ARTICLE
Auteur(s) : Forrest H Nielsen,
LuAnn K Johnson, Huawei Zeng
United States Department of Agriculture, Agricultural
Research Service, Grand Forks Human Nutrition Research Center,
Grand Forks, North Dakota, USA
Over 75 years ago, findings were obtained that suggested
magnesium deficiency results in an inflammatory response [1].
Evidence obtained in the past 25 years, mostly from animal
experiments, has confirmed that severely limiting magnesium intake
to less than 10% of the requirement results in an inflammatory
response characterized by the release of inflammatory cytokines and
acute phase proteins, and excessive production of free radicals and
oxidative stress [2]. The United States (US), National Health and
Nutrition Examination Survey (NHANES) 2005-2006 data indicated that
the usual magnesium intake from food of about 60% of all adults
does not meet the American Estimated Average Requirement (EAR) of
255-265 mg/day for females and 330-350 mg/day for males [3, 4].
However, severe human magnesium deficiency caused by low dietary
intake is unlikely. Based on dietary surveys, most people have
intakes that meet at least 50% of the EAR [3]. Moderate to marginal
or subclinical (~ 50% to < 100% of requirement) magnesium
deficiency alone apparently does not affect variables associated
with chronic inflammatory stress in animal models [5, 6]. However,
some animal findings indicate that moderate magnesium deficiency
can enhance the inflammatory or oxidative stress induced by other
factors [7-9].
One factor that may increase inflammatory stress is disrupted
sleep/sleep deprivation [10]. Inadequate sleep duration has been
associated with increases in several inflammatory biomarkers
including plasma C-reactive protein (CRP) [10]. Sleep quality also
has been associated with increased morning concentrations of
inflammatory biomarkers IL-6 in healthy adults, elderly women and
spousal Alzheimer's caregivers, and circulating IL-1β in women but
not men [10]. Magnesium intake has been found to be inversely
related to elevated circulating CRP concentrations [11-15]. Thus,
subclinical magnesium deficiency through exacerbating a low grade
inflammation may be a factor in sleep disruption or deprivation.
The possibility that magnesium deprivation affects sleep quality is
supported by a few human and animal studies. In a
placebo-controlled, randomized cross-over experiment with
12 older (aged 60 to 80 years) participants, magnesium
supplementation significantly reversed electroencephalogram (EEG)
changes, including decreased slow wave sleep, that occur during
aging [16]. Another study found that 27 patients with
parasomnias displayed hypomagnesemia and nocturnal EEG
abnormalities occurring during slow wave sleep [17]. Magnesium
treatment of alcohol-dependent patients (who often have magnesium
metabolism disturbances) significantly decreased sleep onset
latency and improved subjective sleep quality as assessed by the
Pittsburg Sleep Quality Index (PSQI) [18]. In rats, magnesium
deficiency significantly increased wakefulness at the expense of
slow wave sleep; magnesium supplementation restored sleep
organization to its original pattern [19]. In addition to a
chronic inflammatory stress relationship, sleep architecture and
magnesium may have a biochemical relationship. It has been
suggested than magnesium regulates sleep because it is an
N-methyl-D-aspartate antagonist and a γ-aminobutyric acid (GABA)
agonist [16, 19]. Sleep architecture, especially slow wave sleep,
apparently is closely associated with the glutamatergic and
GABAergic system.
The lack of controlled studies using a relatively large number
of participants was the impetus for an experiment to determine
whether magnesium supplementation improved sleep behavior
(quantity, quality, and disturbance), and whether this was
associated with a change in inflammatory stress measured by plasma
CRP concentrations. In addition, because it has been suggested that
people who have a missense variant of Thr-1482 to isoleucine (Ile)
in the transient receptor potential melastatin 7 (TRPM7) gene may
be at increased risk for magnesium deficiency [20], the possible
influence of this polymorphism on the response to magnesium
supplementation was determined.
Subjects and methods
Subjects
Male and female adults older than 51 years (age group with
increased sleep disorders and likelihood of low magnesium status
[21]) with sleep complaints were recruited for the study until
100 had completed the eight-week experimental protocol.
