Answer: Saccharin

There’s something quite curious about the discoveries of artificial sweeteners—a significant number of them were discovered by accident. The first artificial sweetener ever discovered came about entirely by accident thanks to lax lab safety practices.

Constantin Fahlberg, a German scientist, discovered saccharin—the first artificial sweetener—in 1879. He was doing research entirely unrelated to sweeteners, but was instead conducting research on coal tar derivative products. Specifically, Fahlberg was searching for a way to turn by-products of the coal industry into something usable (and profitable). Fahlberg, in an 1886 interview with Scientific American, explained how he stumbled upon the sweetener:

“How did I discover saccharin?” he said. “Well, it was partly by accident and partly by study. I had worked a long time upon the compound radicals and substitution products of coal tar, and had made a number of scientific discoveries that are, so far as I know, of no commercial value. One evening I was so interested in my laboratory that I forgot about supper until quite late, and then rushed off for a meal without stopping to wash my hands. I sat down, broke a piece of bread, and put it to my lips. It tasted unspeakably sweet. I did not ask why it was so, probably because I thought it was some cake or sweetmeat. I rinsed my mouth with water, and dried my moustache with my napkin, when, to my surprise, the napkin tasted sweeter than the bread. Then I was puzzled. I again raised my goblet, and, as fortune would have it, applied my mouth where my fingers had touched it before. The water seemed syrup. It flashed upon me that I was the cause of the singular universal sweetness, and I accordingly tasted the end of my thumb, and found that it surpassed any confectionery I had ever eaten. I saw the whole thing at a glance. I had discovered or made some coal tar substance which out-sugared sugar. I dropped my dinner, and ran back to the laboratory. There, in my excitement, I tasted the contents of every beaker and evaporating dish on the table. Luckily for me, none contained any corrosive or poisonous liquid.”

Fahlberg was hardly exaggerating about the sweetness of his accidental discovery. Saccharin is about 300-400 times sweeter than sucrose (sugar). What amounted to a dusting of powdered sugar on his fingertips was the equivalent of dozens of spoons of sugar distilled down into an intensely sweet surprise.

Fahlberg would hardly be the last in a line of researchers who accidentally stumbled upon artificial sweeteners while pursuing other research. In 1965, James M. Schlatter discovered aspartame when he synthesized it as an intermediate step in generating a tetrapeptide of the hormone gastrin for use in assessing an anti-ulcer drug candidate. He licked his finger to pick up a piece of paper and found that it tasted extraordinarily sweet.

In 1976, Shashikant Phadnis, a graduate researcher at Queen Elizabeth College, was helping with research into chlorinated sugar compounds. He misheard a telephone call from a large sugar company requesting samples of the chlorinated sugars for “testing”, thinking they said “tasting” instead, so he tried the compounds first. That accidental slip up led to the discovery of yet another artificial sweetener: sucralose.

Thanks to the lax hand washing routines and accidental slip ups of multiple scientists over the last century and a half, you can enjoy sweet treats and a dash of “sugar” in your coffee guilt-free.