D-aspartic acid supplementation combined with 28 days of heavy resistance training has no effect on body composition, muscle strength, and serum hormones associated with the hypothalamo-pituitary-gonadal axis in resistance-trained men.
Study Goal
The researchers aimed to determine whether D-aspartic acid supplementation increases endogenous testosterone levels or improves muscular performance in resistance-trained men.
Results Summary
The study found no significant changes in testosterone levels or muscle strength with D-aspartic acid supplementation compared to placebo, though body composition and strength improved equally in both groups due to resistance training. Serum D-aspartate oxidase levels increased slightly in the D-ASP group.
Population
Resistance-trained men
Effective Dosage
3 g/day
Duration
28 days
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
resistance training | increase | body composition | resistance-trained men | - | significantly increased | #1 |
resistance training | increase | muscle strength | resistance-trained men | - | significantly increased | #2 |
D-ASP supplementation | no change | total testosterone | resistance-trained men | - | unchanged | #3 |
D-ASP supplementation | no change | free testosterone | resistance-trained men | - | unchanged | #4 |
D-ASP supplementation | no change | luteinizing hormone | resistance-trained men | - | unchanged | #5 |
D-ASP supplementation | no change | gonadotropin-releasing hormone | resistance-trained men | - | unchanged | #6 |
D-ASP supplementation | no change | estradiol | resistance-trained men | - | unchanged | #7 |
D-ASP supplementation | increase | serum D-ASP | resistance-trained men | - | slight increase | #8 |
D-ASP supplementation | increase | serum DDO | resistance-trained men | - | slight increase | #9 |
D-ASP supplementation | increase | serum DDO | resistance-trained men | - | significantly increased | #10 |
D-ASP supplementation | no change | gonadal hormones | resistance-trained men | - | unaffected | #11 |
D-ASP supplementation | no change | activity of the hypothalamo-pituitary-gonadal axis | resistance-trained men | - | ineffective in up-regulating | #12 |
D-ASP supplementation | no change | skeletal muscle | resistance-trained men | - | has no anabolic or ergogenic effects | #13 |
It was hypothesized that D-aspartic acid (D-ASP) supplementation would not increase endogenous testosterone levels or improve muscular performance associated with resistance training. Therefore, body composition, muscle strength, and serum hormone levels associated with the hypothalamo-pituitary-gonadal axis were studied after 28 days of resistance training and D-ASP supplementation. Resistance-trained men resistance trained 4 times/wk for 28 days while orally ingesting either 3 g of placebo or 3 g of D-ASP. Data were analyzed with 2 × 2 analysis of variance (P < .05). Before and after resistance training and supplementation, body composition and muscle strength, serum gonadal hormones, and serum D-ASP and d-aspartate oxidase (DDO) were determined. Body composition and muscle strength were significantly increased in both groups in response to resistance training (P < .05) but not different from one another (P > .05). Total and free testosterone, luteinizing hormone, gonadotropin-releasing hormone, and estradiol were unchanged with resistance training and D-ASP supplementation (P > .05). For serum D-ASP and DDO, D-ASP resulted in a slight increase compared with baseline levels (P > .05). For the D-ASP group, the levels of serum DDO were significantly increased compared with placebo (P < .05). The gonadal hormones were unaffected by 28 days of D-ASP supplementation and not associated with the observed increases in muscle strength and mass. Therefore, at the dose provided, D-ASP supplementation is ineffective in up-regulating the activity of the hypothalamo-pituitary-gonadal axis and has no anabolic or ergogenic effects in skeletal muscle.