It’s
salt war time again: new research, arguments over public health recommendations, and issues of conflicts of interest
Posted: 14 Aug 2014 06:06 AM PDT Here are the burning questions about sodium (which is 40% of salt) intake: (a) Does too much dietary sodium cause high blood pressure? Answer: an unambiguous yes (although
not necessarily in everyone). (b) Are public health recommendations to reduce salt intake warranted? I think so, but others disagree. (c) If so, to what level? Although virtually all committees reviewing the evidence on salt and hypertension view public health recommendations
as warranted, and advise an upper limit of about 2 grams of sodium (5 grams of salt, a bit more than a teaspoon (see
table from the Wall Street Journal), these too are under debate. These recommendations are strongly opposed by
The Salt Institute, the trade association for the salt industry, its industry supporters, and some groups of investigators. Now the New England Journal of Medicine weighs in with three new studies, an editorial, and a cartoon video. The papers:
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Association
of Urinary Sodium and Potassium Excretion with Blood Pressure: A. Mente and Others | N Engl J Med 2014;371:601-611
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Urinary
Sodium and Potassium Excretion, Mortality, and Cardiovascular Events: M. O’Donnell and Others | N Engl J Med 2014;371:612-623
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Global
Sodium Consumption and Death from Cardiovascular Causes: D. Mozaffarian and Others | N Engl J Med 2014;371:624-634 Start with
the video, narrated by the editor, Dr. Jeffrey Drazen (click on video link on the right side). It gives an excellent
summary of the three papers. Despite their methodological differences, all confirm (a). They disagree on (c) and, therefore, (b). Are public health recommendations warranted? But note Dr. Drazen’s suggestion: “throw away the salt shaker.” He is in favor of reducing salt intake. But the salt shaker is not where most dietary salt comes from. At least 75% of salt in American diets
comes from restaurant and processed foods. As
Dr. Yoni Freedhoff explains:
Individuals cannot cut down on salt on their own. That’s one reason why public health policies are needed—to get restaurants and processed
food manufacturers to reduce salt content. Two of the papers say that the only people who need to cut down on salt are those with hypertension and older people (one of the studies says
that means people over age 55).
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How many Americans have hypertension? 67 million (1 out of every 3 adults)
according to the CDC.
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How many Americans are over age 55? More
than 80 million, and rising. You can’t expect 70 or 80 million people to reduce salt intake on their own. Hence: public health recommendations. Conflict of interest alert Some of the investigators report receiving grants or fees from companies that make anti-hypertensive drugs but the
editorial accompanying the papers is of special concern. Written by Dr. Suzanne Oparil, it says about one of the studies:
These conclusions sent me right to
her conflict-of-interest disclosure statement. Although Dr. Oparil reports receiving grants or fees from companies making anti-hypertensive drugs—-and, even more remarkable, from The Salt Institute—she states that she has no conflicts of interest. I think she does. Implications Her editorial is especially unfortunate because it influences the way reporters write about the studies. The
Associated Press account, for example, begins:
As well they should. Blood pressure rises with age and huge swaths of the population would be healthier eating less salt. The AP reporter
quoted me saying so:
The three studies are complicated to interpret because of differences in methods and discrepancies in outcomes. They agree that if you already
have hypertension or are “elderly,” or eat a lot of salt, you should cut down. This seems like a good idea for just about anyone. People don’t eat salt; they eat foods containing salt, and foods high in salt tend to
be high in other things best consumed in small amounts. The studies also talk about the protective effects of potassium, best obtained from vegetables. Eat a lot of vegetables and not too much junk food, and you don’t have to worry about any of this. |
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