Coca-Cola and milk are two seemingly innocuous substances that most of us probably have in our kitchens. When combined, however, they produce something unexpected and potentially stomach-churning.


Now consider the health risks of consuming too many soft drinks: In this comprehensive article published by the Harvard T.H. Chan School of Public Health, these sugary beverages are linked to increases in diabetes, heart disease, and other obesity-related ailments in individuals who regularly indulge. The studies and statistics are chilling in an abstract way, but the video below provides a much more concrete demonstration that allows us to visualize the potential damage soft drinks may be doing to our bodies.
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The premise for this experiment is simple enough to be replicated in a science fair or even a for high school science project, especially since it only requires two ingredients (both of which are readily available). As you may have guessed, the "scientist" in the video simply pours milk into a bottle of Coca-Cola, then waits. After only 15 minutes, the solution begins to visibly change. An hour later, the Coca-Cola and milk form a transparent liquid with what can only be described as chunks of sediment settled on the bottom.

A blog post on Steve Spangler Science (a website dedicated to making science experiments more accessible and the man responsible for the 2005 "Diet Coke and Mentos" viral video) and the YouTube video description for this experiment attribute this "invisible soda" phenomenon to Coca-Cola's high phosphoric acid content. The soda and milk react to each other in this way because the phosphoric acid molecules in Coke adhere themselves to the milk, which in turn creates a dense solid. That solid separates from the liquid and sinks to the bottom of the container. The coagulate is essentially curdled milk, and looks about as appetizing as it sounds. 

While this experiment is a cool way to visually demonstrate a chemical reaction in progress, it also reveals a harrowing health hazard in a tangible way. According to WebMD, there has been an observed connection between high soda intake and increased risk of bone fractures, but it wasn't until recently that theories about why this might happen have surfaced. The article mentions that the increased occurrence of osteoporosis in frequent soda drinkers was previously attributed to those people consuming soft drinks instead of calcium-rich beverages like milk or orange juice.

However, recent studies have shown that the phosphoric acid in colas may reduce bone density due to the chemical reaction demonstrated below. Katherine Tucker, associate professor of nutritional epidemiology at Tufts University, published a study examining the relationship between regular soft drink consumption and bone health in adults. Tucker found that the differences between her subjects' bone densities, after eliminating other variables, "was not due to lower calcium, it was not due to the caffeine in the cola, it was not due to the sugar, and we adjusted for calcium and vitamin D as well as body size. It seems the thing that's left is the phosphoric acid." There is still more research to be done, of course, to find an unequivocal answer. In the meantime, to counteract potential bone loss, it's important to increase calcium intake in your diet.

Watch this experiment in the video below, and be sure to share your thoughts with us in the comments section.