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Effect of Zinc and Selenium Supplementation on Serum Testosterone and Plasma Lactate in Cyclist After an Exhaustive Exercise Bout

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Zinc and selenium are essential minerals and have roles for more than 300 metabolic reactions in the body. The purpose of this study was to investigate how exhaustive exercise affects testosterone levels and plasma lactate in cyclists who were supplemented with oral zinc and selenium for 4 weeks. For this reason, 32 male road cyclists were selected equally to four groups: PL group, placebo; Zn group, zinc supplement (30 mg/day); Se group, selenium supplement (200 μg/day); and Zn-Se group, zinc-selenium supplement. After treatment, free, total testosterone, and lactate levels of subjects were determined before and after exhaustive exercise. Resting total, free testosterone, and lactate levels did not differ significantly between groups, and were increased by exercise (P > 0.05). Serum total testosterone levels in Zn group were higher than in Se group after exercise (P < 0.05). Serum-free testosterone levels in the Zn group were higher than the other groups (P < 0.05).There was an insignificant difference between levels of lactate in the four groups after exercise (P > 0.05). The results showed that 4-week simultaneous and separately zinc and selenium supplementation had no significant effect on resting testosterone and lactate levels of subjects who consume a zinc and selenium sufficient diet. It might be possible that the effect of zinc supplementation on free testosterone depends on exercise.
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Effect of Zinc and Selenium Supplementation on Serum
Testosterone and Plasma Lactate in Cyclist
After an Exhaustive Exercise Bout
Leila Shafiei Neek &Abas Ali Gaeini &Siroos Choobineh
Received: 19 June 2011 / Accepted: 29 June 2011 /
Published online: 9 July 2011
#Springer Science+Business Media, LLC 2011
Abstract Zinc and selenium are essential minerals and have roles for more than 300
metabolic reactions in the body. The purpose of this study was to investigate how
exhaustive exercise affects testosterone levels and plasma lactate in cyclists who were
supplemented with oral zinc and selenium for 4 weeks. For this reason, 32 male road
cyclists were selected equally to four groups: PL group, placebo; Zn group, zinc
supplement (30 mg/day); Se group, selenium supplement (200 μg/day); and ZnSe group,
zincselenium supplement. After treatment, free, total testosterone, and lactate levels of
subjects were determined before and after exhaustive exercise. Resting total, free
testosterone, and lactate levels did not differ significantly between groups, and were
increased by exercise (P>0.05). Serum total testosterone levels in Zn group were higher
than in Se group after exercise (P<0.05). Serum-free testosterone levels in the Zn group
were higher than the other groups (P< 0.05).There was an insignificant difference between
levels of lactate in the four groups after exercise (P> 0.05). The results showed that 4-week
simultaneous and separately zinc and selenium supplementation had no significant effect on
resting testosterone and lactate levels of subjects who consume a zinc and selenium
sufficient diet. It might be possible that the effect of zinc supplementation on free
testosterone depends on exercise.
Keywords Exhaustion exercise .Lactate .Road cyclists .Testosterone .Selenium
supplementation .Zinc supplementation
Introduction
Many researchers concentrate on the relation between exercise and antioxidant supplemen-
tation; therefore, it can be stated that there is an increasing interest about evaluation of the
ergogenic effects of minerals such as zinc and selenium on exercise.
Biol Trace Elem Res (2011) 144:454462
DOI 10.1007/s12011-011-9138-2
L. Shafiei Neek (*):A. A. Gaeini :S. Choobineh
Faculty of Physical Education and Sport Sciences, University of Tehran, Tehran, Iran
e-mail: shafieineek@gmail.com
Zinc is the fourth most abundant intercellular metal, and a biologically essential trace
metal is found in over 200 enzymes and proteins [1]. Since zinc is necessary for the activity
of a number of enzymes in the energy metabolism, low muscle zinc levels may lead to a
reduction in endurance capacity [2]. Zinc plays a key role in reproductive physiology [3,4].
There was a positive relation between zinc and testosterone [5]. Lactic dehydrogenase is a
Zn-containing enzyme. Adequate muscle zinc concentration may facilitate the reduction of
lactic acid to pyruvate through the action of lactic dehydrogenase in exercising skeletal
muscle and, therefore, may decrease muscle fatigue [6]. Kaya et al. [7] reported that zinc
supplementation leads to a significant increase in testosterone levels and a significant
decrease in lactate levels in response to exhaustive exercise.
Also, selenium, which is commonly found in nature, is an essential trace element
required for the normal development of human and animal organisms [8,9]. The
increase in oxidative stress caused by exercise and the recognition of the stimulation of
antioxidant activity by selenium inevitably entails a relation between selenium and
exercise [10]. Selenium is also needed for normal testosterone metabolism and testicular
morphology, which may explain the presence of several other selenoproteins in the male
gonads [11]. Akil et al. [10] reported that the increase in free radical production and
lactate levels due to acute swimming exercise in rats might be offset by selenium
supplementation.
A relationship between exercise and testosterone, which has important effects on energy
metabolism, seems inevitable. From a large number of studies exploring the relationship
between exercise and testosterone, no definite conclusion can be drawn [1214]. Bosco et
al. [15] reported that short-term strenuous exercise increased total and free testosterone
levels by 12% and 13%, respectively. But Kilic et al. [16] reported that exhaustive exercise
decreased thyroid hormone and testosterone concentrations in elite athletes.
Studies on the relation between selenium and exercise and zinc and exercise mainly
focus on the antioxidant role of selenium and the distribution of zinc in the body on
response to exercise. There is limited information about the effect of zinc and selenium
supplementation especially around their relationship with testosterone hormone and
exercise. Accordingly, this topic needs to be studied. The purpose of this study was to
examine how exhaustion exercise affects testosterone and lactate levels in athletes who
consume a zinc and selenium sufficient diet, and without any lack of selenium and zinc,
who are supplemented oral zinc and selenium for 4 weeks.
