Three studies reported the effects of zinc complexes with strong ligands present in molar excess relative to zinc. Bristol Myers Products sponsored a study in which extramolar citric acid was used to flavor-mask zinc gluconate, resulting in approximately 1-day increase in common cold duration. An Australian study used several strong zinc chelators to provide an effervescent effect, resulting in severe worsening of symptoms and substantial lengthening of common cold duration. A study using zinc gluconate with glycine produced anomalous positive (mixed) results.