Junkfood Science: Who decides what you can eat? Sating on salt

January 29, 2009

Who decides what you can eat? Sating on salt

Most consumers trust that public health policies are guided by the best science and are enacted after medical experts have carefully weighed the health benefits for the public against the potential risks for harm. The fact that this does not happen was demonstrated this week with the launch of a major nationwide campaign that could put millions of people at risk. But this story received barely a blip of news coverage.

This new program is being led by the commissioner of New York City’s Department of Health and Mental Hygiene. — Yes, the same department that is requiring hospitals to give itself full access to your medical records and has also mandated that every lab in the state report to it all blood sugar results without patients’ knowledge (or informed consent or ability for patients to opt out) so that it can identify people for state “disease management.”

Dr. Thomas R. Frieden wants to put the entire population on a low-salt diet and is leading a nationwide low-salt initiative, partnering state, local and federal governments and private stakeholders to cut salt in our foods in half within the next decade. The significance of this initiative may have been lost on media. Perhaps it sounded harmless and intuitively helpful because “everyone knows salt is bad.”

It deserves to be out in the open, though, because the best science for nearly half a century — including the government’s own findings on examinations reflecting 99 million Americans; more than 17,000 studies published since 1966; and even a recent Cochrane systematic review of the clinical trial evidence — fails to support the hypotheses that salt reductions offer health benefits for the general public. Cochrane’s reviewers specifically concluded that such interventions are inappropriate for population prevention programs.

It’s not just that the salt reductions being proposed will be costly programs that won’t be of much help to people, but that they could hurt people. Even more troubling, the public health messages in this new campaign appear to be most targeting minorities, fat people, the elderly and poor.

Public health bulletins on the program’s website tell New York consumers that salt is harmful, bad for their health, and that eating too much salt means people are more likely to have high blood pressure, heart attacks and strokes. And “heart diseases is New York City’s biggest killer.” Echoed by the City’s director of cardiovascular health, Dr. Sonia Angell, M.D., MPH, consumers are being told that they’re eating twice the salt they need and that “a low salt diet (1,500mg) can help lower or even control blood pressure.” It even claims that those who don’t have high blood pressure can prevent high blood pressure by eating a low salt diet. “Lower sodium levels by 50 percent, and 150,000 American lives a year might be saved,” said Dr. Frieden.

None of these claims can be scientifically supported.

Missing: a crisis of heart disease. The latest vital statistics data from the CDC National Center for Health Statistics was just released and reported that age-related deaths from heart disease, cancer, diabetes, liver disease and hypertension — all of the causes some want us to believe are due to unhealthy lifestyles, rather than mostly aging — have continued to drop significantly for more than 50 years. The latest Health US report from the CDC found our life expectancy has reached another record high and age-adjusted mortality for the leading causes of death have been cut nearly in half since 1950, including heart disease.

Missing: a crisis of hypertension. The latest National Heart, Lung and Blood Institute study using National Health and Nutrition Examination Survey (NHANES) data found no epidemic of hypertension, either. Actual average blood pressures among American adults changed little between 1988 and 2004. There’s been no statistical change for some two decades in systolic blood pressures among people being treated for hypertension. And average systolic blood pressures among Americans without hypertension has gone from 115 to 117, changes too small to be clinically meaningful. Meanwhile, among all groups, average diastolic blood pressures has decreased during this period (an overall average of 73 to 72).

Missing: a crisis of high salt intake. It may be popular to believe that we’re eating dramatically more salt over recent decades, because of all that processed food and all. The evidence doesn’t support this oft-repeated claim, as was covered in the salt shaker article. Researchers at the Department of Epidemiology and Population Health at Albert Einstein College of Medicine in New York, found Americans aren’t eating anywhere near the amounts of salt being claimed. Their third study in a series examining NHANES data representing 99 million non-institutionalized adults in the United States between 1988 and 1997, showed average sodium intake among Americans has remained about 3,200 mg/day.

