Grocery shoppers face a growing array of percentages, vitamins, adjectives and health claims up and down the aisles. The information is emblazoned on the packaging if it's something the producer wants to tout, or in the smallest typeface allowable if the facts aren't so encouraging.

Not that some shoppers even care.

"A lot of people shop only by price and flavor," said Donna Byrne, a professor of law at William Mitchell College of Law in St. Paul where she teaches food law. She's not judging, really; for many, price has to be a consideration.

But those who also are motivated by personal health or environmental concerns, their choices have an economic impact. The trick is understanding how to parse the facts and the marketing nuances of food labeling.

We recently went shopping with Byrne through the aisles of Oxendale's Market in south Minneapolis.

The produce section was our first stop, where she explained that the country of origin must be displayed for all fresh and frozen produce, peanuts, pecans, macadamia nuts, ginseng and meats. Ideally, that's on a sticker on each piece of produce, but it also can be noted on the price cards in the shelves' metal tracks.

On the one hand, this info lets you know how far the produce has traveled, but also points you toward learning more about a country's agricultural practices, if you're inclined.

Then there's the organic label.

"Organic means that no chemicals or pesticides have been used on the fields for three years," she said. That's the biggest umbrella, but there are many, many other regulations toward being able to use that label. To learn more at the U.S. Department of Agriculture website, visit www.usda.gov and search "organic."

A further wrinkle comes with mixes or prepared foods, where some may declare that they are "made with organic flour" or tomatoes or whatever. Federal standards say that "made with" products "must contain at least 70 percent organic ingredients."

It's then the shopper's responsibility to read the list of ingredients to see which ones aren't identified as organic, and whether, say, nonorganic cheese on a pizza made with otherwise organic ingredients is no big deal, or a deal-breaker, Byrne said.

The meat counter offers more lessons, mostly in the importance of appearance. Some meats are swathed in plastic that's in direct contact with the meat, while others are in sealed foam trays, or "modified atmosphere packaging," in which a blend of gases keeps the meat from oxidizing, or naturally changing color over time. She's not a fan.

"It's intentionally misleading because people think the meat is fresher than it is," she said. "People reject meat that's perfectly good because the color has changed." The takeaway: Products in such packaging are perfectly safe, but just don't assume that the ground turkey came out of the grinder that morning.

Similarly, check labels on salmon. Wild-caught salmon is deeply colored because it's eaten krill, a tiny pink crustacean. Farm-raised salmon that's also a vibrant pink has eaten feed to which artificial color has been added. While Oxendale's had no farm-raised salmon in its case, Byrne said such a label would have to note "color added to feed."

Milk offers another wrinkle in the labeling requirements. A food label cannot be false or misleading, Byrne said, holding up a carton of milk that stated "no artificial growth hormones." Which is true. But the argument successfully has been made that even this language could be misleading, because it may lead consumers to think that the product is different and therefore worthy of a higher price or safer.

So there's also this language: "Made from cows not treated with rBGH. The FDA has said that there is no significant difference between milk from cows treated with rBGH and untreated cows. No test can now distinguish between milk from treated and untreated cows."

Those concerned with hormone use lobby for continued testing, she said, while others urge that milk from treated cows be labeled as such. For now, the standoff continues. Byrne just smiled. "The way I see it, milk that doesn't say this also is labeled."

In many ways, savvy shopping also means paying attention to what a label doesn't say. If an egg carton doesn't say "cage-free," you can assume the eggs came from tightly-confined chickens, she said. If a can of vegetables doesn't say "BPA-free lining," referring to bisphenol-A in the linings of many cans these days, you can assume the lining contains that chemical.

As to the current concerns about sugar, Byrne looks forward to coming language about "added sugar."

"I mean, milk has lots of sugar, but that's what helps us process the lactose," she said.

Byrne, who follows a vegan diet, said her interest in food labels is driven not so much by concern for personal health as by environmental impacts.

"There are a lot of things that are well-labeled that are bad for us," she said. "What I want to know is, was the food responsibly produced? When I make grocery decisions, I want to know how something was grown or made."

Food labels are becoming more complex, she said, which doesn't make a shopper's job any easier. But that's OK.

"The idea that consumers can't take in too much information is wrong."

Kim Ode • 612-673-7185