In the present study, the effects of fermented ingredients containing microorganisms beneficial to the intestinal flora on the lifespan of F-1 and F-2 generations of Drosophila melanogaster were investigated. The effects of kefir, yogurt, and milk on lifespan were tested via nutrition and in vivo. Milk, which is the basic ingredient of the fermented foodstuffs, was included in the experimental set-up to determine whether fermentation has any positive effect. The ingredients unexpectedly shortened the lifespan of the F-1 and F-2 generations. The longest lifespan was found in the experimental group given yogurt in males and females, while the mean lifespan was found in the group given milk among females and in the group given yogurt among males. Among females the shortest lifespan was found in the group given kefir and among males in the group given milk The average lifespan was shorter in the experimental groups than it was in the control group. The effect in Drosophila did not differ between the fermented and nonfermented ingredients.