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Creatine for women: a review of the relationship between creatine and the reproductive cycle and female-specific benefits of creatine therapy



The creatine/phosphocreatine/creatine kinase circuit is instrumental in regulating high-energy phosphate metabolism, and the maintenance of cellular energy turnover. The mechanisms by which creatine is able to buffer and regulate cellular energy balance, maintain acid-base balance, and reduce the effects of oxidative stress have led to a large number of studies into the use of creatine supplementation in exercise performance and to treat diseases associated with cellular energy depletion. Some of these studies have identified sex-specific responses to creatine supplementation, as such; there is the perception, that females might be less receptive to the benefits of creatine supplementation and therapy, compared to males. This review will describe the differences in male and female physique and physiology that may account for such differences, and discuss the apparent endocrine modulation of creatine metabolism in females. Hormone-driven changes to endogenous creatine synthesis, creatine transport and creatine kinase expression suggest that significant changes in this cellular energy circuit occur during specific stages of a female's reproductive life, including pregnancy and menopause. Recent studies suggest that creatine supplementation may be highly beneficial for women under certain conditions, such as depression. A greater understanding of these pathways, and the consequences of alterations to creatine bioavailability in females are needed to ensure that creatine is used to full advantage as a dietary supplement to optimize and enhance health outcomes for women.
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DOI 10.1007/s00726-016-2199-y
Amino Acids
Creatine for women: a review of the relationship between creatine
and the reproductive cycle and female‑specific benefits of creatine
Stacey J. Ellery1 · David W. Walker1 · Hayley Dickinson1
Received: 19 November 2015 / Accepted: 8 February 2016
© Springer-Verlag Wien 2016
that creatine is used to full advantage as a dietary supple-
ment to optimize and enhance health outcomes for women.
Keywords Women’s health · Nutrition · Reproduction
The creatine/phosphocreatine/creatine kinase circuit is inte-
gral to the maintenance of cellular energy (ATP) turnover,
and thus cellular function (Wallimann et al. 2007), and it
has particular importance in tissues with high and fluctuat-
ing energy demands, such as skeletal muscle, cardiac mus-
cle and the brain (Wallimann et al. 1992). Creatine (Cr)
is readily obtained from a diet containing meat and fish,
and is also synthesized endogenously by the body, via a
two-step enzymatic reaction that consumes arginine, gly-
cine and methionine (Brosnan and Brosnan 2007). Once
absorbed or synthesized, creatine is released into the circu-
lation and actively transported into tissues by the Creatine
Transporter 1 (CrT1), encoded by the SLC6A8 gene (Guim-
bal and Kilimann 1993). Within the cell ~75 % of creatine
is phosphorylated via creatine kinase to produce phospho-
creatine (PCr), which then acts as a phosphate donor for the
regeneration of ATP from ADP.
The phosphagen system provides support to mitochon-
drial oxidative phosphorylation and cellular ATP turno-
ver by mitigating temporal and spatial imbalances in ATP
supply and demand (Ellington 1989). The creatine/phos-
phocreatine/creatine kinase circuit is also tightly coupled
with mitochondrial structure and bioenergetics (Guidi
et al. 2008), and the activity of this biochemical reaction
has a mild antioxidant effect because the rephosphorylation
of ADP via PCr consumes a proton (H+). These proper-
ties give the creatine/phosphocreatine reaction the ability
Abstract The creatine/phosphocreatine/creatine kinase
circuit is instrumental in regulating high-energy phosphate
metabolism, and the maintenance of cellular energy turn-
over. The mechanisms by which creatine is able to buffer
and regulate cellular energy balance, maintain acid–base
balance, and reduce the effects of oxidative stress have led
to a large number of studies into the use of creatine sup-
plementation in exercise performance and to treat diseases
associated with cellular energy depletion. Some of these
studies have identified sex-specific responses to creatine
supplementation, as such; there is the perception, that
females might be less receptive to the benefits of creatine
supplementation and therapy, compared to males. This
review will describe the differences in male and female
physique and physiology that may account for such differ-
ences, and discuss the apparent endocrine modulation of
creatine metabolism in females. Hormone-driven changes
to endogenous creatine synthesis, creatine transport and
creatine kinase expression suggest that significant changes
in this cellular energy circuit occur during specific stages
of a female’s reproductive life, including pregnancy and
menopause. Recent studies suggest that creatine supple-
mentation may be highly beneficial for women under cer-
tain conditions, such as depression. A greater understand-
ing of these pathways, and the consequences of alterations
to creatine bioavailability in females are needed to ensure
Handling Editor: T. Wallimann and R. Harris.
* Hayley Dickinson
1 Hudson Institute of Medical Research and Department
of Obstetrics and Gynaecology, The Ritchie Centre, Monash
Medical Centre, Monash University, 27-31 Wright St.,
Clayton, Melbourne 3168, Australia
S. J. Ellery et al.
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to buffer the pH of the cytosol, thus protecting cells from
damage associated with internal acidification and ATP
depletion (Sestili et al. 2011).
Vertebrates express four different creatine kinase (CK)
isoforms, and it is generally the expression pattern of these
isoforms that govern the way in which creatine is used by
a cell (Eppenberger et al. 1964, 1967; Dawson et al. 1967;
Patra et al. 2012). Muscle creatine kinase (MCK) is a cyto-
solic isoform of CK expressed solely in sarcomeric skeletal
and cardiac muscle cells (Turner et al. 1973; Wallimann
et al. 1977). All other non-muscle cells, including the kid-
ney, bone and neuronal tissue express the ubiquitous brain
(BCK) isoform of creatine kinase (Wallimann et al. 2011).
In addition to these cytosolic isoforms two mitochondrial
isoforms of creatine kinase, located between the inner
and outer mitochondrial membranes have been character-
ized (Jacobs et al. 1964). Sarcomeric mitochondrial CK
(sMITCK) is expressed alongside MCK in striated skeletal
and cardiac muscle cells, whilst mitochondria of other tis-
sue types express a ubiquitous isoform (uMITCK) along
with BCK (Wyss and Kaddurah-Daouk 2000). Despite var-
iations in location and expression patterns, all CK isoforms
catalyse the reversible transfer of the γ-phosphate group of
ATP to the guanidine group of creatine, to yield PCr and
ADP, and vice versa (Wyss and Kaddurah-Daouk 2000).
Increasing dietary consumption of creatine increases the
intracellular pool of creatine/phosphocreatine available for
ATP re-synthesis and can prolong cellular energy homeo-
stasis. The use of dietary creatine supplementation as an
ergogenic aid for exercise performance, and as a targeted
therapeutic for a wide range of conditions where mitochon-
drial demise and depleted ATP underlie the pathology has
been widely studied (see reviews, Feldman 1999; Gualano
et al. 2010; Wallimann et al. 2011). Despite the fundamen-
tal role this phosphagen circuit plays at a cellular level,
from time-to-time studies into creatine homeostasis and the
benefits of dietary creatine supplementation for exercise
performance and disorders of metabolism have identified
differences in the sex-specific responses to creatine load-
ing, with the benefits for women, particularly in regard to
exercise physiology, being less than those reported for men
(Mihic et al. 2000).
Here we review and discuss the physiological differ-
ences between males and females that may lead to differ-
ences in creatine metabolism between the sexes, with a
focus on how the female utilises creatine under different
physiological conditions, including age, sexual maturity
and pregnancy. We discuss the areas where significant
knowledge gaps exist, and highlight the need to overcome
these to ensure that creatine is an effective ergogenic aid for
female athletes; that creatine supply during pregnancy is
maintained for appropriate fetal growth and development;
and its use as a therapeutic intervention to treat a variety
of diseases or conditions, such as clinical depression and
sarcopenia, that are underpinned by cellular energy failure
are realised.
Comparison of creatine metabolism between men
and women
A number of differences in the storage and utilization of
creatine have been identified between healthy males and
females (Brosnan and Brosnan 2007). These are summa-
rized in Table 1. When assessing creatine synthesis rates in
the population, based on age, females produced amounts of
endogenous creatine that were consistently 70–80 % lower
than males (Brosnan and Brosnan 2007). Dietary intake
of creatine of adult females aged 20–39 is also lower than
their male counterparts (Brosnan and Brosnan 2007). This
lowered rate of synthesis and consumption of creatine is
the likely driver behind the reduced mean excretion rate of
creatinine in females, which is ~80 % of the rate of excre-
tion in males (Cockcroft and Gault 1976).
