Supporters of the raw milk cause say pasteurization, the process of heating milk to destroy bacteria and extend shelf life, destroys important nutrients and enzymes.
"We have new science today that shows raw milk contains ... enzymes that kill pathogens and strengthens the immune system," said Sally Fallon Morell, president of the Washington-based Weston A. Price Foundation, a non-profit group pushing for increased access to raw milk.
Enzymes and other nutrients are "greatly reduced in pasteurized milk," she said.
Public health officials disagree, saying raw milk carries an increased risk for bacterial contamination that can lead to illness and even death.
More than 1,500 people became ill from drinking raw milk between 1993 and 2006, the most recent data available from the Centers for Disease Control and Prevention. Of those, 185 were hospitalized and two died.
The CDC said not all foodborne illnesses are reported, meaning the actual number is likely higher.
Fallon Morell said there also have been illnesses and deaths related to pasteurized products and that linking illnesses to raw milk is not an accurate assessment of the nutritional benefits of drinking unpasteurized milk.
The sale of raw milk is prohibited in 23 states, although seven of them let people get milk through so-called herdshare programs, in which customers can buy ownership in a cow in return for raw milk from the animal.
Retail sales of raw milk is allowed in nine states and 19 allow the sale of raw milk from a farm directly to an individual.
Lawmakers in seven states have introduced measures this year seeking to change laws governing raw milk. The Farmer to Consumer Legal Defence Fund also has filed lawsuits in five states challenging various aspects of laws regarding raw milk.
The Iowa lawsuit filed last month challenged the state's ban on herdshare agreements.
Pete Kennedy, president of the Farmer to Consumer group said the state's law contradicts common sense.
"The farmer can drink milk from cows at the farm, so why can't someone with an ownership or interest in that cow drink milk from those animals?" Kennedy said.
Iowa Secretary of Agriculture Bill Northey said in a statement that state officials "feel we have acted within our authority under Iowa code ... in this situation."
The issues in other states include testing requirements and delivery methods for raw milk, and herdshare agreements.
The Iowa legislation, which died in a committee, would have allowed the sale of raw milk from a farmer directly to customers. Supporters said they won't give up.
Nick Wallace, a livestock farmer near Keystone, Iowa, said the state's ban on raw milk sales infringe on consumers' rights.
"We feel it's a consumer's right to put what we want in our bodies and if we want to contract with a farmer who sells raw milk we should be able to buy it," Wallace said.
He said with or without a change in law, people will find a way to get raw milk if they want it.
Those arguments don't fly with public health officials.
"With raw milk the concern is it can be contaminated and it provides a good environment for bacteria to grow to high levels, which increases the chance it can make people sick," said Dr. Ann Garvey, the state public health veterinarian with the Iowa Department of Public Health.
Garvey, along with the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention, support pasteurization and claim the process doesn't significantly change the nutritional content of milk.
But raw milk advocates said governments should step out of the way and let people buy products they want.
Fallon Morell, of the Weston A. Price Foundation, notes Amish farmers in Pennsylvania are "making a fortune" selling raw milk.