ElementalDose: label arithmetic for US magnesium supplement labels (NIH DSLD snapshot 2026-08-10)

Arithmetic on each label's own declaration, always at the reading most favourable to the product: not a laboratory assay, not a finding that any product is mislabeled, and not medical or intake advice. A US Supplement Facts panel declares elemental magnesium per serving, not the mass of the magnesium salt needed to deliver it. This dataset recomputes, for all 716 on-market magnesium labels in the NIH Dietary Supplement Label Database snapshot of 2026-08-10, the compound (salt) mass per serving and per capsule from each salt's molecular formula, and compares it with standard capsule capacities (size 0 about 545 mg, 00 about 730 mg, 000 about 1,100 mg at powder density 0.6–0.8 g/mL). Of 200 capsule labels that name a single salt, 43 declare more magnesium than the named salt alone could deliver from a size 000 capsule, and 62 need the largest standard size. The deposit contains the per-label table (716 rows), the audit subset (105 rows), a registry of 16 peer-reviewed studies that measured magnesium salts (bibliographic metadata and PubMed identifiers in the studies file), and a README with the method and a column dictionary. Retail prices shown on the website are not included. Live pages, charts and per-page CSV files: elementaldose.com/data.