Table 1 Summary of reported differences in creatine metabolism between men and women
Adult male Adult female Source
Circulating creatine
Circulating Guanidinoacetate (GAA) 3.12 ± 0.66 μmol/l 2.02 ± 0.54 μmol/l Kalhan et al. (2015)
Creatine synthesis 3.7–7.7 mmol day12.6–6.2 mmol day1Brosnan and Brosnan (2007)
Serum creatine 40.8 ± 19.0 μmol/l 50.2 ± 20.6 μmol/l Delanghe et al. (1989)
Creatinine clearance 1.0 0.75 Cockcroft and Gault (1976)
Dietary intake
Daily meat consumption 146 g 107 g Delanghe et al. (1989)
Daily creatine intake 7.9 mmol/day 5.0 mmol/day Brosnan and Brosnan (2007)
Skeletal muscle mass 33 kg 21 kg Janssen et al. (2000)
Muscle Creatine content (vastus lateralis) 132 ± 10 mmol/kg 145 ± 10 mmol/kg Forsberg et al. (1991)
Creatine for women: a review of the relationship between creatine and the reproductive cycle…
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As skeletal muscle is the major storage compartment of
creatine in the human body variation in the physical make
up of men and women may be a major determinant of the
difference of creatine homeostasis between the sexes. Jans-
sen et al. (2000) measured skeletal muscle mass and distri-
bution between 468 healthy adult males and females, and
reported that males had significantly more skeletal muscle,
both in terms of total mass (33 kg for men and 21 kg for
women) and percentage body composition (38.4 % mens
and 30.6 % for womens) (Janssen et al. 2000). Interest-
ingly, in a study where biopsies of the vastus lateralis mus-
cle were assessed for creatine content, females appeared to
store about 10 % more creatine compared to males, relative
to alkali-soluble protein (ASP) (Forsberg et al. 1991). This
finding held irrespective of subject age and could not be
attributed to differences in the proportion of fast and slow
twitch fibre types or fibre cross sectional area. The higher
percentage of stored creatine in female skeletal muscle,
but the larger mass of skeletal muscle in men may account
for the fact that on a standard western diet, which includes
animal products, and where females consume around 25 %
less meat than males, serum creatine levels are relatively
similar between the sexes (Delanghe et al. 1989). A recent
comparison between males and females showed that base-
line guanidinoacetate (GAA) levels were lower in women
than men and directly correlated with muscle mass; abso-
lute synthesis rate of creatine was less in females than
males; and after a 5-day creatine loading regime, women
gained weight and men did not (Kalhan et al. 2015). The
authors concluded that the increased body weight of female
subjects was likely due to water retention (Powers et al.
2003) and did not report any other physiological variables
associated with fluid retention, such as changes in blood
pressure or renal function.
Creatine metabolism and exercise performance
in males and females
Concerns about the ergogenic potential of supplemen-
tary creatine in women have been raised, as a higher rest-
ing total creatine content in skeletal muscle could dimin-
ish the capacity for creatine loading prior to exercise, and
a lower total muscle mass has been correlated to lower
CK activity (Norton et al. 1985; Forsberg et al. 1991). A
study conducted by Mihic et al. (2000) directly assessed
potential sex differences of acute dietary creatine loading
on fat-free mass, blood pressure, plasma creatinine and CK
activity, and concluded that increased creatine consumption
increased total body mass and fat free mass for males and
females, but that the effect was significantly greater in men
(Mihic et al. 2000). In addition, only creatine supplementa-
tion in men has been shown to reduce amino acid oxidation
and protein breakdown following strenuous exercise (Par-
ise et al. 2001). This study concluded that the reasons for
the differences between male and female participants were
unclear, but not likely associated with muscle total creatine
or phosphocreatine concentrations (Parise et al. 2001).
While the consensus of these studies is that the perfor-
mance-enhancing effect of creatine in females is less than
it is in males, they have generally failed to consider the role
of sex hormones and the stage of the menstrual cycle of the
female subjects at the time of the study.
Sex hormone regulation of creatine homeostasis
There is substantial evidence supporting the contention
that estrogens and progesterone influence female skeletal
muscle metabolism (Volek et al. 2006). Under standard
exercise conditions there are significant differences (albeit,
small) in substrate utilization between males and females,
with females favoring lipid metabolism over carbohydrate
metabolism (Braun and Horton 2001). These differences
have been attributed to the expression of female sex hor-
mones, with progesterone down-regulating glucose pro-
duction and estrogens mobilizing lipids, with the overall
effect of shifting metabolism to conserve carbohydrates
(Godsland 1996). The degree of these hormone driven
shifts in female muscle metabolism have been linked to
stages of the menstrual cycle, with affects most prominent
in the luteal phase of the menstrual cycle when the level
of estrogens are at their peak (Volek et al. 2006). Stages
of the menstrual cycle and thus circulating levels of estro-
gens have also been linked to reduced muscle damage after
eccentric exercise through preventing CK release (Williams
et al. 2015). Considering these fundamental shifts associ-
ated with sex hormones for skeletal muscle metabolism, the
roles that estrogens and progesterone have for the overall
storage and metabolism of creatine for women certainly
deserves further study.
Creatine kinase activities, along with expression of key
enzymes for the endogenous synthesis of creatine, are
affected by sex hormones (Wyss and Kaddurah-Daouk
2000). Studies conducted in the rat kidney, testis and
decidua have shown that estrogens, diethylstilbesterol and
testosterone all influence the expression of arginine-gly-
cine aminotransferase (AGAT) (Walker 1979; Hasegawa
et al. 1992). As AGAT is the rate-limiting step of creatine
synthesis, up-regulation of AGAT expression is indicative
of increased de novo creatine synthesis. In the tissues that
express receptors for estrogens or androgen, estradiol and
testosterone have also been shown to stimulate CK activ-
ity (Malnick et al. 1983; Sömjen et al. 1989). Of particu-
lar interest for women is the cyclic nature of sex hormone
regulation. Studies have shown that in the rat, CK activity
S. J. Ellery et al.
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increases and decreases in synchrony with the estrous cycle,
and in relation to increased and decreased production of
estrogens (Sömjen et al. 1991). Whether elevated levels of
serum CK correlate with the endometrial tissue breakdown
that progesterone withdrawal induces during menstruation
is yet to be elucidated, but can not be ruled out as contribu-
tor to these changes (Emera et al. 2012). In terms of the
effectiveness of dietary creatine supplementation either for
athletic performance or for other therapeutic purposes, the
implications of the possible changes in creatine metabo-
lism in line with reproductive status of women has not been
thoroughly investigated. In a study of serum CK levels in
110 school-aged girls, the 21 subjects who were reported as
menstruating on the day that blood was collected for assay
of serum CK levels returned values at the upper end of the
normal range distribution for their age group (46.6 IU/l),
compared to the non-menstruating aged-matched controls
(39.5 IU/l) (Bundey et al. 1979). This study did not take
into consideration the diet, body composition, or exercise
status of the subjects, hence the nature of this relationship
between the menstrual cycle and CK activity still warrants
further investigation.
Female age, sexual maturity and creatine metabolism
Studies conducted through the 1960s and 1970s inves-
tigating the usefulness of serum CK levels as a predictor
of being a carrier of the duchenne muscular dystrophy
(DMD) gene mutation revealed that serum CK levels vary
in women of different ages and sexual maturity. Bun-
dey et al. (1979) examined serum CK levels in women
of different reproductive stages, including pre- and post-
menarche, pregnancy and menopause, and found the high-
est serum CK values were in pre-menarche teenage girls,
and decreased progressively in post-menarche teenagers
and into reproductive maturity. The lowest range of CK
values were present in early pregnancy (16 weeks or less),
when CK values were <50 % of those reported in teenage
girls (Bundey et al. 1979). The relationship between the
different stages of reproductive life and CK levels is not
known. We speculate that age related changes in estrogens
may be associated with these CK levels, however, given the
overwhelming evidence that high CK levels indicate tissue
damage, further work in this area is required to tease out
these associations.
