Dietary Salt Wars: Manufactured Controversy?

A recent Scientific American article calling for an end to “the war on salt” rips long-standing medical concerns about high-sodium diets, citing for support a 2011 meta-analysis of seven studies published in the American Journal of Hypertension and a 2011 observational study in JAMA, among other background. If the U.S. does “conquer salt,” all we are sure to gain is “bland french fries,” the Scientific American writer believes.

Salt crystals photo by Mark Schellhase (Wikimedia Commons).

That view is opposed by a legion of professional health organizations recommending dietary sodium reductions, including the American Heart Association, the American Society of Hypertension, the American Medical Association, the American Public Health Association, the National Academy of Sciences, the National Research Council, the Pan American Health Organization, the World Health Organization, and the World Hypertension League. Not to mention the governments of the United States, Canada, European Union, United Kingdom, Ireland, Finland, Australia, and New Zealand.

What’s going on here? Are all these medical organizations and countries disregarding the data?

Hardly, Dr. Lawrence J. Appel said at the 2011 scientific congress of the American Diabetes Association. Dr. Appel, who chaired the salt committee for the U.S. Dietary Guidelines for Americans, 2010, summarized the extensive medical literature on the effects of sodium intake and reduction of sodium intake. You can find a similar summary in a 2011 “call to action“ in an American Heart Association Presidential Advisory, “The Importance of Population-wide Sodium Reduction as a Means to Prevent Cardiovascular Disease and Stroke,” for which Dr. Appel was the lead author.

“If you reduced sodium ingestion by 1,200 mg per day, which is roughly 1/3 of average intake, you would reduce the number of heart attacks by an estimated 100,000 per year. Interestingly, that’s what you get with drug therapy for hypertension, or if you got 50% of people who smoke to stop,” said Dr. Appel, professor of medicine at Johns Hopkins University, where he is chair of the Welch Center for Prevention, Epidemiology and Clinic Research.

 

And since the Scientific American article appeared, a study in the Archives of Internal Medicine by the U.S. Centers for Disease Control and Prevention reported a 20% increase in risk for all-cause mortality with higher sodium intake in the general U.S. population.

 

So, is the “controversy” just a case of sometimes conflicting data? Is there something fueling this besides data?

In 2010, the Institute of Medicine recommended regulating the levels of sodium that manufacturers put into products. In the United States, 77% of the sodium in our diet comes from processed foods. More than half the total U.S. population and the majority of U.S. adults fit into categories of people who are at higher risk for adverse health consequences of high-sodium diets (including anyone older than 50 years; African-Americans ages 2 and up, and anyone age 2 or older with high blood pressure, diabetes or chronic kidney disease).

That strategy has been stymied by “a counteroffensive that is fueled by commercial interests” such as the Salt Institute, with support from a handful of scientists, Dr. Appel said.

Photo by Garitzko (Wikimedia Commons).

He spoke before the Scientific American article appeared, but some of the comments on the article’s website seem to back him up. For example, the article repeatedly cites a skeptic of sodium-reduction strategies, Dr. Michael H. Alderman, professor emeritus of epidemiology at Albert Einstein College of Medicine. But the article doesn’t mentioning that Dr. Alderman has been a paid consultant to the Salt Institute and failed to disclose that conflict of interest in journal articles, one commentator noted.

For the record, Dr. Appel disclosed having no conflicts of interest in his talk at the American Diabetes Association.

Critics of regulating dietary sodium make three arguments that sometimes get major press attention, Dr. Appel said. The first is that nothing should be done until we have a large, controlled clinical trial of the effects of sodium reduction. “Such trials are almost impossible because of logistical, financial and ethical considerations,” he counters. The second argument suggests that only “salt sensitive” persons should reduce their salt intake, but there is no test to tell whether an individual is salt sensitive and the scope of the hypertension epidemic makes this argument irrelevant, Dr. Appel said. Lastly, some claim that sodium reduction might be harmful, which is “a myth based on cohort studies with methodological flaws and over-interpretation of biomarker data,” he said.

So if you or your patients hear cries in the media about an unfair war on salt, here’s my suggestion: Take it with a grain of salt.

—Sherry Boschert (On Twitter @sherryboschert)