Applicants for the study were not accepted for the study if they
were consuming supplements providing 100 mg of magnesium or
greater per day or consuming sleep medications. Because they were
likely to have sleep disorders not related to magnesium status,
applicants with a body mass index (BMI) greater than
40 kg/m2, respiratory tract disease, chronic
obstructive pulmonary disease, or using oxygen or continuous
positive airway pressure were not accepted. Individuals on
angiotension converting enzyme inhibitors for blood pressure
control, other magnesium-retaining drugs, or potassium-sparing
drugs were not accepted because of the possibility these drugs
would cause retention of magnesium and potassium upon magnesium
supplementation that could lead to heart rhythm changes.
Eligible applicants were invited to an information meeting that
explained the purpose of the study, procedures involved, and
expectations of the participants. After consenting, the applicants
had blood drawn for complete blood count and liver and kidney
functions tests and completed the PSQI. Applicants invited to
participate in the study had blood results in the normal range and
a global PSQI score of greater than five (indicator of poor sleep
quality). Based on a study that used the PSQI to determine the
effect of magnesium supplementation on sleep of alcohol-dependent
patients [18], a power analysis indicated that to detect a
significant effect of magnesium with 0.90 power and an alpha of
0.05 would require 50 participants per placebo and
magnesium-supplemented group. Seventy-eight females and
22 males gave written informed consent to participate in the
experimental protocol that was approved by the Institutional Review
Board of the University of North Dakota, followed the guidelines of
the Department of Health and Human Services and the Helsinki
Doctrine regarding the use of human subjects, and registered in
Clinical Trials.gov as protocol NCT00833092. Beginning or baseline
average ages, PSQI scores, BMIs and plasma CRP concentrations of
the participants with no detected health problem or drug use are
given in Table 1. The number of subjects
consuming less than the EAR is also indicated because this was a
factor in some of the responses to magnesium supplementation.
Table 1 Baseline (mean ± SEM) age, Pittsburg Sleep
Quality Index (PSQI), Body Mass Index (BMI), and plasma C-reactive
protein (CRP) of subjects grouped by food diary magnesium
intakes.
|
Magnesium intake
|
Sex
|
N
|
Age1
|
PSQI
|
BMI
|
CRP, mg/L
|
|
< EAR (265 mg/d)
|
Female
|
44
|
59.4 ± 1.2 (51-85)
|
11.1 ± 0.5
|
29.1 ± 0.8
|
2.74 (2.38, 3.14)2
|
|
≥ EAR (265 mg/d)
|
Female
|
34
|
58.6 ± 1.1 (52-76)
|
10.5 ± 0.4
|
27.2 ± 0.8
|
1.84 (1.57, 2.16)
|
|
< EAR (350 mg/d)
|
Male
|
14
|
57.9 ± 2.7 (51-81)
|
8.9 ± 0.6
|
31.1 ± 1.0
|
3.12 (2.44, 3.99)
|
|
≥ EAR (350 mg/d)
|
Male
|
8
|
62.4 ± 2.2 (52-68)
|
8.9 ± 0.9
|
28.4 ± 1.6
|
1.30 (0.94, 1.79
|
|
< EAR
|
All
|
58
|
All Subjects 59.2 ± 0.8 (51-85)
|
10.6 ± 0.4
|
29.6 ± 0.63
|
2.924 (2.50,3.19)
|
|
≥ EAR
|
All
|
42
|
10.2 ± 0.4
|
27.4 ± 0.7
|
1.55 (1.50, 1.98)
|
Experimental protocol
The experiment was an eight-week, double-blind, placebo-controlled,
supplementation trial. Following baseline assessment during week
one of blood and urine biochemical variables, BMI, diet, and sleep
quality, the participants were randomly assigned to two groups
matched by gender and global PSQI score. One group was given a
320 mg/day magnesium supplement as magnesium citrate provided
in five capsules, each containing an analyzed 64 mg of
elemental magnesium. The other group was given five capsules
containing a sodium citrate placebo. The capsules provided about
1.75 g citrate/day. The placebo and magnesium supplements were made
by Gallipot, Inc. (St. Paul, Mn) from magnesium citrate and sodium
citrate supplied by Dr. Paul Lohmann, Inc. (Islandia, NY). The
participants were instructed to consume two capsules with a morning
meal, one with the noon meal, and two during an evening meal. Final
assessments of blood and urine biochemical variables, BMI, diet,
and sleep quality were made five and seven weeks after
supplementation initiation, which were averaged for statistical
analysis to reduce intra-individual variation.