Serum creatine kinase and pregnancy
A study by King et al. (1972) looked more specifically
at serum CK levels across pregnancy. Findings of this
study were consistent with those of Bundey et al. (1979)
described above, in that maternal serum CK decreased
significantly between 8 and 20 weeks of gestation. The
authors discussed the potential role of hemodilution in
these observations, but concluded that the degree of change
was too large to be attributed solely to the normal, preg-
nancy-related increase in maternal blood volume (King
et al. 1972). An earlier study by Konttinen et al. (1963)
described serum CK levels during late pregnancy, delivery
and early postpartum. They found a large range of serum
CK values during late pregnancy (6.04 ± 5.77 IU/ml),
compared to relatively consistent values obtained from
healthy non-pregnant controls (2.1 ± 0.9 IU/ml). Interest-
ingly, the highest CK levels were detected not at delivery,
but a day later (Konttinen and Pyörälä 1963). This finding
was later confirmed in another study of 80 healthy pregnan-
cies where a significant increase in maternal serum CK lev-
els was observed on the first day postpartum (Emery and
Pascasio 1965). Strikingly, values of serum CK detected in
pregnant women at term (Konttinen and Pyörälä 1963) are
comparable to CK values commonly observed following
myocardial infarction (Konttinen and Halonen 1963). This
study also compared the CK levels in three term pregnant
and three non-pregnant uterine muscle samples, to find that
CK levels of pregnant uterine muscle (average, 219,500;
range 199,000–234,500 units/g wet weight) was substan-
tially higher than that of the non-pregnant uterus (average,
16,200; range 13,500–21,500 units/g wet weight) (Kont-
tinen and Pyörälä 1963). It was therefore concluded that the
physical exertion of labor and creatine kinase efflux from
the contracting and then involuting uterus were the major
contributors to the increase in serum CK in women for the
first 1–4 days postpartum. The study of Emery and Pasca-
sio (1965) supported these findings, showing that CK levels
of the pregnant myometrium were significantly higher than
the myometrium of non-pregnant females. This study also
described that there appeared to be a difference (although,
not quite significant) of CK values for the myometrium
directly under the placenta compared to other sites of the
uterus (Emery and Pascasio 1965).
In addition to changes in maternal serum CK lev-
els due to postpartum muscle breakdown, it is also likely
that changes in female sex hormone expression during
pregnancy, labor, delivery, and postpartum contribute sig-
nificantly to changes observed in serum and tissue CK
levels. In addition to estrogens, progesterone has been
linked to CK activity in the myometrium (Lanza 1974).
In non-gravid women injected with various concentrations
of progesterone prior to hysterectomy, CK levels meas-
ured in fundus biopsies were lower than for biopsies from
untreated women; exposure of uterine tissue to 500 mg of
progesterone for 24 h before biopsy was associated with a
decrease of CK levels in the myometrium by ~30 %. Sig-
nificantly, progesterone had no effect on CK levels in the
rectus muscle, indicating a specific effect of progesterone
on CK in uterine muscle fibres (Lanza 1974).
Creatine for women: a review of the relationship between creatine and the reproductive cycle…
1 3
A limitation in evaluating the above studies is that data
collection was usually cross-sectional, and the relative
expression of CK isoforms were not examined in detail.
As many of the studies discussed have used CK as a bio-
marker for other conditions (e.g., serum CK to indicate car-
riers of the gene mutation associated with DMD) there has
been limited discussion of the physiological relevance of
changes to serum CK levels during different phases of the
reproductive cycle. To the knowledge of the authors there
are no studies (in any species) that provide longitudinal
data of changes to serum CK levels over the life course of
male, or female, individuals. With respect to the findings
associated with changes to serum CK levels throughout a
female’s reproductive life, how increased CK levels (serum/
tissue) influence creatine/phosphocreatine utilization; what
increased CK levels tell us about the metabolic demands of
those cells at that particular time; whether these changes
affect creatine synthesis; and what the consequences are
if these shifts do not occur as required, are questions that
should be explored in more detail. Nevertheless, the age
and stage of reproductive cycle of females should be taken
into consideration whenever studies of creatine metabolism
in females are undertaken; as it is clear that creatine kinase
activity (and perhaps creatine metabolism) is intrinsically
connected to changes in the female reproductive cycle.
Creatine metabolism and pregnancy
Is creatine an essential dietary metabolite
of pregnancy?
The link between creatine and the feto-placental unit was
established in 1974, with studies by Miller et al. describ-
ing the active transport of creatine into the human placenta
from the maternal circulation, where it appears to pool and
then diffuse down a concentration gradient into the fetal
circulation (Miller et al. 1974). Similar observations have
also been made in the pregnant rat and spiny mouse (Miller
et al. 1977; Ireland et al. 2008). The potential role of the
placenta in fetal creatine supply from early in gestation is
supported by identification of SLC6A8 mRNA in the human
placenta from 13 weeks gestation (Miller et al. 1974; Nash
et al. 1994). Hormones known to be up-regulated during
pregnancy (IGF-1, triiodothyronine) are known mediators
of increased SLC6A8 expression (Osathanondh et al. 1976;
Furlanetto et al. 1978) and may induce increased expres-
sion of SLC6A8 in the placenta and increase creatine uptake
by virtue of their effects on the Na+ transmembrane poten-
tial, as has been shown for skeletal myoblast cells (Odoom
et al. 1996).
In addition to transfer of creatine from the placenta to
the fetus, the high metabolic activity of the placenta itself
raises questions about its direct requirement for creatine/
phosphocreatine. For the creatine/phosphocreatine/CK
circuit to operate as an effective shuttle of ATP from the
site of synthesis at the mitochondria to areas of demand
in the cytosol, there needs to be coordinated expression of
ubiquitous mitochondrial CK (uMITCK) and ubiquitous
brain-type CK (BCK), as genes for these two isoforms of
CK are located on different chromosomes (Stallings et al.
1988; Haas et al. 1989). Thomure et al. (1996) studied CK
mRNA expression in the human placenta across gestation
and concluded that the expression of uMITCK and BCK
was indeed highly coordinated. Both uMITCK and BCK
were expressed, albeit at low levels in the first and second
trimesters of pregnancy, before a substantial increase in the
expression of both enzymes in the third trimester (Thomure
1996). This pattern of expression parallels the increased
metabolic activity of the placenta in late gestation in the
human and many other species, and suggests that the CK
pathway has an integral role in placental metabolism,
an assumption consistent with the evolutionary develop-
ment of CK in other tissues of high and fluctuating energy
demands, such as skeletal muscle (Thomure 1996; Wyss
and Kaddurah-Daouk 2000). It is likely that rising concen-
trations of serum estrogens during pregnancy may regulate
the increases in both uMITCK and BCK expression across
gestation in the human placenta, as response elements to
estrogens have been identified on both the uMITCK and
BCK genes (Payne et al. 1993).
Whilst not considered an essential metabolite to support
fetal growth and development at this point in time, con-
sideration should be given to the effect that low maternal
creatine levels might have on fetal growth and develop-
ment. Dietary preferences that avoid consumption of ani-
mal products, or variations of the de novo synthesis of cre-
atine in the mother, might affect the provision of creatine to
the fetus and placenta. It is not yet known when the reno-
hepatic axis in the human fetus is developmentally mature
enough to be able to synthesize creatine from arginine, gly-
cine, and methionine, and presumably until this time there
is an absolute requirement for transfer of creatine from
the maternal and placental creatine pools. A study of cre-
atine homeostasis in the pregnant spiny mouse showed that
maternal creatine synthesis, excretion, transport and stor-
age were all fundamentally changed by pregnancy (Ellery
et al. 2015b), suggesting that pregnancy provokes sub-
stantial and far-reaching adaptations to creatine balance in
the mother. These changes include a decrease in maternal
plasma creatine concentration, decreased renal excretion
of creatine between mid and late gestation, increased renal
AGAT mRNA and protein expression, and increased CrT1
mRNA expression in the heart and gastrocnemius muscle
just prior to parturition, raising the possibility that altera-
tions to maternal creatine homeostasis might be a necessary
S. J. Ellery et al.
1 3
adjustment of maternal physiology with pregnancy to meet
the metabolic demands of the placenta and developing fetus
(Ellery et al. 2015b). This notion is also supported by stud-
ies conducted by Braissant et al. (2005), describing embry-
onic expression of AGAT, GAMT and CrT1 in numerous
tissue types in the rat, particularly the central nervous sys-
tem, from early in gestation. This study placed emphasis on
the need for creatine for adequate growth and development
in utero (Braissant et al. 2005). These studies are yet to elu-
cidate whether placental and fetal creatine homeostasis is
different for male and female fetuses. There is increasing
evidence that placental function, especially metabolic func-
tion, is modified by the sex of the fetus (O’Connell et al.
2013). This is an area of research that needs further atten-
tion, and may provide useful insights into the role creatine
might have in obstetric conditions where placental cellular
energy failure may be a factor in major pathologies such as
birth asphyxia, intrauterine growth restriction or stillbirth.
A recent retrospective study in pregnant women identi-
fied changes to creatine homeostasis, in terms of plasma
and urinary creatine concentrations with advancing gesta-
tion (Dickinson et al. unpublished observations). This study
provides data to suggest that plasma and urinary creatine
concentrations are higher in pregnant women compared
to non-pregnant women, and that placental and newborn
weight at birth are related to maternal creatine excretion.
