What do monsters eat for breakfast? When Mary Shelley described Frankenstein’s monster, her words were remarkably descriptive. She did not, however, disclose what kind of breakfast cereal the freak of nature might enjoy. Despite this glaring lack of specificity in the great writer’s work, Frankenstein later inspired a breakfast cereal for ordinary mortals. This cereal would have some very peculiar side effects that mothers found horrifying and children found hilarious.

The year was 1971, and a pandemic appeared to be spreading throughout the United States. Hundreds of children were rushed to emergency rooms by frantic mothers. The otherwise-healthy children had all begun to — well — poop pink. While exhibiting no other unusual symptoms, the children began to produce feces that was the color of strawberry ice cream. Hospitals all around the country were inundated with frantic requests to test the children for rectal bleeding. Thankfully, that was not the problem. What could be causing such a bizarre malady? After frantic investigation, researchers discovered that all of the affected children had one thing in common: they all had the same thing for breakfast.

General Mills had just released a new line of breakfast cereals inspired by the classic monsters. The first two cereals in this series were Count Chocula and Franken Berry. Boo Berry came out in 1973, followed by Fruit Brute the next year.

The peculiar phenomenon of the pink poop was exhibited by children who ate Franken Berry cereal. Careful research concluded it was because the cereal was colored with a dye classified as “Food, Drug and Cosmetics” (FD & C) Red No. 2 and No. 3. The dye was also known as amaranth, a synthetic color named after the natural flower. The synthetic dye worked wonders in producing the desired color for Franken Berry cereal. Since it was indigestible, it passed through children’s digestive systems while retaining its dye properties, and came out the other end with colorful and alarming results.

The condition was dubbed “Franken Berry Stool.” A 1972 case study, “Benign Red Pigmentation of Stool Resulting from Food Coloring in a New Breakfast Cereal (The Franken Berry Stool),” published in Pediatrics describes a typical scenario. A 12-year-old boy was hospitalized for four days after being admitted for possible rectal bleeding. According to physicians, “The stool had no abnormal odor but looked like strawberry ice cream.” Further questioning of the mother revealed that the child had enjoyed a bowl of Franken Berry cereal two days and one day prior to his hospitalization. To test the hypothesis that the cereal was the cause, doctors fed the boy four bowls of Franken Berry cereal. For the next two days, he passed bright pink stools. But other than pink poop, there were no other symptoms.

Artificial coloring in other cereals caused similar side effects. When Boo Berry was released, its use of Blue No. 1 resulted in green poop for its consumers. In 1982, Post Foods introduced Smurfberry Crunch Cereal. In what must have been an absolute delight for Smurf fanatics, consumption of that cereal turned one’s poop blue.

Although medical professionals found no negative health consequences from the dyes, General Mills pulled the cereals from the market until they could be reintroduced with a less-colorful fecal influencer.

Not all experiments with food additives were as harmless as the Franken Berry Stool incident. In the fall of 1950, many children became ill from eating an orange Halloween candy containing one to two percent FD&C Orange No. 1.

A Russian study in 1971 about the long-term effects of Franken Berry’s original coloring, Red Dye No. 2, created much alarm. Researchers reported a link between consumption of the dye and the development of tumors in female rats. The FDA later concluded the study was quite flawed. They could not, for example, be entirely satisfied that the Russian study used the dye in question. Nevertheless, in 1976, the FDA removed the dye from its Generally Regarded As Safe (GRAS). These days, the only red colors accepted by the FDA are Red No. 40, which appears in all of the General Mills monster cereals, and Red No. 3, typically used in candied fruits.

In response to the outcry caused by the Russian study, Mars stopped producing red M&M’s, even though Red No. 2 was not used in their production. The public had concluded that any red food coloring must be harmful.

As far as we know, none of the breakfast cereals currently on the market retain any colorful digestive byproduct side-effects. The best children can hope for these days is that the left-over milk at the bottom of the bowl might have a colored hue to highlight the massive sugar rush.