Junkfood Science: The good-bad salt debate gets a hearing at the FDA

November 28, 2007

The good-bad salt debate gets a hearing at the FDA

The FDA is convening a public hearing tomorrow to decide if salt should be regulated as a potentially dangerous food additive and whether to revoke salt’s status as “generally recognized as safe.” Is this a sign that we should be concerned? Is this hearing in response to troubling new science showing that the population is at risk from salt, necessitating government intervention? Has evidence come out showing that salt reductions would benefit everyone?

No, no and no.

Reading the Federal Register Docket (No. 2005P-0450), we learn it is only in response to the latest petition from CSPI (Center for Science in the Public Interest). As CSPI’s press release said yesterday, it has been urging the FDA for years “to do something—anything” to get people to eat less salt.

In its Docket, the FDA reviewed those regulatory and legal efforts that began in 1978:

In 1978, CSPI submitted a citizen petition requesting that FDA establish limits for sodium in processed foods and reclassify salt as a food additive....The 1978 CSPI citizen petition also requested that FDA require sodium content labeling on packaged foods and require a special symbol on the labels of high-sodium foods.... In a letter dated August 18, 1982, FDA denied the petition....

In 1981, CSPI submitted a citizen petition requesting that FDA require warning labels on packages of salt weighing half an ounce or more. FDA denied that petition in a letter dated October 7, 1982. In that denial letter, FDA considered an isolated warning appearing on the label of one class of food products to be inappropriate given that many foods contribute to an individual's sodium intake.

In 1984, CSPI sought review of FDA's actions in the United States District Court of the District of Columbia...The district court concluded that FDA's decision was consistent with its regulations and the act and rejected the argument that FDA had unreasonably delayed reconsideration of the GRAS status of salt. CSPI did not appeal.

In 2005, CSPI sought a writ of mandamus, in the United States Court of Appeals for the District of Columbia, compelling FDA to publish in the Federal Register a proposed rule either affirming or denying the GRAS status of salt and providing an opportunity for comment on the proposal. The court dismissed CSPI's petition for lack of jurisdiction,

In a petition dated November 8, 2005, CSPI requested that the agency take certain regulatory actions regarding salt. Specifically, CSPI requested that FDA initiate rulemaking to revoke the GRAS status for salt, amend prior sanctions for the use of salt, require food manufacturers to reduce the amount of sodium in all processed foods, require a health message on retail packages of salt one-half ounce or larger, and reduce the DV [daily value] for sodium from its current level of 2,400 mg/d to 1,500 mg/d. CSPI also requested that FDA take regulatory action to reduce the amount of sodium in processed foods sold directly to restaurants...

Tomorrow’s hearing will examine two issues:

The first, is whether to revoke salt’s status as generally recognized as safe and if it should be regulated as an additive. As readers may know, back in 1959 the Federal Food, Drug and Cosmetic Act was passed which defined food additives subject to government regulation, excluding commonly used substances that are “generally recognized, among experts qualified by scientific training and experience to evaluate their safety as having been adequately shown through scientific procedures (or, in the case of a substance used in food prior to January 1, 1958, through either scientific procedures or through experience based on common use in food) to be safe under the conditions of their intended use.” Among the substances listed in the FDA’s GRAS list were common food ingredients such as salt, pepper, vinegar and baking powder.

Even so, during the 1970s, the FDA initiated a comprehensive review of GRAS substances to ensure their safety. As such, it contracted with the Federation of American Societies for Experimental Biology (FASEB) for a committee of scientific experts to summarize the available scientific literature regarding substances presumed to be GRAS, including salt. In the FDA’s 1982 policy notice, it outlined the findings of the FASEB’s report on salt and labeling recommendations. Concerning the safety of salt for the vast majority of the population, the FASEB concluded: “The evidence on sodium chloride is insufficient to determine that the adverse effects reported are not deleterious to the health of a significant proportion of the public when it is used at levels that are now current and in the manner now practiced.”

