The recommended daily limit for an average adult is 2,300 milligrams;too much sodium can cause high blood pressure.By the USDA's reckoning,a food is low in sodium if it contains
no more than 140 milligrams.(A serving of Cheerios has 210 milligrams and is therefore not low in sodium.)A single serving of soup or a frozen dinner may contain 1,000 milligrams or more of sodium,which is nearly half the daily limit