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D-Aspartic Acid

D-aspartic acid is sold as a natural testosterone booster on the strength of one small 2009 study that later, better-controlled trials failed to replicate. In resistance-trained men the good evidence is uniformly null — and at 6 g/day it may actually lower testosterone.

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What the science says

  • Raising testosterone in resistance-trained men Limited evidence

    Willoughby's randomised trial gave 3 g/day for 28 days alongside heavy resistance training and found no effect on total or free testosterone, body composition or strength. Melville's 2015 trial went further: 6 g/day significantly decreased total and free testosterone, while 3 g/day did nothing. The original positive finding was in untrained men with low baseline testosterone and has not replicated in trained populations.

  • Increasing muscle mass and strength Limited evidence

    Melville's 2017 three-month randomised controlled trial in resistance-trained men found no significant benefit of D-aspartic acid on body composition, muscle mass or strength versus placebo. Combined with Willoughby's 28-day null result, this is about as clean a negative as sports supplement literature offers.

  • Male fertility and sperm parameters Limited evidence

    Some small trials, often using D-aspartic acid in combination formulas with zinc and ubiquinol, report improvements in semen parameters in men with idiopathic infertility. Because these are combination products, the contribution of D-aspartic acid specifically cannot be isolated.

Dosage & safety

Studied doseStudies have used 3 g/day and 6 g/day for 14-90 days. Given that 6 g/day suppressed testosterone in one trial and 3 g/day did nothing in two, there is no dose we can recommend for testosterone support.
SafetyShort-term trials report few adverse effects beyond occasional headache, irritability and GI upset, but long-term safety data are essentially absent. The suppression of testosterone at 6 g/day is itself a safety signal, plausibly via negative feedback or downregulation of testicular D-aspartate oxidase. Not recommended for men with hormone-sensitive conditions, for anyone under 18, or in pregnancy. Not a WADA-prohibited substance, but products marketed as testosterone boosters are a common source of undeclared steroid contamination — a real doping risk for tested athletes.

How to take it

TimingTiming does not matter, and neither does the dose — no schedule has produced a testosterone benefit.
With food?With or without food.
Worth knowingIf you are drug tested, treat testosterone-booster products as a genuine doping risk: undeclared steroid contamination is common in this category.

Frequently asked questions

Does D-aspartic acid boost testosterone?

Not in trained men — the evidence is limited. At 3 g/day, D-aspartic acid did nothing to testosterone in two trials, and at 6 g/day it actually lowered total and free testosterone.

Does D-aspartic acid build muscle?

No — the evidence is limited. A three-month controlled trial in resistance-trained men found D-aspartic acid gave no benefit to body composition, muscle mass or strength versus placebo.

Is D-aspartic acid safe?

Short-term trials report few side effects beyond headache, irritability and stomach upset, but long-term safety data for D-aspartic acid are essentially absent. The testosterone drop at 6 g/day is itself a safety signal.

Can testosterone boosters like D-aspartic acid fail a drug test?

Products marketed as testosterone boosters, including D-aspartic acid products, are a common source of undeclared steroid contamination, so treat them as a real doping risk if you are drug tested.

Scientific references

Where to buy

ALLMAX, D-Aspartic Acid, 3.53 oz (100 g)

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