We're an equal opportunity critic of cooking the books on medical studies. As an FDA panel this week will (again) examine the relationship of salt and health, JunkfoodScience reminds us of the games-playing in the "gold standard" ENHANCE trial, "Even gold can be tarnished." Don't miss it. Let's hope the FDA panel reads it too!
It's a deadly double play combining the Big Lie with the Devil in the Details. But this is no game.
Epidemiological studies are often used inappropriately for common illnesses like cardiovascular disease and cancer, according to British cardiologist Guy Lloyd.
Randomized controlled trials are more reliable. Epidemiology is most effective in identifying large risks in rare diseases. Just in the field of cardiology, the results of observational studies are often seriously flawed.
Observational studies of the cardioprotective effects of female sex hormones, the usefulness of antioxidants or homocysteine lowering strategies, and rhythm control for atrial fibrillation suggested a clear treatment effect and greatly influenced practice. But subsequent randomised trials refuted each hypothesis.
The main problem, he explained, is all of the interacting factors among cohorts that can't be statistically accounted for in an epidemiological study.
Concerns with the reporting of medical studies are multiplying. A recent blog on Junkfoodscience highlights the efforts of a new project, STROBE (Strengthening the Reporting of Observational Studies in Epidemiology). We wish them all success.
Since the early 1950s the health promoting qualities of the Mediterranean diet have been universally acknowledged. The Mediterranean diet "is characterized by abundant plant foods (fruit, vegetables, breads, other forms of cereals, beans, nuts and seeds), fresh fruit as the typical daily dessert, olive oil as the principal source of fat, dairy products (principally cheese and yogurt) and fish and poultry consumed in low to moderate amounts, zero to four eggs consumed weekly, red meat consumed in low amounts, and wine consumed in low to moderate amounts, normally with meals. This diet is low in saturated fat (less than or equal to 7-8% of energy) with total fat ranging from less than 25% to greater than 35% of energy throughout the region." In fact, the famous DASH diet was designed using the Mediterranean diet as the model. What is never revealed, however, is that the level of salt in the Mediterraneam diet is considerably higher than that the levels recommended for the US diet.
Drs. Leclercq and Ferro-Luzzi of the WHO Collaborating Centre for Nutrition, at the National Institute of Nutrition in Rome, Italy reported in that males consumed 4400mg sodium per day based upon 24 hr Urinary excretion, equivalent to 11grams of salt per day . It was also observed that the discretionary intake of salt for adults varied from 36% (males) to 39% (females) of the total intake. The discretionary intake alone, of salt in Italy amounts to almost 75% of the total sodium recommended in the US (2300 mg). Since many of the Mediterranean foods are naturally well salted (cheeses, olives, salted fish (cod, anchovies), fish eggs, etc., it is natural to expect that a majority of the discretionary salt is used to improve the palatability of the variety of vegetables that are such a conspicuous and essential part of the diet.
When the DASH-Sodium trial is examined, it is immediately apparent that moving to a DASH-type diet has a far greater impact on blood pressure than lowering salt consumption. Dropping from the current level of sodium consumption to the recommended dietary level dropped the systolic pressure by an average of 2.1 mm Hg. However, simply changing from a regular to the DASH diet, without any changes to sodium consumption, reduced the systolic blood pressure by 5.9 mm Hg, almost three times the drop resulting from the sodium reduction. This clearly explains why Mediterranean people enjoy an excellent cardiovascular status despite their high salt consumption. With a DASH diet, the impact of sodium on the blood pressure of hypertensives is minimal (and of no significance to normotensive people - the majority in the population).
Considering that significantly increased fruit and vegetable consumption is a key element to the DASH/Mediterranean diet models, it is entirely realistic to question whether the current recommended daily intake of sodium (2300mg/day) is realistic, given the Italian example above. Amongst the most important foods are the bitter cruciferous vegetables. While they have so much nutrition to offer, without salt, they are not palatable to adults or children (who are even more sensitive to bitterness). In addition to the benefits of the DASH/Mediterranean diet for cardiovascular disease outcomes, all other health parameters are significantly improved. Based on all the scientific evidence we have available, fruits and vegetables are the cheapest, most readily available, and most beneficial foods we can consume to give a significant degree of protection from the modern health challenges we face. Considering the hierarchy of positive health impacts, maintaining the DASH/Mediterranean diet is far more significant than reducing salt - the one safe condiment that has traditionally made this diet so agreeable.
Three weeks ago, at the GMA/FPA and CSPI Salt Conference, Michael Jacobson of CSPI categorically stated in his opening remarks, "The debate on sodium is over. There is no longer a debate whether salt is good or bad." He was followed by Steve Havas of the AMA who stated that he did not believe any additional research was necessary to prove the beneficial impacts of a dramatic sodium reduction in the diet. This attempt to stifle discussion and pronounce, as if by imperial fiat, that there was no longer any debate concerning the benefits of salt reduction in the diet backfired.
