D-Aspartic acid and Testosterone

D-Aspartic acid (or DAA) is an amino acid, naturally produced by your body and found in your nervous and endocrine systems.

The endocrine system is the name given to the glands that produce hormones and regulate our metabolism, sexual and reproductive functions, physical development, moods, sleep and more. It’s very important to us on a host of levels.

Studies have shown that DAA is concentrated in the glands responsible for sexual functioning, namely the testes, pineal and pituitary glands in men. It has been shown to play an important role in the release of hormones (testosterone in particular), because it is responsible for triggering the release of Luteinizing hormone which in turn prompts the testes to produce and release free testosterone.

D’Aniello, A. (2007). D-Aspartic acid: an endogenous amino acid with an important neuroendocrine role

Why does D-Aspartic acid encourage testosterone and Free Testosterone Production?

First of all a bit of back history on this subject. Whilst the role DAA played in the release of testosterone had been established using studies based on the reaction of lab rats, there was no real evidence that the same effects would necessarily occur within the human body.

Clinical Studies

We now look at the four main clinical studies on the effects D-Aspartic acid supplements have on testosterone levels, working upwards in chronological order;

Study 1: The Topo et al Study (2009)

Researchers: Enza Topo, Andrea Soricelli, Antimo D’Aniello, Salvatore Ronsini, and Gemma D’Aniello

Title: The role and molecular mechanism of D-aspartic acid in the release and synthesis of LH and testosterone in humans and rats

Sponsor: Department of Obstetrics and Gynecology, and Reproductive Medicine (IVF Unit), Hospital ‘S. Luca’, Vallo della Lucania, Italy

Read More: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2774316/

In 2009 a clinical study by Topo et al was the first to be done on both human and rats. The study’s principle aim which involved human participants was designed to establish the effect DAA had on the release of Luteinizing hormone and therefore free testosterone.

If you feel inclined you can read more about the study here » http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2774316/ but suffice to say the results were astonishingly positive about the effects DAA had on testosterone release. So much so, in fact, that a whole new industry exploded on the back of them.

Testosterone is always big news in the supplements market, suddenly D-Aspartic acid was big news too. Some quotes from the paper;

1. Concerning the LH pattern, the results demonstrated that after 12 days of D-Asp treatment, 20 out of 23 (87%) participants had significantly increased concentrations of LH in their blood with respect to basal values (the value of LH found in the same subjects before starting treatment). Statistical analysis demonstrated that the value (mean ± SEM) of serum calculated for all the 23 subjects treated with D-Asp increased by 33.3%
2. Concerning the effect of D-Asp on the induction of testosterone release, after 12 days of D-Asp treatment, the levels of testosterone in the serum of the participants were significantly increased compared with basal levels. Out of 23 participants, 20 had increased testosterone.

So suddenly it was crucial to have D-Aspartic acid in anything related to testo boosting and supplement providers were adding it to both boosters as well as selling pure DAA alone.

Comment about the Topo et al study

This was a properly conducted clinical study supported by the Department of Obstetrics and Gynecology, and Reproductive Medicine (IVF Unit), Hospital ‘S. Luca’, Vallo della Lucania, Italy. It was conducted by five academics with no commercial conflicts of interest that could have led to bias in the results.

In other words: they were qualified to run this trial, did so using proper clinical techniques, and were impartial.

Study 2: The Willoubhy et al Study (2014)

Researchers: Darryn S. Willoughby, Mike Spillane, and Neil Schwarz

Title: 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

Sponsor: Department of Health, Exercise and Biochemical Nutrition Lab, Human Performance, and Recreation, Baylor University, Waco, TX, USA

Read More: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3918557/

This study aimed to disprove any relationship between D-Aspartic acid supplements and increases in testosterone levels amongst athletes who regularly trained.

And lo and behold it did. Wouldn’t you know it? See comment below.

