In this vid, I discuss the popular “Testosterone booster” supplement D-Aspartic Acid (DAA) and update my opinions of this general category of supplements. Note the 2015 study below  published  found at higher doses, it actually lowered testosterone. The 2016 study, found no impact on T levels, but improvements in strength on squats and a positive “trend” on the bench press.


Study mentioned in the vid:

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


This new study found no impact on T or body composition, but did find a statistically significant effect on strength. The study was short and given more time, it’s possible there would be improvements  in body comp (as being able to lift more weight in a given lift usually leads to positive changes in body comp) but it was a short lived and small study, so no real conclusions can be made from the results, other than DAA appears to have increased lifts in the short time period. It’s also possible, especially when viewing it in the larger picture of other studies, the DAA was not responsible for the effects found in the study and it was due to some confounding variables they didn’t account for.

Effect of Aspartate Supplementation on Athletic Performance and Testosterone Levels in Young Men

April 2016 The FASEB Journal vol. 30 no. 1 Supplement 898.12

D-aspartic acid has been suggested to enhance athletic performance by regulating the hypothalamus-pituitary-gonadal axis by increasing plasma testosterone. Aspartate supplementation may be useful to increase testosterone for individuals with low plasma testosterone due to aging and other conditions.

PURPOSE: To determine the effect of D-aspartic acid supplementation on athletic performance and testosterone production in young male athletes.

METHODS: After screening for ACSM low risk, 15 healthy male athletes (average age = 22y, body weight = 79.1 kg and body fat = 9.2%) were randomized to two groups for supplementation using a double blinded parallel arm experimental design. They ingested either 3 grams of d-aspartic acid (Aspartate, n=9) or a Placebo (n=6) for 14 days supplied in capsule form. Subjects recorded and replicated previous 3 day diets prior to testing. Physical assessments were performed prior to and after supplementation included a peak VO2 test by cycle ergometer, 1 maximal repetition bench press and 1 maximal repetition squat (average values ±SD before supplementation were 41.7 ±6.4 ml/kg/min, 117.9 ±11.1 kg and 151.7 ±19.0 kg, respectively).

RESULTS: The Aspartate group had a positive trend in performance during the 1 maximal repetition bench press by 3.5 ±6.8kg (average ±SEM, p=0.06) and a significant increase in the 1 maximal repetition squat by 8.5 ±10.5kg (average ±SEM, p=0.013). No change in performance measures were observed in the Placebo group. There was no change in testosterone levels in the control group: Pre-731.2± 70.4 ng/dL, Post-733.7± 77.8ng/dL (average±SEM) or in the experimental group: Pre-720.56±79.9ng/dL, Post-719.8±72.8ng/dL (average±SEM). Body composition did not change for either group.

CONCLUSION: D-aspartic acid supplementation may lead to improved acute skeletal muscle synthesis improving upper and lower body muscle performance. D-Aspartic Acid supplementation does not have a significant effect on testosterone levels and the time point observed.

Abstract HERE

2015 study and additional comments:

The criticism of some to prior studies was that it was possible higher doses were needed to impact T levels in younger resistance trained men. This study just out below found higher doses actually decreased testosterone! And the study was done on the appropriate population, resistance trained men, although they didn’t test the impact on TT and FT on strength or LBM as the prior study above did. The two studies combined however, do not paint a good picture for DAA in my view. This only lowers, my already low opinion of “T boosters” as a category of supplements…

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

Journal of the International Society of Sports Nutrition 2015, 12:15



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.


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.


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).


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.

Full paper HERE




Will Brink is the owner of the Brinkzone Blog. Will has over 15 years experience as a respected author, columnist and consultant, to the supplement, fitness, bodybuilding, and weight loss industry and has been extensively published. Will graduated from Harvard University with a concentration in the natural sciences, and is a consultant to major supplement, dairy, and pharmaceutical companies.


His often ground breaking articles can be found in publications such as Lets Live, Muscle Media 2000, MuscleMag International, The Life Extension Magazine, Muscle n Fitness, Inside Karate, Exercise For Men Only, Body International, Power, Oxygen, Penthouse, Women’s World and The Townsend Letter For Doctors.


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