases tight junction perme
ability and thereby increases diffusion through the paracellular
pathway (66, 67). While depletion of Ca and Mg
in the lumen is an extreme state, one can postulate that
physiologic changes in the concentration of Ca or Mg in
the lumen might also influence diffusion through the
paracellular pathway and may be important in the reg
ulation of cation transport through this pathway. Fur
ther investigation will be required to test this hypothesis and to determine its importance in shortand
long-term regulation of Ca and Mg transport.
ושוב תודה!
