Supplement analysis backed by scientific evidence · PT · ES · DE · FR

← All supplements
Limited evidencePhysical performance

Silk Amino Acids

Silk amino acids are hydrolyzed silk fibroin protein, marketed for stamina, muscle growth and libido. The human evidence is a single small immune-marker trial; the performance and libido claims come from mouse studies, and one of the most-cited silk peptide cognition papers was formally retracted.

View on iHerb Ships to 180+ countries · welcome discount for new customers

What the science says

  • Performance and libido claims come from mice, not people Limited evidence

    The foundational study fed silk amino acids to mice and reported improved swim-to-exhaustion time and measures of male reproductive function. No randomized controlled trial in humans has tested silk amino acids for strength, endurance, muscle mass, or sexual function. Rodent stamina data are among the weakest possible bases for a human ergogenic claim.

  • One small human trial, on natural killer cell activity — not performance Limited evidence

    A 2021 randomized trial of a silk peptide product (Sil-Q1) in healthy adults reported increased natural killer cell activity versus placebo at a reduced dose over 8 weeks. It was an industry-linked single-product trial with an immune surrogate endpoint — no illness incidence, no performance measure — and has not been independently replicated.

  • A key cognition paper was retracted Limited evidence

    The widely cited 2013 report that silk fibroin-derived peptides enhance memory in scopolamine-treated mice was formally retracted by the journal in 2016. Marketing copy still circulates the original finding. Treat any silk-peptide nootropic claim tracing back to that work as unsupported.

  • Amino acid profile is poor for muscle building Limited evidence

    Silk fibroin is roughly 45% glycine, 30% alanine and 12% serine, with very little leucine — the amino acid that actually triggers muscle protein synthesis. As a protein source it scores badly on essential amino acid content; whey, casein or a complete EAA blend delivers far more of what drives hypertrophy per gram.

Dosage & safety

Studied doseNo validated human dose exists. Products typically supply 1-3 g/day; the one human trial used a proprietary silk peptide preparation at a reduced dose over 8 weeks. Mouse studies used doses that do not translate meaningfully to humans. If your goal is training adaptation, a complete protein at 1.6-2.2 g/kg/day of total daily protein is the evidence-based approach.
SafetyNo serious adverse events reported in the small human trial, and silk protein has a long history of food use in parts of East Asia. That said, safety data are thin: no long-term human studies, no pregnancy or breastfeeding data, and no established upper intake. People with silk allergy (a recognized occupational allergen, including reports of anaphylaxis to silk protein) should avoid it. Silk-based supplements are frequently sold in blends stacked with stimulants or undisclosed ingredients — check labels and prefer third-party-tested products. Not banned in sport.

How to take it

TimingTiming does not matter — no protocol has been validated in humans.
With food?Either way.
Worth knowingRead the full ingredient panel: silk amino acid products are often sold as a front for stimulant blends.

Frequently asked questions

Do silk amino acids build muscle or boost stamina?

No human trial has tested silk amino acids for strength, endurance or muscle mass; the claims come from mouse studies, so the evidence is limited. Silk protein is also very low in leucine, so whey, casein or a complete EAA blend does far more for muscle.

Do silk amino acids improve libido?

There is no human evidence. The libido claim for silk amino acids comes from a mouse study of male reproductive function, not a trial in people.

Are silk amino acids good for memory?

No. A widely cited 2013 mouse study on silk peptides and memory was formally retracted in 2016, and no human trial supports a cognitive benefit from silk amino acids.

Scientific references

Where to buy

View on iHerb

Ships to 180+ countries · welcome discount for new customers

Referral link — this site may earn a commission on purchases.

Related in Physical performance