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Original Studies |
Exercise Biochemistry Laboratory (G.A.B., E.R.M., M.L.K., W.D.F., D.A.J., D.S.K.), Department of Health and Human Performance, Iowa State University, Ames Iowa 50011; and Human Performance Laboratory (M.D.V.), South Dakota State University Department of HPER, Brookings, South Dakota
Address all correspondence and requests for reprints to: Douglas S. King, Ph.D., Department of Health and Human Performance, 248 Forker Building, Iowa State University, Ames, Iowa 50011. E-mail: dsking{at}iastate.edu
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Abstract |
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 Top Abstract IntroductionSubjects and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Recently, Wallace et al. (10) examined the effects of ingesting 100 mg/day ASD for 12 wk on serum testosterone, DHEA, ASD, prostate-specific antigen (PSA), and insulin-like growth factor-1 in 40- to 60-yr-old men. The hormonal and lipid response to a larger dose of ASD in older men is unknown. Therefore, we evaluated the effects of 100 mg ASD, ingested three times per day for 28 days, on serum free testosterone, total testosterone, estradiol, dihydrotes-tosterone (DHT), PSA, and serum lipid concentrations in 30- to 56-yr-old men. Wallace et al. (10) found no differences in measurements of well-being and libido between placebo (PL) and 100-mg/day ASD ingestion in older men. Therefore, we also evaluated the effect of chronic ASD ingestion on perception of mood states in 30- to 56-yr-old men.
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Subjects and Methods |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Fifty-six men, 30–56 yr old, were recruited from the university and local community to participate in this project. All subjects signed an informed consent, and completed a written medical history to eliminate any subjects with any known chronic disease. Before participating in this study, subjects were questioned to ensure that they were not currently or previously using nutritional supplements. The Iowa State University’s human subjects review board approved this study. Subjects were stratified into age groups representing the fourth (30-yr-olds, n = 20), fifth (40-yr-olds, n = 20), and sixth (50-yr-olds, n = 16) decades.
Supplementation
Subjects were randomly assigned (in a double-blind,
counterbalanced fashion) to treatment groups consuming capsules
containing either PL or 300 mg/day ASD in doses of 100 mg taken three
times daily (Experimental and Applied Sciences, Golden, CO). An
independent laboratory (Integrated Biomolecule, Tuscon, AZ) verified
purity (
99%) and content of the ASD capsules via high-performance
liquid chromatography (HPL-C). Subjects were instructed to consume the
supplement capsules daily before 0900 h, at 1500 h, and
before bedtime, in equal doses throughout the 4 weeks of
supplementation. Compliance was monitored through written records of
supplementation and the return of unused supplements at the completion
of the study.
Diet and activity
Subjects were instructed to maintain their normal diet and activity patterns throughout the 4-week study period. Subjects were given verbal and written instructions regarding the reporting of dietary intake and were instructed to maintain a diet, medication, and exercise record for the 2 days before each blood sampling. The diet and exercise records were collected before weekly blood sampling and were analyzed using commercial software (Nutritionist 4, N-Squared Computing, San Bruno, CA).
Blood sample collection and analysis
Fasting blood samples were collected between 0630 and 0800 h, once per week, on the same day each week. Subjects reclined while blood samples were obtained, without stasis, from an antecubital vein. Blood samples were immediately placed in an ice bath until centrifugation and serum separation. Blood samples were analyzed for lipid, glucose, enzyme, and chemical composition by a commercial laboratory (Quest Diagnostics, Inc., Wood Dale, IL). Serum concentrations of estradiol, total testosterone, free testosterone, and ASD were measured with commercial RIA kits (Diagnostic Products, Los Angeles, CA; and Diagostic Systems Laboratories, Inc., Webster, TX). Commercially available enzyme-linked immunosorbent assays were used to measure serum concentrations of PSA (Bio-Clin, Inc, St. Louis, MO) and DHT (Immuno-Biological Laboratories, Hamburg, Germany). All samples for each subject were analyzed in duplicate within the same assay; and the intraassay coefficients of variation for total testosterone, free testosterone, estradiol, ASD, DHT, and PSA were 6.1, 7.2, 6.6, 5.8, 3.2, and 6.6%, respectively. According to the suppliers of the RIA and enzyme-linked immunosorbent assay kits, there is no detectable cross-reactivity of the assays for ASD , DHT, estradiol, or testosterone.
Profile of mood states
Subjects completed and returned questionnaires each week, assessing perceptions of health and well-being (11). Questionnaires consisted of yes-or-no questions assessing changes in libido, symptoms of illness, or mood change for the 3 days before blood sampling.
