Critics of the AAFCO standards argue that such requirements are too lax. Generational studies conducted by researchers at University of California, Davis have shown some foods that pass AAFCO's feeding trials are still not suitable for long-term use and estimated that of 100 foods that pass the nutritional analysis, 10 to 20 would not pass the feeding trials. Although maximum levels of intake of some nutrients have been established because of concerns with overnutrition, many still lack a maximum allowed level and some contains large disparity between maximum and minimum values. The NRC accepts that despite ongoing research, large gaps still exist in the knowledge of quantitative nutritional information for specific nutrients. Some professionals acknowledge the possibilities of phytochemicals and other vital nutrients that have yet to be recognized as essential by nutritional science. With such broad guidelines and loose feeding trial standards, critics argue that the term "complete and balanced" is inaccurate and even deceptive. An AAFCO panel expert has stated that "although the AAFCO profiles are better than nothing, they provide false securities."