Materials and Methods
Subjects
The study was performed at the National Olympic & Paralympics Academy of Islamic
Republic of Iran (NOPA.I.R.Iran). Thirty-two male road cyclists volunteered to participate
in this experiment. The characteristics of the participants are given as mean±SD in Table 1.
First of all, the subjects provided written informed consent. The cyclists had 34 years of
exercise experiences, and they were members of the Tehran Traffic team. The study
groups were exercised for 120180 min, 5 days a week. One week to study, the
subjects reported to the NOPA.I.R.Iran after an overnight fast. In this session, the
subjects' age, height, mass, body composition (via in body 220), and maximal aerobic
power (Moark ergometer 894Ea) were determined. Also, blood samples were taken for
assessment of zinc and selenium status.
Effect of Zinc and Selenium Supplementation on Serum Testosterone and Plasma Lactate 455
Supplementation Protocol
None of the subjects had ingested zinc and selenium or any other dietary supplements, for a
minimum of 2 weeks before the initiation and during the study. The subjects were assigned
base on body composition, and they were equally divided into four groups by using a
double-blind design.
(a) Placebo (PL, 30 mg of dextrose; n=8), (b) zinc (Zn, 30 mg zinc sulfate), (c) selenium
(Se, 200 μg sodium selenite), (d) zincselenium (ZnSe, 30 mg zinc sulfate200 μg
selenium selenite).
According to their group assignment, all subjects ingested one capsule of zinc, selenium,
zincselenium, and placebo each day for 4 weeks.
Diets' Zinc and Selenium Assay
In the course of trial, the daily intake of zinc and selenium was determined on the base of
diet history interviews (24-h recall and food frequency questionnaire), which were
conducted with Dorosty Food Processor (version 2.1). The interviews were performed by
an experimental nutritionist, and were designed to reflect the habitual dietary intake of the
subjects in the month before and during the trial period. The daily zinc and selenium intake
of all subjects (16/34±1/23 mg d
1
and 64/45±19/03 mg d
1
, respectively) were higher
than the recommended daily allowance of 11 mg d
1
and 55 μgd
1
[17], respectively for
zinc and selenium intake, so all subjects were considered to be not zinc and selenium
deficient; therefore, the usage of supplements was more than their daily needs.
Exercise Tests
One week before the actual experiment started, subjects had to perform a graded exercise
test in order to determine their maximal power output (Wmax) [18]. For 3 days before the
experiments, the subjects were obliged to abstain from strenuous exercise. No caffeine, only
tea was permitted during the 48 h before the experiment. On the experimental days, subjects
reported to the NOPA.I.R.Iran after an overnight fast. Exercise test started with a 10-min
warm-up period at a workload of 50% Wmax. Thereafter, the subjects were instructed to
cycle 2-min block periods at alternating workloads of 90% and 50% of Wmax, respectively.
This was continued until the subjects were no longer able to complete the 2 min at 90%
Wmax. That moment was defined as the time at which the subject was unable to maintain
cycling speed at 60 revolutions per minute. At that moment, the high-intensity block was
reduced to 80% Wmax. Again, the subjects had to cycle until they were unable to complete
a 2-min block at 80% Wmax, after which the high-intensity block was reduced to 70%
Table 1 Anthropometric data and baseline zinc and selenium intake of the cyclist
Group Height (cm) Weight (kg) BMI (kg/m
2
) Aerobic
power (Watt)
Baseline dietary
zinc (mg d
1
)
Baseline dietary
selenium (mg d
1
)
PL 176.87± 8.02 66.15 ± 6.4 21.12± 0.98 291.5± 44.56 15.67 ± 0.89 64.05± 15.02
Zn 176.87 ± 8.2 68.11± 8.66 21.75±2.5 299.88± 30.17 16.40 ± 1.02 59.98±13.29
Se 177.75± 4.23 61.66 ± 4.75 20.5± 1.26 304.06± 31.99 14.98 ± 1.08 56.87±14.67
ZnSe 174.81± 4.3 63.17± 8.45 21.57 ± 2.1 296.12±41.54 16.23±0.45 62.56 ± 12.34
Values are means±SD
456 Neek et al.
Wmax. The subjects were allowed to stop when pedaling speed could not be maintained at
70% Wmax. Water was provided ad libitum during the exercise protocol [19]. To remain
blood samples were taken from all subjects pre and post exercise.
Laboratory Procedures
Blood samples collected from the subjects were centrifuged for 10 min at 3,000 rpm and
were kept frozen at 20°C until analysis. Free and total testosterone analyses were
conducted on the serum samples. Lactate, zinc, and selenium were assessed on the plasma
samples.
Zinc and Selenium Analysis
Plasma zinc and selenium concentrations were assessed on a Younglin AAS 8020 atomic
absorption spectrometer (AAS). Values were expressed as micrograms per deciliter.
Plasma Lactate
Lactate analyses were carried out in the separated plasma samples according to colorimetric
method (using Roche Diagnostic lactate kits) in a Cobas Integra 400 autoanalyzer. Plasma
lactate levels (read at 552 nm wavelength) are expressed as milligrams per deciliter.
Free Testosterone Measurements
Serum-free testosterone analyses were done in Elisa test kit (LDN Company) by enzyme-
linked immunosorbent assay method; the results are expressed as picogram per milliliter.
Total Testosterone Measurements
Serum total testosterone was measured with chemiluminescence immunoassay on a
LIAISON (Diasorin) analyzer. The results are expressed as nanograms per milliliter.
