For decades, nutritionists and physicians have known that excessive intake of table salt (sodium chloride) contributes to high blood pressure and cardiovascular disease. A variety of studies have established upper limits for the amount of salt, expressed in milligrams (mg) of sodium, for our daily diet. One thousand mg equals one gram.
The most recent guidelines for daily intake of sodium, issued by the Food and Drug Administration, establish two different upper limits. For many Americans, daily sodium intake should not exceed 2,300 mg daily, about one teaspoonful of salt. For blacks, all adults over 50 years of age and persons with high blood pressure, diabetes, heart disease or chronic kidney disease, daily sodium intake should not exceed 1,500 mg daily. This restriction applies to almost half of the U.S. population. In both groups, the presumption is that consuming even less salt is beneficial.
Keeping track of our daily sodium intake is a challenge. Salt is a normal component of most fruits, vegetables and dairy products. Concentration of sodium is generally low in these foods. Salt also is a common additive for foods we prepare at home. But an estimated 75 percent of our sodium intake originates in processed foods and meals in restaurants. Sodium content must be listed on most foods we purchase at grocery stores. A sampler of popular items:
• Italian sausage: 570 mg. sodium in a 2 2/3 ounce link.
• Bologna: 240 mg in one ounce.
• Chicken noodle soup: 790 mg per cup.
• Frozen pizza (4 ounce serving): 400-1,200 mg.
Fast food restaurants are another source of high sodium choices. Sodium content is listed online and in most locations, though often in out-of-the way places. A sampler of some popular selections:
• French fries (large): 300 mg sodium
• Chicken nuggets (6 pieces): 500 mg
• Burger (4 ounce) with cheese, and bacon: 1,500 mg
Addition of sauces and ketchup will also boost sodium intake.
Other more traditional, independent restaurants generally do not post sodium or other specific nutritional information. Many of us routinely add salt to the food we are served, sometimes before tasting it. Sauces, dips and salad dressings are hidden sources of substantial doses of sodium. Locally produced breads, pastries, bottled and canned goods are not required to carry nutritional labeling.
Recent studies in the New England Journal of Medicine expand our knowledge of sodium intake. Two international studies used sodium excretion in urine to estimate sodium and potassium intake. Average sodium intake was correlated with subsequent high blood pressure, cardiac events and death during several years of follow-up. The linkage was most pronounced in older persons and those with pre-existing high blood pressure.
The second study challenges recommended limits for sodium intake. Adults whose sodium intake was in the range of 3 to 6 grams daily had a lower risk of cardiovascular events and death than did those consuming lesser or greater amounts of sodium. Higher estimated potassium intake -- greater than 1.5 grams per day -- was associated with reduced rates of death and cardiovascular disease. While affirming that excessive sodium intake is harmful, these studies suggest that current FDA guidelines for Americans may be too stringent for the population at large. The question of inadequate sodium intake needs further study.
A third report evaluated sodium and cardiac-related illness in adults from 66 countries. In 2010, more than 1.6 million deaths were linked with a daily sodium intake that exceeded two grams per day.
All these papers reinforce the potential hazards of dietary salt.
We must be mindful of our daily sodium intake. The U.S. Centers for Disease Control and Prevention offer a useful link at www.cdc.gov/salt. Websites for fast food chains usually present detailed nutritional information including sodium content of items on menus. Your health care provider may offer more detailed recommendations tailored to the status of your health.
While limiting salty foods, we can increase our intake of foods rich in potassium such citrus fruit, bananas, tomatoes, squash and legumes -- peas, lentils and soybeans. Replacing table salt with "light" salt, which is 50 percent potassium chloride is another option.
Detailed labels for foods are useless unless we read them. Fast food restaurants should post sodium content alongside caloric content.
Mindful use of sodium is the key.
Contact Clif Cleaveland at firstname.lastname@example.org.