"Whole grain" is a familiar nutritional buzzword. It implies that a product offers more fiber and nutrients. But looking for the Whole Grain Stamp, developed as a way of making sure you get the benefits of whole grain foods, may not be the best way to select breads and cereals. A survey of the grocery shelves done by the Harvard School of Public Health found that while foods displaying the Whole Grain Stamp do tend to have extra fiber, they also are likely to have more added sugar and calories than similar foods without the symbol.

It's not that the stamp isn't doing its job. It is. It identifies foods that contain at least eight grams of whole grain per serving. But the stamp offers no information about a food's other ingredients. Apparently, manufacturers are adding extra sugar to these foods more often than not, about four grams per serving on average.

Bread with 20 grams of carbohydrate and 1 gram of fiber is not what you're looking for; bread with 16 grams of carbohydrate and 2 grams of fiber is much more like it.

The stamp doesn't tell you when a cereal is loaded with other, less obvious, sugar hidden inside a long ingredient list.

A diet rich in whole grains lowers the risk of heart disease and diabetes. The U.S. Department of Agriculture recommends eating at least three servings of whole grain products daily. But there is no universally accepted way to tell whether a food is whole grain or not. Ingredient lists have gotten that complicated.

Researchers at the Harvard School of Public health tested over 500 grain-containing foods found on the grocery shelves to see which of five methods most often used to identify whole grain products ended up highlighting the healthiest foods. They divided these foods into eight categories: bread, bagels, English muffins, cereals, crackers, cereal bars, granola bars and chips. Aside from looking at a food's grain content, they also looked for foods high in fiber and low in calories, sugar, sodium and trans fat.

They found that a healthier approach to buying breads and cereals is the 10:1 method suggested by the American Heart Association. This refers to the amount of fiber in a food in relation to its total carbohydrate content and looks for foods that have at least 1/10 as much fiber as carbohydrate — a ratio of carbohydrate to fiber of 10:1 or less.

While the 10:1 method sounds complicated, it's actually easy to use and quicker than making change for a dollar. Both carbohydrate and fiber are listed right next to each other on the package label, carbohydrate first. Bread with 20 grams of carbohydrate and 1 gram of fiber is not what you're looking for; bread with 16 grams of carbohydrate and 2 grams of fiber is much more like it.

The 10:1 method originated because 10:1 is very close to the ratio of total carbohydrate to fiber found in whole wheat flour.

The researchers also tested three additional methods commonly used to identify a product as whole grain. One method looks at the first ingredient listed on the label to see if it's a whole grain ingredient. This can be tricky because there are 29 different recognized whole grain ingredients — whole wheat flour is one, wheat flour is not. A second method works just like the first, except it also looks for added sugar, requiring that none of the first three ingredients on the label be one of 21 types of sugar containing ingredient — including fruit juice concentrate. A third method simply looks for the word "whole" appearing before any grain on the ingredient list.

None of these three methods worked as well as the 10:1 system at finding the most healthful foods.

The Whole Grain Stamp was developed by the Whole Grains Council, which describes itself as a non-profit, consumer advocacy group. The Council is partially funded by the food industry; companies pay annual dues to be a member of the WGC and to be able to use the stamp. Companies check their own foods to determine if they are eligible to bear the stamp.

As the Harvard study shows, there's more to food than just its grain content. People still need to read food labels carefully.

The study was published online by Public Health Nutrition and is freely available. The article will also appear in a future print edition of the journal.