These findings indicate that creatine may be an impor-
tant determinant of fetal growth and development, and
that maintenance of maternal creatine homeostasis across
pregnancy may be vital for the health of the newborn. This
notion is supported by a human study dating back to 1913,
where increases in body weight of a newborn was shown
to be roughly proportional to the creatine excreted in the
urine by the mother (indicative of more than adequate cir-
culating levels of creatine) (Mellanby 1913). Indeed, there
is a great need to know when the human fetus can synthe-
size creatine. While important for understanding in utero
development and placental supply of creatine, the increased
numbers of preterm infants, and their subsequent neuro-
logical decline, raise the possibility that cerebral creatine
deficiency is a consequence of preterm birth not yet fully
recognized, clinically.
It is also of interest to note that, in addition to late gesta-
tional and postpartum pregnant women, newborn babies are
reported to have very high levels of serum CK—up to 10
times higher than normal healthy adult levels (Gilboa and
Swanson 1976). These increased levels begin to decline
by 4 days after birth and reach average population levels
by 6–10 weeks of age. These high serum CK values are
thought to arise from the physical stress placed on the new-
born during labor and delivery (Rudolph and Gross 1966),
although Gilboa et al. (1976) reported that mean CK levels
in the cord blood of babies delivered via caesarean section
were higher than the cord blood levels detected in vaginally
delivered babies (Gilboa and Swanson 1976). Conversely,
mean capillary CK levels were higher in vaginally delivered
newborns compared to caesarean delivered babies. Hence,
there is no clear association with birth trauma and newborn
serum CK levels. Also unique to newborns in the first few
days of life is that venous and capillary levels of CK are
similar, unlike the adult where CK levels are slightly but
significantly lower in capillary compared to venous blood
(Gilboa and Swanson 1976). The physiological significance
of increased serum CK levels in newborns is not known.
Again, as these studies were conducted purely to assess the
potential of CK as a biomarker for DMD, the actual physi-
ological relevance of serum CK levels in the newborn has
not been thoroughly investigated. Whether pregnancy com-
plications also affect CK measures in neonates is yet to be
Creatine supplementation as a therapeutic to alleviate
poor pregnancy outcomes
The ability of creatine to maintain ATP turnover, acid–
base balance, mitochondrial function, together with its
antioxidant, vasodilator, and anti-excitotoxic properties
(Wallimann et al. 2011), make it a candidate for use to
treat ischemic/reperfusion injuries, particular when these
occur in the brain. Whether these properties of creatine
could be exploited to the advantage of the neonate were
first assessed by Wilken et al. (1998) in mouse brain
slices, and by Berger et al. (2004) in brain slices of fetal
guinea pigs, both of which described sustained ATP turn-
over and a reduction in neuronal cell injury when brain
slices were exposed to creatine (Wilken et al. 1998;
Berger et al. 2004). Similar benefits were observed in vivo
with rat pups (Adcock et al. 2002). The ability of creatine
to easily load into neuronal cells prior to birth may mean
that creatine is more effective in neonatal conditions of
acquired brain injury than for adult brain injury [reviewed
by (Dickinson et al. 2014)]. These results lead to sugges-
tions that creatine may act to protect the neonatal brain
from injury induced by intrapartum asphyxia. Studies
conducted by Ireland et al. (2011) identified the neuro-
protective capacity of creatine, administered antenatally
by supplementation of the maternal diet, to protect the
spiny mouse pup from the effects of birth asphyxia (Ire-
land et al. 2011). Specifically, the amelioration of neu-
ronal cell death and maintenance of mitochondrial integ-
rity in the presence of creatine was described. These were
promising results for the treatment of neonatal HIE, but
the overall improvement to survival rate of offspring of
creatine-fed dams lead to thoughts that creatine, when
Creatine for women: a review of the relationship between creatine and the reproductive cycle…
1 3
administered and loaded into fetal organs in utero, might
provide protection to other peripheral organs known to be
highly susceptible to the global oxygen deprivation asso-
ciated with an asphyxic episode at birth (Ireland et al.
2008). Exploration of this hypothesis to date has included
characterisation of the diaphragm muscle and kidney fol-
lowing birth asphyxia. The benefits of creatine loading for
the diaphragm included attenuation of muscle atrophy and
improvement of contractile function, such that function
of this important muscle did not differ from diaphragm
samples obtained from pups from a control birth (Can-
nata et al. 2010). Analysis of the kidney showed birth
asphyxia caused structural damage to the neonatal renal
cortex, medulla and renal papillae in the spiny mouse off-
spring (Ellery et al. 2012), and the presence of changes
in young adult male spiny mice suggest the possibil-
ity that neonatal acute kidney injury has the longer term
risk of developing into chronic kidney injury, in males at
least, where reduced nephron endowment and GFR were
detected (Ellery et al. unpublished observation). As these
studies progress into higher order animal models and
human-based analyses, careful consideration of fetal sex
should be given when reporting outcomes. In our own
animal experiments, only 52 % of male spiny mouse off-
spring survive the birth asphyxia insult, compared to 69 %
of females, suggesting that male fetuses are more vulner-
able to this type of insult (LaRosa et al. 2016). The male
vulnerability to prenatal insults is believed to be a result
of the faster in utero growth rate of males, compared to
females (Eriksson et al. 2010). When we supplement the
diet of the mother with creatine before birth asphyxia, sur-
vival of females is improved by 12 % and male survival is
improved by 19 %, suggesting that creatine is beneficial
to fetuses of both sexes, but perhaps slightly more so for
males. Importantly for the progression of these findings
into the clinic, studies on the safety of supplementary cre-
atine in the pregnant spiny mouse have shown that a high
and prolonged oral dose of creatine does not result in any
adverse outcomes for the mother (Ellery et al. 2015a).
It has also been shown that high exposure to creatine in
utero does not affect the expression levels of the enzymes
required for creatine synthesis, 24 h after birth (Dickinson
et al. 2013). A recent study of maternal dietary creatine
supplementation during pregnancy in rats concluded that
creatine exposure in utero had a positive effect on mor-
phological and electrophysiological development of CA1
neurons. However, this affect persisted beyond the half-
life of creatine and may have the potential to increase
epileptogenic focus (Sartini et al. 2016). Studies are now
underway to determine the safety and efficacy creatine
supplementation during pregnancy, using non-human
Creatine as a therapeutic for women
As discussed earlier, the effectiveness of creatine as an
ergogenic aid for female athletes is less than that for men.
The possibility that this reflects the cyclic nature of female
sex hormones, and/or the presence or absence of testos-
terone, requires further studies to characterize the differ-
ences of creatine uptake and utilization between men and
women, and how these might change across the menstrual
cycle, with conception and menopause. Despite the paucity
of data around this, there are a number of conditions for
which treatment of women with dietary creatine is proving
highly effective.
Mental illness
Metabolic impairment within the brain initiates the cellular
injury-death cascade, driven by the production of reactive
oxygen species, lipid peroxidation, DNA damage and apop-
tosis. This pathophysiology has been shown to hinder cellu-
lar resilience and contribute to depressive disorders (Fuchs
et al. 2004; Seifried 2007). It has been hypothesized that
damage to mitochondria in the hippocampus and prefron-
tal lobe could compromise the creatine/phosphocreatine
circuit and instigate depression-like behavior (Allen 2012);
indeed, CK activity is inversely related to the severity of a
depressive episode (Dager et al. 2004; Segal et al. 2007).
Healthy females have less phosphocreatine in the frontal
lobe than healthy males (Riehemann et al. 1999). This may
suggest that females are more susceptible to depressive dis-
orders associated with shifts in brain creatine metabolism.
Indeed, depression occurs twice as often in females than
males (Bebbington et al. 2003), with episodes being more
severe, frequent and prolonged (Kornstein et al. 2000).
Dietary creatine supplementation has been considered
as a potential therapy to counter the reductions in brain
metabolism associated with depression. Encouragingly
for women, the associations of estrogens and increased
CK activity have lead to suggestions that creatine sup-
plementation may be more beneficial in treating depres-
sion in females over males (Allen et al. 2010). In studies
conducted in rats, increasing dietary intake to 4 % of daily
food consumption for 5 weeks prior to assessment, signifi-
cantly improved performance on tests such as the forced
swim test, known to identify depressive-like behaviours
(Allen et al. 2010). This result was not present in male rats.
A recent extension of these studies showed that the pres-
ence of sex hormones was essential to the protective effects
afforded by creatine to depressed rats (Allen et al. 2015).
In human studies, the use of dietary creatine as an adjunct
therapy accelerated treatment response in depressed ado-
lescent (Kondo et al. 2011) and adult females (Lyoo et al.