The FDA said it had considered and rejected the request to revoke salt as GRAS in 1982 for several reasons. The FDA would “have to establish a limitation for each technical effect for which salt is used in each food category, and it would be extremely difficult to prescribe and enforce ‘fair use’ limitations for salt that would be safe and effective for all consumers.” Salt also has many functions in foods and in different steps in food preparation that would be impossible to regulate separately, and the regulatory burden, and costs to consumers, would be extraordinary.

The FDA also said in 1982 that to revoke salt’s GRAS status and take regulatory action, it “would have to show that salt in food is a ‘poisonous or deleterious substance.’” No such evidence at levels consumed exists. Therefore, it concluded that the informational labeling in place would be most responsive to any health concerns about sodium that individual consumers might have.

The second issue that will be examined in tomorrow’s hearing is the food labeling changes requested. As the FDA states:

Our regulations currently require declarative statements on the label about the sodium content of processed food, define nutrient content claims for foods based on their salt content, provide for a health claim regarding low sodium diets and reduced risk of hypertension, and stipulate maximum sodium concentrations for foods that are to be labeled as ‘healthy.’ In addition to the goal of providing information to consumers, these labeling initiatives are also intended to encourage food manufacturers to reduce the salt content of foods and to provide incentives to manufacturers to produce lower sodium foods. CSPI argues that these measures have not ultimately served to reduce salt intake and that further, more aggressive regulatory action is needed.

The core to the FDA’s decisions to date has been the science. Is there good evidence to support CSPI’s beliefs that salt is dangerous and in need of governmental regulation? And, is there good evidence that cutting salt consumption in half, population-wide, to the lowest in the world, will benefit public health and reduce premature deaths?

Let’s look at the three main scientific papers CSPI used to support its petition that were outlined in its paper, “Salt: The Forgotten Killer,” last updated in May.

1. CSPI says: “Reducing sodium consumption by half would save an estimated 150,000 lives per year.” It supported this claim by referencing a 2004 article published in the American Journal of Public Health.

This paper, however, was not a study, but a “Commentary” and “Call for Action” in support of the government’s Healthy People 2010 objectives headed by the National Heart, Lung and Blood Institute (NHLBI) and its National High Blood Pressure Education Program Coordinating Committee. This commentary was authored by Dr. Stephen Havas at the University of Maryland School of Medicine and two others with the NHLBI. Their estimation was based on associations of hypertension among those having heart attacks and strokes, and a calculation of what could happen if salt reduced levels of hypertension. Potential risks were not included in their calculation, nor were the effects on the majority of people in the population who don’t have clinical hypertension.

2. CSPI says: “Reducing salt intake in children quickly lowers their blood pressure. If their blood pressure remains lower, those kids could experience lower rates of heart attack and stroke as they age.” This claim was supported by the study led by professor Graham MacGregor, founder of CASH (Consensus Action on Salt and Health).

JFS reviewed that study thoroughly last December. Essentially, it was only speculations based on no clinically meaningful evidence.

3. CSPI says: “One recent study found that people who are pre-hypertensive and cut back on sodium, reduced their chances of developing cardiovascular disease by 25% and their risk of dying from it by 20%.” In support of this claim, CSPI referenced the study led by Nancy Cook, associate professor at Harvard Medical School in Boston. That study and others, including a Cochrane Review, were reported here.

To summarize, the Cook study was a follow-up of the Trial of Hypertension Prevention (TOHP) trials which had been conducted during the late 1980s to look at the blood pressure effects of salt reduction and weight loss among more than 3,000 people with hypertension (and who were mostly obese). Even extreme salt-restricted diets reduced blood pressures in this cohort by a mere 1.2/0.6 mmHg. While hypertension can be an indicator of cardiovascular disease, salt restrictions have been shown in the scientific literature to reduce blood pressure in about one-third of the population and then only modestly, while it can increases blood pressures for another quarter of people.

