The SNIF-NMR method (site-specific natural isotope fractionation studied by Nuclear Magnetic Resonance) was used to examine the isotopic profile of glucoses derived from plants with different photosynthetic pathways. It is shown that the type of photosynthetic metabolism, either C3 (beet-root, orange, grape), C4 (maize, sugar-cane) or CAM (pineapple), exerts a strong influence on the deuterium distribution in the sugar molecules. The isotopic profile also depends, secondarily, on the physiological status of the precursor plant. Consequently, the isotopic fingerprint of glucose may be a rich source of information in mechanistic comparisons of metabolic pathways. Moreover, from an analytical point of view, it may provide complementary criteria with respect to the ethanol probe for origin inference of sugars.