Benefits
Cognitive function support — memory, attention, mental focus
A review of silk FEH cognitive trials concluded that silk fibroin enzyme hydrolysates exhibit beneficial cognitive effects for memory and learning, attention, mental focus, accuracy, memory recall, and overall memory and concentration. Studies span children (7+ years), high school/college students, adults, and seniors. Doses were 200-600 mg/day for 3-16 weeks, and a placebo-controlled RCT in 76 healthy adults averaging about 55 years found dose-dependent memory gains at 280 to 600 mg a day over 3 weeks. Worth knowing before you weigh this: the review and that trial share the same two authors, and both were funded by the company that makes the ingredient, so this is one line of evidence rather than two.
Modest athletic stamina effect (small trial)
An RCT in elite fin-swimmers showed silk amino acid supplementation improved physiological parameters defining stamina. Mechanism speculatively involves serine/glycine effects on the creatine pool, mild neurotransmitter effects, or combined amino acid contributions. The trial had 16 swimmers in total and used 500 mg of silk amino acids per kilogram of body mass a day, split into three servings, which is about 35 g a day for a 70 kg athlete and far above any supplement label. The same paper reported a larger rise in creatine phosphokinase, a muscle damage marker, in the supplemented group. One small trial in a specialized group at a very high dose, so generalizability is limited.
Skin hydration: animal evidence for sericin, and a null result for fibroin
A mouse study (animal evidence) showed dietary silk protein/sericin improved epidermal hydration with increased filaggrins and free amino acids. In that same study a fibroin diet did not increase epidermal hydration, and fibroin hydrolysate is the form used in silk supplements. Sericin is also used in topical cosmetics, but that is skin contact, not swallowing. No human trial has tested oral silk protein for skin, hair or nails, so treat this as an animal finding about a different silk fraction.
Glucose and lipid profile improvements (animal evidence)
In diabetic mice, silk protein hydrolysates improved blood glucose and lipid profiles. Limited human RCT evidence for these metabolic effects. Animal data interesting but translation to humans not yet rigorously demonstrated.
Mechanism of action
Acetylcholine pathway support (cognitive effects)
Mechanistic studies suggest silk FEH supports cholinergic neurotransmission — acetylcholine is released by cholinergic neurons and plays a key role in encoding new information and learning. Mechanism may involve choline supply enhancement or acetylcholinesterase modulation. This mechanism comes from animal and cell culture work, not from anything measured in people.
Antioxidant and neuroprotective activity
Silk fibroin and sericin demonstrate antioxidant activity (radical scavenging, GSH support) and reduce neuroinflammation in cell and animal models. May contribute to cognitive benefits via neuroprotection — particularly relevant for aging-related cognitive decline. Mechanism comparable to other dietary antioxidants but with some unique sequence-specific peptide effects.
Glycine and alanine high-concentration delivery
Silk fibroin's distinctive amino acid profile — ~43% glycine and ~30% alanine — provides high-dose glycine delivery from a relatively small mass. Glycine has independent CNS effects (NMDA co-agonist, glycine receptor agonist, sleep quality support). Alanine contributes to glucose-alanine cycle and possibly modest performance effects. The unique amino acid profile distinguishes silk from typical dietary proteins.
Anti-inflammatory peptide activity
Silk fibroin peptides demonstrate anti-inflammatory effects in vitro and in animal models — modulating NF-κB and reducing pro-inflammatory cytokines. May contribute to neuroprotective and skin-protective effects observed.
Clinical trials
Comprehensive review (Stohs SJ, Bucci LR 2022, Molecules 27(17):5407, doi:10.3390/molecules27175407).
Review of all known PubMed and Google Scholar studies on silk fibroin enzyme hydrolysates (FEH) and cognitive function. Studies in children, high school/college students, adults, and seniors (ages 7-92). Doses 200-600 mg silk FEH per day for 3-16 weeks.
Silk FEH demonstrate beneficial cognitive effects on memory, learning, attention, mental focus, accuracy, memory recall, and overall memory/concentration across multiple trials. Mechanism involves neuroprotection via antioxidant and inflammation-inhibiting activities. Acetylcholine pathway involvement supports cholinergic encoding of new information. Independence caveat: this review was funded in part by BrainOn Inc. Ltd., which makes the ingredient, and its two authors are also authors of the human memory trial it reviews, where both are listed as consultants to that company. It is a summary written by people close to the product, not independent replication.
Placebo-controlled, double-blind randomized trial (Kang YK, Lee BY, Bucci LR, Stohs SJ 2018, Nutrients 10(2):233, doi:10.3390/nu10020233, PMID 29462997). Funded by BrainOn Inc. Ltd., which makes the ingredient.
76 healthy adults aged 28 to 92 and averaging about 55 years, of whom 61 completed, randomized to 0, 280, 400 or 600 mg of silk fibroin protein enzymatic hydrolysate a day in two divided doses for 3 weeks. Memory was tested with the Rey-Kim Auditory Verbal Learning Test and the Rey-Kim Complex Figure Test at baseline and at 3 weeks.
FPEH ingestion improved memory function compared to placebo. Memory quotient, learning gradient, words recalled, retrieval efficiency and drawing recall all rose dose-dependently, with 400 or 600 mg the better doses depending on the measure, and no adverse effects reported. The trial did not compare enzymatic against acid hydrolysate, so it says nothing about which form works better. Glycine, alanine, serine, tyrosine comprise >90% of fibroin protein — amino acid mix relevant to neurotransmitter synthesis and neuroprotection. This is one of several human trials, but most of the others appear in Korean language journals that PubMed does not index, so a reader cannot check them. One other is indexed: a placebo-controlled trial in 46 healthy children (Kim K et al 2009, J Med Food 12:643-648, PMID 19627215).
Randomized controlled trial (Zubrzycki IZ, Ossowski Z, Przybylski S, Wiacek M, Clarke A, Trabka B 2014, J Int Soc Sports Nutr 11:57, doi:10.1186/s12970-014-0057-4, PMID 25525417).
Sixteen elite male fin-swimmers, eight per group, given a total of 500 mg of silk amino acid hydrolysate per kilogram of body mass a day, split into three servings in a carbohydrate drink, for 12 days, or the drink alone. Outcomes: physiological parameters defining stamina including blood lactate, performance markers.
Silk amino acid supplementation improved physiological parameters defining stamina in this elite athlete population. The change in blood lactate was far smaller than in the control group, and swimming velocity at the 4 mmol/L lactate threshold shifted by about 0.05 m/s, which was the one result that reached statistical significance. Creatine phosphokinase, a marker of muscle damage, rose in both groups and more so in the supplemented one, and the authors concluded that the stamina gain was associated with an augmented level of muscular damage. Generalizability is limited by the very small specialized cohort and by a dose far above any supplement label. Provides supportive evidence for athletic application but not as strong as the cognitive evidence base.