Diet and sleep quality determinations
During baseline and weeks five and seven, the participants kept a
three-day food diary that included one weekend day as instructed by
a dietician. Estimated average daily magnesium intake was
calculated by using U.S. Department of Agriculture food composition
data [22].
Sleep quality was measured by the PSQI, which is a self-rated
questionnaire [23]. The PSQI has 19 individual items that
generate 7 component scores for subjective sleep quality,
sleep latency, sleep duration, habitual sleep efficiency, sleep
disturbances, use of sleep medications, and daytime dysfunction.
The sum of scores for these seven components yields one global
score. In this study, use of sleep medications did not influence
the global score because their use was forbidden. The global score
has a possible range of 0 to 21. In this study, a global PSQI
score of greater than five was considered a sign of poor sleep
quality.
Biochemical variables determinations
Magnesium and calcium in 24-hour urine samples diluted 1:10 were
determined directly by inductively coupled argon plasma emission
spectroscopy (ICP) (Model 3100 XL, Perkin Elmer, Waltham, MA).
Concurrent analyses of Seronorm Urine (SERO AS, Billingstad,
Norway) yielded means (mg/L) ± SD of 107 ± 5 and 69.9 ± 2.3
compared with certified values of 107 ± 4 and 70.1 ± 2.5,
respectively, for calcium and magnesium. Urine citrate was
determined by enzymatic assay by using a commercially available kit
(Cat. # 10 139 076-035, R-Biopharm/Boehringer Mannheim, Marshall,
MI) that determined citric acid. Citrate values were obtained by
using its molar mass of 189.1 g/mol. Quality control determinations
indicated intra assay variation of 0.33 ± 0.01 (SD) mg/dL and inter
assay variation of 1.69 ± 0.07 mg/dL. Urine creatinine was
determined by using Kit # 04810716190 for the Cobas Integra
Analyzer (Roche Diagnostics, Indianapolis, IN).
Blood was processed within 90 minutes to obtain serum or
plasma. Blood was allowed to clot for 20 minutes before
centrifuging at 2,000 RPM for 10 minutes to obtain serum.
Complete blood counts were determined by using the Cell-Dyn 3700
System (Abbott Laboratories, Santa Clara, CA). Serum total
cholesterol, HDL-cholesterol, triglycerides, and glucose were
determined by using standard methods of the Cobas Integra Analyzer
(Roche Diagnostics, Indianapolis, IN). LDL-cholesterol was
calculated by subtracting HDL-cholesterol and VLDL-cholesterol
(triglycerides ÷ 5) from total cholesterol. Ionized magnesium in
heparinized plasma normalized to pH 7.4 was determined by using an
ion-selective electrode (Nova-CRT-8 Analyzer, Nova Biomedical,
Waltham, MA). Quality control determinations indicated an intra
assay variation of 1.31 ± 0.02 (SD). High sensitivity CRP was
determined by using a commercially available kit (Immulite 1000,
Cat. # LKCR1, Diagnostics Products Corp., Los Angeles, CA). Quality
control determinations found intra assay variation of (mean ± SD)
of 0.17 ± 0.01, 0.70 ± 0.02, and 9.32 ± 0.41 mg/dL. The threshold
for elevated CRP was defined ≥ 3.0 mg/L, a concentration the
American Heart Association designated as being associated with high
cardiovascular risk [24], and used by others to associate elevated
CRP with low magnesium intakes [11-13].
Calcium and magnesium in serum samples diluted 1:10 were
directly determined by using ICP (Model 3100 XL, Perkin Elmer,
Waltham, MA). Concurrent analyses of UTAK Serum (UTAK Laboratories,
Valencia, CA) yielded means (mg/dL) ± SD of 7.62 ± 1.2 and 1.67 ±
0.11 compared with certified values of 8.3 ± 2.1 and 1.9 ± 0.5,
respectively, for calcium and magnesium. Magnesium in digested red
blood cells was determined by using ICP (Model 3100 XL, Perkin
Elmer, Waltham, MA). The digestion procedure consisted of placing 2
mL of red blood cells in a glass tube with 2 mL of
HNO3 and allowing to stand at room temperature for four
hours before placing the tube in a heating block to heat contents
to near dryness (not allowed to completely dry). Then, another
2 mL of HNO3 was added to the tube and the contents
heated to near dryness, cooled to room temperature, and brought up
to a 4 mL volume with 2% HNO3.