When the audience, which was composed of professional food scientists, nutritionists, dieticians, epidemiologists and policy makers split into working sessions to consider all that was said, they concluded that the benefits of salt reduction to health outcomes had yet to be proven scientifically and that that a singular focus on salt reduction was not a viable solution. Indeed, the delegates unanimously stated that a more holistic approach was needed to improve overall dietary quality.
Almost as it on cue, within two weeks of the Salt Conference, two peer-reviewed medical journal articles appeared, both demolishing Michael Jacobson's assertion that "the debate on sodium is over." In a paper published in the October issue of the European Journal of Epidemiology , prominent Dutch scientist D.E. Grobbee and colleagues in the Rotterdam Study concluded that urinary sodium is not significantly associated with myocardial infarction, stroke, or overall mortality, adding: "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."
Shortly thereafter, in the Journal of Interactive Cardiovascular and Thoracic Surgery , Drs. Jay Walker, Alastair MacKenzie and Joel Dunning of the Department of Cardiothoracic Surgery at James Cook University Hospital, in Middlesbrough, UK reported their in-depth review of all available evidence to determine if restricting dietary salt intake would provide protection from adverse cardiovascular events or mortality. They found it impossible to find a link between salt and heart disease due to a "lack of adequately powered randomized trials or observational studies conducted with sufficient rigor." Dr Dunning went further - he dismissed the theory that salt can cause strokes and heart attacks as,
...an argument of hope over reason....
These two publications reinforce the conclusions of the recent evaluation of the health outcomes study from Finland's three decade long salt reduction program.
Today saw a scathing denunciation of the poor science that has gone into the UK's public health policies . Dr. Phil Peverley, a GP from Sunderland in Northern England is this year's Magazine Journalists and Designers Association Columnist of the Year. Last year, he won the Press and Periodical Association's columnist of the year award. In his article, "A Very Large Pinch of Salt," Dr. Peverly criticizes
those doctors and politicians who have for years promoted the nannying theory that we should be forced to eat less salt in our diets. The obvious lack of a correlation between elevated blood pressure and salt intake should have been good enough for them.
He goes on to describe Public health minister Dawn Primarolo, who was recently quoted as saying that a low salt intake was an essential part of a healthy diet.
Ms Primarolo's only qualification to spout off on this subject is a six-year pre-MP career as a 'mature student', so I would always have regarded her pontifications as profoundly suspect…
Delving deeper, he states:
However, my remit is a wider one. This is further evidence that it is us, the medical profession, who don't know what we are talking about. I never fell for the bollocks about salt, but I have been as guilty as the rest of spreading disinformation and inaccurate advice about a whole manner of other medical subjects. It is becoming embarrassing.
Bravo Phil Peverly! There are not many like you, but hopefully there will be enough to drive away the fog, so we can get back to the science.
Writing for the American Council on Science and Health , Kathleen Meister offers sound advice for medical and science writers. Available in PDF , here's the executive summary :
• Scientific studies that show an association between a factor and a health effect do not necessarily imply that the factor causes the health effect. Many such studies are preliminary reports that cannot justify any valid claim of causation without considerable additional research, experimentation, and replication.
• Randomized trials are studies in which human volunteers are randomly assigned to receive either the agent being studied or an inactive placebo, usually under double-blind conditions (where neither the participants nor the investigators know which substance each individual is receiving), and their health is then monitored for a period of time. This type of study can provide strong evidence for a causal effect, especially if its findings are replicated by other studies. Such trials, however, are often impossible for ethical, practical, or financial reasons. When they can be conducted, the use of low doses and brief durations of exposure may limit the applicability of their findings.
• The findings of animal experiments may not be directly applicable to the human situation because of genetic, anatomic, and physiologic differences between species and/or because of the use of unrealistically high doses.
• In vitro experiments are useful for defining and isolating biologic mechanisms but are not directly applicable to humans.
• Observational epidemiologic studies are studies in human populations in which researchers collect data on people's exposures to various agents and relate these data to the occurrence of diseases or other health effects among the study participants. The findings from studies of this type are directly applicable to humans, but the associations detected in such studies are not necessarily causal.
• Useful, time-tested criteria for determining whether an association is causal include:
- Temporality. For an association to be causal, the cause must precede the effect. - Strength. Scientists can be more confident in the causality of strong associations than weak ones. - Dose-response. Responses that increase in frequency as exposure increases are more convincingly supportive of causality than those that do not show this pattern. - Consistency. Relationships that are repeatedly observed by different investigators, in different places, circumstances, and times, are more likely to be causal. - Biological plausbility. Associations that are consistent with the scientific understanding of the biology of the disease or health effect under investigation are more likely to be causal.
• New research results need to be interpreted in the context of related previous research. The quality of new studies should also be assessed. Those that include appropriate statistical analysis and that have been published in peer-reviewed journals carry greater weight than those that lack statistical analysis and/or have been announced in other ways.
