Researchers who recently undertook a study with mice in hopes of confirming earlier reports that eating yogurt can help prevent age-related weight gain have discovered a number of unexpected side-effects in their rodent subjects.

First, the Massachusetts Institute of Technology scientists realized that the yogurt-eating mice had shinier, silkier, and thicker coats than the non-yogurt-eating control mice. Then they noticed that the male mice were walking with a “mouse swagger,” which turned out to be due to testicles that were 5% heavier than those of mice fed a standard mouse diet and a full 15% heavier than those of mice forced to live on high-fat, low-nutrient junk food.

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And finally they conducted mating experiments and found that yogurt-eating males “inseminated their partners faster and produced more offspring,” while yogurt-eating females gave birth to larger litters and were more successful in raising them to the age of weaning.

Researchers Susan Erdman and Eric Alm have not yet determined the source of yogurt’s ability to enhance rodent sexuality, but they told Scientific American that they “think that the probiotic microbes in the yogurt help to make the animals leaner and healthier, which indirectly improves sexual machismo.”

A team of Harvard researchers has already begun investigating whether yogurt can also improve semen quality in human males and reports that “so far our preliminary findings are consistent with what they see in the mice.”

Photo by Steve Beger (originally posted to Flickr as Albino Mouse) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons