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Can Science Explain McDonald's Shamrock Shake?

"So... In your professional opinion, would you say that making the Shamrock Shake is more art or science?"

The McDonald's employee looked at me with a befuddled expression.

"It comes out of the machine," she said.

"Ah yes, of course!" I exclaimed. "So science, then?"

Another quizzical look. "Sure..."


Each year, in the weeks leading up to St. Patrick's day, McDonald's shamrock shake makes its triumphant, limited-time-only return. The moment is hailed with media mentions, social media shout-outs, and loosened belts across the country.

For over four decades since it first appeared, the shamrock shake has not been widely available. As a result, it has attained an almost cult status among its followers. In addition, the YouTube arrival of nostalgic advertisements featuring Uncle O'Grimacey has helped fuel the mania.

So what is it about the shamrock shake that makes it so tempting? Is it the sumptuous taste? Many would describe the flavor as "minty" and "creamy," though the technical description is "pure mint McAwesomeness." But the taste alone cannot adequately explain the shake's allure.

Is there something special about the crafting process? I can confirm that the shamrock has its own special nozzle in McDonald's shake machine, though what exactly is going on within the machine's innards remains a mystery. (Leprechaun laborers, perhaps?)

What about the ingredients? Is it the unique, magical concoction of reduced fat vanilla ice cream, high fructose corn syrup, water, sugar, natural flavoring, xanthan gum, citric acid, sodium benzoate, yellow 5, and blue 1 that arouses such mirth and loyalty within the shake's indulgers? (Strangely enough there's no mention of mint or mentha in the ingredients, but there is mention of carrageenan, which is also used in personal lubricants.)

There's obviously something to be said for the shake's combination of sugar and fat, which research has shown to be quite a powerful force indeed. The simultaneous intake of both fat and sugar activates hunger signals, depresses feelings of satiety, and may boost feelings of happiness.

Such a simple explanation surely doesn't do the shamrock shake justice, but barring the involvement of leprechauns, it probably is the most likely answer. If you have a hypothesis of your own, please share! As of this moment, I have run out of legitimate theories, along with the shamrock shake that I purchased earlier for "study."

In the next edition of "shake science," Jack in the Box's bacon shake: "why?"