The Near-Impossibility of Chugging a Gallon of Milk

Have you ever felt the urge to almost guarantee making yourself nauseous? If you’re like the majority and prefer to avoid such discomfort, the gallon of milk challenge likely holds little appeal. However, if you’re someone who thrives on pushing limits, this might be the ultimate test. In this episode of the BrainStuff podcast, host Christian Sager breaks down why this challenge is nearly impossible to complete.

The rules of the challenge are straightforward: Participants must drink a gallon of milk as quickly as possible and then keep it down for an hour without vomiting. While it sounds easy, the failure rate is astonishingly high. Countless attempts have ended in disaster, as evidenced by countless YouTube videos, but is it truly impossible? Not quite—just extremely challenging and somewhat unpleasant.

The real intrigue lies in why this challenge is so tough. Drinking a gallon of any liquid, even water, in a short time frame can be hazardous. A gallon of water overwhelms the circulatory system and kidneys, dilutes blood electrolytes, and causes cells to swell, potentially leading to brain damage or even death. Similarly, most who attempt the milk challenge end up vomiting due to a variety of physiological reasons.

One initial assumption might point to lactose as the primary factor. Lactose, a sugar found in milk, has a limit to how much the human body can process. The enzyme lactase is required to break it down, and those with lactose intolerance struggle to digest even small amounts, sometimes leading to vomiting after a single glass. However, lactose intolerance primarily affects the large intestine, not the stomach. Lactose is digested in the small intestine, and when it reaches the large intestine, bacteria ferment it, causing gas and diarrhea. Thus, lactose isn't the main reason people can't keep the milk down.

Calcium could also play a role. An 8-ounce (237-milliliter) glass of milk contains 300 milligrams of calcium, equivalent to 1.5 chewable Tums tablets, which have 200 milligrams each. Drinking a gallon of milk is akin to consuming 25 Tums tablets, severely disrupting the stomach's acid balance and providing a strong incentive to vomit.

The primary reason this challenge is so difficult lies in the stomach's capacity. On average, a human stomach can only hold about half a gallon (1.9 liters) of any substance. Exceeding this limit activates the stomach's stretch receptors, triggering an emergency response that results in vomiting.

In reality, only professional eaters can consistently complete this challenge. While chugging a gallon of milk is tough, attempting the same with any other liquid would likely end in a similar messy outcome.