Milk is truly one of the oldest, simplest whole foods – and we certainly drink a lot of it. According to the USDA, Americans consumed an average of 1.8 cups of dairy per person, per day in 2005.
But is the milk Americans are drinking today the same milk our ancestors drank thousands of years ago? Is it even the same milk our great-grandparents were drinking a hundred years ago? By and large, the answer is no.
Like many other modern foods, most of the milk sold today has been altered, stripped, and reconstituted. Once minimally processed, milk now undergoes a complicated and energy-intensive process before it ends up bottled and shipped to grocery store shelves. There are so many additives and processes involved that buying a gallon of milk or a cup of yogurt at your grocery store essentially guarantees that you’ll get a mixture of substances from all over the country — and possibly the world. But that’s not where it ends; milk by-products also now appear in a wide variety of other processed foods.
Lloyd Metzger, director of the Midwest Dairy Foods Research Center and Alfred Chair of the Dairy Department at South Dakota State, outlined the process: Milk is received at the processing facilities and is tested for off-flavors and antibiotics. Several tanker trunks worth (from multiple different farms) get combined and placed in holding silos. Then the milk goes through a cream separator to create two products: cream and skim milk. At this point, various percentages of cream are added back into the skim milk in order to create whole and low fat milk. Milk is then homogenized, which is the process of passing it at high speeds through very small holes to create a uniform texture and prevent the cream from separating and rising to the top. It’s then pasteurized, or heated to at least 145 degrees. In some states, non-fat milk solids are added to the milk in order to thicken it and give it a better mouth feel. Then synthetic vitamins A and D are added.
When all is said and done, the product is a far cry from the milk that actually comes out of a cow. And, depending on whom you ask, each step along the way might carry its own risks.
“Homogenization is not good,” says John Bunting, a dairy farmer who researches and writes about dairy for The Milkweed. “The milk is pumped under high pressure which smashes the milk molecules so hard. Homogenization splits and exposes the molecules.” The hard science goes like this: A raw milk molecule is surrounded by a membrane, which protects it from oxygen. Homogenization decreases the average diameter of each fat globule and significantly increases the surface area. Because there’s now not enough membrane to cover all of this new surface area, the molecules are easily exposed to oxygen, and the fats become oxidized.
Critics believe that milk solids, which are sometimes added back into the milk, contain oxidized, or damaged, forms of fat and cholesterol. Nonfat milk solids are created through a process of evaporation and high heat drying which removes the moisture from skim milk. Exposure to high heat and oxygen causes fats to oxidize. And oxidized cholesterol has been shown in numerous studies to lead to atherosclerosis, or hardening of the arteries, and to raise LDL, aka “bad” cholesterol. One study from 2004 found that oxidized dietary fats are a “major cause” in the development of atherosclerosis.
This phenomenon worries Nina Planck, author of Real Food. “This damaged cholesterol is much different than what I call “fresh cholesterol,” which is found in egg yolks, whole milk, and butter,” she said. “We know that fresh cholesterol has one main effect and that is to raise HDL [or ‘good’ cholesterol]. On the other hand, oxidized cholesterol raises LDL.”
What’s more, Planck says that the law does not require manufacturers to tell consumers when milk solids are in food or milk. “It’s a [potential] scandal because it’s unlabeled,” she says. Michael Pollan writes about this as well in In Defense of Food: “In the case of low-fat or skim milk, that usually means adding powdered milk. But powdered milk contains oxidized cholesterol which scientists believe is much worse for your arteries than ordinary cholesterol.”
In California, where the industry reports the ingredients on its website, all industrially produced milk contains nonfat milk solids. Even “whole milk” is a product of reconstitution; it contains at least 3.5 percent milk fat and 8.7 percent nonfat milk solids. This is also true for (industrially produced) organic milk.
Nonfat milk solids are also found in low-fat and fat-free yogurt and cheese, infant formula, baked goods, cocoa mix, and candy bars.
Are these milk solids really as big of a problem as Planck and others in her camp believe them to be? Lloyd Metzger is doubtful. He says there’s virtually no fat left in the milk to oxidize. Bunting agrees, “If it’s skim milk, there might be small amounts — but that’s not a real concern. If you’re worried about oxidized fat, it’s homogenization that is the real culprit.”
Has Bunting seen evidence of the health impacts associated with oxidized fats in milk? “No,” he says. “But who’s going to fund it? The USDA is the largest funder of dairy research in this country and they’re not going to fund a study they don’t want to hear about.”
Regardless, says Plank, “[Industrial] milk is transformed by heat. Why would you consume an adulterated product?”