Statistical Analysis
Statistical analysis was performed with SPSS version 16 program (SPSS Inc., Chicago, IL,
USA). Statistical evaluation was done by KolmogrovSmirnov test at first to examine the
normal distribution and Leven's test for homogeneity. One-way ANOVA was performed in
order to compare between groups in anthropometric data and aerobic power. Two-way
ANOVA was also performed to assess differences between intra and intergroups followed by
Bonferroni's test for multiple comparisons. All results were shown as means±SD in all
statistical comparisons P<0/05 was used as the criterion for statistical significance.
Results
The results of statistical analysis showed that there was an insignificant difference about
physical characteristic between groups (p>0.05). Intra and intergroup comparison,
respectively indicated that resting levels of plasma lactate and free and total testosterone
Effect of Zinc and Selenium Supplementation on Serum Testosterone and Plasma Lactate 457
did not differ significantly differ between groups, and were increased significantly by
exercise. There was a significant difference between effects of exhaustion exercise on serum
total testosterone in Zn group higher than Se group (p<0.05) (Fig. 1). But there was no
significant difference between Zn group with PL and ZnSe groups (p<0.05). It was
resulted that in this case, there was no significant difference between PL, Se, and ZnSe
groups (p<0.05). There was also a significant difference between effects of exhaustion
exercise on serum-free testosterone in Zn group in contrast with other groups (p<0.05)
(Fig. 2). In this case, there was no significant difference between PL, Se, and ZnSe groups
(p<0.05). There was an insignificant difference between effects of exhaustion exercise on
plasma lactate in the four groups (p> 0.05) (Fig. 3).
Discussion
Considering that the results of this study about two different sides of the nutritionexercise
effects (Zn, Se, and ZnSe groups) and exercise effects (PL group) are comparable with the
related obtained results, therefore, the results of this research will be discussed in these two
fields separately.
In results of our study, resting free and total testosterone levels measured were
significantly lower than those measured after an exhaustive exercise bout. This result
reveals that there is a positive correlation between testosterone and exhaustive exercise.
In fact, results of studies examining the relation between exercise and testosterone
illustrates that there is no agreement on this topic. In other words, there are
contradictions about the cause and effect of physical exercise and the amount of
testosterone in different researches [7,16,2022]. Besides the studies reporting that free
and total testosterone levels did not change with exercise [2325], there are also those
noting that free and total testosterone levels significantly decreased with exercise [26
28]. The increase we obtained in free and total testosterone levels immediately after
exhaustion is in contrast with the findings of these researchers. Ransen et al. [29]
showed that there was an important increase in levels of testosterone, epinephrine,
norepinephine, ACTH, cortisol, and growth hormone of the subjects following hight-
intensity endurance exercise on a cycle ergometer. The results of this study are consistent
with our findings.
0
100
200
300
400
500
600
700
800
900
Placebo Zn Se Zn-Se
Total Testosterone (ng/dl)
Pre-Test Post-Test
*
*
*
*
Fig. 1 Variations of total testos-
terone in research groups.
(Mean±SD). Asterisks indicate
p<0.05 pre-test vs. post-test;
Euro sign indicates p<0.05 Zn
group vs. Se group
458 Neek et al.
The mechanisms responsible for the increase in serum testosterone levels during exercise
are controversial, and may include decreased testosterone clearance, hemoconcentration,
increased SHBG, catecholamine, precursor molecule DHEA sulfate, and testosterone
production due to stimulation by factors other than LH and the slight decrease in
progesterone [3035].
Probably, the reason of contradiction around this issue is about the difference between
physical fitness of the subjects, exercise intensity, type and duration, and the work load.
Jezova et al. [36] reported that both plasma testosterone and catecholamine responses to
physical effort depend more on work intensity than on work duration or total work output.
Zinc enhances human chorionic gonadotropin-induced production of cAMP and
consequently testosterone in rat testes [37]. Additionally, zinc may increase the conversion
of androstenedione to testosterone in the periphery tissue [22]. Zinc also interferes with the
metabolism of testosterone by decreasing its hepatic clearance and reducing hepatic 5
alpha-reductase activities [38]. The findings of our study demonstrated that resting free and
total testosterone levels after a 4-week zinc supplementation had no variation relative to PL
group. Exercise increased total testosterone levels in the Zn group than Se group, and also
free testosterone levels in Zn group than other groups. Kilic et al. [16] showed that 4-week
zinc supplementation increased resting levels of both thyroid hormones and testosterone
concentrations, and exhaustion exercise led to a significant inhibition of those hormones,
0
5
10
15
20
25
30
Free Testosterone (pg/dl)
****
Placebo Zn Se Zn-Se
Pre-Test Post-Test
Fig. 2 Variations of free
testosterone in research groups.
(Mean±SD). Asterisks indicate
p<0.05 pre-test vs. post-test; Euro
sign indicates p<0.05 Zn group
vs. Se group; cross indicates
p<0.05 Zn group vs. PL group
0
10
20
30
40
50
60
Plasma Lactate (mg/dl)
*
**
*
Placebo Zn Se Zn-Se
Pre-Test Post-Test
Fig. 3 Variations of plasma lactate
in research groups. (Mean±SD).
Asterisks indicate p<0.05 pre-test
vs. post-test
Effect of Zinc and Selenium Supplementation on Serum Testosterone and Plasma Lactate 459
but that 4-week zinc supplementation prevented this inhibition in wrestlers. Similarly, Kilic
[39] reported mentioned results about sedentary males in response to fatiguing bicycle
exercise. Kilic concluded that administration of a physiologic dose of zinc can be
beneficial to performance.Contradictory, Koehler et al. [40] noted that zinc supplemen-
tation may reverse lowered testosterone levels and restore disturbed testosterone
metabolism in cases of mild or severe zinc deficiency; it is not capable of further
increasing serum testosterone when sufficient zinc is provided by the regular diet.
