People have fought over salt for thousands of years.
In both the Old World and the New, these were sometimes pitched battles that took human lives. Venice and Genoa went to war over the control of salt in the 14th century. Access to salt played a critical role in both the Revolutionary and Civil wars.
Today, the clash over salt is a war of words. For decades, public health experts have exhorted Americans to slash salt consumption. Organizations such as the American Heart Association and the Centers for Disease Control and Prevention recommend that people older than 50 as well as anyone with high blood pressure or diabetes limit sodium intake to 1,500 mg a day (less than half the average daily sodium consumption in the U.S.).
Scientists knew that some people with hypertension could control it by cutting back on salt, although a meta-analysis of studies revealed that salt restriction also raised LDL cholesterol and the stress hormones such as noradrenaline, renin and aldosterone (JAMA, May 6, 1998).
It comes as a shock to most Americans to learn that epidemiological studies have shown that people consuming the least sodium are at the highest risk of premature death (American Journal of Medicine, March 2006; JAMA, May 4, 2011). If there are downsides to lowering sodium intake, public health experts might need to be careful about urging everyone to avoid salt.
The universal warning that Americans need to limit sodium in their diets took a blow, metaphorically speaking, when the Institute of Medicine (IOM) brought out its evaluation of how much sodium restriction is desirable and safe (IOM, May 14, 2013). This prestigious group advises the CDC on health policy. In reviewing recent research, it concluded that lowering excessive sodium intakes would benefit public health, but that the research does not clearly show that limiting sodium to less than 2,300 mg daily would save lives. The IOM's most controversial conclusion was stated cautiously: "The evidence on health outcomes is not consistent with efforts that encourage lowering of dietary sodium in the general population to 1,500 mg/day."
Now, everyone agrees that a diet heavy on lunchmeat, bacon, cheese and french fries provides more salt and fat than is good for us. The scientists are really arguing about realms of salt restriction most people don't even approach. But does it make sense to try to get everyone to struggle toward a diet that is difficult to achieve unless we are sure the rewards will be significant?
It might be better to figure out who is salt-sensitive and learn how to help those people reduce their sodium consumption. Researchers at the University of Virginia have developed a urine test that can identify salt-sensitive individuals (Clinica Chimica Acta, June 5, 2013). About one of four adults will develop high blood pressure if they consume too much sodium. For these people, salt restriction makes sense, though scientists might continue to argue about how low they should go.
One-size-fits-all recommendations are no longer appropriate in an age of personalized medicine. The IOM's report recognizes this and should be taken seriously by public health authorities.
Joe Graedon is a pharmacologist. Teresa Graedon holds a doctorate in medical anthropology and is a nutrition expert.