D-Aspartic Acid: Scientific Supplement Review

D-Aspartic acid, also known as D-AA or D-asp is an amino acid that has been marketed as a testosterone booster. There is a lot of debate concerning it’s effectiveness. This article is going to investigate the evidence available in scientific studies with the dosages noted. You will notice D-aspartic acid as an ingredient in several supplements that claim to boost testosterone levels.

Some of the claimed benefits of D-aspartic acid include increasing exercise output, muscle growth and weight loss. There are several small studies investigating it’s effectiveness as a standalone supplement and the results are not promising. There don’t seem to be any studies as to how d-aspartic acid will work as part of a testosterone boosting stack.

Studies on D-aspartic acid and Testosterone 


D-aspartic acid increases testosterone in both human and rat trials, according to a “Reproductive Biology and Endocrinology” journal study published in 2009. A group of 23 men were given a d-aspartic acid supplement for 12 days while others received placebo for the same duration.

The study found that DAA had an acute effect on boosting testosterone in the 12 days compared to those on placebo. 20 out of the 23 participants experienced an increase in testosterone after 12 days of drinking a d-aspartic supplement daily. The effects seems to be both dose and time dependent as 3 to 6 days of treatment did not produce a statistically significant increase in testosterone.

The study also notes that testosterone remained significantly increased after 3 days of discontinuing d-aspartic acid supplementation.

This study doesn’t address whether the statistically significant increase in testosterone will help with muscle growth or recovery. The participants in the study used 3,000 milligrams of D-AA, which is within the range of a standard dose between 2 grams and 3 grams.

Testosterone Effect on Resistance Trained Men


A current study published in a 2015 issue of the “Journal of the International Society of Sports Nutrition” analyzed the effects of D-AA on experienced weightlifters or bodybuilders.

The participants were 24 resistance trained men that took a placebo, 3 grams of D-AA or 6 grams in the morning for two weeks after a two-week washout period.

The results showed that the trained participants who took the higher dose of 6 grams experienced a significant reduction in testosterone levels compared to those on placebo. There was also no notable difference between those who took 3 grams or 6 grams of D-AA for the 14 day supplementing phase.

These results suggest that trained men have higher testosterone than untrained men and will not benefit from the small boost in testosterone noted in the previous study.

The significant reduction in testosterone in those who took 6 grams or 3 grams suggest that D-aspartic acid has a component that binds to the free testosterone molecules in trained men. This causes a decrease rather than an increase in total testosterone levels.

Based on these results, it’s recommended that well-trained gym goers should avoid taking D-AA to gain lean mass. It is unclear how D-AA will affect energy output during workouts muscle growth.

Effects on Building Muscle 


A study published in a 2013 issue of “Nutrition Research” researched the effects of d-aspartic acid supplementation on muscle strength and exercise performance parameters. The study consist of well-trained participants conducting exercise and taking 3 grams of D-AA or placebo for 28 days. The participants trained 4 days out of the week while being monitored.

The study determined that D-AA did not provide any benefit to muscle strength or growth other than what is expected from resistance training. There was no significant difference between the placebo group and those who took a supplementation of d-aspartic acid. Testosterone and Luteinizing hormone levels were not significantly effected by an increase intake of D-AA.

This is the second study that suggest that d-aspartic acid has no effect when it comes to exercise and building muscle in those who have experience. Also, it’s effect with non-trained individuals are only statistically significant and is unlikely to produce any significant difference when targeting muscle growth.

What are the Benefits of D-Aspartic Acid? 

D-Aspartic acid may be useful for absolute beginners who are looking to build muscle. The effects are temporary and is unlikely to make a significant difference on it’s own. However, as part of a supplement that contains B vitamins, zinc and vitamin D, D-aspartic acid may be useful as a temporary testosterone booster.

Those who are experienced in muscle-building or eat a balanced diet are unlikely to benefit from taking d-aspartic acid. It seems to have very limited usefulness and is not worth the investment.

D-Aspartic Acid in Food 

Aspartic Acid can be found in grass-fed meat sources, such as beef, dairy sources, which include cheese or butter and plant-based foods such as rice, fruits and oats.

Potential Side Effects 

There does not seem to be any side effects associated with taking D-aspartic acid in the standard dosage of 2, 000 milligrams to 3,000 milligrams daily. Studies that test metabolic and organ functions found no safety or toxicology issues for up to 30 days of use. Other sources report that up to 90 day of use is considered safe.

If you are on any medication or suffer from a long-term illness it is best to consult a doctor before considering use.