Dannybex started a thread on how Jarrow's methylB12 contains citric acid, which attacks the teeth. So does ascorbic acid (vitamin C). I asked a dentist friend how we should therefore protect our teeth. She gave these suggestions: Don't brush your teeth straight after acidic things. Brush your teeth before eating acidic vitamins using a high-fluoride toothpaste such as Duraphat 2800 or 5000 (prescription only from your dentist in the UK at least). Sensodyne claim that their Pronamel toothpaste is also protective. Or, use a high-fluoride mouthwash before the acidic vits. Tooth mousse, which you can get from your dentist, contains recaldent which is full of minerals and restores your tooth enamel - rub it onto your teeth with your finger straight after the acidic vits. Rather than chewing Vitamin C tablets, use soluble Vitamin C and drink it through a straw. Eat a piece of cheese after the acidic vits.