Comment about the Willoubhy et al Study

How about this for a hypothesis? “This study was conducted and led by somebody who was determined from the outset to discredit the supplements industry.”

Let’s take a look at the opening two sentences of the write-up – you can read the full introductory paragraph using the link above, but it is an undisguised rant about the supplements industry;

Within the nutritional/sport supplement industry there are a vast amount of products that are marketed as “testosterone boosters.” Many of these products contain a proprietary blend of various ingredients alleged to increase endogenous testosterone levels. However, in most cases there is little data, either on the complete product itself or the various active ingredients typically contained within a proprietary blend, to substantiate manufacturers’ claims

Now – we definitely do not disagree about Mr Willoughby’s statement regarding the efficacy of ‘proprietary blends’.

However the nature of the opening statement in conjunction with Willoughby’s personal profile leads us to suspect that while he doesn’t need to declare any conflicting interests, he is far from impartial.

Willoughby has a staggering array of qualifications – including more degrees that a protractor. But frankly you only have to look at his profile, read his thesis subject “Comparison of Isotonic Free Weights and Omnikinetic Exercise Machines on Strength”, and study the language used in the report to suspect that he wants to support the hypothesis of this study and therefore discredit the supplements industry.

The trouble with initiating any study with the goal of establishing a particular outcome is that if your desire is strong enough you will often find a way (consciously or subconsciously) of producing the result that you were looking for.

Let’s have a look at the list of limitations, using extracts from the study report itself;

  1. We relied on participant self-report for dietary intake and supplement compliance
  2. It is possible that the information reported for both dietary intake and supplement ingestion does not accurately reflect what was actually consumed
  3. A sample size of 20 is somewhat small
  4. We did not assess the serum levels of any of the product’s ingredients
  5. We did not perform a COA in our own laboratory on the NMDA product to confirm the results of the analysis

Hmm. Let’s concentrate on the source of the DAA used in this experiment (according to his report). If you were conducting a funded scientific study into the efficacy of a particular amino acid, would you not make sure that you were testing out a fully verified source of DAA? We would.

Darren wouldn’t though it seems, he decided to pick a random supplement off the shelf and use that instead of ensuring that he was using a specific measurable dose of DAA.

So actually Darren wasn’t evaluating whether DAA worked on trained athletes – he was evaluating whether this Muscle Warfare’s product worked. And as far as he could see, it didn’t. What does that tell us about the effect D-Aspartic acid has on resistance trained men? Not very much, it tells us the effect Muscle Warfare’s supplement had on resistance trained men.

Study 3: The Melville et al Study (2015)

Researchers: Geoffrey W Melville, Jason C Siegler and Paul WM Marshall

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

Sponsor: School of Science & Health, University of Western Sydney, Campbelltown Campus, Penrith 2751, NSW, Australia

Read More: http://www.jissn.com/content/12/1/15

This was a very well conducted study on the effects of D-Aspartic acid supplements on resistance trained men. The underlying background behind this study was that the researchers felt that while Topo et all had proved there were very large increases in the levels of free testosterone within a cross section of men, Willoughy et all had found it inconclusive amongst men who trained regularly (although as mentioned previously we have our reservations about that).

Melville et al hypothesised that the results produced by Willoughby et al were not as conclusive as the results of Topo et al because the dosages in the men used to resistance training weren’t high enough.

Comment about the Melville study

Most people would look at the dates on research and conclude that the most recent is the most relevant. Dismiss that thought if it crossed your mind – human biology has not changed in the last 6 years.

This is a properly conducted, and indeed approved, academic study. The big problem with is that when you look at the results they raise more questions than they answer. Drawing any concrete conclusions from it is impossible because of the wild variations across all groups – including the placebo/control group. If the placebo group had shown little or no change in the levels of free testosterone and Sex Hormone Binding Globulin (SHBG) then it would give a lot more credibility to the results of the 3g and 6g groups.

