Souvenaid (Nutricia, Zoetermeer, the Netherlands) is a medical food for the dietary management of early Alzheimer's disease. The mix of nutrients in this drink is suggested to have a beneficial effect on cognitive function; such implicit health claims for medical foods are not checked by government agencies. Souvenaid has been investigated in three clinical trials. The first trial showed that Souvenaid produced a significant improvement in delayed verbal recall, but not in other psychological tests. The second and largest trial showed no effect on any outcome. The third trial showed no significant effect at 12 or 24 weeks, but a significant difference in the 24-week time course of the composite memory score. None of these outcomes was clearly specified as a primary outcome at trial registration. In conclusion, there is no convincing proof that Souvenaid benefits cognitive function. Better scrutiny of the efficacy of medical foods is warranted.