This post was updated in April 2020 to ensure accuracy and relevancy.

This article is about the actual chemical compound d‑aspartic acid and scientific research focusing on its testosterone boosting properties. To read more about supplements navigate through links in the top menu.

What is DAA / D-Aspartic Acid?

a-aspartic acidD-Aspartic acid is an endogenous (meaning that it is produced by the body) amino acid which has been found in the nervous and endocrine (i.e. hormone producing) tissues of both animals and humans. It is one of 20 building blocks of proteins, called proteinogenic amino acids. D-Aspartic acid was discovered in 1827 by a French pharmacist Plisson, by boiling asparagus and treating it with hydrochloric acid – thus the name.
D-Aspartic acid is present in the brain tissue in the last stage of embryo development and shortly after birth of mammals, suggesting that it takes part in the nervous system development. Also a high concentration of the d-aspartic acid can be found in the testes where it plays a role in sperm production.

D-Aspartic Acid at GNC

D-Aspartic Acid ist the d-form of the amino acid aspartic acid. The l-form of all proteinogenic amino acids build tissues, the d-form is not a building block but a signaling molecule. In specific tissues of the body (testes, pituitary gland, and hypothalamus, all responsible for hormone production), the non-essential amino acid l-aspartic acid (l-form) is converted by a d-aspartate racemase and becomes the d-form, a racemate isomer of the l-form. The d-aspartic acid supplements contain thus the form of the aspartic acid responsible for increasing testosterone levels.

How does d-aspartic acid work?

D-Aspartic acid increases natural testosterone production and release, by increasing the release of gonadotrophin and luteinizing hormone. DAA triggers the release of the GnRH (gonadotropin-releasing hormone that informs the pituitary that testosterone concentration in the blood is falling), oxytocin and vasopressin (the “love hormones”), the luteinizing hormone (LH) and the growth hormone (GH) from the neuroendocrine axis (the hypothalamus and the pituitary gland), and testosterone from the testes. The pituary gland and the testes have the ability to trap circulating d-aspartic acid.

Natural increased release of GnRH and LH resulting in increased testosterone levels can be observed from puberty only to mid-twenties. Men after 30 experience lowered testosterone levels, which leads to a lowered libido, increased body fat levels, problems with sleep, decreased recovery ability, and decreased ability to build up muscle. In other words, DAA supplement causes you body to produce more testosterone as if you were younger and helps to get rid of the above mentioned symptoms. The deciding advantage of d-aspartic acid over direct testosterone supplementation (e.g. with steroids) is that the testosterone is produced by your body and not delivered from outside, which could interfere with body’s own testosterone production.

What are the d-aspartic acid benefits?

Increased testosterone levels triggered by d-aspartic acid benefit sexual performance and muscle growth. Being a male sex hormone testosterone enhances libido and erection quality, intensifies perceived orgasm and extends duration of intercourse. Testosterone makes your energy level rise, low T is responsible for depressions and lowered life satisfaction. By elevating testosterone level, d-aspartic acid makes your workouts more effective and helps you build muscle.

Stimulation with d-aspartic acid increases cyclic adenosine monophosphate (cAMP) in the receiving nerves. cAMP is a cell-regulating compound, probably the most important one. It plays an important role in the cellular reaction on hormones.
Which benefits does increased cAMP have for your body? Among others reactions it increases the force of contraction of the heart muscle, helps the arteries and other smooth muscles to relax, increases the secretion of insulin and increased lipolysis (fat destruction). In other words increased cAMP makes your workouts easier and helps you to burn fat.

D-Aspartic acid has been suggested to help promote normal GABA levels, and dopamine levels, acting anti-depressant. Another benefit of d-aspartic acid is its ability to increase nitric oxide (NO2, NO3) production and its blood level, promoting fast recovery after workouts.

Has D-Aspartic Acid been tested?

D-Aspartic Acid started gaining popularity after the publication of an Italian lab study by D’Aniello. The study has been conducted on human volunteers and on rats. 23 men between 27 and 37 have taken a DAA supplement for 12 days. The testosterone and luteinizing hormone (LH) levels have been significantly increased in comparison with a control group who took placebo (a solution of salt). The increase of LH was 33%, the increase of testosterone – a whooping 42% in only 12 days! Similar results have been observed with rats. An elevated level of testosterone in blood remained even three days after suspension of the treatment, probably due to the concentration of d-aspartic acid trapped in tissues. It is noteworthy that this clinical research has been conducted on healthy men with normal testosterone levels, not hypogonadal men.

