Salt has been grabbing health headlines for years. Mostly it’s been bad news about how the sodium in salt raises blood pressure (table salt is 40% sodium and 60% chloride). But there has also been research to suggest that little connection exists between salt intake and blood pressure for most people. In recent years, sodium has even come under renewed fire for its role in bone loss.
So, should salt shakers be banned from the table? Should sodium in convenience foods and fast foods come under more suspicion? To make sense of the sodium saga, EN takes a look at the ongoing, seemingly contradictory research.
The Latest Salvo Against Salt. The most recent salt headlines came from the DASH-Sodium study, sponsored by the National Institutes of Health. A spin-off from the earlier DASH (Dietary Approaches to Stop Hypertension) study, it specifically looked at the relationship between blood pressure and various sodium intakes.
The researchers found that the less sodium in the diet, the lower the blood pressure, both for people with high blood pressure and, surprisingly, for those with normal blood pressure. The greatest reduction occurred in people who followed the DASH diet that provided the least amount of dietary sodium. This was a diet rich in fruits, vegetables and low-fat dairy foods, low in saturated fat and cholesterol and with sodium limited to 1,500 milligrams a day?a very restricted amount.
Some experts suggest that these findings finally prove that sodium restriction is beneficial for everyone, regardless of blood pressure, a decidedly new concept. They contend that it can decrease the chance of developing high blood pressure with age. It may indeed be helpful for those at high risk of hypertension, such as African-Americans and those who are overweight. But it’s the issue of what to recommend to the general population that has nutrition scientists taking sides.
At Loggerheads Over Restricting Salt. Not everyone thinks the latest DASH study means that limits on sodium should be even lower than the current guideline of 2,400 milligrams a day. Michael Alderman, M.D., of Albert Einstein College of Medicine in New York City, has reported on the potentially harmful effects of such strict sodium restriction. After examining the diets of 11,000 people, he found that those who consumed the least sodium were the most likely to die prematurely.
Researchers from Tulane University have looked at the same data and concluded just the opposite, that reduced intake of sodium does not appear to cause adverse effects, at least not in those who are of healthy weight. Moreover, the study found that a high sodium intake, in fact, did increase the risk of death from heart disease, particularly in overweight people.
Why such different conclusions from the same data? The Tulane researchers excluded people with a history of heart disease for the statistical analysis, while the Alderman group did not.
Norman Kaplan, M.D., of the University of Texas Southwestern Medical Center in Texas, echos the opposition to Alderman on this issue, saying, “I do not know of any harmful effects caused by moderate sodium restriction.”
Critics of sodium restriction argue that no one has actually pinpointed any specific long-term cardiovascular benefits from sodium restriction. Defenders are quick to point out that even if you don’t buy into the high blood pressure theory, cutting back on salt may help protect against osteoporosis.
Sodium’s Threat to Bone Health. While sodium’s connection to blood pressure gets the most attention, evidence continues to grow regarding sodium as an osteoporosis risk. Acting as a calcium robber, a high sodium intake appears to be detrimental to bone density. Excessive sodium increases calcium losses in urine, a sign that calcium is leaching from bone. Consuming additional calcium can minimize sodium’s damage to some degree.
Are You Sensitive to Salt? Much of the controversy surrounding salt is derived from a little-understood phenomenon dubbed “salt sensitivity.” Although there is no precise definition, nutritionists use the term to refer to whether a person’s blood pressure responds to changes in sodium intake. The blood pressure of a person who is “salt-sensitive” rises when too much salt is eaten and drops when it is restricted.
Determining who is salt-sensitive is the problem. There are no foolproof tests for salt sensitivity, only the crude method of restricting sodium intake over a period of time while a physician monitors your blood pressure.
“Everyone probably experiences some sensitivity, so the concept is irrelevant,” contends Kaplan. Other experts believe that only a small percentage of people show roller-coaster blood pressure changes as a result of salt intake.
EN‘s Take. In the U.S., the average daily intake of sodium is about 4,000 to 4,500 milligrams?far more than the 500 milligrams our bodies need to survive. So, no matter what the consensus is for sodium and high blood pressure, most experts agree you should cut back, though not necessarily to extremely low levels. The possibility that less dietary sodium might help fight the growing epidemic of osteoporosis is reason enough to curtail your salt habit.
What many people don’t realize, however, is that banning the salt shaker from the table is not the most effective solution. Only 25% of our sodium intake comes from the salt we add to food, whether from the shaker or from condiments. The majority?75%?comes from sodium that’s added in food processing and from eating out. Read food labels to make lower-sodium choices (see chart).
The very best way to avoid the sodium in processed foods is to eat fewer processed foods’that is, canned and frozen convenience foods as well as fast foods?and more whole fresh foods. This will put you right in line with the DASH diet?a proven blood pressure reducer.
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