Systematic reviews, sometimes including meta-analyses, are often presented as an approach for identifying healthy and sustainable diets. Here we explore to which extent systematic review protocols have been adopted by studies comparing environmental impacts of foods based on Life Cycle Assessment (LCA) results, and to which extent they comply with the PRISMA protocol for transparent reporting. Out of 224 studies screened, seven explicitly define themselves as systematic reviews, and/or claim to carry out meta-analyses. Of these, only one acknowledges a review protocol, while none complies with all the PRISMA criteria. Neither do we believe that reviews of LCA results can comply with all the criteria or carry out meta-analyses, due to underreporting on standard deviations and artificial sample sizes in LCAs. Nonetheless, reviews of food commodities and diets based on LCA results would benefit from better aligning with criteria in systematic review protocols.