Missing: even an association between salt and heart disease or premature death. As covered here, even following the NHANES participants for nine more years through year 2000, the Albert Einstein researchers were unable to show among the general population that those eating the lowest salt diets had lower risks for developing cardiovascular disease or high blood pressure or dying prematurely. In fact, heart disease, high blood pressure and deaths were inversely related to salt intakes: the higher the sodium, the lower the risks; the lower the dietary salt, the higher the risks.

To parse out the effects of dietary sodium intake itself, they factored for confounding influences, including: age, gender, race, education, added table salt, exercise, alcohol use, smoking, history of diabetes, history of cancer, systolic BP, cholesterol, dietary potassium, weight, treatment for hypertension, and calories. [To rule out possibilities that the results could reflect the affects of cancers or illnesses, the authors excluded those Americans who’d died within the first 6 months or those who’d had a previous heart attack, stroke or heart failure.] The associations between low-salt diets and higher rates of cardiovascular disease and all-cause mortality held.

The lowest sodium intakes — the 1500 mg/day that the New York health department says everyone should be eating — were associated with an 80% higher risk of cardiovascular disease compared with those consuming the highest salt diets. The lowest salt intakes were also associated with a 24% higher risk of all-cause mortality. Clearly, low-salt diets are not associated with lower risks for the general population. Conversely, the Albert Einstein researchers were unable to show that even the highest salt intakes were associated with increased risks for developing cardiovascular disease or high blood pressure or for premature death.

A major international research project in thirty-two nations showed that while the incidence of hypertension varied widely, salt intake had little to do with it.

Another major peer-reviewed study published in the European Journal of Epidemiology, examined sodium and potassium intakes and their relationship to cardiovascular disease and mortality. 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, adding, “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.”

Decades of epidemiological evidence simply do not support fears that salt is deadly or that the amounts people naturally eat are associated with harm, or that low-salt diets are associated with improved health or longer life.

Benefits of salt

“By virtue of its central role in maintaining intravascular and extracellular volume, sodium is essential to human survival,” wrote Dr. Michael Alderman, M.D., in the International Journal of Epidemiology. Given free access to salt, humans consume surprisingly similar ranges of salt across a wide variety of diets, cultures, environments and heredities, he said.

In fact, some of the longest-living people in the world also have the highest salt consumptions. Many point to the Japanese, for example — they have one of the highest salt intakes in the world, as well as the highest life expectancy.

Salt not only makes food taste better, it also improves the flavor of foods for those whose tastes or appetites are diminished, helping to prevent nutritional deficiencies especially among vulnerable populations, such as children and elderly. Salt isn’t added to food for malevolent purposes, but because it has had invaluable roles in food preparation and preservation, baking, culturing cheese, and making our food safer to eat since the earliest days of mankind. The healthful benefits of salts, discussed here, also include the importance of the very first functional food: iodized salt.

The European Society of Cardiology guideline experts reported that randomized clinical trial evidence also suggests that “an abundant sodium intake may improve glucose tolerance and insulin resistance, especially in diabetic, salt-sensitive, and or medicated essential hypertensive subjects.”

Other unintended risks of low-salt diet

It’s extremely rare to have too much salt in our bodies, called hypernatremia, (it occurs in about 1% of debilitated hospitalized patients as a symptom of an underlying disease or inability to drink water). But, as covered here, low-salt diets significantly raise people’s risk for hyponatremia, where the amount of sodium in our bodies can become dangerously low. It’s the most common electrolyte disorder and a special risk for infants and elderly, according to Dr. Sandy Craig, M.D., at the Department of Emergency Medicine, University of North Carolina at Chapel Hill. It can result in swelling of our brain, seizures, coma, heat stroke, leg cramps, heart arrhythmias and circulatory collapse. Low-salt diets put elderly especially at added risk for hypodehydration and death.

