The messages are all over the supermarket aisles:

“Made with whole grain goodness,” screams a bag of Tostitos tortilla chips.

“With whole grain guaranteed,” says a box of Chocolate Cheerios.

“One serving of whole grain,” declares a package of frosted strawberry Pop-Tarts.

Whole grains have been the darlings of the food industry ever since the government’s 2005 food pyramid recommended we eat more of them — at least 3 ounces per day. These days, you’ll find them in a wide array of products, some expected, some not: breakfast cereals, crackers, frozen dinners and snack chips. Odwalla has a new smoothie drink that contains a full serving of whole grains. The source: whole-grain brown rice.

But — let’s get real. Just because toaster pastries, say, have whole grains doesn’t automatically make them a nourishing choice. One whole-grain chocolate fudge Pop-Tarts pastry has 190 calories per serving, 2 grams of saturated fat and 14 grams of sugar.

“Adding whole grains to Pop-Tarts is not going to take the sugar out,” says Bonnie Jortberg, a senior instructor in the department of family medicine at the University of Colorado School of Medicine in Denver. “Even if Pop-Tarts contain whole grains, I would put them on a list of foods to eat less often … the actual real nutrient value is pretty low.”

And the Wholly Grains smoothie from Odwalla has 54 grams of sugar in a 16-ounce bottle, almost 13 teaspoons of sugar.

“Buyer beware,” Jortberg says. “Not everything is as advertised.”

Here’s a primer.

A whole grain contains all the parts of a seed — including the starchy endosperm, which has few nutrients; the bran, or outer layer of the kernel, which is the main source of fiber, and the germ, where most of the nutrients are found, including B vitamins and iron. Types of whole grains include whole-wheat berries, bulgur, brown rice, whole cornmeal, popcorn, whole oats and millet.

Refined flours, in contrast, remove the bran and the germ, leaving just the endosperm, though enriched refined flour is fortified with missing nutrients: thiamine, riboflavin, folic acid, niacin and iron.

Whole grains are good (although not the only) sources of B vitamins (which include riboflavin, folate and niacin), vitamin E, iron, selenium and magnesium. One cup of whole-wheat flour has 26% of the recommended daily value of iron, 36% of thiamine, 38% of niacin, 20% of vitamin B6, 13% of folate and 121% of selenium.

Putting more whole grains in food usually translates into more fiber, but not always. If a product has just a bit of whole grains, chances are the fiber content will be low. For example, a serving (55 pieces) of cheddar Goldfish crackers made with whole grain has only 2 grams of dietary fiber.

The trend toward adding more whole grains to food has been growing steadily since the U.S. Department of Agriculture and the Department of Health and Human Services revised the dietary guidelines in 2005, recommending that at least half of all grains eaten be whole grains and that 3 or more ounces of whole grains be consumed per day. As a 1-ounce equivalent of whole grains has about 16 grams of whole grains, the recommendation is to eat 48 grams of whole grains a day.

Those guidelines were based on information in large studies published in peer-reviewed journals such as the New England Journal of Medicine, Obesity and the Archives of Internal Medicine that were assessed by the dietary guidelines committee, says Robert Post, deputy director of the Center for Nutrition Policy and Promotion, a USDA agency.

“The [committee] found that consuming at least 3 ounces of whole grains reduced the risk of diabetes [and] coronary heart disease, and also helped with weight maintenance,” Post says.

Post added that whole grains “will be as important or even more important than before” in the guidelines being released later this year and that there may be more emphasis placed on whole grains as a good source of dietary fiber.

The studies continue: One published online May 10 in the journal Circulation found that women with diabetes who ate more whole grains and bran lived longer and had less risk of dying of cardiovascular disease than those who ate lesser amounts.

Not known for missing a marketing opportunity, many companies have jumped on the whole grains bandwagon — adding new products featuring whole grains or reformulating old ones to include them. This may be good news for consumers who want more healthful choices, but some people are undoubtedly confused about what and how much to eat.

Are whole-grain Pop-Tarts as good as a bowl of unadulterated steel-cut oats? (OK, you can go to the back of the class if you don’t know the answer to that one.) And how does one calculate 48 grams, anyway?

“I don’t think people understand it hardly at all,” says registered dietitian Jo Ann Carson, a professor of clinical nutrition at the University of Texas Southwestern’s Center for Human Nutrition in Dallas. “I think if you surveyed 20 registered dietitians, half wouldn’t be able to tell you either.”

The Whole Grains Council, a trade organization formed in 2002 to promote whole grains, devised the Whole Grain Stamp, a postage-stamp-sized symbol on food packages that lets consumers know how many grams of whole grain are in a serving of the product. The minimum amount a product can contain to earn a stamp is 8 grams, or a half serving of whole grains.

Carson advises people to keep things simple and follow a very general approach toward eating whole grains, the way she does: Choose good-quality whole-grain sources (ones low in sugar, sodium and saturated and trans fats), but put away the pocket calculators.

“I’m not concerned about adding up grams of whole grains,” she says. “In a day, if I have five to six servings of grains, half should be coming from whole grain — the oatmeal I ate was a whole grain, but the white pasta wasn’t.”

To get more pointers, read our related story.

jeannine.stein@latimes.com