The disparity in results in the aforementioned studies with our findings might be due to
variations in the consumed dose of zinc supplement, status of zinc in subjects, amount of
zinc intake on diet, as well as the improper time duration for the effect of supplementation
does in our study.
Previous studies demonstrated that significant decrease in polymorphonuclear leukocyte
and lymphocyte activity, and high-density lipoprotein cholesterol after 6 weeks of 150 mg Zn
per day [41,42]. Similarly, that consumption of zinc supplements in excess of 50 mg/day
have been linked to impair copper absorption [43]. For these reasons, use of Zn supplements
should be limited to those containing no more than 30 mg/d [44]. Therefore, in the present
study, the considered supplementation of consumed dose 30 mg/d was performed by its
practical order.
In the Leydig cells, glutathione peroxidise (se-dependent) has been localized
immunocytochemically in the cytoplasm in close relationship to the smooth endoplasmic
reticulum, and it is possible that the metabolic pathway of testosterone biosynthesis requires
protection against peroxidation and is thus affected by a decrease in the activity of this
enzyme [45]. In our study, 4-week selenium supplementation had no effect on resting levels
of total and free testosterone and plasma lactate in cyclist. Probably, the normal status of
selenium in cyclists and the enough amount of intake selenium from diet can be the other
reasons of the results about the selenium group.
It is known that plasma lactate concentration increases together with increased exercise
[46]. This study showed that 4-week zinc and selenium supplementations had no effect on
plasma lactate in pre and post-exhaustive exercise. There are only a limited number of
studies about how selenium, which is known to reduce oxidative damage in exercise,
affects glucose metabolism, lactate levels, and tiredness in physical activity [47]. Akil et al.
[10] investigated the effects of selenium on lipid peroxidation and lactate levels in rats
subjected to acute swimming exercise. He reported that the increase in free radical
production and lactate levels due to acute swimming exercise in rats might be offset by
selenium supplementation. Selenium supplementation may be important in that it supports
the antioxidant system in physical activity. Baltaci et al. [48] demonstrated that 4-week zinc
deficiency increased plasma lactate in rats after acute swimming and zinc supplementation
(3 mg/kg weight) has the opposite effect.
In summary, even though supplementation may reverse negative effects of nutritional
deficiencies (and consequently improve athletic performance), this cannot be transferred
directly to non-deficient athletes. In most cases, if energy intakes are sufficient, the mineral
needs of athletes are analogous to healthy individuals. Some athletes, however, may have
greater requirements as a consequence of disproportionate losses of I nutrients in sweat and
urine. For these athletes, supplementation may need to be considered on an individual basis
to maintain normal body stores, not for ergogenic purposes. A systematic approach to the
study of minerals and exercise performance is needed. This approach needs to use the same
protocol to evaluate whether minerals can be effective ergogenic aids. It would require
longer supplementation periods, control of exercise settings, multi-center trials, men and
women participants, elite and recreational athletes, and precise measures of mineral status.
460 Neek et al.
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... The activity of the enzyme glutathione peroxidase (GPx), a highly-efficient antioxidant enzyme, is strictly dependent on the presence of its co-factor Se [16]. Increases in blood levels of Se have been reported through exogenous Se intake, mostly in its organic form of selenomethionine [17] and inorganic salts of sodium selenite (Na2SeO3) [18,19]. Elevated blood concentrations of Se may stimulate the activity of the GSH-Px enzyme in the muscle [11]. ...
... Among the selected articles, 1 study included active subjects [18], 4 studies regularly trained athletes [13,26,29,30], and 1 study had a population who lacked regular training before the study [19]. Furthermore, in 4 studies, supplementation was organic Se in the form of selenomethionine [13,26,29,30], while in 2 studies, supplementation was in form of salts of sodium selenite [18,19]. ...
... Among the selected articles, 1 study included active subjects [18], 4 studies regularly trained athletes [13,26,29,30], and 1 study had a population who lacked regular training before the study [19]. Furthermore, in 4 studies, supplementation was organic Se in the form of selenomethionine [13,26,29,30], while in 2 studies, supplementation was in form of salts of sodium selenite [18,19]. Regarding the daily dose of Se, 3 studies used 180 µg [13,26,29], 2 studies used 200 µg [18,19], and 1 study used 240 µg [30]. ...
Article
Exercise overproduces oxygen reactive species (ROS) and eventually exceeds the body’s antioxidant capacity to neutralize them. The ROS produce damaging effects on the cell membrane and contribute to skeletal muscle damage. Selenium (Se), a natural mineral trace element, is an essential component of selenoproteins that plays an important role in antioxidant defense. The activity of the enzyme glutathione peroxidase (GPx), a highly-efficient antioxidant enzyme, is closely dependent on the presence of Se. These properties of Se may be potentially applicable to improve athletic performance and training recovery. We systematically searched for published studies to evaluate the effectiveness of Se supplementation on antioxidant defense system, muscle performance, hormone response, and athletic performance among physically active individuals. We used the Preferred Reporting Elements for Systematic Reviews and Meta-Analysis (PRISMA) guidelines and searched in SCOPUS, Web of Science (WOS), and PubMed databases to identify published studies until March 2020. The systematic review incorporated original studies with randomized controlled crossover or parallel design in which intake of Se administered once a day was compared with the same placebo conditions. No exclusions were applied for the type of physical exercise performed, the sex, nor the age of the participants. Among 150 articles identified in the search, 6 met the criteria and were included in the systematic review. The methodological quality of the studies was evaluated using the McMaster Critical Review Form. Oral Se supplementation with 180 µg/day or 240 µg/day (selenomethionine) and 200 µg/day (Sodium Selenite), significantly decreased lipid hydroperoxide levels and increased GPx in plasma, erythrocyte, and muscle. No significant effects were observed on athletic performance, testosterone hormone levels, creatine kinase activity, and exercise training-induced adaptations on oxidative enzyme activities or on muscle fiber type myosin heavy chain expression. In addition, Se supplementation showed to have a dampening effect on the mitochondria changes in chronic and acute exercise. In summary, the use of Se supplementation has no benefits on aerobic or anaerobic athletic performance but it may prevent Se deficiencies among athletes with high-intensity and high-volume training. Optimal Se plasma levels may be important to minimize chronic exercise-induced oxidative effects and modulate the exercise effect on mitochondrial changes.