S. J. Ellery et al.
1 3
2003). In a recent pilot study by Hellem et al. (2015), six
females with a major depressive disorder, in addition to
methamphetamine dependence, received dietary creatine
supplementation for a period of 8 weeks. During this time,
the subjects displayed lower levels of depression and anxi-
ety, as evaluated by the Hamilton Depression Rating Scale
and Beck Anxiety Inventory Scales (Hellem and Renshaw
Another interesting aspect of female mental health and
wellbeing associated with levels of estrogens are episodes
of premenstrual tension (PMT). Low levels of estrogens
can characterize this syndrome, which affects women from
the mid-luteal phase of the menstrual cycle until menstrua-
tion. Whether there is a link between low circulating estro-
gens associated with PMT and creatine metabolism is yet
to be established. However, administration of estrogens at
this time has been shown to reduce cyclic bouts of worsen-
ing mood (Hammarbäck et al. 1985). Such treatment would
be most important for those women who suffer from a rare
form of PMT who undergo severe episodes of depression,
insomnia, forgetfulness and confusion during the mid-
luteal phase of their menstrual cycle (Hammarbäck et al.
1985). Characterization of the hormone profile of these
women show disproportionately low estrogens compared
to progesterone during these depressive episodes (Abraham
1983). As with other depressive conditions, increasing CK
activity through enhanced creatine dietary consumption
may be a safe and beneficial treatment to reduce the symp-
toms of PMT.
Morbidities associated with ageing
Due to the changes in sex hormone production during
and after menopause, females are particularly suscepti-
ble in their older years to bone and muscle degeneration
(Evans 2004). Age-related bone loss is accelerated during
menopause, leading to osteoporosis and contributing to
osteoarthritis (Hernandez et al. 2003). Creatine is show-
ing promise in targeting the progression of these ailments.
The differentiation of bone and cartilage cells is a highly
energy dependent process, which has been previously
shown to utilize the creatine/phosphocreatine/CK circuit
(Wallimann and Hemmer 1994). Whether dietary creatine
supplementation could be used to aid bone regeneration
was first assessed in cultured osteoblast-like cells (Ger-
ber et al. 2005). This study found that the addition of cre-
atine to culture media promoted differentiation of primary
osteoblast-like cells by increasing alkaline phosphatase
activity, and concluded that dietary creatine may be benefi-
cially to aid fracture healing or prevent the progression of
osteoporosis (Gerber et al. 2005). In addition to frail bones,
ageing is associated with sarcopenia or reduced muscle
mass. Together, these conditions reduce the capacity for
rapid muscle contraction, and can lead to loss of balance,
increased falls and injury (Schneider and Guralnik 1990).
Dietary creatine supplementation has thus been trialed in
aged individuals to assess its capacity for rebuilding and/
or maintaining lean muscle and bone mass. When creatine
was given in conjunction with moderate exercise, signifi-
cant improvements in physical function and lower limb
lean mass were observed in aged men and women (Got-
shalk et al. 2008). Preliminary studies in postmenopausal
women aged 50–65 years suffering from osteoarthritis have
also shown that introducing a standard dietary creatine sup-
plementation regime in conjunction with resistance train-
ing improved physical function, lower limb lean mass and
overall, improved quality of life for these women (Neves
et al. 2011).
With an ageing population in the western world, simple
nutritional interventions with the capacity to reduce the
burden of fall related injuries on our healthcare system,
prolong functional independence, and overall improve the
quality of life should be held in the highest regard. Whilst
manipulation of the creatine/phosphocreatine/CK circuit to
target these aliments is somewhat in its infancy, compared
to studies of exercise performance in younger individu-
als, it shows much promise, particularly for women where
changes to hormone production rates underpin tissue loss
and reduced tissue regeneration.
Conclusions and recommendations for future
Assessment of the literature as a whole clearly suggests that
males and females store, metabolize and utilize creatine in
a sex-specific manner. However, this remains an incom-
plete story, with evidence spread across an array of studies,
mainly conducted in the 1960s–1990s, where sex-depend-
ent effects were not the primary outcome. As a whole, this
topic of sex-specific differences in creatine metabolisms is
deserving of new investigations using modern technolo-
gies, including in vivo tracer and imaging techniques and
high throughput genomics, to establish which aspects of
the creatine/phosphocreatine/creatine kinase circuit are
most influenced by gender, and which of the isoforms of
creatine kinase are affecting serum CK levels throughout a
female’s reproductive life. There also remains the need to
conduct population-based studies that characterize creatine
homeostasis in women, taking into consideration age, body
composition and stage of the reproductive cycle, and the
further effects of conception, pregnancy, and parturition. It
is probably essential that these studies should be conducted
on cohorts of women followed through the menstrual cycle,
or followed from conception to birth, and then post-par-
tum. Such longitudinal studies would provide data integral
Creatine for women: a review of the relationship between creatine and the reproductive cycle…
1 3
to understanding the adaptability of this phosphagen sys-
tem for females, and how this can be used to optimize and
enhance health outcomes for women.
Acknowledgments HD is an NHMRC Career Development Fel-
low & DWW is a Distinguished Researcher of the Cerebral Palsy
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict
of interest.
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... A main contributor to skeletal muscle metabolism during exercise and exercise recovery is the depletion and replenishment of muscle glycogen. Males and females exhibit similar increases in total PCr post-supplementation, while females have exhibited higher levels of intramuscular PCr, suggesting sex-divergent responses to creatine monohydrate supplementation [7]. Though creatine monohydrate supplementation improves mechanisms implicated in accelerated exercise recovery, little research has evaluated the effects on acute post-exercise recovery. ...
... If creatine increases the efficiency of the body to elicit the recovery process, as reflected by parasympathetic drive, HRV values such as the root mean square of successive differences (RMSSD) or the standard deviation of normal-to-normal intervals (SDNN) could see significant changes post-exercise and post-supplementation; these mechanisms can also be influenced by the menstrual cycle. Creatine metabolism could potentially vary based on the menstrual phase due to the suppressive effect of estrogen on glycolytic enzymes, fluctuation in creatine kinase (CK), as well as the effect of estrogen levels on the rate-limiting enzyme in creatine synthesis, arginine-glycine aminotransferase [2,7,21]. ...
... To date, the mechanistic potential for creatine to enhance recovery has yet to be evaluated in women, particularly when controlled for the menstrual cycle [2,7]. Due to the significant physiological differences between women and men, particularly related to the menstrual cycle and exogenous hormones (i.e., oral contraceptives), it is expected that exercise recovery will be affected [21]. ...
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Creatine supplementation improves anaerobic performance and recovery; however, to date, these outcomes have not been well explored in females. This study evaluated the effect of creatine monohydrate loading on exercise recovery, measured by heart rate variability (HRV) and repeated sprint performance, in women across the menstrual cycle. In this randomized, double-blind, cross-over study, 39 women (mean ± standard deviation: age: 24.6 ± 5.9 years, height: 172.5 ± 42.3 cm, weight: 65.1 ± 8.1 kg, BF: 27.4 ± 5.8%) were randomized to a creatine monohydrate (n = 19; 20 g per day in 4 × 5 g doses) or non-caloric PL group (n = 20). HRV was measured at rest and after participants completed a repeated sprint cycling test (10 × 6 s maximal sprints). Measurements were conducted before and after supplementation in the follicular/low hormone and luteal/high hormone phases. Creatine monohydrate supplementation did not influence HRV values, as no significant differences were seen in HRV values at rest or postexercise. For repeated sprint outcomes, there was a significant phase × supplement interaction (p = 0.048) for fatigue index, with the greatest improvement seen in high hormone in the creatine monohydrate group (−5.8 ± 19.0%) compared to changes in the PL group (0.1 ± 8.1%). Sprint performance and recovery were reduced by the high hormone for both groups. Though not statistically significant, the data suggests that creatine monohydrate could help counteract performance decrements caused by the high hormone. This data can help inform creatine monohydrate loading strategies for females, demonstrating potential benefits in the high hormone phase.
... Compared to men, females exhibit 70-80% lower endogenous intramuscular phosphocreatine stores and consume considerably lower amounts of dietary creatine [307] yet have higher reported (~10%) resting levels of intramuscular creatine concentrations [308], indicating supplementation at higher doses may be more efficacious [309]. Moreover, creatine kinase perturbations have also been shown to align with the cyclical pattern of estrogen across the menstrual cycle [310,311]. It has been suggested that supplementation in the luteal phase may be more effective for the mechanistic support of creatine supplementation with regard to muscle protein kinetics, growth factors, satellite cells, myogenic transcription factors, glycogen and calcium regulation, oxidative stress, and inflammation [312,313], but original investigations are needed to further explore this notion. ...
