by Marion Nestle

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Jul 15 2011

Interview with Scientific American on the complexities of salt science

I complained to Scientific American about one of its blog posts about salt, which I viewed as rather one-sided.  The result was a conversation with Michael Moyer that ended up in the form of a Q and A.  I did not have a chance to review it before it was posted, so please see addendum at the end). 

The Salt Wars Rage On: A Chat with Nutrition Professor Marion Nestle

A researcher explains why there may never be a good study on whether excess dietary salt causes hypertension and heart disease

By Michael Moyer | Thursday, July 14, 2011

 Is salt bad for us? In just the past few months researchers have published seemingly contradictory studies showing that excess sodium in the diet leads to heart disease, reduces your blood pressure, or has no effect at all. We called Scientific American advisory board member Marion Nestle, a professor of Nutrition, Food Studies, and Public Health at New York University and the author of Food Politics, to help parse the latest thinking regarding salt and heart health.leads to heart disease, reduces your blood pressure, or has no effect at all. We called Scientific American advisory board member Marion Nestle, a professor of Nutrition, Food Studies, and Public Health at New York University and the author of Food Politics, to help parse the latest thinking regarding salt and heart health.

[An edited transcript of the interview follows.]

I understand this area is controversial.

Hugely.

Could you take us through some of the controversy?

If you talk to any kidney specialist or anybody working on hypertension they will tell you that the first thing they do is try to lower the amount of salt their patients are eating because it helps with blood pressure control. But if you do a clinical trial where you try to put large amounts of people on a low-salt diet, you just don’t see much difference between the people who say they eat a lot of salt and the people who say they don’t eat a lot of salt. In clinical trials the relationship doesn’t show up.

Why not?

Two reasons: One that it’s impossible to put a population of people on a low-salt diet. Roughly 80 percent of the salt in the American food supply is in foods before people eat them—either in processed food or in restaurant food. Because so much salt is added to the food supply and because so many people eat out, it’s impossible to find a population of people who are eating a low-salt diet. They basically don’t exist.

In the one comparative epidemiological study they did some years ago—the Intersalt study—they managed to find two populations of people in remote areas of the jungle someplace who weren’t eating a lot of processed foods and who weren’t eating in restaurants. They were on a low-salt diet, and they never developed hypertension.

So in that trial did they put one group on a high-salt diet and put one on a low-salt diet?

No, no, no. It wasn’t a comparative trial. They just looked at the amount of salt that populations were eating and the amount of hypertension that they had. Only in these two populations were there very low rates of hypertension. With everybody else the salt intake was so high that they couldn’t see any difference between high and higher.

So except for people living in the jungle somewhere, there aren’t any populations on Earth that are eating a low amount of salt?

Not anymore. Maybe we used to be, but not anymore. We have a global food supply, so it’s impossible to do a really careful study.

What’s the other issue?

Not everybody responds to a low-salt diet. There’s a proportion of people in the population who are sensitive to salt—if you lower their intake of salt, then their blood pressure goes down. There’s another (probably larger) percentage of the population who doesn’t respond. They are people who can eat as much salt as they want and still their blood pressure is low.

So you have this curious anomaly where whenever you do a clinical trial you get these complicated, difficult-to-interpret results that don’t show much of an effect. But everybody who works with patients who have hypertension think they do better [on a low-salt diet]. And every committee, body, and group that has ever in my lifetime considered whether salt has anything to do with hypertension says, “yes,” and has recommended salt reduction as a public health measure. That’s the curious situation that we are in.

There’s one other wrinkle and has to do with people’s taste for salt. Campbell’s soup, for example, just announced yesterday that can’t sell low-sodium soups and so they’re adding salt back. And part of the reason they can’t sell it is that if you’re on a high-salt diet, food that isn’t salty tastes terrible to you. And if you’re on a low-salt diet it takes three to six weeks to get accustomed to being on a low-salt diet and then everything you eat tastes salty. And so the more salt in the food supply the more salt people need to bring the flavor you associate with salt. That complicates things, too.