Calculations and statistics
Data were analyzed using commercial software (SPSS, Inc., Chicago, IL). Statistical analyses of age group effects were performed using a 3-factor (week by supplement by age group) repeated-measures ANOVA. Specific mean differences (P < 0.05) were identified using Student’s Newman-Keuls post hoc comparisons. Relationships between the effects of supplementation and measured variables were analyzed using simple linear regression. The percent change in serum hormones and blood lipids was calculated as the mean percent change in serum concentrations during weeks 1–4. Data are presented as means ± SE.
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Results |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Subjects came from diverse occupations and physical activity
levels. Regular participation in aerobic exercise (such as walking,
jogging, and racquetball) was reported in 10 PL subjects and 12 ASD
subjects, whereas 6 PL and 5 ASD subjects reported regular
participation in resistance training. Subjects reported no changes in
their day-to-day physical activity pattern throughout the study
duration, including the day before blood sampling. Height, body mass,
and body mass index (BMI) were not different between treatment or age
groups (Table 1
). Body mass and BMI were
not altered by supplementation. One 50-yr-old subject in the PL group
was diagnosed with noninsulin-dependent diabetes mellitus during the
study, was informed of his condition, and his data have been excluded
from all analyses.
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There were no significant age or treatment group differences in dietary energy, protein, carbohydrate, total fat, saturated fat, or polyunsaturated fat intake.
Hormonal response to supplementation
Basal serum ASD levels were higher in the 30-yr-olds
(P < 0.05) than in the 40- or 50-yr-olds (Fig. 1). Ingestion of ASD resulted in
significant and similar mean increases of 268, 300, and 357% in serum
ASD concentrations throughout the 4 weeks of supplementation for 30-,
40-, and 50-yr-olds, respectively (P < 0.05). Mean
changes in serum ASD concentrations in ASD subjects during weeks 1–4
were not correlated to age (r2 = 0.024) or BMI
(r2 = 0.00).
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). There was also no age-related effect
of supplementation on serum total testosterone concentrations
(r2 = 0.018).
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). Ingestion of ASD resulted in elevated
serum concentrations of free testosterone during weeks 1–4
(P < 0.05), by 37, 51, and 46% for the 30-, 40-, and
50-yr-olds, respectively. The change in serum free testosterone
concentrations was related to basal free testosterone concentrations
(r2 = 0.284) but not to age
(r2 = 0.00) or BMI (r2 =
0.038).
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). Serum DHT was
unchanged throughout the 4-week supplementation period in PL
subjects, whereas ingestion of ASD increased (P
< 0.05) serum DHT concentrations in the 30-, 40-, and 50-yr-olds by
56, 81, and 113%, respectively, throughout the 4-week supplementation
period. There was a significant (P < 0.05)
relationship between age and the mean increase in serum DHT during the
4 weeks of ASD supplementation (r2 = 0.244). BMI
did not correlate with changes in serum DHT (r2 =
0.023).
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). There was no relationship between age
and the mean increase in serum estradiol throughout weeks 1–4 in ASD
subjects (r2 = 0.029). The mean increase in serum
estradiol concentrations throughout weeks 1–4 was also unrelated to
the BMI (r2 = 0.133).
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)
were initially higher (P < 0.05) for the 50-yr-olds
taking ASD (4.4 ± 0.6 ng-mL) than any other age or supplement
group (2.5 ± 0.4 ng/mL for all others combined). However, serum
PSA concentrations were not altered during the 4 weeks of
supplementation.
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Serum high-density lipoprotein cholesterol (HDL-C) levels were
reduced by 10% (P < 0.05) at week 1 in ASD subjects
and remained depressed throughout the remainder of the 4 weeks of
supplementation, with no observed age-related effect
(r2 = 0.037; Table 2). There was a significant inverse
correlation between the mean changes throughout weeks 1–4 in serum ASD
and HDL-C concentrations (r2 = 0.284).
Concentrations of serum low-density lipoprotein cholesterol (LDL-C),
total cholesterol (Total-C), and the Total-C/HDL cholesterol ratio were
not changed in either ASD or PL.
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Serum concentrations of 
-glutamyltransferase, aspartate
aminotransferase, and alanine aminotransferase were unchanged
throughout the 4-week supplementation period and were not affected by
age. There were also no age- or supplement-related changes in
concentrations of serum protein, albumin, globulin, or other indices of
blood chemistry.
Profile of mood states
Decreased libido was reported on 1 occasion by 2 PL subjects and on 1 occasion by 1 ASD subject during the 4-week supplementation period, whereas increased libido was reported 6 times by 4 subjects on PL and 8 times by 4 subjects on ASD, suggesting that libido is not altered by ASD ingestion. There were no differences between PL and ASD in the frequency of reported changes in energy level, memory, stress, appetite, chest pain, headaches, or overall sense of health. The most commonly reported side effect of supplementation was heartburn, with an increased frequency of heartburn reported on 13 occasions by 10 subjects on ASD and 5 occasions by 5 subjects on PL.
