We as humans are always looking for a way to optimize our health. Whether it’s better sleep, recovery, enhanced muscle gain, athletic performance, or even enhancing your sex life, optimization and biohacking is endogenously integrated within our existence. Aspartic acid is a non-essential amino acid, that is found in two forms, L and D-aspartic acid. Studies have shown that D-aspartic acid may play a role in testosterone synthesis and could in fact help increase human growth hormone. Testosterone and human growth hormone can enhance mood, libido, and improve quality of life. We’re going to investigate the research behind D-aspartic acid, to find out if the claims truly match the research and science.

What Is D-aspartic Acid 

D-aspartic acid (DAA) is a non-essential amino acid that exists in the central nervous system and reproductive tissues. Research shows that DAA supplementation can influence the hypothalamic-pituitary-gonadal axis (HPG). The accumulation of DAA at this site is associated with an upregulation of testosterone production in animals, as well as luteinizing hormone.

How Does D-aspartic Acid Work 

Aspartic acid is found naturally in two forms, L-aspartic acid and D-aspartic acid. Both are synthesized in the human body and are also obtained through protein sources in the diet. 

D-aspartic acid is found in the synapses and neurons in the brain. DAA has similar structure to the neurotransmitter N-methyl-D-aspartate (NMDA), and can bind to NMDA receptors, therefore it works as a neurotransmitter.  D-aspartic acid directly affects neuroendocrine function in the hypothalamus and pituitary gland in the brain, which cause the secretion of several hormones, including gonadotropin-releasing hormone, prolactin, luteinizing hormone, and human growth hormone. It also affects testosterone secretion. However, the etiology and direct mechanisms of how D-aspartic acid works, has only been researched in vitro or in animal studies, therefore relevance related to humans is not completely understood but only hypothesized.

D-aspartic Acid Benefits

1. May Improve Testosterone Levels 

A large body of evidence has investigated the effects of D-aspartic acid on testosterone production. While there is some evidence that D-aspartic acid can increase plasma levels of testosterone in rodents, human evidence is limited. Although there is little to no evidence that D-aspartic acid has these same effects on testosterone and human growth hormone in humans, D-aspartic acid supplements have been marketed to increase strength and muscle mass when combined with resistance training. However, the current evidence does not support these claims.  

Early human research demonstrated that 3g of DAA supplementation per day, increased total testosterone by 42% in untrained participants [R]. However, there was no elicited changes in resistance trained men, after 30 days of supplementation. Subsequently, researchers even found that a larger dose at 6g per day, decreased testosterone by 12.5% suggesting a deleterious effect on negative feedback mechanisms of the HPG axis.

2. May Increase Fertility

Although there have been mixed results with other therapeutic applications, D-aspartic acid does have some promising research as a tool to help men with fertility. A group of 30 men suffering from infertility were treated with a daily dose of sodium D-aspartate for 90 days. After which, the change in spermatozoa concentration and their motility and the pregnancies that occurred with their partners were recorded. Results indicated that supplementation with aspartate significantly increased the concentration and the motility of spermatozoa [R].

3. May Increase Strength

One study published in the journal PLoS One, investigated the effects of DAA supplementation over a 3-month training period. Basal hormones, testosterone, estradiol, and isometric strength were a few of the parameters which were evaluated. After three months of supplementation, study results indicated that there was no change in testosterone or free testosterone between groups, yet both ground experienced an increase in isometric strength, as well as hypertrophy in free muscle mass. With no change between groups, DAA does not have an effect on muscle strength or improvement in resistance training measures.

Another study found that supplementing with D-aspartic acid and participating in a resistance trainign program for 28 days, study participants experienced a 2.9-pound (1.3-kg) increase in lean mass. However, those in the placebo group experienced a similar increase of 3 pounds (1.4 kg) [R].

D-aspartic Acid Dosage 

The standard dosage for D-aspartic acid, is between 2,000 – 3,000mg taken daily.

D-aspartic Acid: Takeaway

The bottom line, is that there isn't enough evidence to show that D-aspartic acid, will provide any therapeutic benefit to help increase free and total testosterone, or improve overall qualify of life indicators. 

With so many different supplements on the market, it is important to research what natural testosterone boosters really work. Although, preliminary studies show that 3g of D-aspartic acid, did have a positive affect on tesosterone levels, every study following has shown no increase, and even a negative affect on test levels. 

However, there is some evidence that D-aspartic acid may benefit sperm quantity and quality in men experiencing fertility problems. Therefore, more research is needed to confirm if DAA can be used as a potential therapeutic treatment for infertility and low testosterone levels. 

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