So from a public health standpoint, if you want to deal with the percentage of the population that seems to be extremely responsive to a low-salt diet what you want to do is get the sodium level in the food supply as low as you can. And that makes the people who sell salty food go nuts. And it makes the people who like salty foods go nuts. They think the food tastes bland. And so there are different stakeholders in this system who have very different views and that accounts for the level of passion, I think, in a situation where the science is murky.

Couldn’t you just make the case that people should eat fewer processed foods?

Well what about restaurants? I’m a food professional. I eat out professionally.

Well chefs need to make their food taste good—otherwise people won’t go to their restaurant.

No, they need to make the food taste good by their standard. And chefs, because they’re dealing with a great deal of salt in their food, tend to raise the sodium level. It just goes up and up and up and up. As they get more used to a certain level of salt taste it no longer tastes salty to them and they have to raise it. So the pressure is to raise the salt in the food supply. And reducing it is very difficult.

So you advocate regulation to limit the amount of salt in restaurants?

Yeah, I do. Certainly for processed food. I think everybody would be healthier if they ate less salt. You can always add salt if you don’t think it’s salty enough, whereas I can’t take it away if it’s presented to me. And that’s the dilemma. And the ferocity of the arguments gets into the whole question of personal responsibility and “nanny state” and all of these other enormous debates that really don’t get at the public health question. And the public health question is hard to resolve because the science is really difficult to do.

Couldn’t you imagine a study where you look at sodium levels in urine, which is a direct measure of salt intake, and correlate that with hypertension?

Yeah they’ve done that, and they don’t see any difference in hypertension rates. The reason is that the baseline [level of salt intake] is so high that it doesn’t make any difference. To suggest that people get down to 1,500 mg a day—the recommended level—would be really really hard, and that level may be too high. And it’s unclear that that’s the right level because you can’t do a really decent dose response, and because people vary so much.

Will there ever be a good study?

I don’t know!

Is it possible that this represents the limits of science? It’s black hole event horizons and salt intake?

It may be. It very well may be. Or the science that we have is completely adequate and we already have the answer. I was once at a sodium meeting at which there were a bunch of statisticians. And I left with the statisticians and they said that “anyone who thinks that salt has anything to do with hypertension is delusional.” And that was on the basis on the clinical trials that show so little. And yet every single committee that has dealt with this question says, “We really need to lower the sodium in the food supply.” Now either every single committee that has ever dealt with this issue is delusional, which I find hard to believe—I mean they can’t all be making this up—there must be a clinical or rational basis for the unanimity of these decisions.

But that’s the thing—these committees should be able to point to the evidence that supports their recommendations. But they seem to rely so much on anecdote and individual experience.

Or on some clinical trials that everybody argues about. Everybody argues about every clinical trial no matter what the conclusion. So I find the whole thing completely fascinating. I don’t think anybody can underestimate the difficulty of doing nutritional research. Because people aren’t eating just sodium. They’re eating sodium in food. And it may be that high-sodium diets are a marker for some other things in the food supply or it may be that the physiological differences are so profound that you just don’t get clean results. That human variation is so great. I don’t know the answer to that. I just know it works for me. That’s anecdotal. With an “n” of one.

Addendum

If I had been given the opportunity to review this before it was posted, I would have edited it carefully.  Yes, this is the way I talk but I don’t think what I said reads clearly in print.  In reading over this piece, I think it may give the wrong impression of my views on how expert committees decide on salt recommendations.  The piece may give the impression that committees make dietary recommendations basied on anecdotal evidence, not science.  That’s not true.  They base their recommendations on their interpretation of the experimental and clinical evidence, including that from clinical trials.

For example, the Advisory Committee for the 2010 Dietary Guidelines concluded that “a strong body of evidence has documented that in adults, as sodium intake decreases, so does blood pressure.”  Was this committee delusional in viewing the evidence as strong?  I don’t think so.

Apr 26 2011

Should food labels say salt or sodium?

According to today’s Food Chemical News (which, unfortunately, requires a subscription to read), the FDA is arguing to make the international standard for food labels say sodium, not salt.

