The claims are appealing: Milk straight from the cow's udder is a "living food" that can help fend off illnesses, such as asthma, and has kept farm families healthy for generations.
Anecdotally, the claims are supported by people who drink raw, unpasteurized milk. Some have said it has reduced behavioral problems in children and has cured autism.
"One mother's anecdote is science to her," said Sally Fallon, president of the Weston A. Price Foundation, which sponsors a national campaign in favor of raw milk sales.
Yet as Wisconsin's Legislature considers a measure that would allow raw milk sales under certain circumstances, dairy industry experts - including University of Wisconsin-Madison scientists - dismiss claims that it is any healthier than pasteurized milk.
In fact, public health agencies and epidemiologists say raw milk can be dangerous because of the harmful bacteria it may carry. There were "astounding, huge outbreaks" of food-borne illnesses before pasteurization was common, said Rob Tauxe, a deputy director at the Centers for Disease Control and Prevention.
Unpasteurized milk "was the No. 1 food safety problem in the nation," Tauxe said in an interview Monday. "People embraced pasteurization because they knew there was a problem."
With pasteurization, milk is briefly heated to a temperature high enough to kill off most bacteria. Federal officials say it's essential, since pathogens in untreated milk may include E. coli, salmonella and campylobacter, which can cause severe illness or even death.
In the 1930s, before the U.S. dairy industry widely adopted the heat treating process, 25% of all food-borne disease outbreaks were from milk. Today that figure is 1%."If you pass a law that makes it easier to buy raw milk, you certainly will have more instances of illnesses and deaths. That's inevitable," said Bill Keene, senior epidemiologist with the Oregon Division of Public Health.
Twenty-five states allow some form of raw milk sales to the general public. Oregon rewrote its law to largely ban the practice, but it's still allowed on farms with three or fewer milk-producing cows where people pick up the milk themselves.
"I think after a few dead kids, people will lose their enthusiasm for raw milk," Keene said. "We know that raw milk is a high-risk product, and that a low-risk alternative (pasteurized milk) was introduced 80 years ago. So if you are trying to thumb your nose at medical science, then good luck to you."
The U.S. Food and Drug Administration says the risks of unpasteurized milk greatly outweigh any purported benefits.
Drinking raw milk or eating raw milk products is like playing Russian roulette with your health, the FDA says on its Web site.
"Raw milk is inherently dangerous," FDA official John Sheehan said at a recent state legislative hearing on whether its sale should be allowed in Wisconsin. "It should not be consumed by anyone, at any time, for any reason."
The FDA's opinion is backed by the American Medical Association, which says all milk sold for human consumption should be pasteurized.
"Claims that raw milk has miraculous disease-curing properties are not supported by the scientific literature," Sheehan said. "The scientific literature is, however, rife with reports of food-borne illnesses attributed to the consumption of raw milk."
The Centers for Disease Control and Prevention, the Center for Science in the Public Interest, Wisconsin Department of Health Services and the Marshfield Clinic all have warned people about the dangers of unpasteurized dairy products.
"Many parents have never heard of E. coli 0157 and would not recognize that raw milk poses a serious health threat," Marshfield Clinic doctors said in written testimony submitted at the legislative hearing.
"If children knew that raw milk might cause them to develop a severe and painful illness, with a chance of kidney failure or even death, would they choose to drink it anyway?" wrote Edward Belongia, director of Marshfield's epidemiology research center.
But raw milk advocates, including a physician from Michigan, say the health risks are exaggerated.
They also point to a small number of scientific studies, mostly from Europe, that say raw milk's beneficial properties include an ability to reduce allergies in children.
A study of more than 4,000 children in England found that children who drank unpasteurized milk were 40% less likely to have symptoms of eczema, an inflammatory skin condition. A New Zealand study, published in the journal Allergy, reported similar results.
