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Three and six grams supplementation of d-aspartic acid in resistance trained men.

Melville GW, Siegler JC, Marshall PW - J Int Soc Sports Nutr (2015)

Bottom Line: D-aspartic acid supplementation revealed no main effect for group in: estradiol; sex-hormone-binding-globulin; and albumin.Total testosterone was significantly reduced in D6 (P = 0.03).Analysis did not reveal any significant differences between D3 and D0.

View Article: PubMed Central - PubMed

Affiliation: School of Science & Health, University of Western Sydney, Campbelltown Campus, Locked Bag 1797, Penrith, NSW 2751 Australia.

ABSTRACT

Background: Although abundant research has investigated the hormonal effects of d-aspartic acid in rat models, to date there is limited research on humans. Previous research has demonstrated increased total testosterone levels in sedentary men and no significant changes in hormonal levels in resistance trained men. It was hypothesised that a higher dosage may be required for experienced lifters, thus this study investigated the effects of two different dosages of d-aspartic acid on basal hormonal levels in resistance trained men and explored responsiveness to d-aspartic acid based on initial testosterone levels.

Methods: Twenty-four males, with a minimum of two years' experience in resistance training, (age, 24.5 ± 3.2 y; training experience, 3.4 ± 1.4 y; height, 178.5 ± 6.5 cm; weight, 84.7 ± 7.2 kg; bench press 1-RM, 105.3 ± 15.2 kg) were randomised into one of three groups: 6 g.d(-1) plain flour (D0); 3 g.d(-1) of d-aspartic acid (D3); and 6 g.d(-1) of d-aspartic acid (D6). Participants performed a two-week washout period, training four days per week. This continued through the experimental period (14 days), with participants consuming the supplement in the morning. Serum was analysed for levels of testosterone, estradiol, sex hormone binding globulin, albumin and free testosterone was determined by calculation.

Results: D-aspartic acid supplementation revealed no main effect for group in: estradiol; sex-hormone-binding-globulin; and albumin. Total testosterone was significantly reduced in D6 (P = 0.03). Analysis of free testosterone showed that D6 was significantly reduced as compared to D0 (P = 0.005), but not significantly different to D3. Analysis did not reveal any significant differences between D3 and D0. No significant correlation between initial total testosterone levels and responsiveness to d-aspartic acid was observed (r = 0.10, P = 0.70).

Conclusions: The present study demonstrated that a daily dose of six grams of d-aspartic acid decreased levels of total testosterone and free testosterone (D6), without any concurrent change in other hormones measured. Three grams of d-aspartic acid had no significant effect on either testosterone markers. It is currently unknown what effect this reduction in testosterone will have on strength and hypertrophy gains.

No MeSH data available.


Related in: MedlinePlus

The absolute change of free testosterone. *statistically significant (P < 0.05).
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Fig2: The absolute change of free testosterone. *statistically significant (P < 0.05).

Mentions: Analysis of the POST values revealed no main effect for group with E2 (P = 0.47), SHBG (P = 0.07) and ALB (P = 0.32). Post values of D6 TT were significantly reduced (~12.5%) as compared to the pre values (P = 0.03; 5.9 to 5.1 ng.ml−1). FT in group D6 was significantly decreased (429.1 to 363.4 pmol.l−1) as compared to D0 (439.6 to 480.9 pmol.l−1) (P = 0.005) but not D3 (534.9 to 524.3 pmol.l−1) (P = 0.06) (Figure 2). Diet analysis revealed no significant changes in macronutrient (CHO: P = 0.74; PRO: P = 0.99; FAT: P = 0.54) and caloric intakes (P = 0.64) during the study. Regression analysis revealed no significant correlation between baseline total testosterone levels and total testosterone change (r = 0.10, P = 0.70), and no significant correlation between baseline free testosterone and free testosterone change (r = 0.32, P = 0.23).Figure 2


Three and six grams supplementation of d-aspartic acid in resistance trained men.

Melville GW, Siegler JC, Marshall PW - J Int Soc Sports Nutr (2015)

The absolute change of free testosterone. *statistically significant (P < 0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4384294&req=5

Fig2: The absolute change of free testosterone. *statistically significant (P < 0.05).
Mentions: Analysis of the POST values revealed no main effect for group with E2 (P = 0.47), SHBG (P = 0.07) and ALB (P = 0.32). Post values of D6 TT were significantly reduced (~12.5%) as compared to the pre values (P = 0.03; 5.9 to 5.1 ng.ml−1). FT in group D6 was significantly decreased (429.1 to 363.4 pmol.l−1) as compared to D0 (439.6 to 480.9 pmol.l−1) (P = 0.005) but not D3 (534.9 to 524.3 pmol.l−1) (P = 0.06) (Figure 2). Diet analysis revealed no significant changes in macronutrient (CHO: P = 0.74; PRO: P = 0.99; FAT: P = 0.54) and caloric intakes (P = 0.64) during the study. Regression analysis revealed no significant correlation between baseline total testosterone levels and total testosterone change (r = 0.10, P = 0.70), and no significant correlation between baseline free testosterone and free testosterone change (r = 0.32, P = 0.23).Figure 2

Bottom Line: D-aspartic acid supplementation revealed no main effect for group in: estradiol; sex-hormone-binding-globulin; and albumin.Total testosterone was significantly reduced in D6 (P = 0.03).Analysis did not reveal any significant differences between D3 and D0.

View Article: PubMed Central - PubMed

Affiliation: School of Science & Health, University of Western Sydney, Campbelltown Campus, Locked Bag 1797, Penrith, NSW 2751 Australia.

ABSTRACT

Background: Although abundant research has investigated the hormonal effects of d-aspartic acid in rat models, to date there is limited research on humans. Previous research has demonstrated increased total testosterone levels in sedentary men and no significant changes in hormonal levels in resistance trained men. It was hypothesised that a higher dosage may be required for experienced lifters, thus this study investigated the effects of two different dosages of d-aspartic acid on basal hormonal levels in resistance trained men and explored responsiveness to d-aspartic acid based on initial testosterone levels.

Methods: Twenty-four males, with a minimum of two years' experience in resistance training, (age, 24.5 ± 3.2 y; training experience, 3.4 ± 1.4 y; height, 178.5 ± 6.5 cm; weight, 84.7 ± 7.2 kg; bench press 1-RM, 105.3 ± 15.2 kg) were randomised into one of three groups: 6 g.d(-1) plain flour (D0); 3 g.d(-1) of d-aspartic acid (D3); and 6 g.d(-1) of d-aspartic acid (D6). Participants performed a two-week washout period, training four days per week. This continued through the experimental period (14 days), with participants consuming the supplement in the morning. Serum was analysed for levels of testosterone, estradiol, sex hormone binding globulin, albumin and free testosterone was determined by calculation.

Results: D-aspartic acid supplementation revealed no main effect for group in: estradiol; sex-hormone-binding-globulin; and albumin. Total testosterone was significantly reduced in D6 (P = 0.03). Analysis of free testosterone showed that D6 was significantly reduced as compared to D0 (P = 0.005), but not significantly different to D3. Analysis did not reveal any significant differences between D3 and D0. No significant correlation between initial total testosterone levels and responsiveness to d-aspartic acid was observed (r = 0.10, P = 0.70).

Conclusions: The present study demonstrated that a daily dose of six grams of d-aspartic acid decreased levels of total testosterone and free testosterone (D6), without any concurrent change in other hormones measured. Three grams of d-aspartic acid had no significant effect on either testosterone markers. It is currently unknown what effect this reduction in testosterone will have on strength and hypertrophy gains.

No MeSH data available.


Related in: MedlinePlus