Genotyping assay
Genomic DNA was extracted from blood samples by using a DNA
isolation kit (Qiagen, Valencia, CA). The genotypes of participants
were determined for the TRPM7 gene, and allelic discrimination of
the rs8042919 polymorphism in the TRM7 gene was assessed by using
the TaqMan genotyping assay (Assay ID: C-25756319-10; Applied
Biosystems, Foster City, CA). The final volume for each reaction
was 25 μL, consisting of 12.5 μL TaqMan Universal PCR Master Mix
(Applied Biosystems, Foster City, CA), 1.25 μL primers/TaqMan
probes, and 20 ng genomic DNA. The PCR conditions were: 95 °C
- 10 m for an initial denaturation step; 45 cycles at 95
°C - 15 s, and at 60 °C - 60 s. Fluorescence was measured
with 7300 Real-Time PCR system, genotypes were determined by using
7300 System SDS Software (Applied Biosystems, Foster City, CA).
Data analysis
Statistical analyses were done by using SAS Version 9.2 (SAS
Institute, Cary, NC). Baseline data comparisons were made by the
t-test. Treatment comparisons were made by repeated measures
analysis of variance followed by Tukey contrasts when appropriate.
Sleep component comparisons were made by Chi-square analysis. CRP
data were highly skewed and were logarithmically transformed so
their distribution would more closely approximate a normal
distribution. Results for CRP are reported as geometric mean with a
± 1 SE interval. A p ≤ 0.05 was considered significant.
Statistical analyses did not include three participants who did not
adhere to protocol guidelines for the consumption of supplements
and medications. A fourth subject was not included because she
became ill with an inflammatory condition during week seven that
required antibiotic and anti-inflammatory medication.
Results
The food diaries indicated that dietary (non-supplemented)
magnesium intakes did not change during the experimental period.
The mean intakes ± SEM (mg/day) for periods one, two and three,
respectively, were 287 ± 12, 281 ± 13 and 278 ± 15 for the placebo
group and 280 ± 11, 287 ± 14 and 283 ± 13 for the
magnesium-supplemented group. Based on the mean of the three sets
of food diaries for each individual, 58% of the participants were
consuming less than the EAR for magnesium (44 of 78 women
and 14 of 22 men; table 1). This number is similar to the 60%
number found by NHANES 2005-2006 for adults [1]. The low magnesium
intake was associated with a significantly higher BMI and plasma
CRP concentration at baseline (table 1). Only 40 of the participants
had a plasma CRP concentration higher than 3.0 mg/L
at baseline. Genotyping analysis of TRPM7 gene
found 80 participants were thr1482 homozygous;
18 participants were Thr1482Ile heterozygous; and only two
participants had the Ile1482 homozygous polymorphism.
The data in table 2 indicate
that most participants followed protocol guidelines for consumption
of supplements. Urinary citrate excretion (mg/24 hr) tended (p =
0.07) to increase upon consumption of the supplements, which
contained citrate. Urinary magnesium increased in participants
supplemented with 320 mg magnesium/day but not in participants
receiving the placebo. At the end of the study, the
magnesium-supplemented participants excreted significantly more
magnesium, and slightly, but not significantly (p = 0.10 for diet x
week interaction), more calcium than participants consuming the
placebo.
Figure 1
shows that regardless of treatment, global PSQI scores decreased
from baseline to the end of the study. The decreases were from a
mean of 10.4 to 7.0 in the magnesium-supplemented participants and
10.4 to 6.3 in the placebo group. Analyses of the seven components
of the global PSQI, which were similar at the beginning of the
study, found a significant change in only the number of sleep
disturbances at the end of the study (figure 2). More
magnesium-supplemented than placebo participants had sleep
disturbance component scores of 2 or more vs 0-1 at the end of
the study.
When all participants were included in the analysis, serum total
and ionized magnesium and serum calcium concentrations were not
significantly affected by treatment (table 3). In addition, when all participants
were included in the analysis, blood cell counts, cholesterol,
cholesterol fractions, triglycerides, and glucose were not affected
by treatment (data not shown). However, erythrocyte magnesium
expressed per cell or per gram of hemoglobin increased between
baseline and the end of the study regardless of treatment (table 3).