Citing relative risks, as CSPI did, makes the effects of salt-reduction sound much more significant than they really are. After 5 to 10 years, the Cook researchers found that the difference in the number of cardiovascular-related deaths between the intervention and control groups was only 5 people. These differences were so insignificant that the authors made no assertions that salt reduction lowered mortality among the study populations. In fact, they also specifically cautioned that high blood pressure is not a cardiovascular event (a clinical outcome), but a surrogate endpoint, and not sufficient evidence to call for large scale sodium reductions.

What about more recent studies?

Walker et al. The most recent analysis of the evidence examining if dietary salt restrictions provided protection from cardiovascular events or deaths was published last month in the Journal of Interactive Cardiovascular and Thoracic Surgery. Led by Dr. Jay Walker of the Department of Cardiothoracic Surgery, James Cook University Hospital, Middlesbrough, UK, the researchers identified 14 studies which presented the best evidence, included among them were the TOHP studies.

Their paper was aptly titled: “Does reducing your salt intake make you live longer?” That’s really what matters, isn’t it?

Most studies to date, they observed, have looked at the effects of low-sodium diets on blood pressure or blood pressure medication use among people with hypertension, and only a few examined mortality. An NHANES (National Health and Nutrition Examination Surveys) study of 9,485 people followed for 19 years after a 24-hour sodium questionnaire found no difference in clinical risks among the ‘normal’ weight patients and among the ‘obese,’ and only a 3% difference in any clinical outcome (heart disease and mortality) between the lowest and highest salt intakes.

The most recent analysis the Walker researchers examined was the one of the TOHP trials on hypertension by Cook and colleagues. While the Cook authors had reported that cardiovascular events were 25% lower among the patients given counseling on salt reductions as compared to the control patients, this is another example of how we can be misled by relative risks versus actual (absolute) numbers. “On looking further into this study” and actual incidences, Dr. Walker and colleagues cautioned, “this difference was 7% compared to 9% over 10 years for cardiovascular events (of which there were 200 across over 3000 patients).” The bottom line, they concluded, while salt restrictions may reduce blood pressures, “the ability of dietary sodium restriction to reduce the incidence of cardiovascular events is more controversial.”

Grobbee et al. Another major peer-reviewed study was also published last month, this one in the European Journal of Epidemiology, examining sodium and potassium intakes and their relationship to cardiovascular disease and mortality. We didn’t hear much about this study in the news, either, so let’s look briefly at what it found.

Researchers from Wageningen University in The Netherlands followed a general population sample of people 55 years and older for five and a half years. Clinical exams were done at the beginning of the study, including body measurements, blood pressure, blood tests and 24-hour urine samples to measure sodium and potassium levels. Dietary data was obtained from food-frequency questionnaires.

They found no association between any of the levels of sodium, potassium or sodium/potassium ratios and cardiovascular or all-cause mortality, nor was there a tenable relationship among the overweight study participants. “The absence of a relationship between salt intake and mortality in our study corroborates the findings from the large Scottish Heart Health Study among almost 12,000 middle-aged subjects with 24-h urine samples,” they wrote. Also, “follow-up data of the MRFIT trial neither showed a relationship between dietary sodium intake estimated by 24-h recall and cardiovascular events or mortality.”

They concluded: “The effect of sodium and potassium intake on CVD morbidity and mortality in Western societies remains to be established.”

In fact, while there have been more than 17,000 studies published on salt and blood pressure since 1966, none has shown population-wide health benefits from low-sodium diets, only some select subgroups of people appear to respond. According to Dr. David Klurfeld, Ph.D., professor and chairman of the Department of Nutrition and Food Science at Wayne State University, editor-in-chief of the Journal of the American College of Nutrition, “the better controlled studies fail to show a significant benefit on blood pressure for large groups with sodium restriction.”

The other side of the coin

If there is no support that salt reduction among the general population, versus people with specific medical issues, will save lives and help ensure that everyone will enjoy longer, healthier lives; any evidence that such reductions might harm vast numbers of the population becomes even more critical to consider. Yet, the possible adverse effects of salt reductions aren’t mentioned by CSPI and rarely in the media.

