DAA and Testosterone: A Complete Scientific Review
D-Aspartic acid (DAA) is a widespread ingredient in test booster supplements.
Companies claim that it is scientifically proven to work. But is it true?
This article will go over the five human trials that studied the interaction between D-AA and testosterone and my analysis between the two.
TL;DR: D-AA supplementation seems to increase testosterone levels in the short-term (6-12 days). Although this increase may persist in infertile men, T-levels return to baseline within a month or so in otherwise healthy men.
What is D-Aspartic Acid?
D-Aspartic acid is an alternate form of the amino acid known as Aspartate.
Amino acids are the building blocks of protein, and Aspartate is one of the 20 main structural amino acids.
D-AA is naturally present in the human body, primarily in the pineal and pituitary glands. The pituitary is the area of your brain that triggers the production of anabolic hormones.
D-AA has been shown to increase the secretion of Gonadotropin-releasing hormone (GnRH), which, in turn, increases the release of Luteinizing hormone (LH) (1). LH is the precursor for testosterone synthesis, so D-AA supplementation has been theorized to increase T-levels in the body.
Rat studies have shown D-AA injections to increase testosterone levels by up to 300% (2), but this does not mean that the same effect carries on to humans as well.
Does D-AA Increase Testosterone In Humans?
After scrounging the web, I was able to find five human studies that observed the interaction between D-AA supplementation and testosterone. My aim with the rest of this article is to go over each of these trials so that you can know for sure whether D-AA boosts testosterone or not.
Human Trial #1
Effect
Increase
Trial Design
Double-blind
Trial Length
12 days
Number of Subjects
43
Gender
Male
Body Type
Healthy
Methods
Forty-three healthy men (without ED), aged 27-37, were given a daily dose of either 3.12 grams of D-aspartate or placebo for 12 days.
Blood samples from each participant were collected at six days of treatment, 12 days of treatment, and three days after the treatment ended.
Results
Twelve days after treatment, the men receiving D-aspartate experienced, on average, a 33% increase in LH and a 42% increase in total testosterone levels.
Three days after the treatment was over, LH levels dropped by 14% and total T by about 9%.
My takeaway: D-AA seems to have potent testosterone-boosting properties in the short-term; a 42% increase in 12 days is no joke.
Human Trial #2
Effect
None
Trial Design
Double-blind
Trial Length
28 days
Number of Subjects
20
Gender
Male
Body Type
Resistance-trained
Methods
Resistance-trained men received a daily dose of either 3g of D-aspartic acid or placebo for 28 days. During this time, they were also put on a 4-day/week resistance-training program.
Body composition, muscular strength, and anabolic hormone measurements were taken once before the experiment began and once at the 28-day mark.
Results
Researchers found that all the variables measured remained relatively the same across both groups. They concluded that D-AA supplementation is not associated with increases in muscular strength or anabolic hormone concentrations.
My takeaway: Compared to Human Trial #1 (which lasted only 12 days), this study took place over 28 days. So although D-AA supplementation may boost testosterone over the short term, the effect does not seem to prolong past the 28-day mark.
Human Trial #3
Effect
Increase
Trial Design
Cohort
Trial Length
90 days
Number of Subjects
60
Gender
Male
Body Type
Infertile
Methods
60 infertile men were split into two groups based on their sperm quality:
- Oligo-asthenozoospermia (reduced sperm motility and low sperm count)
- Asthenozoospermia (reduced sperm motility)
Sperm motility refers to how well the sperm in a given semen sample are moving. Sperm count is measured as the amount of sperm/mL of semen.
Each man was given a daily dose of 2.66g of D-aspartic acid over 90 days.
Semen samples were collected by masturbation - once before D-AA supplementation and once at the 90-day mark. Blood samples were also collected.
Results
In oligo-asthenozoospermic patients, D-AA supplementation increased total sperm count by 52% and sperm motility by 78%.
In asthenozoospermic patients, D-AA supplementation increased total sperm count by 57% and sperm motility by 81%.
Another interesting finding of the study was an increased pregnancy rate in the treated patients’ partners by 26.6%.
Also, LH and testosterone levels increased between 30-60%.
