The Short Version
This claim significantly overstates the evidence. While a few small, short-term clinical trials (6–12 months) of specific supplements like TA-65 reported no serious adverse effects, the best available systematic review explicitly states that long-term cancer risk and chronic toxicity remain unaddressed, and a 12.4% treatment-emergent adverse-event rate was observed. Mechanistic and epidemiological evidence also links telomerase activation with cancer risk. Declaring these supplements broadly "safe for human use" is not supported by current science.