How we grade evidence
A — strong evidence: multiple randomized controlled trials with consistent effect sizes; FDA-approved for at least one indication, or a meta-analysis supporting effect.
B — solid evidence: several RCTs with directional evidence, but heterogeneity or limited dose-response data.
C — emerging: mostly mechanistic data plus a few small trials. Reasonable to try, low downside, but not a slam dunk.
D — weak / mixed:popular but the trial evidence is thin or contradicts the marketing. Generally we don't list these.
What we explicitly leave off
Most of the supplement-aisle bestsellers fall here. Apple cider vinegar gummies, cinnamon for blood sugar, biotin for hair growth in non-deficient adults, “detox” blends, generic “greens” powders, most testosterone boosters, most nootropic stacks, raspberry ketones, garcinia. Either the evidence is weak or the dose in the supplement is well below what the trial used.
When you should actually skip a supplement
Whenever the food version is realistic. Fiber from oats and beans is cheaper and better than a fiber gummy. Omega-3 from two servings of fatty fish per week beats most fish-oil capsules. Magnesium from leafy greens, nuts, and seeds beats most magnesium supplements. The stack is for genuine gaps, not as a substitute for boring basics.