D-aspartic acid (DAA) supplements are taken for their testosterone- and libido-boosting effects.
Its found in many testosterone boosters.
Research is also underway to evaluate its cognitive-enhancing effect.
D-aspartic acid is a type of amino acid that plays a role in increasing the release of a hormone in the brain that spurs the production of testosterone. It is believed to stimulate the production and release of testosterone through multiple pathways of the hypothalamic-pituitary-gonadal axis.
D-aspartic acid boosts testosterone in some studies. In a 2009 study, 23 men were given a daily dose of D-aspartate for 12 days, while another group of 20 men were given a placebo. Rats were also tested in the study and were given a solution of D-aspartate or a placebo for 12 days.
Researchers discovered that in humans and rats, D-aspartate effectively regulated the synthesis and release of luteinizing hormone (LH) and testosterone by 33 percent and 42 percent respectively (1). LH is produced and released in the anterior pituitary gland. It stimulates the production of testosterone from Leydig cells in the testes. Testosterone, in turn, stimulates sperm production.
In a 2015 pilot study, researchers evaluated the impact of a supplementation of D-aspartic acid, sodium nitrate and vitamin D3 on blood testosterone and nitrate/nitrite levels in middle-aged, overweight men.
Ten overweight or obese men were given supplementation either one or two times a day for 28 days. Testosterone and nitrate/nitrite levels were measured before and after day 14 and 28 of supplementation. Researchers also evaluated other health indicators, such as libido and energy level.
The results showed that supplementation increased total and free testosterone a modest 5 to 10 percent; men with relatively low basal testosterone values, however, experienced higher increases exceeding 20 percent. In addition, blood nitrate/nitrite increased and participants reported improved feelings of vitality and libido (2).
Not all studies had a positive effect. In a 2015 study of 24 resistance-trained young males, daily supplementation of 6g for two weeks actually resulted in a decrease in testosterone (3).
In a follow-up study, researchers set out to evaluate the effects of supplementation in resistance-trained men over a longer period of three months. All participants performed 12 weeks of supervised resistance training with a program focusing on all muscle groups. They were given 6 g of supplement each day.
The results indicated that supplementation is ineffective at changing testosterone levels, or positively affecting training outcomes even when taken for a longer testing period (4).
D-aspartic acid may improve male fertility. In a 2012 Italian study, researchers investigated the impact of supplementation of sodium D-aspartate on sperm quality and motility. Thirty sub-fertile patients were treated for 90 days with a daily dose of sodium D-aspartate.
At the conclusion of the study, it was noted that due to supplementation, there was an increase in sperm concentration and motility. As a result, there was also a significant increase in number of pregnancies in the partners of the tested patients (5).
D-aspartic acid may play a role in fertility of women. Samples of pre-ovulatory follicle fluid were obtained from 20 patients undergoing IVF in England and tested for concentrations of D-aspartic acid.
Results show that this amino acid is present at a relatively higher concentration in younger women than in older patients and there appears to be a relationship between the concentration of D-aspartic acid and fertility outcome parameters.
In younger women aged 22-34 years the amino acid was found at a concentration of 19.11 nmol/ml, whereas in patients aged 35-40 years it decreased to 10.86 nmol/ml.
In addition, this amino acid was linked to oocyte quality. An oocyte is the immature female reproductive cell prior to fertilization. Poor oocyte quality could be the key reason for unsuccessful pregnancy outcomes during IVF.
These findings suggest that follicular D-aspartic acid concentration may be considered as an alternative or additional biochemical marker for oocyte quality in patients undergoing IVF (6).
D-aspartic acid may be a memory and learning booster. In a 2010 study, researchers evaluated the effect of oral administration of sodium D-aspartate (40 mM) on improving rats’ cognitive capability. Rats were given supplementation for 12 to 16 days or placebo and assessed on their ability to find a hidden platform in the Morris water maze system.
A significant increase in the cognitive effect was observed in the treated group compared to the placebo group. Five further sessions of repeated training, involving a change in platform location, also displayed a significant treatment effect.
It was also noted that 20 randomly selected rats possessing relatively high concentrations of D-aspartic acid in the hippocampus were much faster in reaching the hidden platform, suggesting a correlation between high concentrations of D-Aspartic and an increase in learning and memory (7).
Some studies show that when taken short term (up to 90 days) there are no adverse side effects.
In another study, some men reported irritability, headaches and nervousness.
Most studies using D-aspartic acid supplements did not report whether side effects occurred; long-term studies have not yet been performed using D-aspartic acid. More research is needed to confirm its safety.
Current recommendations based on a study published in Reproductive Biology and Endocrinology suggests using 3.12 g per day (8).
Some manufacturers of products containing D-aspartic acid recommend using the product for periods of four to 12 weeks followed by a period of cessation from the product lasing two to four weeks.
Further study is needed to determine whether it should be cycled.
D-aspartic acid is an amino acid occurring primarily in the pituitary gland and testes and has a role in the regulation of the release and synthesis of LH and testosterone.
It is taken as a supplement to boost testosterone, libido and to improve the quantity and quality of sperm in men with infertility. Limited studies also show a correlation between the concentration of this amino acid and oocyte quality in women.
Although abundant research has investigated the hormonal effects of D-aspartic acid in rat models, there is limited research on humans.
Research on the effects of D-aspartic acid on raising testosterone levels in men has produced mixed results. While it has been shown to increase testosterone in inactive men, it has not been shown to boost testosterone in men who weight train.
This amino acid is also being investigated for its role in improving memory and learning.