Omega-3 / Fish Oil
Most labels report oil weight, not EPA/DHA content — the biggest, messiest verifiability gap found in this project. Marine/krill/algae and plant-based (ALA) sources kept in separate, never-mixed comparison lanes.
Creatine
No established Daily Value. Plain monohydrate labels already state pure creatine mass, but patented/proprietary blends (HCl systems, ethyl ester) often hide the actual creatine content in a compound or blend weight.
Vitamin D3
Has an established Daily Value — IU and mcg convert on a fixed 40:1 ratio, so every product's dose is already directly comparable. The real finding here is a brand/format price premium, not a verifiability gap.
Vitamin C
Has an established Daily Value — ascorbic acid, calcium ascorbate, sodium ascorbate, Ester-C, and liposomal forms are all directly comparable. The real finding is a large "liposomal" delivery-format price premium.
Calcium
Has an established Daily Value — carbonate, citrate, gluconate, coral, and hydroxyapatite forms all report the elemental-calcium-equivalent amount directly. Coral and capsule formats carry a real, sizable price premium over plain carbonate.
Protein Powder
Grams of protein per serving is always comparable, regardless of source (whey, casein, egg, plant). The nuance is blend transparency — some multi-source blends disclose their source ratio, most don't.