A few years ago, the slogan was "milk does a body good." Then the thinking went "organic milk does a body better."

Now the point of contention is the toll that both regular and organic milk take on the environment, even before that cold white drink can leave the ubiquitous mustache.

The dairy industry says there's little difference between regular and organic milk and the impact each has on the health of both humans and the Earth.

Environmentalists counter that the upswing of organic foods, including milk, is a boon to both.

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They say producing organic milk is a much better use of resources, and better for the environment overall, than regular dairy farming.

"Organic production is more environmentally sound because organic farmers are not using toxic and persistent synthetic pesticides that can remain in the air, water or soil for years to come," says Holly Givens, public-affairs manager at the Organic Trade Association, based in Greenfield, Mass.

Givens says that since organic production dictates what pesticides and fertilizers a farmer can use, as well as how farmers manage manure so it doesn't contaminate crops, soil or water, organic production is better for the environment.

To be credited with the label 'organic,' four criteria must be met by the milk farmers.

— Cows milked under the "organic" umbrella can't have been treated with bovine growth hormone

— They can't have been given antibiotics while in a herd. (If a cow gets sick enough to warrant such treatment, it is separated from the group)

— The cows' food — be it good old grass or feed — cannot have been treated with pesticides or grown from genetically modified seeds

— Cows in organic farming have to have "access to pasture"

Gray areas within these four general rules — for instance, what exactly counts as "access to pasture" — can cause disagreement between organic and regular milk makers.

Organic dairy farming isn't a perfect scenario, however. Since its standards reject many of the time-saving and cost-cutting innovations of the past few decades, it can be difficult and expensive for regular farmers to make changes and then maintain them.

Nor is the image of smiley, happy cows on organic farms true to life, says Stephanie Hill, a dairy specialist and assistant professor of animal science at North Carolina Agricultural & Technical State University in Greensboro.

Since organic producers can't use conventional methods of treating illness, organic dairy farming makes it likelier that a sick cow will be culled, either by being cut from the herd or killed outright, she points out. And today's land constraints make it difficult to adhere to the access-to-pasture rule.

"The price to raise an organic cow is more expensive [than a regular cow]," Hill says.

As to whether antibiotics get into non-organic milk, Hill doubts it. It's illegal to give antibiotics to a lactating cow, she says, adding that farmers are responsible for any antibiotics that show up in tanker-truck samples, which would force the dumping of the entire truck's contents.

On another health-related issue, scientists are still not sure whether recombinant bovine growth hormone (rBGH, also known as rBST), injected into cows to make them produce more milk, has any effects on humans.

It's not similar enough to human hormones to directly affect us, but rBGH does increase the likelihood that a cow will develop an udder infection — which must be treated with antibiotics.

Of more immediate concern is the fact that rBGH-produced milk contains higher levels of insulin-like growth factor 1 (IGF-1) — a powerful steroid-like hormone that is identical in cattle and humans, which is crucial to childhood growth and may also speed the aging process.

Monsanto, the company that makes rBGH, argues that all hormones in milk are destroyed by pasteurization. The FDA gave rBGH the green light in 1994 and continues to defend its safety.

But Australia, Canada and New Zealand have rejected its use, and the European Union, while officially regarding it as safe, has placed an indefinite moratorium on its use since 1993.

The Grass Is Greener

Despite higher retail costs, American consumers are opting to dig deeper into their pockets to shell out for organic goods.

Organic dairy products — including milk, cream, butter, cheese, yogurt and eggs — accounted for nearly $2.7 billion in 2006 in the United States.

That's about a 4.1 percent slice of the dairy pie, according to the Organic Trade Association. (The National Dairy Council claims the figure is closer to 3 percent.) And it's up from $939 million in sales and a 1.7 percent share just five years previously.

For all the hype, the mainstream dairy industry, as well as experts like Hill and many regular Joes, just doesn't see any reason to spend nearly double the money for a gallon of organic milk.

"To date, there's no scientific research that shows a definitive environmental advantage with one production system or the other, especially given the many steps all dairy farmers must take to minimize their environmental impact these days," says Mary Martin Nordness, RD, at the National Dairy Council, an organization set up by the dairy industry for research and education and based in Rosemont, Ill.

"Both regular and organic milk are wholesome, safe and nutritious, and there's no additional health benefits with organic milk," she adds.

Hill says the U.S. Department of Agriculture has taken many steps to ensure that what is called organic truly is. Still, she says, all milk, organic or regular, is held to the same safety standards before it hits store shelves.

"If it says 'certified organic,' than they can be sure it's organic, but is there a health benefit to that? We don't know," she says.

Organic milk proponents, meanwhile, are sticking to their guns.

"In terms of the environment, organic management practices that are required by law protect the soil and ground and surface waters from pollution," says Mark Kastel, co-director at The Cornucopia Institute, a farm policy research group and organic industry watchdog based in Cornucopia, Wis. "In essence, it prohibits industrial-scale, 'factory-farm' production."

As experts continue to square off, some consumers have already decided.

Eileen O'Hara, for one, is hedging her bets. The New York mother of four, the youngest a girl, buys half a gallon of organic milk for every gallon of regular milk.

Buying only organic milk would be cost-prohibitive, but O'Hara wants the health benefits the organic milk might bring, especially for her daughter, whom she believes would be more affected by hormones than her sons would be.

"It's worth it," she says of the added cost and peace of mind.

Organic cows everywhere are smiling.