Frozen foods -- particularly prepared meals -- are often high in sodium. Excess sodium can lead to high blood pressure, which is linked to heart disease and stroke. You should limit your sodium consumption to no more than 2,300 milligrams per day, recommends the Centers for Disease Control and Prevention. If you're over age 50 or have high blood pressure, diabetes or chronic kidney disease, you should limit sodium to no more than 1,500 milligrams per day. For comparison, one piece of frozen lasagna with meat sauce may contain more than 900 milligrams of sodium.