The U.S. delegation to the Codex Committee on Food Labeling will push for requiring the term “sodium” rather than “salt” on nutrition labels.

The European Union and its allies prefer “salt,” arguing that it is better understood by consumers.  But:

The United States is strongly opposed to removing “sodium” from the list of nutrients requiring disclosure. “We hope to achieve compromise and not remove sodium from the list,” said Schneeman. Asked about resolution of the dispute, she replied, “We still have our feelers out [to potential supporters]. Sodium is the nutrient, not salt.”

Maybe, but salt is what people eat.

I think “salt” makes more sense.  You?


Mar 19 2011

The latest on the salt restriction politics

The New York City Health Department announces good news and bad news.  The good news is that seven companies have agreed to reduce the salt in their products.  The bad news:

  • The average sodium intake in New York is 3.1 grams (2.3 grams is recommended for people who are not at risk of hypertension; for those who are, it’s 1.5 grams )
  • 79% of New Yorkers exceed sodium recommendations
  • 89% of New Yorkers at high risk of hypertension exceed sodium recommendations

Reminder: salt is 40% sodium.  This means that 3.1 grams of sodium is equivalent to nearly 8 grams of salt (two teaspoons).

The health department is working hard to bring restaurants and packaged food companies on board with salt reduction initiatives.  Packaged foods are easier (they have to label the amount of sodium).  The salt in restaurant foods is up to the chef, and one meal can easily exceed recommended levels for a day.

As for the effect of such efforts on food companies, FoodNavigator.com has compiled its recent pieces on salt restriction, all from the viewpoint of industry:

Salt restriction could increase risk of iodine deficiency: Restricting salt intake could increase risk of iodine deficiency, particularly among women, according to a new study published in the American Journal of Hypertension…

Mandatory sodium reduction 20 times more effective, finds study: Imposing mandatory sodium limits for processed foods could be 20 times as effective as voluntary reduction measures, suggests a new study published in the journal Heart…

Review shows steady US sodium consumption: Rising obesity rates may be a more important factor for hypertension than rising sodium consumption, claim the authors of a new study that suggests US sodium intake has remained relatively constant over the past 50 years…

Food makers look to umami as they cut sodium, says Bell Flavors: Food manufacturers are increasingly looking to boost the taste of their products with mouth-filling umami-type flavors as they reduce sodium in their products, according to Bell Flavors and Fragrances…

Concerted industry effort needed for sodium reduction: In order to cut sodium from American diets food manufacturers must work in unison to reduce sodium in their products – and their efforts have gained momentum, according to major industry players…

Packaged food makers have to label the sodium in their products

Oct 22 2010

The latest salvos in the sodium debates

Scientific debates about the role of sodium in high blood pressure go on and on.  Committees of scientists reviewing the research invariably conclude that people would be healthier if they ate less salt (salt is sodium chloride).  The 2010 Dietary Guidelines Advisory Committee is only the most recent group to urge population-wide reductions in sodium intake.

The Institute of Medicine has just issued a new report on reducing sodium.  Its Report in Brief gives a quick summary

As its primary strategy for sodium reduction, the committee recommends that the FDA set mandatory national standards for the sodium content in foods…beginning the process of reducing excess sodium in processed foods and menu items to a safer level. It is important that the reduction in sodium content of foods be carried out gradually…Evidence shows that a decrease in sodium can be accomplished successfully without affecting consumer enjoyment of food products if it is done in a stepwise process that systematically and gradually lowers sodium levels across the food supply.

But wait!  Hypertension rates have been increasing for years without any change in sodium excretion, says a report in FoodNavigator.com.  The report refers to new study in this month’s American Journal of Clinical Nutrition reviewing trends in sodium excretion from 1957 to 2003.

Sodium excretion, a precise reflection of intake, say Adam Bernstein and Walter Willett of the Harvard School of Public Health, has not changed in the last half century, despite rising rates of high blood pressure.   Instead, they suggest that rising rates of obesity might be the cause.