To determine whether differences in inflammatory stress or
magnesium status had an effect on the response to the magnesium
supplementation, analyses were performed on data obtained from
participants with indicators suggesting a low magnesium status or
low-grade inflammation. Sleep quality responses were not different
from any participants when the 37 participants with baseline
serum magnesium concentrations less than 1.8 mg/dL
(an indication of deficient magnesium status) were included in
the analysis (data not shown). However, in these
37 participants, both serum calcium and total magnesium
increased from baseline to the end of the study regardless of
treatment (table 4). The increase
resulted in the mean being in the normal range (≥ 1.8 mg/dL) for
the magnesium-supplemented participants; however, their increase
was not significantly different from that of the participants given
the placebo. Ionized magnesium increased slightly, but not
significantly (p = 0.10) across both groups. Although total and
ionized magnesium were lower, the percentage of serum magnesium
that was ionized was significantly higher (74.6 vs 68.9, p <
0.0001, t-test) in these participants than in those with baseline
serum magnesium greater than 1.8 mg/dL. Although the increase from
baseline to the end of the study in erythrocyte magnesium appeared
to be the same as when all participants were included in the
analysis, this was not significant; apparently this was caused by
the increased variability with a smaller number
participants.
The magnesium supplementation was beneficial to the
36 participant who had plasma CRP concentrations higher than
3.0 mg/L (an indication of chronic inflammatory stress) at
baseline. Figure
3 shows that the magnesium-supplemented participants showed
a decline of 1.6 mg/L while the participants consuming the placebo
showed an increase of 1.5 mg/L between baseline and the end of the
study; the difference between the two groups was significant (p
< 0.002). Figure
4 shows the changes in CRP as a ratio between baseline and
the end of the study. The difference between the
magnesium-supplemented mean (0.81) and the placebo mean (1.23) was
significant (p < 0.008).
The participants who were heterozygous for the Thr1482Ile
polymorphism in the TRPM7 gene did not exhibit any magnesium status
characteristics different than those with the normal TRPM7 gene.
Only two participants (both female and on the placebo treatment)
had a homozygous 1482Ile polymorphism, which is not a sufficient
number to make any conclusive statements about an effect on
magnesium status. However, these two participants had serum total
magnesium (1.63 and 1.72 mg/dL), percent ionized magnesium (80% and
84%), and urinary magnesium excretion (68 and 48 mg/day) that
indicated a deficient magnesium status with dietary intakes of
238 and 289, respectively.
Table 2 Effect of treatment on urinary excretion
of magnesium, calcium and citrate.
|
Treatment
|
N
|
Period
|
Magnesium
|
Calcium
|
Citrate
|
|
|
|
mg/24hr
|
mg/mg Cr
|
mg/24hr
|
mg/mg Cr
|
mmol/dL
|
mmol/mmol Cr
|
|
Placebo
|
49
|
Baseline
|
91a (86, 96)1, 2
|
0.084a (0.079, 0.087)
|
138 (127, 150)
|
0.127 (0.117, 0.137)
|
1.78 (1.64, 1.94)
|
1.85 (1.69, 2.02)
|
|
Placebo
|
49
|
End
|
83a (79, 87)
|
0.077a (0.073, 0.081)
|
115 (106, 125)
|
0.107 (0.099, 0.116)
|
2.17 (1.99, 2.36)
|
2.28 (2.09, 2.49)
|
|
+300 mg Mg/d
|
46
|
Baseline
|
83a (79, 87)
|
0.082a (0.078, 0.087)
|
127 (117, 137)
|
0.126 (0.117, 0.136)
|
1.42 (1.31, 1.54)
|
1.60 (1.47, 1.74)
|
|
+300 mg Mg/d
|
46
|
End
|
120b (114, 126)
|
0.115b (0.110, 0.121)
|
138 (128, 150)
|
0.133 (0.123, 0.144)
|
1.59 (1.46, 1.72)
|
1.73 (1.59, 1.88)
|
|
Analysis of variance of ln values – p values
|
|
Treatment
|
0.009
|
0.0002
|
0.54
|
0.19
|
0.001.
|
0.01
|
|
Week
|
0.009
|
0.01
|
0.56
|
0.48
|
0.07
|
0.10
|
|
Treatment x Week
|
< 0.0001
|
< 0.0001
|
0.10
|
0.17
|
0.61
|
0.44
|
Table 3 Effect of treatment on serum (mean ± SEM)
total and ionized magnesium, erythrocyte (RBC) magnesium, and serum
calcium in all subjects.
