This study evaluated the action at the cellular level of long life whole milk, full type of six renowned companies operating in the Brazilian market, as well as in other South American countries. The evaluation was performed using root meristem cells of Allium cepa L., at exposure times 24 and 48 hours, directly in milk products marketed. The results indicated that all the milk samples reduced root meristem cell proliferation, proving, in this study, a significant cytotoxic effect. Still, exposure to milk resulted in a significant frequency of mitotic spindle changes in meristem cells, characterizing these foods as genotoxic and mutagenic under the study conditions. It can be concluded that the long life milk samples caused significant genetic instability to cells of the examined tissue. The results obtained for cytotoxic, mutagenic and genotoxic action of these long life milks are of great relevance because, to date, there are no published toxicity studies on such foods and food additives present in the composition.