Sodium

Daily Value: 2,400 milligrams

Good Food Sources: Cheeses, including cottage cheese; most meats, especially ham and bacon; canned soups; canned vegetables; processed lunchmeats; shellfish; canned tuna; cereals; breads; baked goods; salad dressings; potato chips; pickles; sauces. Note: Although we all need a certain amount of sodium to survive, most people get too much rather than too little.

Despite getting bad press, sodium is a mineral that your body needs as much as any other. It regulates the amount of fluid that your body contains, it facilitates nerve and muscle impulses, and together with potassium, it maintains the permeability of your cells' walls. This is a vitally necessary job if nutrients and other substances involved in cell maintenance are to be able to come and go as they're needed.

But scientists have also believed for decades that sodium has a direct effect on blood pressure--an effect that is proving to be highly controversial. The controversy is fueled by studies indicating that people with high blood pressure who reduce their consumption of sodium can lower their blood pressure readings by about five points. Lowering pressure just a few points cuts the risk of heart disease and stroke. By the same token, other studies indicate that low-salt diets do not lower blood pressure in about half of the people who try them.

Doctors have suspected for quite a while that low-salt diets won't help many people. Figuring that low-salt diets might help some and couldn't hurt others, however, they have continued to recommend that people with high blood pressure watch their salt intakes, says David McCarron, M.D., professor of medicine and head of the Division of Nephrology, Hypertension and Clinical Pharmacology at Oregon Health Sciences University in Portland.

That may be changing. Researchers at Cornell University Medical College and the Albert Einstein College of Medicine, both in New York City, decided to actually count the number of heart attacks among men with high blood pressure who consumed low amounts of sodium, then compare that figure with the number of heart attacks among men who had high blood pressure and higher sodium intakes.

The results? The men who ate the least sodium were four times more likely to have heart attacks than those who ate the most. And the less sodium they ingested, the higher their risk.

In effect, a low-sodium diet among people with high blood pressure was associated with the very problem it was designed to prevent. For more details on sodium and blood pressure, see page 297.

Using Sodium Safely

The amount of sodium your body needs to perform the nutrient's normal functions and keep your blood pressure on an even keel is a hot topic within the scientific community.

Some scientists feel you need no more than 500 milligrams a day of sodium chloride, the form in which sodium is usually found in foods or your saltshaker. Others say that your body is naturally constituted to readily handle 4,000 to 5,000 milligrams a day without a problem. And still others point out that the amount of sodium in your body at any given time is actually determined by aldosterone, a kidney hormone, anyway. So why worry about how much you're eating? Too much sodium in the body, and your kidneys will act to excrete the excess; too little, and they'll make sure enough sodium is retained in your body's fluid.

Clearly, more research is needed to sort out sodium's role in the body. But until that happens, how much sodium chloride should you allow in your diet?

Well, don't run out and start scarfing down salty chicken noodle soup, pickled herring or processed lunchmeats such as bologna laden with excess salt. You can still do well on 2,400 to 3,000 milligrams in your diet on a day-to-day basis, according to Dr. McCarron, who has spent the better part of 15 years researching the subject. One teaspoon of table salt contains about 2,000 milligrams of sodium.