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
"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.
Milk solids
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?"
Yet another product that ends up in industrial dairy products is milk protein concentrates. MPCs, as they're called, are made by ultra-filtration -- milk is forced through a membrane to remove some of the lactose. MPCs have less carbohydrates and more protein than other milk solids and are often used in protein bars and drinks as well as in some processed cheeses, according to Metzger. Nonfat milk solids are approved for food use but MPCs are not considered GRAS, or generally regarded as safe by the FDA.
"MPCs have undergone a change," says Bunting. "They cannot be reconstituted into anything called milk." He suspects that the protein in MPCs is not as digestible as that in milk, but it has never been tested. He says Kraft, in particular, uses a lot of MPCs.
Lorraine Lewandrowski, a fourth-generation dairy farmer in Newport, N.Y., is also concerned about MPCs. "MPCs are derived from milk, but they're not really milk," she said. "There have been a lot of complaints by farmers concerned about MPCs being added to cheese to boost production." She says that typically around 10 pounds of milk yields one pound of cheese. MPCs -- many of which come from overseas -- can increase yields considerably.
Planck is troubled that most MPCs are being imported from countries such as New Zealand, Mexico, and China. "We cannot trust foreign governments with the safety of these ingredients," she says. According to Metzger, MPCs must appear in ingredient lists, but the country of origin doesn't have to be labeled.
An alternative
Milk doesn't have to contain nonfat milk solids, MPCs, or any other additives. Mark McAfee, founder of Organic Pastures, offers an alternative in California. "What is in our bottle comes straight from grass-fed, pasture-grazed cows. All we do is chill it and test it," he said.
In the New York region, where the sale of raw milk is illegal, small dairies leave their milk unhomogenized and pasteurize it at low temperatures to avoid damaging the milk molecules. Unfortunately, most Americans don't have access to real milk from a local dairy farmer whose operations are transparent. "The real issue is trust," Bunting said. "If people could buy from someone they trusted, we wouldn't even need pasteurization. It extends shelf life, but it's not a safer product."
Even when milk is produced regionally, farmers still encounter processing hurdles. Lewandrowski raises 60 cows on pasture and knows them each by name. But since she can't afford her own bottling facility, her grass-fed milk gets mixed with that from farms across the region (many of them large-scale dairies that feed their cattle grain and keep them in confinement) and gets shipped off for use in a myriad of dairy products. "People tell me I should bottle my own milk," she says. "But I don't have the $50,000 it would cost."
Meanwhile, industrial milk production is being shaped to increase profits in counter-intuitive ways. "Americans are drinking more skim milk, while they're consuming more milk fat, in the form of ice cream and half and half," says Bunting. In some areas, he points out, school districts have banned whole milk and are serving students skim milk.
"Part of the idea is to take that fat and use it somewhere else more profitable," he says. McAfee agrees, "They have butchered milk into its parts and now make more money because of the low fat craze."
So how can Americans gain access to real, unadulterated milk? This would require a re-localization of dairy production, which would mean more dairy farmers. "Look," Bunting says, "if you don't want industrial processes, then we need more people producing food." Of course, in order to make that work, we'll also need a much more robust support system for dairy farmers, and a larger base of consumers willing to pay more for milk produced on a smaller scale.
Dr. Oz is right to be concerned about arsenic contamination in our food supply. 