Growing numbers of clinical studies in the medical literature are suggesting other unexpected negative health effects of low-salt diets, such as activating the rennin-angiotensin system and the sympathetic nervous system and increasing insulin resistance and worsen glucose tolerance, especially for diabetics. These effects could actually raise risks for cardiovascular disease, according to the European Society of Cardiology Guidelines.

Low-salt diets fail to lower blood pressure, heart disease and mortality

Cochrane recently released a systematic review of the clinical trial evidence on reduced dietary salt for the prevention of cardiovascular disease, as well as the effects of low-salt diets on blood pressure and mortality. After 1 to 5 years of follow-up, those who’d received low-salt diets and intensive behavioral interventions, saw their systolic blood pressures reduced by a mere 1.1 mmHg, and diastolic blood pressures by 0.6 mmHg, even while successfully lowering salt intakes as confirmed by urinary 24-hour sodium excretions by 35.5 mmol. As the reviewers wrote: “This reduction was not enough to expect an important health benefit.” Changes in blood pressures were also unrelated to the degree sodium had been reduced — in other words, more wasn’t better. Deaths were also no different between those on low-salt diets and control groups.

The Cochrane reviewers concluded that even “intensive interventions, unsuited to primary care or population prevention programmes, provide only minimal reductions in blood pressure during long-term trials.”

In fact, while there have been more than 17,000 studies published on salt and blood pressure since 1966, even following populations for decades, none has shown notable health benefits for the general population with low-sodium diets. 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 source of claims that reducing sodium intake by half would save 150,000 lives a year, used to petition the FDA to revoke salt as generally recognized as safe, was a CSPI paper. As reviewed here, the claims were not supported by the research, nor even the study researchers’ own conclusions. Similarly, media claims that salt kills or that cutting down on salt adds 12 years to your life also proved unsupported.

The Albert Einstein College of Medicine authors were especially cautious about establishing population guidelines based on currently available evidence. Guidelines calling for reductions are based on the modest blood pressure changes associated with low-sodium diets in short term clinical trials, they said. “However, these trials could not assess the long-term cardiovascular morbidity and mortality consequences.” They 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.

Even the New York Times reported that Dr. Friedman might encounter resistance to his low-salt campaign “on scientific grounds.” Different people have different responses to sodium, dictated by genetics, with some people sensitive to high levels and for others low salt levels can be unhealthy, it concurred.

Dr. Michael Alderman found this campaign alarming. “Advocates of universal restriction of sodium intake,” he wrote, “base their case on the belief that this will produce a population-wide reduction of blood pressure which, in turn, will reduce cardiovascular morbidity and mortality. Indeed, these dogma are often preached with a fervour usually associated with religious zealotry.” He argued, however, “that the available data provides insufficient evidence to justify any universal target for sodium intake for either the whole population or for its hypertensive subset.”

What’s up?

As the New York City-led nationwide low-salt initiative is clearly not founded on a true health crisis, on the medical evidence, or on proven health interventions for the primary prevention of high blood pressure or heart disease, what might it really be about?

As the New York Times pointed out today, the target is going after packaged foods and chain restaurant meals. Reducing salt to levels unpalatable to their consumers appears to primarily be about getting people to eat less of foods these public officials don’t think people should eat or others should sell.

His plan is based on the UK’s traffic light program, reports the newspaper, earmarking such “prime suspects” as cheese, breakfast cereals, bread, pastas, cake mixes, condiments and soup. “Dr. Frieden says a quiet, mass reduction in sodium levels — stealth health, they like to call it around the department — might be more effective,” wrote the New York Times, than relying on people to comply with the government’s dietary recommendations.

Professor Lawrence O. Gostin, director of the Center for Law and the Public's Health at Georgetown and Johns Hopkins Universities, may have called it when he commented:

You can imagine it getting to the point where you have a public health worker showing up at your door and asking, ‘Did you remember to exercise, eat right and take your medication today?’

That appears to already be in the planning.

© 2009 Sandy Szwarc

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