What foods are high in d-aspartic acid?

As mentioned before there are two forms of aspartic acid, L-Aspartic acid and D-Aspartic acid. Only L-Aspartic acid, a non-essential amino acid, is incorporated into proteins. D-Aspartic acid plays an entirely different role, it is used for signaling mostly in the reproductive system and in the nervous tissue (e.g. brain). Chemically synthesized aspartic acid is a mixture of L-Aspartic acid and D-Aspartic acid, called racemate. However, aspartic acid synthesized enzymatically, i.e. by a living organism, is either the L- or D- kind but not both.

Some reputable sources on the internet seem to mix them up. A livestrong.com article gets it totally wrong: “One amino acid, called D-aspartic acid — more commonly called aspartic acid […]”. Well, not really.

Why is the difference important? If you hope to naturally supplement d-aspartic acid by eating e.g. meat or poultry, because they are full of amino acids, you’re going to get a whole lot of l-aspartic acid. L-Aspartic, not D-aspartic acid. A 2000 Study by D’Aniello and others researched the concentration of d-aspartic acid in various mammalian tissues. The subject of the study were rats, however we can fairly assume that the results are valid for all mammals. The concentrations were:

  • Hind leg – 3 nmol/g tissue
  • Kidney – 8 nmol/g tissue
  • Liver – 7 nmol/g tissue
  • Brain – 15-53 nmol/g tissue
  • Testes – 90 nmol/g tissue

For comparison the L-Aspartic acid concentration in legs of rats is on average 713-938 nmol/g tissue (source). 300x more!

So where can you find natural d-aspartic acid? According to this 1987 Study  d-aspartic acid can be found in the muscle tissue of a clam Scapharca broughtonii. It looks like oysters are really an aphrodisiac after all. If you don’t like oysters – just get a supplement.

Who should take DAA?

The short answer is ‘non-athletes and men with low testosterone’.

The research body at the time of the study was limited and d-aspartic acid seemed to be the cheapest and best testosterone booster ever. Since the research had been conducted, the scientific and bodybuilding communities have learned many new facts about DAA. The compound is researched a way better than it was a few years ago:

  • too much of DAA seems to decrease the free testosterone levels:
    One study involving young resistance trained men taking 6g of DAA a day resulted in significantly decreased in total and free testosterone. Athletes taking only 3g DAA a day didn’t experience any change in the gonadal hormones.
  • healthy athletes seem not to benefit from DAA supplementation.
    A previously mentioned research in which athletes performing heavy resistance training took 3g DAA a day has shown no change of gonadal hormones. Another study using NMDA (N-Methyl-D-Aspartic Acid) on a similar test group (also young active athletes) also couldn’t confirm any positive effects on testosterone levels.
  • infertile (or sub-fertile) men with low testosterone levels seem to benefit the most from DAA supplementation. A numerous studies confirm this.
  • the above mentioned D’Aniello study indicates that d-aspartic acid supplemented to non-athletes induces an increased release of testosterone and luteinizing hormone.

Is d-aspartic acid any good for bodybuilding?

The short answer based on the research up till now is ‘no’.

There is a noticeable correlation between the testosterone levels before the DAA supplementation and the results of the supplementation. The worse off in terms of hormonal health were the studied individuals to begin with, the more they have gained from taking DAA. It seems that there is a negative feedback in the body, via the degradative enzyme, d-aspartate oxidase (link):

  • Athletes who have had higher levels of testosterone than average Joes didn’t benefit from the DAA supplementation, some have even suffered lower testosterone levels.
  • Healthy average men have gained a little. Short term usage of DAA seems to raise testosterone, prolonged usage doesn’t bring a significant change.
  • Men with testosterone and fertility problems have benefited a lot.

D-Aspartic Acid at GNC

A word of caution for the ladies – the research has been performed only on men. Another study gives clues how a supplementation of d-aspartic acid works on females – it increased the levels of estrogens. Probably DAA supplements should not be taken by women. However the study mentioned involved only animals (lizards), so the results should be taken with a pinch of salt.

What is the d-aspartic acid dosage?

The DAA dosage used in the famous D’Aniello study was 3 gram taken in the morning for 14 days.

As with all testosterone boosters I would suggest you to cycle it to avoid building up a tolerance. Allmax, a manufacturer of the d-aspartic acid supplement, suggests a cycle 2 weeks on and 1 week off the supplement. A 2017 study shows that prolonged supplementation of DAA doesn’t increase testosterone.
(Read more about DAA Dosage here.)