... The activity of the enzyme glutathione peroxidase (GPx), a highly-efficient antioxidant enzyme, is strictly dependent on the presence of its co-factor Se [16]. Increases in blood levels of Se have been reported through exogenous Se intake, mostly in its organic form of selenomethionine [17] and inorganic salts of sodium selenite (Na2SeO3) [18,19]. Elevated blood concentrations of Se may stimulate the activity of the GSH-Px enzyme in the muscle [11]. ...
... Among the selected articles, 1 study included active subjects [18], 4 studies regularly trained athletes [13,26,29,30], and 1 study had a population who lacked regular training before the study [19]. Furthermore, in 4 studies, supplementation was organic Se in the form of selenomethionine [13,26,29,30], while in 2 studies, supplementation was in form of salts of sodium selenite [18,19]. ...
... Among the selected articles, 1 study included active subjects [18], 4 studies regularly trained athletes [13,26,29,30], and 1 study had a population who lacked regular training before the study [19]. Furthermore, in 4 studies, supplementation was organic Se in the form of selenomethionine [13,26,29,30], while in 2 studies, supplementation was in form of salts of sodium selenite [18,19]. Regarding the daily dose of Se, 3 studies used 180 µg [13,26,29], 2 studies used 200 µg [18,19], and 1 study used 240 µg [30]. ...
Article
Full-text available
Exercise overproduces oxygen reactive species (ROS) and eventually exceeds the body’s antioxidant capacity to neutralize them. The ROS produce damaging effects on the cell membrane and contribute to skeletal muscle damage. Selenium (Se), a natural mineral trace element, is an essential component of selenoproteins that plays an important role in antioxidant defense. The activity of the enzyme glutathione peroxidase (GPx), a highly-efficient antioxidant enzyme, is closely dependent on the presence of Se. These properties of Se may be potentially applicable to improve athletic performance and training recovery. We systematically searched for published studies to evaluate the effectiveness of Se supplementation on antioxidant defense system, muscle performance, hormone response, and athletic performance among physically active individuals. We used the Preferred Reporting Elements for Systematic Reviews and Meta-Analysis (PRISMA) guidelines and searched in SCOPUS, Web of Science (WOS), and PubMed databases to identify published studies until March 2020. The systematic review incorporated original studies with randomized controlled crossover or parallel design in which intake of Se administered once a day was compared with the same placebo conditions. No exclusions were applied for the type of physical exercise performed, the sex, nor the age of the participants. Among 150 articles identified in the search, 6 met the criteria and were included in the systematic review. The methodological quality of the studies was evaluated using the McMaster Critical Review Form. Oral Se supplementation with 180 µg/day or 240 µg/day (selenomethionine) and 200 µg/day (Sodium Selenite), significantly decreased lipid hydroperoxide levels and increased GPx in plasma, erythrocyte, and muscle. No significant effects were observed on athletic performance, testosterone hormone levels, creatine kinase activity, and exercise training-induced adaptations on oxidative enzyme activities or on muscle fiber type myosin heavy chain expression. In addition, Se supplementation showed to have a dampening effect on the mitochondria changes in chronic and acute exercise. In summary, the use of Se supplementation has no benefits on aerobic or anaerobic athletic performance but it may prevent Se deficiencies among athletes with high-intensity and high-volume training. Optimal Se plasma levels may be important to minimize chronic exercise-induced oxidative effects and modulate the exercise effect on mitochondrial changes.
... There are two studies on the interaction between selenium intake and testosterone levels. In one RCT, Neek et al. selected male road cyclists (n = 32) into four groups: to take placebo; zinc supplement (30 mg/day); selenium supplement (200 µg/day); or zinc and selenium supplement for 4 weeks [27]. After treatment, free and total testosterone were determined before and after exhaustive exercise. ...
... Total testosterone and free testosterone levels in the zinc group were even higher than in the selenium group after exercise (p < 0.05). The authors concluded that selenium supplementation for 4 weeks had no significant effect on testosterone levels [27]. ...