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Based on a comprehensive review and critical analysis of the literature regarding the nutritional concerns of female athletes, conducted by experts in the field and selected members of the International Society of Sports Nutrition (ISSN), the following conclusions represent the official Position of the Society: 1. Female athletes have unique and unpredictable hormone profiles, which influence their physiology and nutritional needs across their lifespan. To understand how perturbations in these hormones affect the individual, we recommend that female athletes of reproductive age should track their hormonal status (natural, hormone driven) against training and recovery to determine their individual patterns and needs and peri and post-menopausal athletes should track against training and recovery metrics to determine the individuals' unique patterns. 2. The primary nutritional consideration for all athletes, and in particular, female athletes, should be achieving adequate energy intake to meet their energy requirements and to achieve an optimal energy availability (EA); with a focus on the timing of meals in relation to exercise to improve training adaptations, performance, and athlete health. 3. Significant sex differences and sex hormone influences on carbohydrate and lipid metabolism are apparent, therefore we recommend first ensuring athletes meet their carbohydrate needs across all phases of the menstrual cycle. Secondly, tailoring carbohydrate intake to hormonal status with an emphasis on greater carbohydrate intake and availability during the active pill weeks of oral contraceptive users and during the luteal phase of the menstrual cycle where there is a greater effect of sex hormone suppression on gluconogenesis output during exercise. 4. Based upon the limited research available, we recommend that pre-menopausal, eumenorrheic, and oral contraceptives using female athletes should aim to consume a source of high-quality protein as close to beginning and/or after completion of exercise as possible to reduce exercise-induced amino acid oxidative losses and initiate muscle protein remodeling and repair at a dose of 0.32-0.38 g·kg-1. For eumenorrheic women, ingestion during the luteal phase should aim for the upper end of the range due to the catabolic actions of progesterone and greater need for amino acids. 5. Close to the beginning and/or after completion of exercise, peri- and post-menopausal athletes should aim for a bolus of high EAA-containing (~10 g) intact protein sources or supplements to overcome anabolic resistance. 6. Daily protein intake should fall within the mid- to upper ranges of current sport nutrition guidelines (1.4-2.2 g·kg-1·day-1) for women at all stages of menstrual function (pre-, peri-, post-menopausal, and contraceptive users) with protein doses evenly distributed, every 3-4 h, across the day. Eumenorrheic athletes in the luteal phase and peri/post-menopausal athletes, regardless of sport, should aim for the upper end of the range. 7. Female sex hormones affect fluid dynamics and electrolyte handling. A greater predisposition to hyponatremia occurs in times of elevated progesterone, and in menopausal women, who are slower to excrete water. Additionally, females have less absolute and relative fluid available to lose via sweating than males, making the physiological consequences of fluid loss more severe, particularly in the luteal phase. 8. Evidence for sex-specific supplementation is lacking due to the paucity of female-specific research and any differential effects in females. Caffeine, iron, and creatine have the most evidence for use in females. Both iron and creatine are highly efficacious for female athletes. Creatine supplementation of 3 to 5 g per day is recommended for the mechanistic support of creatine supplementation with regard to muscle protein kinetics, growth factors, satellite cells, myogenic transcription factors, glycogen and calcium regulation, oxidative stress, and inflammation. Post-menopausal females benefit from bone health, mental health, and skeletal muscle size and function when consuming higher doses of creatine (0.3 g·kg-1·d-1). 9. To foster and promote high-quality research investigations involving female athletes, researchers are first encouraged to stop excluding females unless the primary endpoints are directly influenced by sex-specific mechanisms. In all investigative scenarios, researchers across the globe are encouraged to inquire and report upon more detailed information surrounding the athlete's hormonal status, including menstrual status (days since menses, length of period, duration of cycle, etc.) and/or hormonal contraceptive details and/or menopausal status.
... Creatine, a nonproteinogenic amino acid derivative, is produced endogenously in the human liver, kidney, and pancreas, and is naturally present in animal-based foods (Alraddadi et al., 2018;Antonio et al., 2021;Ellery et al., 2016;Wyss & Kaddurah-Daouk, 2000). It mainly serves as a critical metabolic intermediary of energy transfer by facilitating the recycling of Adenosine Triphosphate (ATP), the source of energy for use and storage at the cellular level. ...
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Aims: The purpose was to examine the relationship between dietary creatine intake obtained in food and selective attention and inhibitory control processes in older adults. Methods: Forty-five (n = 11 males; n = 34 females) participants over 60 years of age volunteered. Participants completed a 5-day dietary recall survey to estimate creatine intake and a cognitive assessment which included an adaptation of the Eriksen flanker task and a mini-mental state examination (MMSE). Cohorts for two groups were derived based on higher (HCr) versus lower (LCr) median creatine intake. To compare the groups, an unpaired Mann-Whitney U test was performed. In addition, Spearman’s correlation analysis was used to test a potential association between the daily amount of creatine with selective attention and inhibitory processing task results. Results: There were significant differences between the groups in the flanker task. In the incongruent condition, HCr responded on average about 646 ms faster than LCr (p = .005). HCr also responded about 25% more accurately than LCr in the incongruent condition (p < .001). Response time to incongruent stimuli (Spearman’s -0.424) and per cent correct (Spearman’s rho 0.565) showed moderate correlations with daily creatine intake. Conclusions: Creatine intake from food is positively associated with selective attention and inhibitory processing in older adults.
... Creatine (methyl guanidine-acetic acid) is derived and synthesized from reactions involving the amino acids arginine, glycine, and methionine in the kidneys and liver or can be ingested exogenously primarily from animal-based foods (i.e., red meat, seafood) or through dietary supplements (8)(9)(10)(11). Ninety-five percent of creatine is found in skeletal muscle with the remaining 5% dispersed across the brain, liver, kidney, and testes (8,12). Once creatine is transported into the skeletal muscle, ~2/3 is converted to phosphocreatine (CrP) with the remainder stored as free creatine. ...
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Creatine (Cr) has been proposed as an ergogenic resource and the adhesion to its therapeutic use has gained relevance in the last 2 decades. The role of Cr in the aging process has been highlighted, with many studies aiming to understand how aging affects the depletion of Cr resources in muscle and brain, especially because Cr is a natural regulator of energy homeostasis and plays a recognized role in brain function and development, justifying the rising hypothesis that Cr supplementation can help mitigate the effects of aging. Thus, we aimed to review the role of Cr (supplemented or obtained in daily diet) and its metabolism in the aging brain, with emphasis on cognition/memory. PubMed, PsychInfo, EBSCO, Medline, BioMed central and Science Direct, constituted the searched databases. Inclusion criteria specified peer-reviewed studies investigating creatine metabolism and/or creatine supplementation, and assessing cognition, and memory in old adults, and published between January, 2000 to September, 2022. The importance of creatine in the brain’s energy metabolism is well established. The relationship between the decline of cognitive function and brain creatine storage still lacks stronger evidence. Evidence is also lacking on whether creatine supplementation is beneficial in mitigating the neural effects of aging, remaining an open field of studies that brings optimistic perspectives.
... Incidentally, type I muscle fibers display relatively lower total creatine content compared with their fast-twitch counterparts, suggesting a type-II-fiber-dominant male advantage with regards to muscle creatine content. Despite these supposed sex differences, the impacts of creatine supplementation on females during their reproductive lives are not only heavily under-investigated, but wholly non-existent with respect towards its effect on the clearly aerobic-related cardiovascular parameters [21,22]. Therefore, the purpose of this investigation was to test the hypothesis that young, healthy females would display increased body mass and enhanced performance, commensurate to favorable cardiovascular parameters, relative to placebo-matched controls across a four-week training timeline. ...
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Creatine monohydrate supplementation in females is largely under-represented in the literature, and their potentially differential hemodynamic responses are unknown. Methods: Twentyeight resistance-trained women (25.5 ± 6.1 years, 59.7 ± 6.3 kg, 163 ± 5 cm) were randomly assigned to the supplement creatine monohydrate (CRE; 5 g creatine monohydrate + 5 g dextrose) or placebo (PLA; 10 g dextrose) four times per day for 7 days in a double-blind fashion. Each subject subsequently completed resistance training sessions (3 × week) for four weeks with four sets to muscular failure of both half-squat and leg press exercises. The change in body mass (BM), exercise repetition number (REP), rated perceived exertion (RPE), and cardiovascular variables were assessed (sessions 1, 6, and 12). Statistical analyses were performed at a significance level of p ≤ 0.05. Results: Analyses revealed a significant CRE-specific BM increase (p = 0.013), as well as significantly greater halfsquat (p = 0.006) and leg press (p = 0.017) REP per set versus PLA. Additionally, CRE demonstrated significantly lower relative RPE values at session 12 compared with previous sessions. Any significant main or interaction effects were observed for the studied cardiovascular variable. Conclusions: The present data substantiate the creatine’s efficacy to improve muscular performance in females while demonstrating the safety of combined creatine monohydrate supplementation and resistance training on cardiovascular parameters.
