by Marion Nestle
Aug 14 2014

It’s salt war time again: new research, arguments over public health recommendations, and issues of conflicts of interest

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:

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:

If you’d like to reduce the sodium in your diet, rather than keep a running tally of how much you’re actually consuming, why not try instead to determine what percentage of your diet comes from restaurants and boxes? Sure, there’s data to suggest you might simply find other ways to add salt to your diet. But visit restaurants and consume processed foods less frequently, and I’d be willing to wager that you’ll be far more likely to see health benefits than were you to simply fill your grocery cart with low-sodium versions of highly processed foods.

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).

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 provocative findings beg for a randomized, controlled outcome trial to compare reduced sodium intake with usual diet. In the absence of such a trial, the results argue against reduction of dietary sodium as an isolated public health recommendation.

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:

A large international study questions the conventional wisdom that most people should cut back on salt, suggesting that the amount most folks consume is OK for heart health — and too little may be as bad as too much. The findings came under immediate attack by other scientists.

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:

“People don’t eat salt, they eat food,” she said. “Lots of people have high blood pressure and lots of people are getting older,” making salt a growing concern, she said. “That’s the context in which this is taking place.”

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.

Comments

  • Glen
  • August 14, 2014
  • 8:50 am

The paragraph:

Start with the video, narrated by the editor, Dr. Jeffrey Drazen. It gives an excellent summary of the three papers. Despite their methodological differences, all confirm (a). They disagree on (c) and, therefore, (b).

References a video, but the link does not go to a video. Can you post the correct link?

[…] Marion Nestle writes about the NEJM papers I’m losing my s#$t over: […]

  • Donna
  • August 14, 2014
  • 2:15 pm

this is a fantastic blog post. For exercises tips and health JoActive will post articles on blog page http://www.JoActive.com JoActive provides in home personal training in Stouffville and Toronto areas

The video is hard to find, but it is on the link: in the middle of the page, small print. Pretty good animation!

  • Hal
  • August 14, 2014
  • 8:53 pm

Marion- From your own estimate, less than 1/3 of people are predisposed to hypertension. Why should we all limit our intake of NaCl because of this?

If we find in time that our BP is affected by salt, we can change our dietary choices.

If you truly want the answer, go back to the first RDA recommendations and you will see that there is absolutely no evidence in the scientific research supporting these arbitrary limits of 1500 to 2300 mg per day. None. I followed it back then and I worked in a Navy research lab.

Re Dr. Suzanne Oparil’s editorial comment: anybody on the take from the Salt Institute is quite clearly in a conflict of interest position on this topic, and has no business editorializing on behalf of those who give her money.

  • Tom Maguire
  • August 15, 2014
  • 10:14 pm

Re: “Answer: an unambiguous yes (although not necessarily in everyone).”

In other words, an unambiguous yes, except when it’s no.

Could you please clarify the meaning of “unambiguous”?

  • Duy Quoc Vu
  • August 16, 2014
  • 3:39 pm

This article published in the NEJM vol 371 no 7 reopens the discussion due to several reasons:
the variables used do not describe accurately the subpopulation involved nor help refine each subgroup (low, medium, high intake). In the low subgroup we find in high incidence of stroke. This observation may be due to the fact that people in that group already have a cardiovascular condition that required them to lower salt intake, the data published didn’t mentioned the condition of those people i.e htn, kidney etc… and obviously those people, who have this condition, are at risk for additional complications such as stroke. More variables are desirable than less in statistics. In business they used hundred of variables to look at an outcome. Time for medicine to catch up. My two cents.

  • Morton Satin
  • August 17, 2014
  • 8:37 pm

Marion, It is amazing how you manipulate the concept of conflict of interest when the actual evidence does not support your case. You use it as a propagandist uses innuendo. And look, one of your commenters already claims Oparil is ‘on the take’. That is simply not the case – I know this because I am with the Salt Institute. At least Michael Jacobson had the decency to call us and ask for the facts, rather than to depend upon the natural tendency to think the worst of everyone. Marion, a long time ago, I said you were on the wrong side of the evidence on this, and all the actual evidence (not the flawed models that don’t account for renin aldosterone reaction to sodium reduction) will continue to show this in future – so be prepared to face the evidence. I am indebted to the huge group that Mozaffarian leads, because they logged sodium intake around the world in standard UN format, so now anyone, including you or your readers can chart sodium intake against all UN/WHO published data on actual cardiovascular metrics, which is also published in UN format. There you will immediately see that those few countries that adhere to the 1500-2300 mg sodium recommendations all have worse health outcomes than the rest of the world, which consumes between 2800-4800 mg sodium. This is, of course, most evident with WHO’s “Healthy Life Expectancy” data. According to this data, tHe more salt you consume, the longer you are expected live. Of course, this does not prove ’cause and effect’ because there are too many variables in life expectancy. However, it does show compatibility of current salt consumption with steadily increasing life expectancy and better health outcomes.

[…] needed, but none of the research published last week counters what is the overwhelming (though not universal) scientific consensus: that in general we eat too much salt and that it poses health risks, […]

  • MarcyB
  • August 27, 2014
  • 9:29 am

I know there is alot of salt in the foods we eat but what about using sea salt to put on our foods, I heard it is much better for you and does not contain as much sodium.

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