Vitamins
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.
Minerals
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.
Magnesium
Has an established Daily Value — oxide, citrate, glycinate, threonate, and malate forms all report the elemental-magnesium-equivalent amount directly. Threonate (Magtein) carries an over-80x price premium over plain oxide for the same mineral.
Performance
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.
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.
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.