Article
Full-text available
“Testosterone boosters” (TB)—are supplements that are claimed to increase testosterone levels in the human body. While the consumption of TB may be popular among athletes, there is insufficient evidence both about the safety and the real efficacy of TB. In our review, we searched MEDLINE/PubMed and Cochrane Library for studies on the effects of 15 substances that are claimed to increase testosterone levels Anacyclus pyrethrum; Bulbine natalensis; Epimedium (horny goat weed); L-arginine; L-carnitine; magnesium; Mucuna pruriens; pantothenic acid; selenium; shilajit Eurycoma longifolia (Tongkat Ali); Serenoa repens (saw palmetto); boron; Withania somnifera (ashwagandha); and Trigonella foenum-graecum (fenugreek) in athletes and healthy adults under 55 years of age. We found such studies regarding 10 out of 15 substances: L-arginine (3 studies); L-carnitine (2); magnesium (1); selenium (2); shilajit (1); Tongkat Ali (2); Serenoa repens (1); boron (3); ashwagandha root (2); and fenugreek (7). Many of them fail to prove the efficacy of these substances to increase testosterone levels. Tongkat Ali, ashwagandha, and fenugreek were the substances with the strongest evidence. The positive effect of magnesium and shilajit on testosterone concentration was shown in single studies. Conflicting data found that L-arginine, L-carnitine, Serenoa repens, selenium and boron do not appear to increase testosterone levels. There are almost no data on the safety profile of various TB components; however, certain TB components may be linked to coagulation, and pancreatic and hepatic disorders. Based on the review, the authors conclude that at present TB cannot be recommended for use by athletes due to insufficient data on their efficacy and safety. Lazarev A, Bezuglov E. Testosterone Boosters Intake in Athletes: Current Evidence and Further Directions. Endocrines. 2021; 2(2):109-120. https://doi.org/10.3390/endocrines2020011
... However, Se metabolism could be modified during physical exercise [4]. Previous studies researching Se concentrations have mainly been based on the effects of the intake of Se-rich supplements [10][11][12][13][14]. Research concerning the influence of physical exercise on Se concentrations in different compartments is limited [15][16][17][18]. ...
Article
Full-text available
Trace mineral element concentrations are under homeostatic control. Selenium (Se) is a very important micronutrient for the antioxidant and immune system. Se metabolism could be modified due to physical training. This research aimed to analyze the extracellular (plasma, urine and serum) and intracellular (platelets and erythrocytes) concentrations of Se in athletes and to compare it with subjects with low levels of physical training. Forty young men divided into a control group (CG; n = 20; 19.25 ± 0.39 years) and a training group (TG; n = 20; 18.15 ± 0.27 years) participated in this study. The TG was formed by semi-professional soccer players. The analysis of Se was determined by inductively coupled plasma mass spectrometry. The TG obtained higher values of maximum oxygen consumption and muscle percentage (p < 0.05). The TG showed reduced absolute (p < 0.01) and relative (p < 0.05) Se concentrations in erythrocytes and platelets in comparison to CG. Trace element assessments should not be limited only to extracellular compartments as there could be deficiencies at the intracellular level.
... Investigators reported that zinc supplementation increased both TT and FT concentrations prior to and following the exhaustive exercise protocol compared to presupplementation results. In contrast, others reported no difference in either the TT or FT response to exhaustive exercise between male cyclists supplemented with zinc sulfate (30 mg) for four weeks compared to a placebo-controlled group [160]. Although zinc has an important role in the regulation of testosterone production, long-term studies in competitive athletes have not been conducted. ...
Article
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Elevations in the circulating concentration of androgens are thought to have a positive effect on the anabolic processes leading to improved athletic performance. Anabolic-androgenic steroids have often been used by competitive athletes to augment this effect. Although there has been concerted effort on examining how manipulating training variables (e.g., intensity and volume of training) can influence the androgen response to exercise, there has been much less effort directed at understanding how changes in both macronutrient and micronutrient intake can impact the androgen response. Thus, the focus of this review is to examine the effect that manipulating energy and nutrient intake has on circulating concentrations of testosterone and what the potential mechanism is governing these changes.
... On the contrary, low-carbohydrate ketogenic diets preferably consumed by athletes for body composition benefits increase Se intake because of the nature of the consumed animal food [141]. However, supplementation with additional Se seems to provide limited beneficial effects on aerobic or anaerobic performance [142][143][144][145]. However, the association between Se levels and the risk of death from COVID-19 is noteworthy [146,147]. ...
Article
Full-text available
Adequate amounts of a wide range of micronutrients are needed by body tissues to maintain health. Dietary intake must be sufficient to meet these micronutrient requirements. Mineral deficiency does not seem to be the result of a physically active life or of athletic training but is more likely to arise from disturbances in the quality and quantity of ingested food. The lack of some minerals in the body appears to be symbolic of the modern era reflecting either the excessive intake of empty calories or a negative energy balance from drastic weight-loss diets. Several animal studies provide convincing evidence for an association between dietary micronutrient availability and microbial composition in the gut. However, the influence of human gut microbiota on the bioaccessibility and bioavailability of trace elements in human food has rarely been studied. Bacteria play a role by effecting mineral bioavailability and bioaccessibility, which are further increased through the fermentation of cereals and the soaking and germination of crops. Moreover, probiotics have a positive effect on iron, calcium, selenium, and zinc in relation to gut microbiome composition and metabolism. The current literature reveals the beneficial effects of bacteria on mineral bioaccessibility and bioavailability in supporting both the human gut microbiome and overall health. This review focuses on interactions between the gut microbiota and several minerals in sport nutrition, as related to a physically active lifestyle.
... In cattle, deficiency of minerals and trace elements causes growth retardation, immune system deficiency and dermatological lesions (Kahn and Line, 2010;Radostits et al., 2007). Zinc and selenium play roles in numerous metabolic reactions in the body (Shafiei Neek et al., 2011). Zinc deficiency may lead to the development of dermatophytosis, chronic infection and expansion of lesion area (Szczepanik and Wilkolek, 2004). ...
