The application relates to novel aqueous oral care compositions useful for combining and delivering incompatible stannous fluoride or stannous chloride or stannous pyrophosphate, potassium salts, and an amino acid (e.g., a basic amino acid) in a high-water composition, for example, to provide effective caries prevention, protection against dental erosion, and relief from dental hypersensitivity. Additionally, oral care compositions described here useful in order to naturally promote nitrate reduction from the oral microbiome, which can eventually result in systemic increases of nitric oxide in blood plasma, and can form part of an overall regimen to maintain or control blood pressure. Compositions comprise stannous fluoride, stannous chloride or stannous pyrophosphate, nitric acid or a water-soluble nitrate salt such as potassium nitrate, a water-soluble alkali metal polyphosphate such as tetrasodium pyrophosphate or trisodium polyphosphate, a basic amino aid such as arginine and more than 10 wt % water.