Mining for Perspective on Dietary Salt

Our recent column on sugar generated questions about another white, granular substance--salt.

Cutting down on salt (specifically sodium) continues to be among the most controversial of the current dietary recommendations. Debate rages between the American Heart Assn. and other organizations that link excess sodium intake to hypertension (and perhaps even osteoporosis and certain cancers), and other experts who claim that restricting sodium as a general preventive measure is unnecessary and undesirable.

Let’s see if we can put this debate into some perspective.

* What is it about salt that is such a problem?

Well, it is not salt per se, but the sodium that it contains. Ordinary table salt (sodium chloride) is 40% sodium and 60% chloride. Sodium is essential for life, playing a crucial role in regulating body fluids and blood pressure.

Unfortunately, most of us consume far more sodium than we need in the processed foods, snacks and junk food that have become part of the American diet. A single teaspoon of table salt contains an entire day’s recommended sodium intake.

* What effect does sodium have on high blood pressure?

We know that many variables besides sodium intake can influence blood pressure, such as other dietary factors, genetics, excess weight, lack of exercise, mental stress, smoking and alcohol consumption.

For example, high intake of calcium and potassium seems protective against high blood pressure, but too much sodium, on the other hand, can send blood pressure into the danger zone in 10 to 20% of the population.

The real problem is that there is no way to know in advance whether you are salt-sensitive, and given the seriousness of hypertension, it would seem prudent to assume that you are and reduce your sodium intake while your blood pressure is still under control.

* What about stomach and colorectal cancer?

Researchers who examine disease trends in large population groups tell us that stomach cancer rates are way down in the developed world. One of the explanations they offer--the dramatic decline in our consumption of salt-preserved foods in recent years--may indeed indicate a possible connection between high salt intake and stomach and colorectal cancers. Of course, other dietary practices, like low intake of fiber, fruits, vegetables and vitamin C, may prove more closely linked to development of these cancers, and consumption of these important foods and nutrients is on the rise.

* Is there a link between sodium intake and kidney stones? There has been some preliminary work in this area, but it is far too soon to draw conclusions.

* Does sodium intake relate to osteoporosis?

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There seems to be an indirect association between sodium and osteoporosis in that every teaspoon of salt you consume causes you to excrete a significant amount of calcium in your urine. Over time, such losses could be a problem, especially in post-menopausal women.

* What about claims that a high-salt diet promotes longevity?

A highly publicized study a year or so ago suggested a connection between high salt intake and long life. However, the study was too short-term to furnish definitive information about longevity, and the researchers themselves hedged on the results. Of course, the media jumped all over it and just muddied the waters even more.

* What is the bottom line?

--Err on the side of caution. There is nothing to be gained from a high-sodium diet and much to be lost if you happen to be salt-sensitive.

--Unless there is some medical reason to severely restrict your sodium intake, stay within the recommended maximum level of about 2,400 milligrams per day. This is easier than you might think, especially if you get in the habit of reading labels.

--Be sure to read labels carefully. Watch out for ingredients like MSG (monosodium glutamate), sodium citrate, sodium nitrate, sodium phosphate and sodium saccharin.

--To reduce the sodium content of canned foods like beans and tuna, drain the liquid and run the food under cold water before cooking or eating.

--Don’t use your salt shaker until after you taste your food. People who eat a lot of salty foods crave salt more than those who don’t. Once you get used to less salt, you really won’t miss it.

--Avoid sodium land mines like fast and processed foods. One big fast-food hamburger and fries contains almost half your recommended daily intake. Other foods to look out for are canned foods, crackers, frozen dinners, soy sauce and most Asian-style foods, pickles, cheese, catsup, salsa and cold cuts.

Fortunately, many of these foods now come in low-sodium varieties. But be careful. “Unsalted” does not mean sodium free. It just means that sodium has not been

added. The food itself may be naturally high in sodium.

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“Low sodium” on a food label means 140 milligrams or less per serving. “Reduced sodium” means that the product has 25% less sodium than the regular version. The lowest-sodium foods will be labeled “very low sodium” (35 milligrams or less per serving) or “sodium free” (less than 5 milligrams per serving).

--Build your diet around fruit and vegetables that are naturally low in sodium and offer lots of other benefits as well. Low-fat dairy products and whole grains are also low in sodium and should be part of a healthy diet.

--Stay away from potassium-based salt substitutes. Most of them are bitter and just make you miss salt even more. Instead, try seasoning your food with lemon juice or a variety of herbs and spices.

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If you have questions you’d like to see answered in this column, please e-mail us at daogar@uclink4.berkeley.edu, fax us at (510) 642-2857 or send regular mail to Dale Ogar, School of Public Health, UC Berkeley, Berkeley CA 94720-7360. We regret that we cannot answer questions personally.

Dr. Sheldon Margen is professor of public health at UC Berkeley; Dale A. Ogar is managing editor of the UC Berkeley Wellness Letter. They are the authors of several books, including “The Wellness Encyclopedia of Food and Nutrition.”