Article
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In this study, it was aimed to evaluate oxidative stress, serum biochemistry, trace elements, minerals, and testosterone and thyroid hormone levels in weaned calves with dermatophytosis. A total of 28 weaned Holstein calves were used in the study, including 6-8 months old, 14 with dermatophytosis (7 males, 7 females) and 14 healthy (7 males, 7 females). The animals were grouped as the diseased and healthy animals, 14 animals in each group as well as the male diseased and the male healthy animals were grouped as 7 animals in each group for the comparison of testosterone levels. The blood analyses were performed using ELISA kits and biochemistry automatic analyzer. There was a significant difference between the diseased and healthy groups for NO (nitric oxide) (P <0.05), TOS (total oxidative stress) (P <0.001), TAC (total antioxidant capacity)(P <0.01). However, in comparison of the diseased and healthy groups, serum biochemistry, trace elements except manganese, minerals, and thyroid hormone levels were not statistically different (P>0.05). In comparison of the diseased and healthy animals for testosterone levels it was not determined any difference (P>0.05). The present study revealed that dermatophytosis could affect oxidant status in calves with dermatophytosis and that TOC (total oxidant capacity) and NO as oxidative stress marker might be increased for fungicidal effect in the diseased animals with dermatophytosis. Keywords: Calves with dermatophytosis, oxidative stress, trace elements, serum biochemistry, hormones.
Article
Cadmium (Cd) could reduce abnormal cell morphology and membrane permeability, however, there are few studies on the detoxification of Cd-reduced cell membrane toxicity. In the present study, we firstly studied the effects of zinc chloride (ZnCl2), n-acetyl-L-cysteine (NAC), and calcium/calmodulin dependent protein kinase II inhibitor (KN93) on cell membrane permeability, respectively; then, we studied the inhibitory effects of ZnCl2, NAC, and KN93 on Cd²⁺-induced abnormal cell membrane permeability by scanning electrochemical microscopy (SECM) scanning imaging, transverse scanning curve and DPV technology. Our results showed that 10 μmol·L⁻¹ ZnCl2, 0.5 mmol·L⁻¹ NAC and 5 μmol·L⁻¹ KN93 could significantly improve the activity of MCF-7 cells, while did not destroy the cell morphology and membrane permeability. 0.5 mmol·L⁻¹ NAC and 5 μmol·L⁻¹ KN93 could significantly inhibit the effects of Cd²⁺ on the morphology and membrane permeability of MCF-7 cells (p < 0.01). 10 μmol·L⁻¹ ZnCl2 could significantly inhibit the effect of Cd on the membrane permeability of MCF-7 cells, however, it cannot completely eliminate the morphological changes of MCF-7 cells caused by Cd²⁺. The results of cell activity experiment showed that 10 μmol·L⁻¹ ZnCl2, 0.5 mmol·L⁻¹ NAC and 5 μmol·L⁻¹ KN93 could inhibit the effect of Cd²⁺ on the activity of MCF-7 cells. By comparing the inhibitory effects of ZnCl2, NAC and KN93 on Cd²⁺- induced cytotoxicity, 5 μmol·L⁻¹ KN93 had the robust effect on the maintenance of MCF-7 cell morphology and cell membrane integrity. Our research provided evidence on Zn supplement, NAC as antioxidant drugs, and KN93 as special inhibitor for the detoxification of Cd²⁺-reduced abnormal cell morphology and membrane permeability.
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To determine the acute effect of a single high-intensity interval training (HIIT) session on testosterone and cortisol levels in healthy individuals, a systematic search of studies was conducted in MEDLINE and Web of Science databases from inception to February 2020. Meta-analyses were performed to establish the acute effect of HIIT on testosterone and cortisol levels immediately after a single HIIT session, after 30 minutes, and 60 minutes (primary outcomes) and after 120 minutes, 180 minutes, and 24h (secondary outcomes, only for pre-post intervention groups). Potential effect-size modifiers were assessed by meta-regression analyses and analyses of variance. Study quality was assessed using the Cochrane's risk of bias tool and the Physiotherapy Evidence Database scale. The meta-analyses of 10 controlled studies (213 participants) and 50 pre-post intervention groups (677 participants) revealed a significant increase in testosterone immediately after a single HIIT session (d=0.92 and 0.52, respectively), which disappeared after 30 minutes (d=0.18 and -0.04), and returned to baseline values after 60 minutes (d=-0.37 and -0.16). Significant increases of cortisol were found immediately after (d=2.17 and 0.64), after 30 minutes (d=1.62 and 0.67), and 60 minutes (d=1.32 and 0.27). Testosterone and cortisol levels decreased significantly after 120 minutes (d=-0.48 and -0.95, respectively) and 180 minutes (d=-0.29 and -1.08) and return to baseline values after 24h (d=0.14 and -0.02). HIIT components and participant's characteristics seem to moderate the effect sizes. In conclusion, testosterone and cortisol increase immediately after a single HIIT session, then drop below baseline levels, and finally return to baseline values after 24h. This meta-analysis provides a better understanding of the acute endocrine response to a single HIIT session, which would certainly be valuable for both clinicians and coaches in the prescription of exercise programs to improve health and performance. Testosterone and cortisol may be used as sensitive biomarkers to monitor the anabolic and catabolic response to HIIT.
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This study was performed to assess how 4 weeks of magnesium supplementation and exercise affect the free and total plasma testosterone levels of sportsmen practicing tae kwon do and sedentary controls at rest and after exhaustion. The testosterone levels were determined at four different periods: resting before supplementation, exhaustion before supplementation, resting after supplementation, and exhaustion after supplementation in three study groups, which are as follows: Group 1-sedentary controls supplemented with 10 mg magnesium per kilogram body weight. Group 2-tae kwon do athletes practicing 90-120 min/day supplemented with 10 mg magnesium per kilogram body weight. Group 3-tae kwon do athletes practicing 90-120 min/day receiving no magnesium supplements. The free plasma testosterone levels increased at exhaustion before and after supplementation compared to resting levels. Exercise also increased testosterone levels relative to sedentary subjects. Similar increases were observed for total testosterone. Our results show that supplementation with magnesium increases free and total testosterone values in sedentary and in athletes. The increases are higher in those who exercise than in sedentary individuals.