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Discussion |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Two recent studies concluded that serum total testosterone concentrations in men increase after ingestion of ASD (5, 12). Earnest et al. (12) reported that the incremental area under the curve for serum testosterone concentrations, during 90 min after the ingestion of 200-mg ASD, was higher than with PL. However, neither free nor total testosterone concentrations were significantly higher at any time point after ingestion of ASD. In addition, the values reported for the area under the curve apparently included the area attributable to baseline serum testosterone concentrations, which were slightly higher in the group of subjects ingesting ASD. In agreement with the present results, as well as our previous findings (3, 4), Leder et al. (5) observed that ingestion of 100-mg ASD did not increase serum total testosterone concentrations. In contrast, these authors observed that serum testosterone concentrations during 8 h after a single 300-mg ASD dose increased by 34%. Because blood samples in the current study were collected approximately 10 h after the previous 100-mg dose of ASD, it was not possible to assess peak hormonal changes after ASD ingestion. Our previous research indicates that after ingesting 100 mg ASD, peak increases in serum ASD concentrations occur approximately 120–300 min after ingestion, while changes in serum estradiol concentrations are not evident during the 6 h after ingestion, and serum total testosterone concentrations are not altered (3, 4). Although transient increases in serum total testosterone after ingestion of 100 mg of ASD cannot be ruled out, the present results support our previous findings (3, 4) and those of others (2, 5, 10) that total testosterone concentrations are not chronically increased by ingestion of ASD in doses of up to 300 mg per day, when taken in 100 mg doses. The current study extends these findings by demonstrating that ingestion of 100 mg of ASD three times daily does not alter serum total testosterone concentrations in middle-aged men.
A novel finding was that, whereas serum total testosterone was unaffected, serum free testosterone increased by 37–51% in these 30- to 56-yr-old men. These results are in contrast to our previous finding that 100 mg of ASD three times daily does not chronically increase serum free testosterone concentrations in 23-yr-old men (3, 4). Consistent with the previously observed age-related declines in serum free testosterone concentrations (7, 8, 9), the serum free testosterone concentrations in the current subjects were lower than in the younger subjects in our previous research (3, 4). In addition, the mean increase in serum free testosterone concentrations during weeks 1–4 was significantly related to basal serum free testosterone concentrations in the current study. These findings suggest that oral ASD ingestion may promote increases in serum free testosterone concentrations in men with low serum free testosterone concentrations.
The finding of unchanged serum total testosterone, albumin, and protein concentrations, together with the significant increase in free testosterone concentrations, suggests that ingestion of 100 mg ASD three times daily changes the concentration of SHBG bound testosterone. Although ASD is a weaker androgen than testosterone (13), exogenous testosterone administration decreases serum SHBG concentrations (14). In addition, because SHBG may have a greater binding affinity for DHT than for testosterone (15), it is also possible that the increase in serum free testosterone concentrations that we observed was a result of a decoupling of SHBG from testosterone, to bind with DHT or other steroids.
The metabolic significance of the transient increase in serum total
testosterone concentrations found by Leder et al.
(5) and the chronic elevation of free testosterone in the
present study is uncertain. Increased rates of muscle protein synthesis
(16) and increased muscular strength (14, 16)
have been observed after testosterone administration resulting in very
large increases in serum testosterone concentrations (100–600%).
It is unknown whether more prolonged, small elevations in serum
testosterone concentrations, of the magnitude observed in the current
study and by Leder et al. (5), would produce
measurable effects on muscle size and strength.
The significant increase in the serum DHT concentrations observed in
the current study suggests that a significant amount of the elevated
serum ASD and free testosterone underwent conversion to DHT. The
conversion of ASD to DHT can occur in prostate, skin, or adipose
tissue, which all contain appreciable concentrations of 5
-reductase
(13, 17, 18). Longcope and Fineberg (17)
estimated that 14% of total serum ASD is converted to DHT in adipose
tissue alone. Serum ASD concentrations increased by approximately 19
nmol/L, and serum DHT concentrations increased by approximately 1500
pmol/L in the present study, corresponding to an 8% conversion of ASD
to DHT. Although the increases in serum DHT concentrations were weakly
related to age (r2 = 0.24), consistent with
age-related increases in 5-reductase concentrations
(19), the mean DHT concentrations were not different
during weeks 1–4 in the three age groups. These findings suggest that
ASD ingestion will increase serum DHT concentrations in men of all
ages.
Although DHT is the most potent naturally occurring androgen, the
metabolic effects of DHT seem to occur primarily in reproductive
organs, because skeletal muscle tissue does not contain appreciable
quantities of 5-reductase (13, 17). Recently, it has
been observed that the administration of DHT to castrated rats restored
the levator ani and bulbocavernosus muscles to precastration size but
had no effect on the size of plantaris muscle (20),
supporting the notion that the anabolic effect of DHT is limited to
tissues involved with reproduction. Although we did not measure serum
DHT in our previous study in which ASD intake did not alter muscle size
or strength in 19- to 29-yr-old men (4), it is likely that
serum DHT concentrations during supplementation were similar to those
observed in the present study. Taken together, these findings suggest
that the increases in circulating DHT observed in the current study are
unlikely to have any anabolic effects on skeletal muscle of older
men.
