Testosterone-Boosting Ingredients: What the Clinical Research Actually Supports

HathawayMD.com Clinical Review Team

Why These Ingredients Matter and How They Compare

Testosterone is a hormone that affects muscle, bone, energy, and sexual function in people assigned male at birth. As people age, testosterone naturally declines—about 1% per year after age 30. Many supplements claim to “boost” testosterone using plant extracts, minerals, and amino acids. However, not all of these ingredients have equal scientific support.

This guide compares six commonly marketed testosterone-boosting ingredients by looking at what clinical trials (real studies in humans) actually found. We'll show you the difference between what research used and what supplement labels typically contain. Understanding these differences helps you make informed choices about whether these ingredients might be worth trying.

Tongkat Ali (Eurycoma longifolia)

What It Is: Tongkat ali is a plant root from Southeast Asia that has been used in traditional medicine for centuries. Supplement manufacturers extract compounds from the root and concentrate them into pills or powders.

How It May Work: Tongkat ali contains compounds called quassinoids that might affect how the body produces and uses testosterone. Some research suggests it could increase testosterone levels and reduce compounds that bind to and deactivate testosterone in the bloodstream.

Clinical Evidence: Tongkat ali has moderate-to-strong clinical support. Multiple studies show it may help increase testosterone levels in men with low testosterone. A 2016 review found that men taking tongkat ali standardized to 22% eurycomanone (the active compound) showed improvements in testosterone and sexual function. Studies typically lasted 4-12 weeks.

Typical Dose: Clinical trials used 200-300 mg daily of standardized extract. Many supplements offer 100-200 mg, which may be lower than tested doses.

MODERATE EVIDENCE

Ashwagandha (Withania somnifera)

What It Is: Ashwagandha is an ancient Indian herb classified as an adaptogen—a substance believed to help the body manage stress. The root is dried and processed into supplements.

How It May Work: Ashwagandha may lower cortisol, a stress hormone that can interfere with testosterone production. By reducing stress and cortisol, testosterone levels might naturally increase. It may also directly support testosterone-producing cells.

Clinical Evidence: Ashwagandha has moderate evidence. A 2019 study found that men taking ashwagandha for 8 weeks showed increases in testosterone and improved sexual function compared to placebo. However, studies are still relatively small and results vary. Most positive findings came from research in men with stress-related concerns.

Typical Dose: Research used 300-600 mg daily of standardized extract (usually 5% withanolides, the active compounds). Supplement labels often match these doses, making it easier to get clinically-tested amounts.

MODERATE EVIDENCE

Zinc

What It Is: Zinc is a mineral found in foods like meat, shellfish, and seeds. It's an essential nutrient, meaning your body needs it to function but cannot make it on its own.

How It May Work: Zinc is required for testosterone production and maintenance. It helps regulate luteinizing hormone (the hormone that tells your body to make testosterone). Without enough zinc, testosterone production declines. Supplementing with zinc might restore testosterone if you're deficient.

Clinical Evidence: Zinc has strong evidence, but with an important caveat: it works best if you're deficient. Men with normal zinc levels who take extra zinc don't typically see testosterone increases. Studies show that zinc supplementation restores testosterone in men with documented deficiency. The relationship is clear and well-established.

Typical Dose: Clinical studies and recommendations use 25-30 mg daily. Most supplements provide this amount. Taking more than 40 mg daily long-term can cause problems.

STRONG EVIDENCE (if deficient)

Fenugreek

What It Is: Fenugreek is a seed from a plant in the legume family. It's used as a spice in cooking and also sold as a supplement in powder or capsule form.

How It May Work: Fenugreek seeds contain compounds that may inhibit enzymes that break down testosterone. This could theoretically allow testosterone to remain active longer in the body. Some compounds in fenugreek may also have mild hormonal effects.

Clinical Evidence: Fenugreek has preliminary evidence. Only a few studies exist, and they're mostly small. One 2011 study found modest improvements in testosterone and sexual function with fenugreek supplementation over 6 weeks. However, more research is needed to confirm these findings and determine optimal doses.

Typical Dose: Available studies used 500-600 mg daily. Supplements vary widely in concentration and dosing.