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The effects of 4 weeks of calcium supplementation on free- and total testosterone levels were established in active and sedentary adult males at rest and exhaustion. Thirty healthy male athletes were equally divided into three study groups, as follows: Group 1-non-exercising subjects receiving 35 mg calcium/kg body weight; Group 2-subjects receiving 35 mg calcium/kg body weight undergoing training routines for 90 min/day, 5 days a week and Group 3-subjects undergoing training routines for 90 min/day, 5 days a week. The testosterone levels were determined before and after supplementation, at rest and following a hard training routine. The plasma free- and total testosterone levels increased at exhaustion before and after supplementation relative to resting values (p < 0.05). This was also true when active subjects were compared to inactive subjects (p < 0.05). Our results show that training results in increased testosterone levels in athletes and that the increase is greater if accompanied by calcium supplementation, which may be useful for increasing overall athletic performance.
Article
Zinc administration in rats is associated with a rise in serum cholesterol level. This study examined the effect of zinc administration on serum lipoprotein values in man. Twelve healthy adult men ingested 440 mg of zinc sulfate per day for five weeks. High-density lipoprotein-cholesterol concentration decreased 25% below baseline values (40.5 to 30.1 mg/dL). Total cholesterol, triglyceride, and low-density lipoprotein-cholesterol levels did not change throughout the study. The sharp fall of the "antiatherogenic" lipoprotein, high-density lipoprotein, associated with zinc administration supports the concept that zinc ingestion may be atherogenic in man.(JAMA 244:1960-1961, 1980)
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Background: Physical activity has been reported to affect endocrine function in elderly men. Objective: To establish an association between regular moderate physical activity and endogenous anabolic hormone levels in healthy aging men. Participants: Twenty four middle-aged (57.4+/-4.7 years) and 24 elderly (68.3+/-2.6 years) physically active men who in the past 10 years had been regularly bicycling during leisure time were compared with 24 middle-aged (57.9+/-4.0 years) and 24 elderly (67.2+/-1.7 years) sedentary men. Groups did not differ for body composition. Measurements: Serum dehydroepiandrosterone sulfate (DHEAS), insulin-like growth factor-I (IGF-1), free testosterone (FT), and thyroid hormone levels were assessed. Results: In general, elderly men had lower IGF-1 (P<0.001), DHEAS (P=0.013), and triodothyronine levels (P<0.001) than their middle-aged counterparts. Independently of age, however, physically active men had on average higher IGF-1 (P=0.031), DHEAS (P=0.001), and triodothyronine serum levels (P<0.001) than sedentary men. FT and thyroid stimulating hormone (TSH) serum concentrations did not differ across age groups, but physically active men had lower TSH values than sedentary men (P=0.021). Conclusions: Our results suggest that, in aging men, regular moderate physical activity is associated with higher levels of IGF-1 and DHEAS levels and with thyroid function alterations.
Article
The present study aims to evaluate the effect of selenium supplementation on lipid peroxidation and lactate levels in rats subjected to acute swimming exercise. Thirty-two adult male rats of Sprague-Dawley type were divided into four groups. Group 1, control; group 2, selenium-supplemented; group 3, swimming control; group 4, selenium-supplemented swimming group. The animals in groups 2 and 4 were supplemented with (i.p.) 6 mg/kg/day sodium selenite for 4 weeks. The blood samples taken from the animals by decapitation method were analyzed in terms of erythrocyte-reduced glutathione (GSH), serum glutathione peroxidase (GPx) and superoxide dismutase (SOD), and plasma malondialdehyde (MDA) and lactate using the colorimetric method, and serum selenium values using an atomic emission device. In the study, the highest MDA and lactate values were found in group 3, while the highest GSH, GPx and SOD values were obtained in group 4 (p < 0,001). Group 2 had the highest and group 3 had the lowest selenium levels (p < 0,001). Results of the study indicate that the increase in free radical production and lactate levels due to acute swimming exercise in rats might be offset by selenium supplementation. Selenium supplementation may be important in that it supports the antioxidant system in physical activity.
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Non-glucoregulatory hormones (T4, T3, rT3, TSH and testosterone) were studied by radioimmunoassay in juvenile-type diabetics in moderate control and in ketosis due to insulin withdrawal and in age matched “normals” during a mild prolonged exercise test. The basal serum hormone levels revealed the following findings: Serum testosterone was markedly lower in diabetics than in normals (177 ± 24 resp. 618 ± 52 ng/dl). This is in contrast to other studies, but it may reflect decreased testicular function due to an early, clinically not apparent atherosclerotic disease. Serum T3 was significantly lower in diabetics than in normals (110 ± 16 resp. 145 ± 19), suggesting an early “low T3-syndrome” in juvenile-type diabetics. However, increased serum rT3 levels were not observed, and serum T4 and TSH were normal. Mild prolonged exercise had no major effects on these nonglucoregulatory hormones. In juvenile-type diabetics the degree of metabolic control had no influence on the response of the mentioned hormones. However, an increased cortisol/testosterone ratio in ketotic diabetics in the basal state with a further increase during exercise was demonstrated, indicating an aggravation of the catabolic state in these patients during exercise.
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Zinc is a very important element in the reproductive cycle of species. In humans, it is necessary for the formation and maturation of spermatozoa, for ovulation, and for fertilization. During pregnancy, zinc deficiency causes a number of anomalies: spontaneous abortion, pregnancy-related toxemia, extended pregnancy or prematurity, malformations, and retarded growth. Delivery is adversely affected by deficiency. These different effects of zinc can be explained by its multiple action on the metabolism of androgen hormones, estrogen and progesterone, together with the prostaglandins. Nuclear receptors for steroids are all zinc finger proteins. Zinc supplementation has already proven beneficial in male sterility and in reducing complications during pregnancy. However, it would be worth conducting larger-scale trials to confirm these beneficial effects.