The free and total testosterone in the placebo group rocketed, whilst that of the 6 gram/day group plummeted. The question then is – why? This article isn’t the place to be delving into the why’s and wherefores of the placebo effect but when the placebo group shows such a marked improvement and all groups demonstrate an erratic and, frankly, inexplicable set of results it makes it difficult to give too much credence to the study.

The authors themselves suggest that ‘The need for longer-duration research utilising six grams of d-aspartic acid is clear’.

Study 4: The LaMacchia et al Study (2015)

Researchers: Zach LaMacchia, Peter Horvath, Brian Williams

Title: Effect of Aspartate Supplementation on Athletic Performance in Young Men

Sponsor: University at Buffalo

Read More: http://digitalcommons.brockport.edu/surc/2015/schedule/333/

The purpose of the study was to determine the effects of athletic performance in young male athletes. Note that last word – not a randomised sample, a specific study on young athletic males. The study never used blood samples but on physical assessments – Squats and Bench Presses. The assessment was based on their physical performance after the trial. So did they perform better in the gm after taking DAA supplements?

The results were again in favour of using D-Aspartic acid supplements to improve athletic performance, with the control group showing no improvement whilst those taking 3 grans of DAA a day showed a statistically significant improvement.

The conclusion?: “D-aspartic acid supplementation may lead to improved acute skeletal muscle synthesis improving upper and lower body muscle performance.”

Comment about the LaMacchia study

The abstract notes that “Aspartate supplementation may be useful to increase testosterone for individuals with low plasma testosterone due to aging and other conditions”. Which is a fair point given the results of previous studies on DAA, but an odd one to make if you are then going to conduct a study of athletic participants with an average age of 22.

Issues with all studies

Experimental Period

One of the main issues that is common to all these trials is the very short experimental period they were run over. Topo et al ran for 12 days, Melville for 14 days and the LaMacchia study for 14 days. Willoughby at least ran the trial for a around a month, with a 29 day duration.

We’ve actually seen some of the supplement nay sayers describe the Melville study as ‘long term’. Long term? 2 weeks? This is the main issue with all of these studies, most suppliers of natural testosterone boosters would suggest that you won’t see any gains at all in the first month and that it takes time for the ingredients to build up in your system and increase the free and total levels of testosterone. This is borne out by the observations you’ll get when you read the reviews of testosterone boosting supplements that contain D-Aspartic acid – very rarely do you find any which claim they made massive gains, or felt better, or their sex lives improved within only two weeks.

What is clear from all of the these studies, as can be seen from the control/placebo groups is that testosterone levels can be up and down like a yoyo amongst all kinds of men, whether they train or not. It seems that you don’t just have ‘your level’ that your body tends to stick to, it will vary greatly over short timeframes.

Sample Sizes

We appreciate that time is money, the people organising studies have a budget to work to they have to balance the books but…..the sample sizes were all pretty small in these studies too. Topo et al ran had 23 subjects on DAA and a control group of 20, so 43 in all. Willoughby 20 and Melville had 24 participants in total, split into three groups of 8. The LaMacchia study had only 9 participants in total, which is a bit of a joke really – they couldn’t even have gone outside for a game of 5 a-side at lunch time.


So…. does D-Aspartic Acid supplements help to boost your testosterone levels or not?

Yes, is the short answer to this question. On the balance of evidence it would seem that there are more than one properly conducted research studies which demonstrate that D-Aspartic Acid plays a role in increasing free testosterone levels in both sedantry and atheletic males. The de facto study shows big gains across a wider spectrum of lifestyles, whilst the other shows gains in young athletic males.

Counter this with a study which, despite it’s clinical authenticity, produces an inexplicable set of results which the authors themselves suggest needs further investigation, possibly by conducting a longer study.

We would use a product that contains DAA, but we wouldn’t solely use a DAA supplement until further studies can absolutely confirm it’s clinical efficacy.


Write a comment