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Aspartic Acid: Testosterone Booster or Dud?

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Aspartic acid - Dr. Axe

You may have heard about D-aspartic acid for boosting testosterone levels and helping build muscle, but does it really work? While some studies suggest that it’s effective, others show that it doesn’t cause any difference in testosterone or body composition. So the question remains: What does aspartic acid do in the body, and does it work?

Like all amino acids, it plays a role in many body functions, and it helps keep the body in homeostasis. But our bodies make these non-essential amino acids naturally, and supplementing with them may not always be necessary or effective.


What Is Aspartic Acid?

Aspartic acid is a non-essential amino acid that plays a role in hormone production and nervous system function. It’s one of the two acidic amino acids, the other being glutamic acid. Acidic amino acids are responsible for maintaining the solubility and ionic bonding of proteins. It has an overall negative charge and plays a role in the synthesis of other amino acids, such as citric acid. Asparagine, arginine and lysine are synthesized by the amino acid, among other nucleotides.

The aspartic acid structure is almost the same as alanine, another amino acid, but with one of the beta hydrogens replaced by a carboxylic acid group. Aspartic acid and oxaloacetate, a compound that is known to boost brain health, are interconvertible and can transfer from one amino group to another.

Aspartic acid can occur in two different forms: L-aspartic acid and D-aspartic acid (also called DAA), which have the same chemical formula but mirror image molecular structures.

The two forms of the aspartic acid amino acid play different roles in the body. L-aspartic acid is produced by the human body and serves as a building block for proteins, like other amino acids. D-aspartic acid, on the other hand, isn’t used to build proteins but works to produce and release hormones in the body.

Where does D-aspartic acid come from?

The amino acid occurs naturally in the body and is found in the nervous and endocrine systems of humans and many animals. Studies involving humans and animals show that DAA is found in the central nervous system, as well as endocrine organs, including the pineal gland, pituitary gland, pancreas, adrenal gland and testes.

Is aspartic acid the same as asparagine?

Both are non-essential amino acids that are involved in various body functions. Asparagine is a derivative of aspartic acid and a metabolic precursor to aspartate amino acid. Aspartate commonly occurs in the L-form, which is found in animals and plants. L-aspartate is the conjugate base of L-aspartic acid, which means that it’s formed when it loses a hydrogen ion. So when looking at aspartic acid vs. aspartate, it’s really just a difference of a hydrogen ion. Both types of amino acids promote normal body function.


Effects on Testosterone

What is the best testosterone booster?

This amino acid is known for its ability to increase testosterone production naturally. That said, D-aspartic acid reviews are mixed, with some studies showing that it isn’t effective.

A systematic review published in the International Journal of Reproductive BioMedicine evaluated 23 animal studies and four human studies. Researchers found that D-aspartic acid for testosterone enhanced the hormone levels in animal studies but showed inconsistent results in human trials.

A study conducted in Italy found that D-aspartic acid has a role in the regulation of the release and synthesis of luteinizing hormone and testosterone in humans and rats. For humans, a group of 23 men were given a daily dose of D-aspartate for 12 days, while a group of 20 men received a placebo. Researchers found that D-aspartate is synthesized in the pituitary gland and testes and able to increase testosterone levels.

study published in the Journal of the International Society of Sports Nutrition found that when males involved in resistance training took six grams of D-aspartic acid per day for 14 days, testosterone levels actually decreased. Those taking three grams of DAA supplement per day did not experience any changes in testosterone markers.

There have also been studies evaluating the efficacy of D-aspartic acid for bodybuilding. Research conducted at Baylor University found that DAA supplementation was not effective for increasing muscle strength and mass after taking supplements for a 28-day period while resistance training.

It’s safe to say that the jury is still out on whether or not aspartic acid works to increase testosterone levels. More human studies are needed to determine its efficacy and appropriate dosage for boosting testosterone and promoting muscle building.

Related: Threonine: The Amino Acid Needed for Collagen Production


Aspartic Acid Benefits

1. Promotes Nervous System Function

Research shows that D-amino acids are found in the nervous and endocrine systems. DAA is found in the nervous system and is known to control numerous glands throughout the body that are in charge of producing and secreting hormones.