... Creatine (methylguanidine-acetic acid) is derived and synthesized from reactions involving the amino acids arginine, glycine, and methionine in the kidneys and liver or can be ingested exogenously primairly in animal-based foods (i.e. red meat, seafood) or through dietary supplements (Alraddadi et al., 2018;Antonio et al., 2021;Ellery et al., 2016;Ostojic and Forbes, 2022;Wyss and Kaddurah-Daouk, 2000). Ninety-five percent of creatine is found in skeletal muscle with the remaining 5% dispersed across the brain, liver, kidney, and testes Rackayova et al., 2017;Wyss and Kaddurah-Daouk, 2000). ...
Aims: The purpose was to examine the relationship between habitual dietary creatine intake obtained in food and visuo-spatial short-term memory (VSSM). Methods: Forty-two participants (32 females, 10 males; > 60 yrs of age) completed a 5-day dietary recall to estimate creatine intake and performed a cognitive assessment which included a visuospatial short-term memory test (forward and reverse corsi block test) and a mini-mental state examination (MMSE). Pearson correlation coefficients were determined. Further, cohorts were derived based on the median creatine intake. Results: There was a significant correlation between the forward Corsi (r = 0.703, P < 0.001), reverse Corsi (r = 0.715, P < 0.001), and the memory sub-component of the MMSE (r = 0.406, P = 0.004). A median creatine intake of 0.382 g/day was found. Participants consuming greater than the median had a significantly higher Corsi (P = 0.005) and reverse Corsi (P < 0.001) scores compared to participants ingesting less than the median. Conclusions: Dietary creatine intake is positively associated with measures of memory in older adults. Clinical Implications: Older adults should consider food sources containing creatine (i.e. red meat, seafood) due to the positive association with visuospatial short-term memory.
... Another limitation is the inclusion of male individuals only. It has been suggested that females may have lower muscle Cr concentration and that they may be less receptive to Cr supplementation due to hormone-related changes in Cr metabolism [66]. ...
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The aim of the present study was to examine the effects of creatine (Cr) supplementation on power output during repeated sprints on a non-motorized treadmill. Sixteen recreationally active males volunteered for this study (age 25.5 ± 4.8 y, height 179 ± 5 cm, body mass 74.8 ± 6.8 kg). All participants received placebo supplementation (75 mg of glucose·kg−1·day−1) for 5 days and then performed a baseline repeated sprints test (6 × 10 s sprints on a non-motorised treadmill). Thereafter, they were randomly assigned into a Cr (75 mg of Cr monohydrate·kg−1·day−1) or placebo supplementation, as above, and the repeated sprints test was repeated. After Cr supplementation, body mass was increased by 0.99 ± 0.83 kg (p = 0.007), peak power output and peak running speed remained unchanged throughout the test in both groups, while the mean power output and mean running speed during the last 5 s of the sprints increased by 4.5% (p = 0.005) and 4.2% to 7.0%, respectively, during the last three sprints (p = 0.005 to 0.001). The reduction in speed within each sprint was also blunted by 16.2% (p = 0.003) following Cr supplementation. Plasma ammonia decreased by 20.1% (p = 0.037) after Cr supplementation, despite the increase in performance. VO2 and blood lactate during the repeated sprints test remained unchanged after supplementation, suggesting no alteration of aerobic or glycolytic contribution to adenosine triphosphate production. In conclusion, Cr supplementation improved the mean power and speed in the second half of a repeated sprint running protocol, despite the increased body mass. This improvement was due to the higher power output and running speed in the last 5 s of each 10 s sprint.
Creatine monohydrate is the most widely used supplement form of Creatine (Cr). It is de novo synthesized from the amino acids: arginine, glycine, and methionine or supplied exogenously from red meat and fish. Tissues store Cr in both free and phosphorylated forms (Phosphocreatine, PCr). Cr and PCr, through the Phosphocreatine shuttle system, play an important role in the regulation and homeostasis of cellular energy metabolism especially in muscles and the central nervous system, where the mitochondria are key players in this energy production machinery. This chapter will focus on the application of Cr monohydrate as a mitochondrial nutrient and an energy-boosting compound by increasing Cr/PCr stores. This results in improvement of physical performance, increased muscular strength, improved recovery after exercise, improved memory and neuronal activity. The application of Cr supplementation as a possible treatment for muscular, neurological, and neuromuscular diseases and its relation to the mitochondrial creatine kinase will be reviewed.
As a global public health problem, postmenopausal osteoporosis (PMOP) poses a great threat to old women's health. Bone is the target organ of PMOP, and the dynamic changes of bone marrow could affect the bone status. Kidney is the main organ regulating calcium and phosphorus homeostasis. Kidney, bone marrow and bone play crucial roles in PMOP, but the relationships of the three tissues in the disease have not been completely described. Here, metabolomics was employed to investigate the disease mechanism of PMOP from the perspectives of kidney, bone marrow and bone, and the relationships among the three tissues were also discussed. Six-month-old female Sprague-Dawley (SD) rats were randomly divided into ovariectomized (OVX) group (with bilateral ovariectomy) and sham group (with sham surgery). 13 weeks after surgery, gas chromatography–mass spectrometry (GC–MS) was performed to analyze the metabolic profiling of two groups. Multivariate statistical analysis revealed that the number of differential metabolites in kidney, bone marrow and bone between the two groups were 37, 16 and 17, respectively. The common differential metabolites of the three tissues were N-methyl-L-alanine. Kidney and bone marrow had common differential metabolites, including N-methyl-L-alanine, 2-hydroxybutyric acid, (R)-3-hydroxybutyric acid (β-hydroxybutyric acid, βHBA), urea and dodecanoic acid. There were three common differential metabolites between kidney and bone, including N-methyl-L-alanine, α-tocopherol and isofucostanol. The common differential metabolite of bone marrow and bone was N-methyl-L-alanine. Some common metabolic pathways were disturbed in multiple tissues of OVX rats, such as glycine, serine and threonine metabolism, purine metabolism, tryptophan metabolism, ubiquinone and other terpenoid-quinone biosynthesis and fatty acid biosynthesis. In conclusion, our study demonstrated that profound metabolic changes have taken place in the kidney, bone marrow and bone, involving common differential metabolites and metabolic pathways. The evaluation of differential metabolites strengthened the understanding of the kidney-bone axis and the metabolic relationships among the three tissues of OVX rats.
The enzymes glycine amidinotransferase, mitochondrial (GATM also known as AGAT) and guanidinoacetate N-methyltransferase (GAMT) function together to synthesize creatine from arginine, glycine, and S-Adenosyl methionine. Deficiency in either enzyme or the creatine transporter, CT1, results in a devastating neurological disorder, Cerebral Creatine Deficiency Syndrome (CCDS). To better understand the pathophysiology of CCDS, we mapped the distribution of GATM and GAMT at single cell resolution, leveraging RNA sequencing analysis combined with in vivo immunofluorescence (IF). Using the mouse as a model system, we find that GATM and GAMT are coexpressed in several tissues with distinct and overlapping cellular sources, implicating local synthesis as an important mechanism of creatine metabolism in numerous organs. Extending previous findings at the RNA level, our analysis demonstrates that oligodendrocytes express the highest level of Gatm and Gamt of any cell type in the body. We confirm this finding in the mouse brain by IF, where GATM localizes to the mitochondria of oligodendrocytes, whereas both oligodendrocytes and cerebral cortical neurons express GAMT. Interestingly, the latter is devoid of GATM. Single nucleus assay for transposase-accessible chromatin sequencing (snATAC-seq) analysis of 4 brain regions highlights a similar primacy of oligodendrocytes in the expression of GATM and GAMT in the human central nervous system. Importantly, an active putative regulatory element within intron 2 of human GATM is detected in oligodendrocytes but not neurons.
