D-Aspartic Acid

Boost your testosterone with this amino

Written By Jim Stoppani, PhD

Updated November 29, 2018

At my ripe ol' age of 49 I have to be worried about my testosterone levels.

After all it is THE male hormone and it is responsible for muscle growth, strength, fat loss and sex drive. And if it's levels drop so does muscle size, muscle strength, and sex drive, while body fat goes up. And low testosterone levels can predispose a man to depression. Since test levels peak when men are in their early to mid-20's and start to really fall by the time we're 30, I have a lot to be concerned with. But I've researched a number of testosterone boosters and experimented with numerous ones to see which ones work well. And luckily there are quite a few that work well.

One natural testosterone booster that works very well is D-aspartic acid or D-aspartate.

Aspartic acid is an amino acid, much like arginine and glutamine. It's used to build proteins in the body. However, the only form of amino acids that the body recognizes for building protein is the L (left-handed or levorotatory) form, such as L-arginine, L-glutamine, L-leucine and L-aspartic acid. The L refers to the configuration of the molecule. The other configuration that amino acids can be in is the D (right handed or dextrorotatory) form. Most D-amino acids are not recognized by the body, yet D-aspartic acid is. D-aspartic acid is formed when the enzyme aspartate racemase converts L-aspartic Acid into D-aspartic acid. This usually occurs in the testicles, pituitary gland, and nerve cells. It's this D-form of aspartic acid that has testosterone-boosting properties.

When D-aspartic acid is produced in the pituitary gland of the brain, it appears to stimulate the release of luteinizing hormone (LH).

LH is then released from the gland into the bloodstream and it travels to the testicles where it encourages the production of testosterone.

When D-aspartic acid is produced inside the testicles it acts on the Leydig cells, which are special cells inside the testicles that produce testosterone.

This appears to work through its ability to increase levels of the nucleotide cyclic AMP, which is a cellular messenger that acts to boost testosterone production. The amino acid also works to increase sperm production as well.

Most of the research discovering what D-aspartic acid does and how it does it has been done in animals.

However, Italian scientists did study the effects of D-aspartic acid supplementation in men aged 27-37 years old. Every morning for 12 days 43 men took either 3 grams of D-aspartate along with the B vitamins B6, B12 and folic acid or a placebo, which contained just the vitamin B6, B12 and folic acid without the D-aspartate.

The researchers from Italy reported in a 2009 issue of the journal Reproductive Biology and Endocrinology that the subjects taking the D-aspartate supplement increased their LH levels by over 30% and subsequently their testosterone levels by over 40% as compared to the guys getting just the B-vitamin placebo.

Jim's take-home message:

D-asparate works well as the clinical study found, but also as thousands of people have reported to me on their own experience. And personally I have used it with good success to keep my own falling test levels up. Since the Italian study used 3 grams of D-aspartate per day, most D-aspartate products supply that much per dose. And that is the dose that I recommend going with as well. Although the clinical study supplied all 3 grams of D-aspartic acid in one sitting, you can also try splitting the dose throughout the day in two or three doses. Some guys report that D-aspartate supplements irritate their stomachs similar to the way that creatine did in the days before it was micronized. Taking smaller doses more frequently throughout the day may help to avoid these stomach issues yet still provide testosterone-boosting benefits.

I recommend cycling most testosterone boosters due to what is known as a negative-feedback loop on testosterone. In other words, when you increase testosterone levels, the higher test levels influence the brain to reduce LH production, which then results in lower testosterone levels. You can try several different cycles with D-aspartate. The simplest one is taking it for eight weeks straight and then stopping it for four weeks before repeating for another 8-week cycle. Another option is to take it for two weeks and stop for one week and cycle it in that fashion. No one is sure yet what the best cycle is for D-aspartate. We're not even sure yet if 3 grams is the optimal dose, since it's all based on one study. So the cycle depends more on your body's own biochemistry. If it gives you quite a big boost in testosterone levels then you may need to do a shorter cycling scheme. If it results in only a small boost in T levels, you may not need to ever cycle it. And in that case taking D-aspartate long term may be your best bet to keep D-aspartic acid levels optimal in the pituitary and the testicles. So try different cycles to see which one works best for you and let me know what you find works for you.

There is some data in boars that shows D-aspartate actually increases the activity of an aromatase enzyme in the testicles that converts testosterone into estrogen. So some experts are warning that D-aspartate increases estrogen levels. However, the only data on estrogen and D-asp is in boars. Althought the Italian study in humans did not measure estrogen levels, the fact that testosterone levels increased so dramatically, it is unlikey that D-aspartic acid is converting testosterone to estrogen in male testicles. So at this point it looks like this is estrogen effect is specific to certain animals. However, taking a natural aromatase inhibitor is a good idea whenever you take any testosterone booster. When testosterone levels go up, estrogen levels also can go up a bit. By taking a supplement that inhibits the aromatase enzyme you can keep estrogen low and bump testosterone levels up even higher. A good supplement to do this is damiana, also known as Turnera diffusa. Research from the University of Mississippi discovered that damiana contains the active ingredients pinocembrin and acacetin, which are potent inhibitors of the aromatase enzyme. Take 300-1000 mg of Damiana extract three times a day such as morning mid-day and night.

D-aspartic acid is not a supplement that females should take. It will not increase testosterone levels in females since women obviously do not have testicles, but also because an increase in LH provides different effects in women. Namely it triggers ovulation. By falsely raising LH levels, it could interfere with the normal menstrual cycle. For a supplement that can help women to naturally increase testosterone levels, read my Female-Friendly Supplements article.

References:

D'Aniello, A. D-Aspartic acid: an endogenous amino acid with an important neuroendocrine role. Brain Res Rev 2007;53(2):215-34.

Furuchi T, Homma H. Free D-aspartate in mammals. Biol Pharm Bull 2005;28(9):1566-70.

Homma, H. Biochemical behavior and function of free D-aspartate in the mammalian body. Seikagaku 2008 Apr;80(4):277-86.

Nagata Y, Homma H, Lee JA, Imai K. D-Aspartate stimulation of testosterone synthesis in rat Leydig cells. FEBS Lett 1999;444(2-3):160-4.

Topo, E., et al. The role and molecular mechanism of D-aspartic Acid in the release and synthesis of LH and testosterone in humans and rats. Reproductive Biology and Endocrinology 7(120), 2009.

D'Aniello, S., et al. D-Aspartic acid is a novel endogenous neurotransmitter. FASEB J. 2011 Mar;25(3):1014-27.

Lamanna, C., et al. Involvement of D-Asp in P450 aromatase activity and estrogen receptors in boar testis. Amino Acids. 2007 Jan;32(1):45-51.

Lamanna, C., et al. Endogenous testicular D-aspartic acid regulates gonadal aromatase activity in boar. J Endocrinol Invest. 2006 Feb;29(2):141-6.

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