My takeaway: D-AA supplementation seems to be very effective at increasing fertility and testosterone levels in infertile men.
Human Trial #4
Effect
None
Trial Design
Double-blind
Trial Length
14 days
Number of Subjects
15
Gender
Male
Body Type
Healthy
Methods
Fifteen healthy men (average age=22) were randomly assigned to ingest a daily dose of either 3g of D-AA or placebo over 14 days.
Blood samples were taken once before the experiment and once at the 14-day mark.
Strength measurements, as the 1-rep maximum on the bench press and squat, were also recorded. Once before and once after 14 days of D-AA supplementation.
Results
The subjects given D-AA experienced increased strength levels (3% stronger on the bench press and 5.6% stronger on squat), while the placebo did not.
Testosterone levels across both groups, however, remained relatively unchanged.
My takeaway: Another study that shows no interaction between D-AA supplementation and testosterone levels in otherwise healthy men. Although strength did increase in the D-AA group, it did not increase by much.
Human Trial #5
Effect
Decrease
Trial Design
Double-blind
Trial Length
Four weeks
Number of Subjects
24
Gender
Male
Body Type
Resistance-trained
Methods
Twenty-four resistance-trained men (aged 21-28) were randomly assigned to three experimental groups: 1) placebo, 2) 3g of D-AA, 3) 6g of D-AA.
All participants were put on a 4-day/week resistance training program for the full month.
Supplementation was introduced during the final two weeks of the experiment.
Blood samples were collected at three intervals:
- Before the experiment began
- At the 2-week mark, and
- Once at the 4-week mark.
Results
The subjects supplementing with 6g of D-AA experienced a 12.5% decrease in total testosterone and a 15.3% decrease in free testosterone.
The subjects supplementing with 3g of D-AA experienced a 0.7% decrease in total testosterone and a 2% decrease in free testosterone.
The placebo subjects experienced a 0.7% increase in total testosterone and a 9.4% increase in free testosterone.
My takeaway: The fact that the control group experienced the best results in this experiment is surprising. Based on this study’s results, it seems like D-AA supplementation has a negligible effect on testosterone and that using too much of it can cause a decrease.
The Bottom Line
Out of the five human trials, two of them showed D-AA supplementation to increase testosterone levels. Of these two, one experiment lasted only 12-days while the other was carried out in infertile men. The other three showed no significant interaction between D-AA and testosterone.
On the surface, D-AA seems to be a powerful testosterone booster.
After all, it is naturally present in the brain and has been shown (in petri-dish and test-tube studies) to stimulate LH production. But when the experiments are run on humans, the results are inconclusive.
D-AA For Bodybuilding
Based on Trial #2 cited above, 28-days of D-AA supplementation did not affect muscle growth. Nor did it affect power output, as assessed by leg press and bench press 1-rep maximum measurements.
Trial #4 showed D-AA supplementation to increase strength on the leg press and bench press, but even then, the extent was negligible.
Does D-AA Have Any Benefits?
Based on the research, the only situation where D-AA supplementation seems to provide any benefits is in the case of fertility.
For infertile men, D-AA supplementation seems to have tremendous benefits in improving sperm quality and increasing testosterone levels.
In otherwise healthy men, D-AA can increase testosterone levels within 2 weeks, but there don’t seem to be any benefits over the long-term.
D-AA Side Effects
In doses under 4 grams, there are very few reported negative side-effects of D-AA supplementation.
In some rare cases, D-AA supplementation has led to acne, digestive issues, irritability, mood changes, and headaches.
(source)
The Low-Down On D-Aspartic Acid
D-AA is perhaps, after Tribulus Terrestris, the most common ingredient added to testosterone booster supplements. But just because you read that it is “scientifically proven” to boost testosterone levels doesn’t mean that it will do so in every situation.
Context is always important, which is why, even with the research, it is valuable to observe how many subjects were involved in the experiment, how long the experiment took place, and what factors led to certain results.
In the short-term (up to 2 weeks), D-AA supplementation can increase testosterone levels. Although this positive interaction may last longer in infertile men, the effect in otherwise healthy men is diminished past the 14-day mark.