|
Treatment
|
N
|
Period
|
Serum Magnesium
|
RBC Magnesium
|
Serum Ca
|
|
|
|
Total, mg/dL
|
Ionized, mg/dL
|
Ionized, %
|
pg/cell
|
μg/g Hb
|
mg/dL
|
|
Placebo
|
47
|
Baseline
|
1.85±0.02
|
1.33±0.01
|
72.3±0.8
|
4.78±0.09
|
157±3
|
8.8±0.08
|
|
Placebo
|
47
|
End
|
1.86±0.02
|
1.35±0.02
|
73.5±0.7
|
4.94±0.12
|
162±4
|
8.7±0.07
|
|
+300 mg Mg/d
|
49
|
Baseline
|
1.87±0.03
|
1.31±0.01
|
70.0±0.8
|
4.72±0.11
|
155±4
|
8.7±0.08
|
|
+300 mg Mg/d
|
49
|
End
|
1.92±0.03
|
1.33±0.02
|
69.9±0.7
|
5.15±0.14
|
168±4
|
8.8±0.07
|
|
Analysis of variance - p values
|
|
Treatment
|
0.15
|
0.20
|
0.0001
|
0.53
|
0.57
|
0.79
|
|
Week
|
0.22
|
0.14
|
0.44
|
0.01
|
0.02
|
0.79
|
|
Treatment x Week
|
0.44
|
0.99
|
0.36
|
0.26
|
0.28
|
0.36
|
Table 4 Effect of treatment on serum (mean ± SEM)
total and ionized magnesium, erythrocyte (RBC) magnesium, and serum
calcium in subjects with baseline serum magnesium
concentrations less than 1.8 mg/dL.
|
Treatment
|
N
|
Period
|
Serum magnesium
|
RBC magnesium
|
Serum Ca
|
|
|
|
Total, mg/dL
|
Ionized, mg/dL
|
Ionized, %
|
pg/cell
|
μg/g Hb
|
mg/dL
|
|
Placebo
|
17
|
Baseline
|
1.69±0.02
|
1.27±0.02
|
75.3±1.3
|
4.94±0.21
|
160±7
|
8.43±0.11
|
|
Placebo
|
17
|
End
|
1.73±0.02
|
1.30±0.03
|
75.1±1.2
|
4.94±0.21
|
159±7
|
8.52±0.11
|
|
+300 mg Mg/d
|
20
|
Baseline
|
1.69±0.02
|
1.25±0.01
|
74.1±1.1
|
4.70±0.19
|
154±6
|
8.36±0.10
|
|
+300 mg Mg/d
|
20
|
End
|
1.82±0.03
|
1.29±0.02
|
71.1±1.1
|
5.22±0.19
|
170±6
|
8.74±0.13
|
|
Analysis of variance – p values
|
|
Treatment
|
0.07
|
0.44
|
0.03
|
0.91
|
0.78
|
0.49
|
|
Week
|
0.001
|
0.10
|
0.19
|
0.20
|
0.27
|
0.04
|
|
Treatment x Week
|
0.12
|
0.93
|
0.24
|
0.20
|
0.19
|
0.21
|
Discussion
CRP apparently readily responds by increasing with sleep
deprivation [25], but sleep quality apparently is not as
consistently associated with an increase in chronic inflammation
[10, 26]. Finding that only 40% of the participants in the present
study reporting poor sleep quality, as assessed by the PSQI, had
CRP values of 3.0 mg/L or greater suggests that some of the
participants in the present study, who scored high on the PSQI
(poor sleep quality), were not sleep-deprived. Their poor sleep
quality was apparently caused by factor(s) other than an inadequate
number of hours of sleep, which often causes an increase in CRP.
This may have influenced the finding that magnesium supplementation
vs a placebo did not significantly affect sleep quality. Sleep
quality improved from a mean of 10.4 during the study for all
participants such that the average global PSQI score (6.6) was only
slightly above the lowest score for poor quality sleep (5.0). The
reason for this improvement is unclear but one possibility is that
the increase was the result of a placebo effect.