The accompanying editorial, by David McCarron and his colleagues, takes the argument even further as can be seen just from its title: “Science trumps politics: urinary sodium data challenge US dietary sodium guideline.

The editorial says that this new study provides:

plausible, scientific evidence of a “normal” range of dietary sodium intake in humans that is consistent with our understanding of the established physiology of sodium regulation in humans. This scientific evidence, not political expediency, should be the foundation of future government policies….Guidance for sodium intake should target specific populations for whom a lower sodium intake is possibly beneficial. Such an approach would avoid broad proscriptive guidelines for the general population for whom the safety and efficacy are not yet defined.

Is this review likely to change the Dietary Guidelines due out later this year?  The Advisory Committee was convinced that the preponderance of evidence favors the importance of sodium as a causative agent in high blood pressure.

Because so much is at stake for the processed food industry, this argument is not likely to be resolved quickly.  Stay tuned.

Jul 2 2010

The latest on salt for the 4th of July

In preparation for eating over the 4th of July weekend, here’s what’s happening on the salt frontier.

The CDC says fewer than 10% of Americans meet sodium recommendations. Only 5.5% of adults who should be consuming low sodium diets(≤1,500 mg/day) actually do so.  Less than 20% of adults consume the amount currently recommended for healthy adults, ≤2,300 mg/day. Overall, only 9.6% of adults met their applicable recommended limit.

The British Food Standards Agency (FSA) says the U.K. is making great progress on reducing salt consumption. Even though UK salt intakes are still above the target of 6g/day after seven years of campaigning, FSA is happy about what the campaign achieved: a 10% reduction in average daily intakes from 9.5g/day to 8.6g/day.  This is substantial progress, given “the complexity of the task and the FSA’s modest budget.”

The New York Times explains part of the complexity: food industry resistance.  In an article titled, “The hard sell on salt” (May 29), the Times interviews food company executives who talk about why they must, must use salt and lots of it in processed foods.

The Salt Institute attacks the Dietary Guidelines Advisory Committee report. The report recommends a limit of 1,500 mg/day sodium because 70% of the U.S. population is at risk of high blood pressure. According to Food Chemical News (June 16), the Salt Institute claims that reducing salt intake to recommended levels would only make the obesity epidemic worse: “Most nutritionists agree that reduced sodium in food preparations will very likely increase the obesity crisis because individuals will consume more calories just to satisfy their innate sodium appetite.”

Most?  I don’t think so.  Because 77% of salt (sodium chloride) is in processed and restaurant foods, I see the salt issue as one of consumer choice.  Consumers can always add salt to foods.  They cannot take it out.

Enjoy a happy, healthy, safe, and lower salt 4th of July!

Jun 2 2010

Salt is under siege

In April, the Institute of Medicine published a study concluding that salt poses so serious a health hazard that the FDA should start regulating it as a food additive.

Last week, Mitchell Moss produced a lengthy piece in the New York Times, “The hard sell on salt,” detailing the food industry’s resistance to salt reduction:

The industry is working overtly and behind the scenes to fend off these attacks, using a shifting set of tactics that have defeated similar efforts for 30 years, records and interviews show. Industry insiders call the strategy “delay and divert” and say companies have a powerful incentive to fight back: they crave salt as a low-cost way to create tastes and textures. Doing without it risks losing customers, and replacing it with more expensive ingredients risks losing profits.

Now we have Judith Shulevitz’s piece in The New Republic, Is salt the new crack?”  She concludes:

We need to stop ingesting all these substances in ludicrous amounts…We need to be taught not just what’s in processed food, but how historically anomalous its manufacture and our consumption of it are. We need to understand the mechanisms that addict us to it. We need to relearn how to prepare real meals, and we need to start rethinking the social dynamics of that chore (it can’t just be up to wives and mothers anymore). It’s pretty hard to imagine the government conducting that education campaign, but, 20 years ago, it may have been just as hard to imagine the “truth campaign” that exposed the tobacco industry’s marketing techniques and the transformation of social norms that made it déclassé to smoke.

