Independent supplement ratingsUS and Canada · Updated weekly
A ratings desk for a category that has spent thirty years grading its own homework.
A ratings desk for a category that has spent thirty years grading its own homework.
D-aspartic acid is the classic example of a supplement whose marketing outran its evidence. A 2009 study reported a testosterone increase, and the industry ran with it. But subsequent, better-controlled trials — including in resistance-trained men — largely failed to reproduce any benefit, and at least one found higher doses did nothing helpful.
It remains a headline ingredient in expensive boosters precisely because it once had a positive study to point to, even though the weight of evidence has since moved against it.
On current evidence, it's a low-value ingredient. A transparent label that features it prominently is spending your money on a story the research walked back. Research on PubMed →
On the weight of the evidence, no. A 2009 study reported a testosterone increase and the industry built a category on it. The better-controlled trials that followed — including in resistance-trained men — largely failed to reproduce any benefit, and one found that raising the dose did nothing helpful. It earns a D on our evidence scale for exactly that reason.
Roughly 2,000–3,000 mg a day. Knowing the number is useful mainly in reverse: a product carrying a fraction of it has not even bought a ticket to the argument, and one carrying more is not buying a bigger effect.
It has a positive study to point at, and that is worth money. A single supportive trial from 2009 lets a label imply research backing without saying what happened next. The full story is in the ingredient that built a category, then failed.
Reviewed by the NFS editorial team · Educational only — not medical advice.