These hormones regulate the body’s many physiological processes, including reproduction, sleep, blood pressure and energy utilization. Without the proper production and synthesis of hormones, our bodies wouldn’t be in balance — or homeostasis.

2. Boosts Hormone Production and Release

We know that amino acid D-aspartic acid plays a major role in hormone production and release. This promotes the regulation of various body activities, including blood pressure, sleep patterns, use of energy, reproduction, digestion, appetite changes and metabolism. By consuming foods high in aspartic acid, you work to balance your hormones naturally.

The studies on DAA supplements for boosting hormone regulation are mixed, but in vitro rat studies have demonstrated that it increases levels of testosterone, luteinizing hormone, progesterone and growth hormone. There is some evidence in humans that D-aspartic acid may work to increase testosterone levels. DAA may help increase hormone production by accumulating in the pituitary gland and testes, triggering a hormonal response.

3. May Boost Male Fertility

Like its effects on testosterone levels, the research on D-aspartic acid for male fertility is limited, but there are some promising studies. One study published in Advances in Sexual Medicine found that supplementation of D-aspartate significantly increased the concentration and motility of sperm in a group of 30 males.

In patients with low sperm counts and sperm motility, the increase of sperm concentration was found to be twofold. Researchers found that using D-aspartate for a 90-day period improved the rate of pregnancies of their partners, with 27 percent of them becoming pregnant during the study.


Aspartic Acid Side Effects

When it comes to aspartic acid side effects and safety, it seems to be safe when consumed in supplement form. Some possible supplement side effects include headaches and irritability. Most studies involving D-aspartic acid supplements do not report on its side effects, so more research may be needed to fully understand the risks.

Does D-aspartic acid cause weight gain?

There is no evidence to suggest that DAA will make you gain weight. For studies that evaluated DAA’s ability to increase muscle gains and weight training performance, results indicate that supplementing with the amino acid has no impact.


Aspartic Acid Foods

What food contains aspartic acid?

The amino acid is found naturally in plants and animals. The top D-aspartic acid foods include:

  1. avocado
  2. asparagus
  3. molasses
  4. chicken
  5. turkey
  6. beef
  7. fish
  8. eggs
  9. dairy products
  10. seafood (spirulina)

Adding these DAA foods into your diet can help increase amino acid levels naturally and reduce your reliance on supplements that have not been deemed effective by recent studies.


Supplement and Dosage Recommendations

DAA supplements are commonly used to increase testosterone levels. A typical D-aspartic acid dosage is between 2.5–3 grams per day. According to research conducted at the University of Western Sydney in Australia, “supplement companies are currently recommending three grams of the amino acid once to twice a day and these recommendations have been drawn from the only dosage studies in humans.”

Some research suggests that men who practice resistance training or bodybuilding may need higher doses of the amino acid to increase hormone levels, but there isn’t enough evidence to make this recommendation. In fact, one study showed that taking six grams of DAA a day actually decreased testosterone levels in men.

Taking D-aspartic acid before bed or after workouts is the most common.


Is Aspartic Acid Safe? Precautions and Drug Interactions

Taking into account possible D-aspartic acid side effects, the amino acid is considered safe when taken in appropriate amounts. Follow the instructions on the product label, keeping in mind that a typical dosage is between 2.5–3 grams per day.

There is not enough evidence to recommend using aspartic acid supplements while pregnant or breastfeeding, so it’s best to avoid it unless advised otherwise by your health care professional.

Is D-aspartic acid a banned substance?

Even though DAA supplements are sometimes used to improve muscle gain and strength, it is not banned by the World Anti-Doping Agency.


Final Thoughts

  • What is aspartic acid? It’s a non-essential amino acid that occurs in two forms, L-aspartic acid and D-aspartic acid.
  • The body needs these important amino acids to maintain homeostasis. It works to produce and secrete important hormones that keep the body functioning properly.
  • Does aspartic acid work? Even the best DAA supplements may not help increase testosterone levels or muscle gain, according to some studies. But there is evidence that it helps to improve male infertility.
  • The typical DAA dose is between 2.5–3 grams per day. You can also increase your DAA levels by eating organic meats and fish, as well as asparagus, avocado, eggs and dairy products.

Read Next: 6 Benefits of BCAAs (Branched-Chain Amino Acids), Including Muscle and Performance

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