Pasteurization, since its adoption in the early 1900s, has been credited with dramatically reducing illness and death caused by contaminated milk. But today, some people are passing up pasteurized milk for what they claim is tastier and healthier "raw milk."
Public health officials couldn't disagree more.
Drinking raw (untreated) milk or eating raw milk products is "like playing Russian roulette with your health," says John Sheehan, director of the Food and Drug Administration's Division of Dairy and Egg Safety. "We see a number of cases of foodborne illness every year related to the consumption of raw milk."
More than 300 people in the United States got sick from drinking raw milk or eating cheese made from raw milk in 2001, and nearly 200 became ill from these products in 2002, according to the Centers for Disease Control and Prevention.
Raw milk may harbor a host of disease-causing organisms (pathogens), such as the bacteria campylobacter, escherichia, listeria, salmonella, yersinia, and brucella. Common symptoms of foodborne illness from many of these types of bacteria include diarrhea, stomach cramps, fever, headache, vomiting, and exhaustion.
Most healthy people recover from foodborne illness within a short period of time, but others may have symptoms that are chronic, severe, or life-threatening.
People with weakened immune systems, such as elderly people, children, and those with certain diseases or conditions, are most at risk for severe infections from pathogens that may be present in raw milk. In pregnant women, Listeria monocytogenes-caused illness can result in miscarriage, fetal death, or illness or death of a newborn infant. And Escherichia coli infection has been linked to hemolytic uremic syndrome, a condition that can cause kidney failure and death.
Some of the diseases that pasteurization can prevent are tuberculosis, diphtheria, polio, salmonellosis, strep throat, scarlet fever, and typhoid fever.
Pasteurization and contamination
Milk can become contaminated on the farm when animals shed bacteria into the milk. Cows, goats, and sheep carry bacteria in their intestines that do not make them sick but can cause illness in people who consume their untreated milk or milk products.
But pathogens that are shed from animals aren't the only means of contamination, says Tom Szalkucki, assistant director of the Wisconsin Center for Dairy Research at the University of Wisconsin-Madison. Cows can pick up pathogens from the environment just by lying down--giving germs the opportunity to collect on the udder, the organ from which milk is secreted. "Think about how many times a cow lays down in a field or the barn," says Szalkucki. "Even if the barn is cleaned thoroughly and regularly, it's not steamed. Contamination can take place because it's not a sterile environment."
The health hype
This is simply not the case, says Sheehan. Research has shown that there is no significant difference in the nutritional value of pasteurized and unpasteurized milk, he says. The caseins, the major family of milk proteins, are largely unaffected, and any modification in whey protein that might occur is barely perceptible.
"Milk is a good source of the vitamins thiamine, folate, B-12, and riboflavin," adds Sheehan, "and pasteurization results in losses of anywhere from zero to 10 percent for each of these, which most would consider only a marginal reduction."
While the major nutrients are left unchanged by pasteurization, vitamin D, which enhances the body's absorption of calcium, is added to processed milk. Vitamin D is not found in significant levels in raw milk.
"Pasteurization will destroy some enzymes," says Barbara Ingham, Ph.D., associate professor and extension food scientist at the University of Wisconsin-Madison. "But the enzymes that are naturally present in milk are bovine enzymes. Our bodies don't use animal enzymes to help metabolize calcium and other nutrients."
"Enzymes in the food that we eat and drink are broken down in the human gastrointestinal tract," adds Ingham. "Human bodies rely on our own native enzymes to digest and metabolize food."
"Most of the native enzymes of milk survive pasteurization largely intact," says Sheehan, "including those thought to have natural antimicrobial properties and those that contribute to prolonging milk's shelf life." Other enzymes that survive are thought to play a role in cheese ripening.
Ingham says that pasteurization will destroy some bacteria that may be helpful in the fermentation of milk into products such as cheese and yogurt, "but the benefit of destroying the harmful bacteria vastly outweighs the supposed benefits of retaining those helpful microorganisms. Plus, by adding the microorganisms that we need for fermentation, we can assure a consistently high quality product."
Science has not shown a connection between drinking raw milk and disease prevention. "The small quantities of antibodies in milk are not absorbed in the human intestinal tract," says Ingham. "And there is no scientific evidence that raw milk contains an anti-arthritis factor or that it enhances resistance to other diseases."
Fans of raw milk often cite its creamy rich taste, says Szalkucki, who adds that it may be creamier because it is not made according to the standards for processed milk. "If you go to a grocery store and buy fluid milk, it's been standardized for a certain percentage of fat, such as 2 percent," he says. "Raw milk is potentially creamier because it has not been standardized and it has a higher fat content."
In states that prohibit intrastate sales of raw milk, some people have tried to circumvent the law by "cow sharing," or "cow leasing." They pay a fee to a farmer to lease or purchase part of a cow in exchange for raw milk, claiming that they are not actually buying the milk since they are part-owners of the cow. Wisconsin banned cow-leasing programs after 75 people became infected with Campylobacter jejuni bacteria in 2001 from drinking unpasteurized milk obtained through such a program.
Raw milk cheeses
The FDA's Center for Food Safety and Applied Nutrition (CFSAN) is currently examining the safety of raw milk cheeses and plans to develop a risk profile for these cheeses. This information will help FDA risk managers make future decisions regarding the regulation of these products to protect public health.
Ensuring milk safety
Under the Grade A program, state personnel conduct inspections and assign ratings and FDA regional milk specialists audit these ratings, says Richard Eubanks, M.P.H., a senior milk sanitation officer on CFSAN's Milk Safety Team. "It's a rigorous process of inspection and auditing," he says, and "it covers from cow to carton," starting with the dairy farm and continuing through the processing and packaging of products at milk plants. Products that pass inspection may be labeled "Grade A."
The FDA Grade A milk program includes pasteurized milk from cows, goats, sheep, and horses. Raw milk and raw milk cheeses cannot be labeled Grade A, since they are not pasteurized and not covered under the program.