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The two chicken creatine kinases from brain and from muscle have been purified as well as the chicken hybrid enzyme. The brain and muscle enzymes from the rabbit have also been purified and compared to the chicken enzymes. There are significant differences in amino acid composition between the brain and muscle types; the hybrid enzyme has an intermediate composition. Peptide maps of the muscle and brain types further indicate that the sequences of the two types are considerably different. Antibodies prepared against the chicken muscle type enzyme do not cross-react, as measured by complement fixation methods or by Ouchterlony tests, with the chicken brain type enzymes; antibodies against the purified brain type enzyme do not react with the muscle type enzyme. However, the hybrid enzyme reacts with both antibodies, although quantitatively less than with the pure enzymes. The two brain type enzymes from the chicken and rabbit, or the two muscle enzymes, are more similar in their properties than are the brain and muscle forms of one species.
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Four purified creatine kinases have been studied with respect to their s value, sedimentation equilibrium, and elution volume on gel filtration. These studies indicate that the creatine kinases all have approximately the same molecular weight, near 80,000. The chicken muscle enzyme at low pH in the presence of a reducing agent had a molecular weight one-half that of the native enzyme. On electrophoresis in starch gel the enzymes all migrated differently. The two creatine kinases from muscle (chicken and rabbit) remained near the origin while the brain enzymes (chicken and rabbit) migrated toward the cathode. The dissociation of the enzymes in urea has been studied; when two dissimilar enzymes are dissociated together in urea and allowed to recombine, both parent enzymes, plus a hybrid enzyme, are formed. Two moles of iodoacetate per mole of enzyme will inactivate the creatine kinases; p-hydroxymercuribenzoate will bind to the enzymes but upon dilution recovery of enzymic activity occurs. The results indicate that creatine kinase has a dimeric structure.
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We employed a whole body magnetic resonance imaging protocol to examine the influence of age, gender, body weight, and height on skeletal muscle (SM) mass and distribution in a large and heterogeneous sample of 468 men and women. Men had significantly ( P < 0.001) more SM in comparison to women in both absolute terms (33.0 vs. 21.0 kg) and relative to body mass (38.4 vs. 30.6%). The gender differences were greater in the upper (40%) than lower (33%) body ( P < 0.01). We observed a reduction in relative SM mass starting in the third decade; however, a noticeable decrease in absolute SM mass was not observed until the end of the fifth decade. This decrease was primarily attributed to a decrease in lower body SM. Weight and height explained ∼50% of the variance in SM mass in men and women. Although a linear relationship existed between SM and height, the relationship between SM and body weight was curvilinear because the contribution of SM to weight gain decreased with increasing body weight. These findings indicate that men have more SM than women and that these gender differences are greater in the upper body. Independent of gender, aging is associated with a decrease in SM mass that is explained, in large measure, by a decrease in lower body SM occurring after the fifth decade.
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Using a model of birth asphyxia, we previously reported significant structural and functional deficits in the diaphragm muscle in spiny mice, deficits that are prevented by supplementing the maternal diet with 5% creatine from mid-pregnancy. The long-term effects of this exposure are unknown. Pregnant spiny mice were fed control or 5% creatine-supplemented diet for the second half of pregnancy, and fetuses were delivered by caesarean section with or without 7.5 min of in-utero asphyxia. Surviving pups were raised by a cross-foster dam until 33±2 days of age when they were euthanized to obtain the diaphragm muscle for ex-vivo study of twitch tension and muscle fatigue, and for structural and enzymatic analyses. Functional analysis of the diaphragm revealed no differences in single twitch contractile parameters between any groups. However, muscle fatigue, induced by stimulation of diaphragm strips with a train of pulses (330ms train/sec, 40Hz) for 300sec, was significantly greater for asphyxia pups compared with controls (p<0.05), and this did not occur in diaphragms of creatine + asphyxia pups. Birth asphyxia resulted in a significant increase in the proportion of glycolytic, fast-twitch fibres and a reduction in oxidative capacity of Type I and IIb fibres in male offspring, as well as reduced cross-sectional area of all muscle fibre types (Type I, IIa, IIb/d) in both males and females at 33 days of age. None of these changes were observed in creatine + asphyxia animals. Thus, the changes in diaphragm fatigue and structure induced by birth asphyxia persist long-term but are prevented by maternal creatine supplementation.
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Recent evidence obtained from a rodent model of birth asphyxia shows that supplementation of the maternal diet with creatine during pregnancy protects the neonate from multi-organ damage. However, the effect of increasing creatine intake on creatine homeostasis and biosynthesis in females, particularly during pregnancy, is unknown. This study assessed the impact of creatine supplementation on creatine homeostasis, body composition, capacity for de novo creatine synthesis and renal excretory function in non-pregnant and pregnant spiny mice. Mid-gestation pregnant and virgin spiny mice were fed normal chow or chow supplemented with 5 % w/w creatine for 18 days. Weight gain, urinary creatine and electrolyte excretion were assessed during supplementation. At post mortem, body composition was assessed by Dual-energy X-ray absorptiometry, or tissues were collected to assess creatine content and mRNA expression of the creatine synthesising enzymes arginine:glycine amidinotransferase (AGAT) and guanidinoacetate methyltransferase (GAMT) and the creatine transporter (CrT1). Protein expression of AGAT and GAMT was also assessed by Western blot. Key findings of this study include no changes in body weight or composition with creatine supplementation; increased urinary creatine excretion in supplemented spiny mice, with increased sodium (P < 0.001) and chloride (P < 0.05) excretion in pregnant dams after 3 days of supplementation; lowered renal AGAT mRNA (P < 0.001) and protein (P < 0.001) expressions, and lowered CrT1 mRNA expression in the kidney (P < 0.01) and brain (P < 0.001). Creatine supplementation had minimal impact on creatine homeostasis in either non-pregnant or pregnant spiny mice. Increasing maternal dietary creatine consumption could be a useful treatment for birth asphyxia.
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A formula has been developed to predict creatinine clearance (Ccr) from serum creatinine (Scr) in adult males: (see article)(15% less in females). Derivation included the relationship found between age and 24-hour creatinine excretion/kg in 249 patients aged 18-92. Values for Ccr were predicted by this formula and four other methods and the results compared with the means of two 24-hour Ccr's measured in 236 patients. The above formula gave a correlation coefficient between predicted and mean measured Ccr's of 0.83; on average, the difference predicted and mean measured values was no greater than that between paired clearances. Factors for age and body weight must be included for reasonable prediction.
Serial studies have demonstrated a frequent rise in the activity of the enzyme creatine kinase in the serum of newborn infants following delivery. The rise in activity is independent of the maternal enzyme level. Considerable elevations in serum creatine kinase activity, noted especially at 24 hours of age, have been found in a number of infants delivered as breech presentations, following secondary uterine inertia with oxytocin stimulation, and following emergency Cesarean section after a trial of labor. Muscle damage sustained by the infant during the birth process is suggested as a likely cause for the increase in neonatal serum enzyme activity.
The premenstrual symptom complex many women experience in a moderate to severe form can be divided into four subgroups. Because there is more than one syndrome and nervous tension is one of the most common symptoms, the term premenstrual tension syndromes (PMTS) is used. The most common subgroup, PMT-A, consists of premenstrual anxiety, irritability and nervous tension sometimes expressed in behavior patterns detrimental to self, family and society. Elevated blood estrogen and low progesterone have been observed in this subgroup. Administration of vitamin B6 at doses of 200-800 mg/day reduces blood estrogen, increases progesterone and results in improved symptoms under double-blind conditions. Women in this subgroup consume an excessive amount of dairy products and refined sugar, and have a low intake of fiber, B-vitamins and certain minerals. The second-most-common subgroup, PMT-H, is associated with symptoms of water and salt retention, abdominal bloating, mastalgia and weight gain. The severe form of PmT-H is associated with elevated serum aldosterone. Vitamin B6 at high dosage suppresses aldosterone and results in diuresis and clinical improvement. Vitamin E helps the breast symptoms. Methylxanthines and nicotine should be curtailed and sodium limited to 3 gm/day. PMT-C is characterized by premenstrual craving for sweets, increased appetite and indulgence in eating refined sugar followed by palpitation, fatigue, fainting spells, headache and sometimes the shakes. PMT-C patients have increased carbohydrate tolerance and low red-cell magnesium. Adequate magnesium replacement results in improved glucose tolerance tests and decreased PMT-C symptoms. Deficiency of the prostaglandin PGE1 may also be involved in PMT-C. PMT-D is the least common but most dangerous because suicide is most frequent in this subgroup. The symptoms are depression, withdrawl, insomnia, forgetfulness and confusion. In ten PMT-D patients the mean blood estrogen was lower and the mean blood progesterone higher than normal during the midluteal phase. Elevated adrenal androgens are observed in some hirsute PMT-D patients. PMT-D patients may also have high lead levels in hair tissue and chronic lead intoxication. Therapy should be individualized according to the results of the evaluation.