As I keep saying (see previous posts), the salt issue is one of personal choice.  If I want to eat less salt, I cannot eat processed foods or restaurant foods because that’s where 80% of the salt in American diets comes from.  As Moss explains, PepsiCo cannot make Cheetos without salt.  I can just say no to Cheetos, but eating out is a challenge.

No, salt is not the new crack, but I’m glad that changing food social norms is becoming part of the national conversation.

Apr 27 2010

16 companies say they will reduce salt

New York City Mayor Michael Bloomberg announced yesterday that sixteen food companies have agreed to join the National Salt Reduction Initiative spearheaded by the city’s health department.  The companies have volunteered to reduce the sodium in their products by 25% within the next five years.  Mostly, they say they will do this by 2012 or 2014 (see summary table).

Nation’s Restaurant News points out that four of these companies are restaurant chains – Starbucks, Au Bon Pain, Subway, and Uno Chicago Grill.  One, Boars Head, is a deli chain.  And some food product companies – Mars, for example - are issuing their own press releases.

This is all good news and should encourage many more companies to take the low-salt pledge.

As the New York Times points out, salt lurks in unexpected places in processed foods.  The article came with a great graphic, well worth a look.

To translate the numbers, recall that salt is 40% sodium.  This means that 400 mg sodium = one gram of salt, 200 mg sodium = half a gram of salt, and 4 grams of salt = 1 teaspoon.

Apr 21 2010

FDA to regulate salt? If not now, when?

The Washington Post reported yesterday that the FDA is about to launch an initiative to get food companies to reduce the amount of sodium in their foods.

If true, this would be a major big deal.  But by late afternoon, the FDA had issued a press release denying the Washington Post’s report (and see note below):

A story in today’s Washington Post leaves a mistaken impression that the FDA has begun the process of regulating the amount of sodium in foods. The FDA is not currently working on regulations nor has it made a decision to regulate sodium content in foods at this time.

Over the coming weeks, the FDA will more thoroughly review the recommendations of the IOM report and build plans for how the FDA can continue to work with other federal agencies, public health and consumer groups, and the food industry to support the reduction of sodium levels in the food supply.

The FDA is referring to a report also issued yesterday by the Institute of Medicine: Strategies to Reduce Sodium Intake in the United States. According to the IOM Summary, voluntary efforts by the food industry to reduce sodium intake have failed.  The report’s first recommendation is for the government to set standards for the sodium content of packaged foods.  And that sounds like what the Washington Post thought the FDA was about to do.

The idea is to get all companies to start reducing sodium.  USA Today quotes Jane Henney, the previous FDA Commissioner who chaired the IOM committee: “The best way to accomplish this is to provide companies the level playing field they need so they are able to work across the board to reduce salt in the food supply.”

The IOM is doing a public briefing on the report at 10:00 a.m. today, at the National Press Club in Washington DC.  You can listen to it via audio webcast at www.nas.edu.

The Center for Science in the Public Interest (CSPI) first asked the FDA to start regulating salt in processed foods in 1978.  Its press release and report, Shaving Salt, Saving Lives, explain why the FDA’s action would be such good news for public health.

Salt is as controversial as any nutrition issue can get.  I expect plenty of pushback from the Salt Institute and other industry trade groups if there is any hint that FDA might be about to regulate salt content.  Could the FDA’s denial be the result of industry pressure?  It would be interesting to find out.

Some basic facts: Recall that sodium is 40% of table salt (sodium chloride).  Too much raises the risk of high blood pressure and stroke.  Nearly 80% of salt is in processed and pre-prepared foods that are salted before they get to you.

The recommended maximum for adults is 2300 mg or about a teaspoon a day.  If you are at risk for high blood pressure, the maximum is just 1500 mg, or two-thirds of a teaspoon.  Americans consume more than twice that much on average.

Note added April 20: the FDA has produced a Q and A on its salt regulatory policy.

Additions April 21: Here’s the New York Times story on the IOM report.  The LA Times reports on the amounts of sodium in fast food restaurant meals.  Impressive.

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