D-Aspartic Acid and Testosterone: The Short-Term Result vs. the Longer-Term Reality

3 Studies Compared 2 Products’ Doses Checked

Written by the Health Supplements Lab Editorial Team. We read all three key trials directly, not just the one most commonly cited in marketing.

Last reviewed September 2026

D-Aspartic Acid (DAA) shows up in most testosterone supplements, usually backed by a single, frequently-cited study showing a dramatic short-term increase. What that marketing rarely mentions: two later studies, in the exact population buying these products, found the effect disappears — or reverses.

The Study Everyone Cites

Topo et al., 2009, Reproductive Biology and Endocrinology. 23 men aged 27–37 took 3.12g/day of D-Aspartic Acid for 12 days. Testosterone rose by roughly 42% by the end of the study.

This is the real, original source behind the D-Aspartic Acid testosterone claim you’ll see in most male enhancement and testosterone-support marketing. It’s a genuine result. But two details matter enormously and are almost never mentioned alongside the “42%” figure: the study population was not specifically resistance-trained or athletic, and the entire trial lasted just 12 days. What happens with continued use, or in men who already exercise regularly, is a separate question — and it’s been studied.

What Happened When Researchers Tested Trained Men

Melville et al., 2015, Journal of the International Society of Sports Nutrition. Resistance-trained men took either 3g/day or 6g/day of D-Aspartic Acid for 14 days. At 3g/day — roughly the dose used in the original study — there was no significant change in testosterone. At 6g/day, testosterone decreased by about 12.5%.

This is a meaningfully different result in a meaningfully different population: men who already train regularly. The researchers suggested the higher dose may interfere with the body’s own hormone feedback signaling (the hypothalamic-pituitary-gonadal axis) rather than support it.

The Three-Month Follow-Up

Melville et al., 2017, PLOS ONE. The same research group followed 22 resistance-trained men for a full 3 months of supervised training, taking 6g/day of D-Aspartic Acid or a placebo. Result: no change in testosterone at all over the entire period, a measurable decrease in estradiol, and no improvement in strength or muscle growth beyond what the placebo group achieved through training alone.

The study’s own conclusion is direct: “DAA supplementation is ineffective at changing testosterone levels, or positively affecting training outcomes” in this population. This is about as clear a null result as supplement research produces — from the same lab that ran the shorter trial, specifically designed to test whether a longer timeframe would reveal a benefit. It didn’t.

Who’s Actually Buying These Products

Here’s the practical problem with how D-Aspartic Acid is marketed: the original positive result came from a general population over a very short window. The men most likely to buy a testosterone-support supplement — people who exercise, lift weights, or train regularly — are closer to the population in the follow-up studies, where the effect didn’t show up, or reversed at higher doses. If you’re not already resistance-training, or you’re only planning to use it briefly, the picture might look different. But for the core audience these products are marketed to, the strongest available long-term evidence is a null result.

How Real Products’ Doses Compare

We checked the D-Aspartic Acid dose in two testosterone support products we’ve reviewed:

Product	D-Aspartic Acid Dose	vs. Studied Doses
TestoPrime	2,000 mg/day	Below the 3g dose that showed no effect in trained men
Testogen Ultimate	2,025 mg/day	Below the 3g dose that showed no effect in trained men

Both products use a dose below the amount that already showed no benefit in resistance-trained men over 14 days — let alone the 3-month trial. That doesn’t necessarily make the ingredient useless in a broader formula with other actives, but on its own, D-Aspartic Acid’s role in these specific products’ testosterone-boosting story looks weaker the more closely you read the research behind it.

Worth Knowing

Higher doses (6g/day) have shown testosterone decreases in some studies, not increases
The most favorable results come from short-term use in non-athletic populations
The longest study available (3 months) found no benefit at all in resistance-trained men

FAQ

Does D-Aspartic Acid really boost testosterone by 42%?

That specific result comes from one 12-day study in a general (not specifically athletic) population. Later studies in resistance-trained men over 14 days and 3 months found no benefit, and one found a decrease at a higher dose.

Should I avoid D-Aspartic Acid entirely?

That’s a personal call, but the strongest, longest-duration evidence available doesn’t support a testosterone benefit for people who already exercise regularly — the core audience for these supplements.

Is more D-Aspartic Acid better?

No — the available research points the opposite direction. A 6g/day dose showed a testosterone decrease in one trial, not an increase.

Why do so many products still use this ingredient?

The original 2009 study remains the most-cited D-Aspartic Acid research in marketing, in part because it’s the one with a dramatic, positive headline number. The less flattering follow-up research gets cited far less often.

See how this fits into our full product scores

Read Our TestoPrime Review

Last reviewed: September 2026 · Read our full rating methodology · Clinical references: Melville et al., 2015 · Melville et al., 2017, PLOS ONE.

D-Aspartic Acid