One of the studies concluded that there were lifelong benefits from consuming raw milk, even if you drank it only when you were a child, said Ted Beals, a retired Veterans Administration pathologist who taught at the University of Michigan Medical School.
Raw milk advocates say they can't replicate the European studies here because the FDA has deemed the farm-fresh product hazardous, making it impossible to conduct human experiments.
The University of Wisconsin has not done comparison tests of raw and pasteurized milk because the testing would cost several hundred thousand dollars, would take several years to complete, and no one has asked for it.
"It could be done. But right now we are doing work on behalf of the dairy industry, on things like low-sodium cheese or protein in sports drinks. That is where the state, and the industry, wants to spend its money," said Rusty Bishop, director of the Center for Dairy Research at the university.
Some of the properties of milk are changed when it's heated to kill harmful bacteria. But raw milk and pasteurized milk are essentially the same in terms of their protein, nutrient, fat and carbohydrate content, according to Bishop.
Advocates for raw milk say it contains enzymes that aid digestion.
"But these are enzymes meant to help a calf digest milk. They have very little if any impact on the digestive system of humans," Bishop said.
There's a mountain of evidence on the benefits of pasteurization, a process invented by French scientist Louis Pasteur in 1864 as a way to preserve wine.
The only nutrient in milk that is degraded up to 10% by pasteurization is vitamin C, according to Bishop.
"But most people don't drink milk for vitamin C content, which is very low," he said. "There are a lot of good things in milk, raw or pasteurized, but the big difference is that a pasteurized product is safer. Milk is a perfect food, but bacteria love it, too. That's why we pasteurize."
The heat-treating process, he added, does not cause lactose intolerance and allergic reactions - two claims made by raw milk advocates.
From 1993 through 2005, 69 outbreaks of human infections related to raw milk were reported to the Centers for Disease Control and Prevention. The outbreaks led to more than 1,500 reported illnesses, about 200 hospitalizations and two deaths, according to the CDC.
In the past 10 years, outbreaks of salmonella, campylobacter, E. coli 0157:H7 and listeria have been documented as the result of drinking raw milk. In 2009, an outbreak in southeast Wisconsin caused at least 35 cases of campylobacteriosis, and 27 of the ill were children.
The incidence rate of E. coli 0157 infection in Wisconsin is highest in children 3 to 5 years old. And the state Division of Health has reported that consumption of raw milk and raw milk products is among the top three causes of the E. coli infection, according to the Marshfield Clinic.
Often, those sickened by raw milk are young users who don't live on farms and have not developed immunities to the harmful bacteria.
"Personal stories from farm residents who routinely drink raw milk without developing illness do not provide any evidence that raw milk consumption is safe for the general population," the Marshfield Clinic physicians wrote.
Many people have consumed unpasteurized milk their entire lives and have never become ill from it.
Others, though, were severely sickened the first time they drank even a small amount of it. "The chances of that happening are not too high, probably," Oregon's Keene said. "But you pay your money and take your chances."
The farm-fresh appeal of raw milk drew some of Bill Marler's clients to the product. He is a Seattle attorney who has represented hundreds of victims of food-borne illnesses, including some attributed to raw milk.
"It was a casual purchase," Marler said. "And they certainly regretted it."
Under the latest version of state Senate Bill 434, raw milk sales could take place only at farms where the milk was produced. Farmers would have to post a sign declaring that raw milk does not provide the benefits of pasteurization and may contain disease-causing pathogens, and warns certain people of other health risks.
Capitol observers say the bill has a good chance of approval, since lawmakers are trying to help small dairy farms.
Public health officials tend to emphasize "worst-case scenarios," said Rep. Chris Danou (D-Trempealeau), one of the bill's sponsors.
"Anything we do in life carries some risk," Danou said. "But we allow sales of sushi, raw oysters and all kinds of other products that could be dangerous. We could have a 10-mph speed limit, too, and that would probably save lives. But it would not stop speeding, and the tradeoff is that people want to get places faster