The placebo effect could explain some of the findings in this
study. Sleep disorders are associated with decreased erythrocyte
magnesium [27, 28]. Thus, if the placebo effect improved sleep,
erythrocyte magnesium may increase. This is consistent with the
finding of increased erythrocyte magnesium in both groups at the
end of the study. The urinary excretion results suggest that the
increased erythrocyte magnesium was reflected by increased
magnesium retention. The magnesium-supplemented group had the
expected increase in urinary magnesium, most likely because more
magnesium was available for absorption. In contrast, the placebo
group showed a numerically decreased, but not significant according
to Tukey's contrast, in urinary magnesium excretion from baseline
to the end of the study, which hints at an increased retention of
magnesium because dietary magnesium intake did not change
substantially during the study with this group. Citrate also might
have had an influence on the findings because it was the only known
factor besides magnesium to which the participants were differently
exposed during the study. The findings suggest that further
studies, in which magnesium is supplemented in another form to
participants with sleep disturbances, that elevate inflammatory
stress are needed to determine whether magnesium deficiency
contributes to morbidity and mortality associated with chronic
inflammation in participants with poor quality sleep or sleep
deprivation.
Although the present study did not definitively show that
improved magnesium status improved sleep quality, it did show that
magnesium supplementation improved magnesium status in participants
who had a low magnesium status, based on serum magnesium
concentrations.
The present study also confirmed that a low dietary magnesium
intake is associated with increased circulating CRP [11-15], which
is a marker of inflammatory stress. In addition, an association
between low magnesium status, indicated by dietary intake and BMI,
was found, which is consistent with reports that a low magnesium
status is associated with chronic inflammation indicators, or with
diseases with a chronic inflammation component, in obesity [29-32].
The finding that magnesium supplementation decreased plasma CRP
concentrations in people with elevated CRP (< 3.0 mg/L) while
those on placebo also showed an increase supports the suggestion
that the magnesium deficiency that occurs in the population
according to NHANES data [1] contributes to chronic inflammatory
stress. The increase in the CRP ratio between baseline and the end
of the study (instead of remaining close to 1.0) in the placebo
group while the ratio decreased in the magnesium-supplemented group
indicates that the unknown factor improving sleep quality and
increasing erythrocyte magnesium did not alleviate chronic
inflammatory stress indicated by a CRP value over 3.0 mg/L.
Genotyping the participants did not help in determining which
subjects were more likely to be magnesium-deficient or have more
severely changed magnesium status indicators with specific
deficient intakes of magnesium. However, the percentage of
participants with heterogeneous Thr1482Ile (18%) and with
homozygous 1482Ile (2%) genotypes were similar to those reported
Dai et al. (25.5% and 1.6% respectively) [20]. The two
participants with the homozygous genotype exhibited serum and urine
magnesium values that support the contention that people with this
genotype may be more susceptible to magnesium deficiency.
Conclusion
A study, in which 22 males and 78 females older than
51 years with poor sleep quality participated, found 58% were
consuming less than the EAR for magnesium and 37% had serum
magnesium concentrations below 1.8 mg/dL, which indicates a
significant number of older adults may have subclinical magnesium
deficiency. The low magnesium status indicated by dietary intakes
less than the EAR was associated with increased plasma CRP and BMI.
The finding that magnesium citrate supplementation compared to a
sodium citrate placebo decreased plasma CRP in participants with
values above 3.0 mg/dL indicates that subclinical magnesium
deficiency may exacerbate conditions that result in chronic
inflammatory stress. Whether magnesium deficiency contributes to
chronic inflammatory stress induced by some forms of poor sleep
quality was not established in the present study because some
unknown factor, possibly a placebo effect, resulted in improved
sleep quality in all participants during the study. However, a
change in erythrocyte magnesium and different urinary magnesium
excretion and the CRP response to magnesium vs placebo suggest that
there is an association between magnesium and sleep quality that
needs further study using different supplements and participants
with sleep changes resulting in inflammatory stress to determine
its nature.
Acknowledgments
The author thanks the members of the Grand Forks Human Nutrition
Research Center human studies staff that made this study possible:
Wesley Canfield (medical affairs), Sandra Gallagher (clinical
chemistry), Bonnie Hoverson (supplements), Craig Lacher (mineral
analyses), Brenda Ling (recruiting), Emily Nielsen (study
coordination), James Penland (sleep assessment methods), Angela
Scheett (food diaries), and Becky Stadstad (PSQI scoring). The
author wishes to thank Ona Scandurra, Dr. Paul Lohmann, Inc.,
Islandia, NY for supplying magnesium citrate and Tyrase Research,
Grand Forks, ND, for funding the research.
Disclosure
None of the authors has any conflict of interest or financial
support to disclose.
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