You care about buying food that's good for you - but how trustworthy are the labels you rely on in making your grocery-shopping decisions?

To learn what's really behind the labels "organic," "natural" and "whole grain," take a look at this guide.

ORGANIC

According to the United States Department of Agriculture, food marked with the USDA organic label is produced through ecologically based practices such as cultural and biological pest management and exclusion of all synthetic chemicals, antibiotics and hormones in crop and livestock production.

Products labeled as "100 percent organic" must contain (excluding water and salt) only organically produced ingredients and processing aids. Products labeled as "organic" must consist of at least 95 percent organically produced ingredients (again, excluding water and salt), and products labeled "made with organic ingredients" must contain at least 70 percent organic ingredients, as well as a list of what ingredients are organic (Soup, for example, could be labeled "soup made with organic peas, potatoes and carrots" or "soup made with organic vegetables").

These labels can be trusted, says Sarah Willis, a dietitian with Heartland Health Wellness Connections.

"If you see the label USDA organic, then that's something that's checked up on," she adds. "That's reliable."

NATURAL

What's not as reliable is the label "natural."

The USDA has a legal definition for "natural," designating it for describing meat products produced without any additives and preservatives. But peruse the aisles of a grocery store, and chances are you'll find more than only meat products bearing the label.

"It's a really popular marketing tool," Ms. Willis says. "It's pretty loose and not regulated, so the manufacturer can put that on any product, and it's not followed up on."

A similar label that actually is trustworthy, she adds, is "certified naturally grown." This is a designation often used by small-scale organic farmers who adhere to USDA standards but are more able to afford this certification than the USDA's.

WHOLE GRAIN

The wording is similar, but "whole grain" and "made with whole grain" can actually be very different.

"'Made with whole grain' is very misleading," Ms. Willis says. "A cereal might say that, but usually the first ingredient on the list - the one that's most abundant - is sugar."

This is why it's so important to read ingredient lists, adds Sheri Caldwell, dietitian at St. Joseph's Hy-Vee. It's recommended that the first ingredient be a whole grain, she says, and something else to look for is the Whole Grain Council's stamp. These stamps feature bold black text on a golden yellow background and come in two forms, indicating either that a product is 100 percent whole grain - containing at least 16 grams of whole grain per labeled serving - or that it contains at least 8 grams, a half serving, of whole grain but may also contain some refined grain.