Part 2. Same respect, same yardstick. The Buck Institute is a serious place with serious scientists, and their supplement guide ranks by human evidence, which is the right way to do it. This is their Tier 2, the "promising" tier. Their own definition of Tier 2 is "encouraging early human data". Their Tier 3 is where "the human data is limited, observational, or mixed". Hold the nine Tier 2 supplements against those two sentences, and most of them read like Tier 3. Where there's a specific job, they're right that human data exists. CoQ10 in heart failure. Probiotics when you're on antibiotics. NAC as a drug. Rehydration salts for diarrhea. Curcumin for sore knees, maybe. For a healthy adult chasing healthspan it's thinner. Urolithin A missed its primary endpoint in both main trials. Ketone esters don't improve performance, and the one aging trial was a 30-person tolerability pilot. Glycine, NAC and glutathione are three entries built on one idea, and in 114 healthy older adults glyci...