There are many functional foods available nowadays. Functional foods are believed to promote health, physical activities, and satisfaction. However, their efficacy should be proved through both laboratory and clinical trials. To evaluate the efficacy, in vitro effects of specific animal model can be used as an objective laboratory screening test. In vivo function tests can be used as a preclinical animal study with or without administration of functional foods. In clinical trials, validated questionnaires and objective function tests can be used according to various study models. Therefore to validate the efficacy of any nutritional supplement, one or more laboratory results and validated clinical study are necessary. In conclusion, the safety and efficacy of functional foods should be decided based on a functional testing guideline, which can substantially decrease the incidence of drug overuse and protect the public health, accordingly.