Assessment of Liver and Kidney Safety of Silver Fir (Abies alba) Branch Extract: An Open-Label Human Study of a Dietary Supplement.

Extracts of silver fir (Abies alba) branches are rich in polyphenolic compounds and are increasingly used as dietary supplements. Despite their growing consumption, systematic human data on their safety remain limited. This study evaluated the effects of a standardized silver fir branch extract on biochemical markers of liver and kidney function in healthy adults. An open-label, single-arm human study was conducted in 15 healthy volunteers (eight men and seven women; mean age 48 years). Following a two-week comparison period, participants consumed 900 mg/day of a standardized silver fir branch extract for 14 days. Serum markers of liver function (AST, ALT, GGT, ALP, and total bilirubin) and kidney function (urea, creatinine, and uric acid) were measured at baseline, after the comparison period, and after supplementation. The study was retrospectively registered at ClinicalTrials.gov. All participants completed the study without reported adverse events. Mean values of all measured liver and kidney markers remained within established reference ranges throughout the study. No statistically significant changes were observed following supplementation, and minor fluctuations were consistent with normal physiological variability. Short-term consumption of a standardized silver fir branch extract at a daily dose of 900 mg did not adversely affect biochemical markers of liver or kidney function in healthy adults. These findings provide human evidence supporting the short-term safety of this polyphenol-rich dietary supplement. Trail Registration: ClinicalTrials.gov: NCT07189143.