When a dairy farm family suffers sickness from a bad batch of raw milk, it's rarely reported. After all, all dairy farm families truly believe their unpasteurized product is as fresh and nutritious as it gets.

But several years ago, a dairy farmer in Perry County, Pa., nearly died from a bad batch of raw milk. And in the last year, several of the Northeast's highly regarded raw milk dairies were hit with temporary shut-downs after consumer allegedly contracted Listeria monocytogenes from their raw milk.

Nearly 30 states permit raw milk sales. But when raw milk crosses state lines, it crosses into disputed territory, according to the U.S. Food and Drug Administration. And that's what landed raw milk producer Dan Allgyer of Kinzers, Pa., back in court this month.

FDA filled a motion in Pennsylvania to forbid the Amish farmer from selling fresh milk through a buying club in Washington, D.C. Allgyer's two-year battle with FDA has elevated him to being the national "poster farmer" for raw milk advocacy groups.

While raw milk advocates zealously believe unpasteurized milk is the more healthful choice than pasteurized milk, that claim is disputed by scientific studies. A 2011 study led by Cornell University's College of Veterinary Medicine's Ynte Schukken, quantified the risks of contracting Listeria from raw milk.

Collaborating with USDA's Agriculture Research Service and New York State Department of Agriculture & Markets, the four-year project studied who was most at risk when buying raw milk from various sources. In brief, farmworkers, pregnant women, young babies and the elderly were more susceptible than intermediate-aged adults.

The researchers analyzed risk across various purchasing methods, including buying from a farm's on-site store, obtaining raw milk directly from the bulk tank, consuming raw milk on the farm and buying raw milk from a third-party retailer. The on-farm scenario assumed that customers brought their own containers and filled their containers directly from the bulk tank.

For raw milk consumed on the farm, it was assumed that milk was transported from the bulk tank to the house, meaning transportation time and temperature were not factors.

Overall risk of listeriosis was low. But it increased with the steps between the bulk tan and consumption. For example, the probability of illness and median number of cases were greatest for raw milk purchased from retail stores. For raw milk sold in both farm and retail stores, the temperature and length of storage and display at the store were the second and third most important parameters affecting the risk.

The relative risk of listeriosis in an intermediate-age population was low and lower than for young children, pregnant women and the elderly if raw milk were purchased directly from milk tanks. Relative risks increased substantially for raw milk purchased from retail stores, with young children and elderly having a higher risk.

Ynte Schukken says the increased risk was likely due to the ability of L. monocytogenes to grow at refrigeration temperatures. Increasing home refrigerator temperature from 4 degrees C to 8 degrees C resulted in a seven-fold increase in listeriosis cases.

Despite its dangers, 28 states permit the sale of raw milk. Enthusiasts claim health benefits from nutritious compounds supposedly destroyed by pasteurization.

"These claims are not backed by scientific evidence, and several studies have shown them to be myths," contends Schukken. "Pasteurization helped revolutionize health, effectively ending diseases such as tuberculosis and Q fever. Bypassing this safety measure could have serious consequences for public health, dramatically increasing bacterial infection and outbreaks."

Free resource on safe raw milk production

Food safety and optimal nutrition aren't mutually exclusive goals concedes organic farming legend Tim Wightman. The president of Farm-to-Consumer Foundation has produced two free educational tools that teach about safely producing food beyond conventional food safety goals.

"We believe all food can be produced safely, including raw milk," says Wightman.  "These materials are the starting point for a collaborative effort to develop 'best practices' to guide dairy farms working to meet the rising demand for raw milk from pasture-raised cows."

These free resources include online copies of Raw Milk Production Handbook and a micro dairy farm educational DVD, Chore Time. They're available at farmtoconsumerfoundation.org/fsr.