Why ketogenic diet (KD) effectively controls seizures in some people with epilepsy is unclear. In a recent issue of Cell, Olson et al. (2018) showed that KD prevents seizures by upregulating key bacterial species (Akkermansia muciniphila and Parabacteroides merdae). These bacteria synergize to decrease gammaglutamylation of amino acids, increase hippocampal GABA/Glutamate ratios, and, ultimately, prevent seizures.