In agreement with previous observations in young men (2, 3, 4, 5, 6), ingestion of ASD caused a significant increase in serum estradiol concentrations in the middle-aged men in the current study, providing evidence that a portion of ingested ASD is aromatized (21, 22). Aromatization can occur in a number of tissues, including adipose tissue (21, 23, 24). Although adipose tissue contains aromatase (23) and the degree of obesity has been related to enhanced aromatization of ASD (25), we found no relationship between the change in serum estradiol concentrations and body mass or BMI. Though our subjects were slightly overweight (110% of ideal body weight), the aromatization of ASD may not be affected by adiposity until 120% of ideal body weight is reached (see Ref. 30). In addition, the enzyme kinetics for the aromatization of ASD (Km = 25 nmol/L) (23) favor the production of estrogens, compared with the 17ß-HSD conversion of ASD to testosterone (Km = 1,500 nmol/L) (26).
The reduction in serum HDL-C associated with ingestion of 100 mg ASD, three times per day, is in agreement with our previous research in young men (3, 4). A decrease of 0.13 mmol/L in serum HDL-C concentrations corresponds to a 10–15% increase in the risk of atherosclerotic lesion development (27) and heart disease (28). Though ingestion of 50 mg ASD, twice daily for 12 weeks, does not alter serum HDL-C in middle-aged men (10), ingestion of 100 mg ASD three times daily reduces serum HDL-C concentrations by 15% (present study and Refs. 3, 4), suggesting that the dosage of ASD may affect the serum lipid response to ASD ingestion.
Though the initial serum PSA concentrations in the 50-yr-olds consuming ASD were above average and may reflect altered prostate function, serum PSA concentrations were not changed by supplementation in any age group. The use of PSA measurements to evaluate prostate function, however, should be viewed cautiously. For example, it has been reported that 30% of patients with prostatic tumors present with normal PSA concentrations, whereas elevated PSA concentrations are found in approximately 2% of healthy men (29). In addition, because elevated serum DHT and estradiol concentrations may cause benign prostate hypertrophy (30), and the blockade of adrenal androgens is advised for the remediation of benign prostate hypertrophy (18), it is possible that more prolonged ASD supplementation may result in detectable changes in prostate function.
Ingesting 50 mg ASD, twice daily for 12 weeks, did not change perceived health or mood in middle-aged men (10). In the present study, there was no difference in the perceptions of mood, health, or libido between subjects ingesting PL or ASD . Taken together, these results suggest that short-term ingestion of ASD, at the doses of 50 mg twice daily or 100 mg three times daily, are associated with no psychological or emotional benefits.
The effects of the 55–80% elevation in estradiol concentrations in the current study are not clear. Although estrogens may produce favorable changes in lipid profiles and cardiovascular reactivity (31), a 21% higher serum estradiol concentration has been observed in male subjects experiencing myocardial infarction, compared with those with no heart disease (32). Increased serum estradiol levels in men have been associated with the development of gynecomastia (24). Though a cause-and-effect relationship has not been established, increased serum ASD concentrations have also been observed in patients with pancreatic carcinoma (33). Thus, the changes in the hormonal milieu associated with ASD ingestion may increase the risk for additional adverse health consequences.
Although there has been speculation that consumers of ASD use doses much higher than have been studied (34), the dosage of ASD used by consumers and the effects of larger doses of ASD are unknown. Moreover, it is likely that any possible benefit of raising serum testosterone concentrations by ingesting higher doses of ASD would be associated with larger increases in serum estradiol, DHT, and a larger decrease in serum HDL-C concentrations.
In summary, ingestion of 100 mg ASD three times per day did not alter serum total testosterone concentrations in 30- to 56-yr-old men. Ingestion of ASD produced elevated serum free testosterone, ASD , estradiol, and DHT concentrations and reduced serum HDL-C concentrations. There was also no change in perceived mood, health, or libido associated with ASD ingestion in 30- to 56-yr-old men. Our results suggest that ingesting 100 mg ASD three times daily is unlikely to provide a desirable hormonal milieu for promoting increases in muscle size and may lead to untoward health effects.
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Footnotes |
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Received February 21, 2000.
Revised June 6, 2000.
Revised July 17, 2000.
Accepted July 30, 2000.
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References |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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-dihydrotestosterone and
17ß- estradiol. Prostate. 26:325–333.[Medline]
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
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, 40- and
50-yr-olds different from 30-yr-olds (main group effect,
P < 0.05).
