Whey protein concentrate.
Sound familiar? You've probably seen it listed on protein bars and in smoothie supplements. Whey is derived from milk, but capturing it is no easy feat, requiring "huge factories that look more like oil refineries than farms," as The Salt notes about a recent visit to the Cabot cheddar cheese factory in Middlebury, Vt. Everyday the Cabot cheese factory separates 1.6 million pounds of milk into solid curds and liquid whey. (Fact: there are nine pounds of whey for every one pound of curds.) Whey used to be considered a waste by-product, but thanks to bodybuilders who "found that in terms of bulking up, putting muscle on their bodies, whey protein was the best protein that they could find," whey now gets divided into its "purified streams" of sugar or concentrated protein.
The sugar (or lactose) is most likely to ship to Asia and end up in infant formulas, while the concentrated protein goes into products like high-protein drinks, protein-rich yogurt, and energy bars.
→ Read more: You Can Thank a Whey Refinery for that Protein Smoothie | The Salt
Related: What Can I Do with Whey from Yogurt?
(Images: Dan Charles/NPR)