PRELIMINARY EVIDENCE

D-Aspartic Acid (DAA)

What It Is: D-aspartic acid is an amino acid (a building block of protein) produced naturally in small amounts by the body. It's marketed specifically for testosterone support in bodybuilding supplements.

How It May Work: DAA was theorized to stimulate release of luteinizing hormone, which signals testosterone production. Early animal studies and one small human study suggested it might increase testosterone.

Clinical Evidence: D-aspartic acid has insufficient evidence. While one initial study showed promise, multiple subsequent human trials failed to replicate results. The weight of current evidence suggests DAA does not reliably increase testosterone in most men. Some studies even found no change or slight decreases.

Typical Dose: Supplements typically contain 2,000-3,000 mg daily. Clinical trials used 3,000 mg daily without consistent results.

INSUFFICIENT EVIDENCE

L-Arginine

What It Is: L-arginine is an amino acid your body makes and obtains from protein-containing foods. It's marketed both as a testosterone booster and for sexual function support.

How It May Work: L-arginine converts to nitric oxide, a signaling molecule that improves blood flow. This might support sexual function, but the link to testosterone production is indirect and less clear. L-arginine does not directly increase testosterone.

Clinical Evidence: L-arginine has preliminary-to-insufficient evidence specifically for testosterone. While some research suggests it may help sexual function through improved blood flow, the evidence for direct testosterone increases is weak. It may be more useful for circulation than hormone production.

Typical Dose: Studies used 3,000-5,000 mg daily. Most supplements provide 2,000-3,000 mg per serving.

PRELIMINARY EVIDENCE

Head-to-Head Comparison

Bottom Line: Zinc offers the strongest evidence but only works if you're deficient. Tongkat ali and ashwagandha have moderate support and reasonable evidence from multiple studies. The remaining three ingredients have weaker evidence and may not reliably increase testosterone. Your choice should depend on your individual situation and what you're trying to address.

Which Ingredient Might Be Right for You

If you suspect low testosterone: Talk to your doctor first. A simple blood test can confirm whether your testosterone is actually low. If it is and your zinc levels are normal, tongkat ali or ashwagandha have the strongest evidence for supplementation. These ingredients may take 4-12 weeks to show effects.

If you're managing stress: Ashwagandha makes sense because its stress-reducing effects are well-documented, and lower stress may support testosterone indirectly. This addresses a real mechanism rather than hoping for a direct testosterone boost.

If you want the cheapest option with decent evidence: Zinc is inexpensive, but only take it if blood work shows you're deficient. Taking unnecessary zinc can cause problems.

If you're interested in sexual function: Ashwagandha or L-arginine may help through different mechanisms—ashwagandha through hormone and stress support, L-arginine through blood flow. However, sexual function involves many factors beyond any single ingredient.

General recommendation: Don't take D-aspartic acid for testosterone. The evidence doesn't support it, and safer options exist. See a doctor before starting any supplement if you have health conditions or take medications.

Safety Considerations

Zinc: Avoid exceeding 40 mg daily long-term. Too much zinc causes nausea, copper deficiency, and immune problems. Zinc interacts with certain antibiotics and osteoporosis medications.

Tongkat ali: Generally well-tolerated but may cause insomnia or anxiety in sensitive people. May interact with blood thinners or diabetes medications.

Ashwagandha: Can cause drowsiness. May interact with sedatives or thyroid medications. People with autoimmune conditions should check with their doctor first.

Fenugreek: May lower blood sugar—risky if you take diabetes medications. Can cause digestive upset. Avoid if pregnant.

D-Aspartic Acid & L-Arginine: Both generally safe at typical doses but may interact with blood pressure or heart medications. L-arginine may worsen herpes symptoms. Always inform your doctor about supplements you're taking.

Frequently Asked Questions

Do testosterone supplements work as well as hormone therapy?

No. Hormone therapy (prescribed testosterone) works reliably and quickly. Supplements show modest effects at best and may not work for everyone. If you have clinically low testosterone, prescription therapy is more predictable, though it requires medical supervision and has its own risks.

How long do