NEW YORK (CNN/Money) - General Mills announced plans Thursday to start using healthier whole grains in all of its ready-to-eat cereals, including children's cereals such as Trix, Cocoa Puffs and Lucky Charms.

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The nation's second largest cereal maker will start to switch about 40 percent of its ready-to-eat cereals to whole grains in the coming weeks and will complete the change by early next year, according to the company.

The other 60 percent -- including Cheerios, Wheaties and Total -- already use whole grains. Company officials said that the taste of the cereals will not be changed by the switch, but it is aimed at improving the health of its customers.

The switch will increase by 1.5 billion a year the number of whole grain servings eaten by Americans without adding calories, according to Susan Crockett, a nutrition researcher at General Mills.

The company said consumers have been demanding improvements in cereal nutrition. General Mills (GIS: Research, Estimates) and competitor Kellogg (K: Research, Estimates), the major U.S. cereal maker, began selling lower sugar versions of their kid-targeted cereals this past summer.