Immune support is the category where a real, measurable effect is most often reported for a condition nobody was going to be seriously harmed by. Duration of a cold is a legitimate endpoint The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score.. It is not evidence about immune aging.
Two features of the grading system matter on a page like this. A grade attaches to a use, not to a molecule, so the same compound can carry different letters for different questions. And a grade is capped by the kind of outcome the trials measured: a surrogate marker A lab value or measurement used in place of the outcome that matters, such as LDL cholesterol standing in for heart attacks. Moving a surrogate does not always move the outcome. or a self-reported score cannot reach Grade A under the EBL rubric no matter how well the trial was run.
Every letter below links to its own page, where the trials, the PMIDs PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. and the reasons for the ceiling are set out in full.