Ines Vuckovic/Dose

There’s a reason for the rumor.

Our Middle School Mysteries series investigates childhood rumors you never bothered to fact-check yourself.

In 1999, Mountain Dew was the fourth-most popular soda in the United States. The soft drink had come a long way: In the early 80s, seeking to boost sales, PepsiCo attempted to market the drink to “hillbillies” with ads tempting people to “tickle your innards.”

As the 80s progressed, PepsiCo changed tactics. They rebranded the soda, targeting cool, young teens and positioning the drink alongside video games and extreme sports.

The name Mountain Dew is reportedly a nod to moonshine, but for many nostalgic millennials, the drink is synonymous with a pervasive myth from the 90s: that drinking Mountain Dew could lower your sperm count.

The rumor caught on quickly and had real implications. America’s youth — supercharged on hormones and undeterred by common sense sexual practices — believed it. In 2008, Florida legislators called for an overhaul to the state’s sexual education program after a survey suggested that teens thought that taking a shot of the soda would work as a contraceptive.

The rumor begins

Mountain Dew is famous for its fluorescent yellow-green color, achievable only through the addition of a food dye called tartrazine, or Yellow №5. Yellow №5 was approved by the Food and Drug Administration in 1969 and is therefore considered safe for human consumption.

A stamp of approval from the FDA, however, was not enough to dissuade adolescents from convincing each other the drink was dangerous: In addition to preventing pregnancy, rumor has it that Yellow №5 could also shrink a man’s penis or prevent it from growing altogether.

The use of Yellow №5 inside processed foods is not uncommon: Doritos, gummy bears, Kool-Aid, Jell-O and drinks like Gatorade, Surge and Fanta also utilize the dye’s properties. If tartrazine really was crippling men’s sex organs and sperm count, Mountain Dew wouldn’t be the only offending food product.

Adding fuel to the fire

To date, there are no reported cases where Mountain Dew or Yellow №5 affected the human reproductive system. The same, however, cannot be said of mice: In 2009, scientists at the University of Oran in Algeria conducted an experiment where they studied how the dye affected rodents.

According to their results, excessive drinking of tartrazine caused lower sperm counts and abnormalities within the mice’s sperm. But the study’s authors didn’t seem to think it would be a real threat to humans, concluding only that people should “estimate their daily intake” of Yellow №5 so that they were aware of how much they were consuming.

The FDA reassessed Yellow №5 in 2009, but maintains that “there were no indications of [Yellow №5]-related adverse effects on reproduction or development.”

Putting the rumor to bed

Everyone from Dear Abby to Snopes has debunked the Mountain Dew rumor. Even so, it persists, likely fueled by poor sexual education and hormonally-charged young men willing to use the Dew to do the dirty.

Still, Mountain Dew truthers aren’t entirely wrong. The soda can help prevent pregnancy — so long as its used to chase a birth control pill.