I Am Milk
If you are a mammal, and I assume you are (Hello!), we are already well acquainted, aren’t we? I was, after all, your first food. I am the sweet secretion that flows from the mammary glands of a mammalian mom, the perfect nutrition for a baby human, cow, dog—what have you. I’m what allows an infant creature to exit its mother’s body and still continue to get everything it needs from her to grow into a larger, intelligent (in your case) being, tremendously jam-packed as I am with protein, fat, and delicious sugars.
The big twist with you humans, of course, is that you figured out how to continue your habit of drinking me well beyond your infancy and into adulthood. And rather than collect human milk and bottle it up, you chose a more efficient lactating creature to supply you: the cow.
This was an udder stroke of genius. By domesticating a milk-supplying animal—actually, over history, a bunch of them, including sheep, goats, buffalo, camels, and yaks—you found a way to take advantage of otherwise nutritionally useless grasslands and pastures. Ruminants such as cows, sheep, and goats are equipped with multiple stomachs and the (somewhat impolite) habit of regurgitating and re-chewing the contents of those stomachs until they’ve squeezed out every last nourishing molecule. With this unrivaled digestive determination, these beasts manage to turn scraggly weeds into copious amounts
of rich and creamy me—and more.
A milk-producing cow makes on average six or seven gallons of me a day. That’s a start, but over the years that same cow will produce several more cows’ worth of valuable side products from me. Cream, for instance: It rises to my top, as you’ll know from that handy aphorism. And then butter: one of the kitchen’s greatest daily indulgences, just cream churned into solid fat. For a while, humans were afraid of my nonskimmed versions, full as they are of saturated fat. But studies conducted since the height of fat phobia in the 1990s have suggested that full-fat dairy can be satisfying and decently healthy. Skim milk and low-fat cheese, while lower in calories, just aren’t as satiating.
The gallon you have of me in your fridge (assuming it’s cow’s milk) probably came from an industrial farm, where the cows are often fed grain and corn. Here’s a tip: When you spend a little extra to get a carton marked “from grass-fed cows,” who are out munching their way through pastures, I taste different—some might say better. Further, my flavor will change with the seasons, as the makeup of the grass changes. You might buy the same cheese all year long, but if it’s from pastured cows, its taste and texture will also evolve as spring turns into summer, and so on.
Spoiler alert—figuring out ways to make me last has always been of utmost importance. And boy, have you: You learned to let microorganisms such as lactobacillus munch on my abundant lactose sugars. This produces lactic acid and seizes me up into clots once I’m heated. Welcome to the sour cream on your baked potato and your tangy morning yogurt.
About 5,000 years ago, a wandering group of you noticed another way I go from perishable liquid to a more longlasting solid. Shepherds transporting me from field to home would open the bags in which they carried their milk and discover me curdling. There was something about those bags, made from the stomachs of sheep and goats, at work: The stomachs contained an enzyme called rennet, which helps young animals digest their mothers’ milk. Thus began the epic food tradition of making cheese. To this day, rennet from calf stomachs is still used to make many cheeses, including Parmesan, Gruyère, and manchego— which means that your vegetarian friends would do well to check before eating them.
Time-tested as I am, Americans have been drinking less and less cow’s milk since the ’70s. Over the past five years, the market shrank by more than $1 billion, while sales of soy, almond, and other nondairy “milks” grew. This was apparently threatening enough that the National Milk Producers Federation started taking issue with the use of my name—milk—to describe anything plant-based. I’m not totally sure what the fuss is about, though, since I’m fairly certain no one is confused about whether an almond has nipples.
(Speaking of nipples: Platypuses, those furry, duck-billed mammals, don’t have them, so they secrete milk through their skin, where it gathers in creases and folds, like sweat, for their young to lap up. Scientists think that mammary glands are just adapted sweat or sebaceous glands and that platypus moms operate the way ancient milk-producing protomammals might have.)
Almonds and platypuses aside, the cattle should perhaps worry: As cow’s milk sales continue to decline, America has increasingly shown interest in the ruminant that dominates the rest of the milk-drinking world: the goat. Excellent as fresh cheese, a bit gentler than cow’s milk on a lactose-sensitive stomach, and often a main ingredient in the recently popular drinkable yogurt kefir, goat milk is trendy. In other words, what’s centuries old is new again.