Multigrain and whole grain are not interchangeable terms. Whole grain means that all parts of the grain kernel - the bran, germ and endosperm - are used. In contrast, multigrain means that a food contains more than one type of grain, although none of them may necessarily be whole grains. The same goes for other variations, such as "seven-grain."
Whole-grain foods are a healthy choice because they contain nutrients, fiber and other healthy plant compounds found naturally in the grain. Look for products that list the first ingredient as "whole wheat," "whole oats" or a similar whole grain. While "whole grains" may signify one of many types of healthy grains, "whole wheat" labels the specific grain used. Either term may identify a food that's a good source of fiber, several B vitamins and minerals.
Healthy adults should eat at least three 1-ounce (28-gram) equivalents of whole grains a day as part of a balanced diet.
~Katherine Zeratsky, R.D., L.D.
Source: Mayo Clinic