Far from being totally benign, the European Society of Cardiology Guidelines for the Management of Arterial Hypertension, for instance, reported recent research showing low-salt diets can have negative effects: activating the rennin-angiotensin system and the sympathetic nervous system, increasing insulin resistance and hypodehydration (especially with the elderly). This, they concluded, could lead to increased risks for cardiovascular disease.

A cardiologist once explained one of the concerns very simply, when commenting that some of the longest living people in the world also have the highest salt consumptions. When most of us eat a lot of salt, we get thirsty and drink water, and our bodies excrete the excess sodium chloride while maintaining the balance of sodium in our blood and our blood pressures. Our bodies are designed to compensate for excess salt without hurting us. When people eat less salt, though, blood levels of sodium can drop below normal. Should you get sick, go out in the hot sun or exercise, when you drink more water, it dilutes the sodium even more, resulting in greatly increased risks for heat stroke or circulatory collapse. Now, that’s not good for your health.

Salt also improves the flavor of many nourishing foods, helping to prevent nutritional deficiencies especially among vulnerable populations, such as children and elderly. It does more than make many of the foods we love taste good. Salt has served invaluable roles in food preparation and preservation, baking, culturing cheese, and making our food safer to eat since the earliest days of mankind. Salt reductions could jeopardize these benefits, at costs to health, safety and enjoyment of foods.

A recent randomized clinical trial of patients with hypertension, published in the American Journal of Hypertension, confirmed the connection with insulin resistance, as noted by the European Society of Cardiology. It found that increasing sodium in their diet appeared beneficial and concluded: “An abundant sodium intake may improve glucose tolerance and insulin resistance, especially in diabetic, salt-sensitive, and or medicated essential hypertensive subjects.”

The authors of the NHANES II follow-up study of a representative sample of U.S. residents were especially cautious about establishing dietary guidelines based on currently available evidence. This study, led by Dr. Hillel W. Cohen, MPH, DrPH, of the Department of Epidemiology and Population Health at Albert Einstein College of Medicine, Bronx, NY, said that guidelines calling for reductions are based on the modest blood pressure changes associated with low-sodium diets in short term clinical trials. “However, these trials could not assess the long-term cardiovascular morbidity and mortality consequences.”

They said that caution was especially advised with making conclusions based on observational studies, as “no single observational study can confirm a causal inference.” We recently saw that when that World Cancer Research Fund Expert Report said that many of the claims of salt being associated with health problems and higher rates of premature deaths are due to confounding factors not considered in observational studies. For example, they noted that “salt is inversely related to the availability of refrigeration in a population, and so to socioeconomic status.”

Dr. Cohen and colleagues added:

[B]asing a lower sodium recommendation primarily on intermediate effects such as blood pressure reduction is also unsatisfactory. Unintended health consequences can result from seemingly reasonable expectations.... In the case of sodium, extrapolations from positive effects on blood pressure may be offset by extrapolations from potentially adverse effects on the sympathetic nervous system, the renin-angiotensin system, insulin resistance, and the potential that other important nutrients might be decreased when free-living individuals alter diets to decrease sodium...

The data here cannot sustain a conclusion that lower sodium is harmful. However, these findings, along with the inconsistent results of other epidemiologic studies, and the propensity for substantial variability among individuals, do not lend support to any universal prescription for salt intake.

In sum, the inverse associations of sodium to CVD mortality observed in this large, nationally representative sample, raise questions regarding the likelihood that a survival advantage will necessarily result from a universal recommendation for a lower dietary sodium intake.

An Associated Press story today mentioned none of this, however. It quoted the director of CSPI, Michael Jacobson, as saying the “current levels of salt in the diet are one of the biggest health threats to the public.” Dr. Havas (who authored that Call to Action mentioned above) was then quoted: “This is truly urgent. We need to act.”

Is salt a killer and a public health crisis? The FDA will hear all sides tomorrow. Whether we’ll hear all sides in the news coverage is another story.

© 2007 Sandy Szwarc

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