Stable carbon isotope ratios are used widely for the authentication of foodstuffs, especially for the detection of added cane sugar in fruit juices, spirits and honey. The major deficiency of stable carbon isotope analysis is that it cannot be used to detect the addition of beet sugar syrups to C3 crops, as the beet plant also uses the Calvin photosynthetic pathway. However, the addition of commercial sweeteners such as beet medium invert syrup can be detected by isotope ratio mass spectrometry if the abundance of deuterium in the sugars is determined.