• Claims of causation should never be made lightly. Premature or poorly justified claims of causation can mislead people into thinking that something they are exposed to is endangering their health, when this may not be true, or that a useless or even dangerous product may produce desirable health effects.
We hope this gets to be a popular site.
Whether it's the health of the planet or of its human inhabitants, it seems we have to learn every generation about the pain and suffering inflicted when we act on improperly-understood "science" -- and, thus, the need to employ a cautionary, evidence-based approach to basing public policy on boldly-asserted scientific truth.
An article in the current American Thinker deals with global warming, but it's not my intent to explore the validity of the scientific clash on that issue, only to "steal" an anecdote to make a further point. Author James Lewis shares this story:
Trofimko Lysenko is not a household name; but it should be, because he was the model for all the Politically Correct "science" in the last hundred years. Lysenko was Stalin's favorite agricultural "scientist," peddling the myth that crops could be just trained into growing bigger and better. You didn't have to breed better plants over generations, as farmers have been doing for ages. It was a fantasy of the all-powerful Soviet State. Lysenko sold Stalin on that fraud in plant genetics, and Stalin told Soviet scientists to fall into line --- in spite of the fact that nobody really believed it. Hundreds of thousands of peasants starved during Stalin's famines, in good part because of fraudulent science.
He then provides context:
When the scientific establishment starts to peddle fraud, we get corrupt science. The Boomer Left came to power in the 1970s harboring a real hatred toward science. They called it "post-modernism," and "deconstructionism" --- and we saw all kinds of damage as a result. Scientific American magazine went so far as to hire a post-modern "journalist" to write for it. John Horgan became famous for writing a book called The End of Science, but never seemed to learn much about real science. It was a shameful episode. ....
Pathological science kills people and ruins lives. Such fake science is still peddled by the PC establishment in Europe and America. ...
Britain is even more vulnerable to politicized science than we are, because medicine is controlled by the Left. That is a huge chunk of all science in the age of biomedicine. But the British Medical Journal and even the venerable Lancet are no longer reliable sources. Their political agenda sticks out like a sore thumb. It was The Lancet that published a plainly fraudulent "survey" of Iraqi civilian casualties a few years ago --- the only "survey" ever taken in the middle of a shooting war. As if you can go around shell-shocked neighborhoods with your little clipboard and expect people to tell the truth about their dead and wounded: Saddam taught Iraqis to lie about such things, just to survive, and the internecine fighting of the last several years did not help. The whole farce was just unbelievable, but the prestigious Lancet put the fake survey into the public domain, just as if it were real science. It was a classic agitprop move, worthy of Stalin and Lysenko. But it was not worthy of one the great scientific journals. Many scientists will never trust it again.
The account continues on global warming, but my point is the broader one: politically-correct science may not be scientifically-correct science and relying on PC science (junk science) risks disasters like that engineered by Stalin. That's true for environmental science. And it's true for nutrition science.
For years, the anti-salt advocates have ducked the scientific evidence and relied on the support of the largest medical and health institutions to prop up their contention that there is an unassailable link between salt intake and cardiovascular disease. This fallacious strategy is known as Argumentum ad Verecundiam - the reliance on known institutions and entrenched doctrines, rather than experimental data - the sort of thing that Francis Bacon grappled against in his struggle to bring us the scientific method.
Predictably, science eventually finds it way to the surface and in this case, the Argumentum ad Verecundiam is showing signs of collapse in the face of mounting evidence against a link between salt intake and cardiovascular disease.
In the most recent issue of the Journal of Interactive Cardiovascular and Thoracic Surgery , Drs. Jay Walker, Alastair MacKenzie and Joel Dunning of the Department of Cardiothoracic Surgery at James Cook University Hospital, in Middlesbrough, UK carried out an in-depth study of all available evidence to determine if restricting dietary salt intake would provide protection from adverse cardiovascular events or mortality. Using reported search parameters, 462 papers were identified of which 14 papers represented the best evidence on the subject. They concluded that restricting sodium intake to levels below 6 g per day as most international guidelines, such as those of the AHA, the US Dietary Guideline Committee and the Scientific Advisory Committee on Nutrition recommend may reduce blood pressure, but found it impossible to find a link between salt and heart disease due to a "lack of adequately powered randomised trials or observational studies conducted with sufficient rigor."
This information corresponds with the recent publication of the Rotterdam Study by Geleijnse et al, as well as the evaluation of the health outcomes from Finland's three decade long salt reduction program .
The myth-information about salt and cardiovascular health outcomes has gone on for a long time and misdirected our focus from more practical and effective approaches to achieving good health. It's time we start devoting our resources to solutions that have scientific merit, such as improving the overall diet through systems and products that encourage greater consumption of fruits, vegetables and low-fat dairy products.
A new Dutch study of 2,896 subjects studied for 5-6 years has concluded that there is no health benefit for healthy subjects to reduce dietary salt. The risk for subjects with cardiovascular disease and diabetes was not reported.
This, the 16th study of the health outcomes of reduced-salt diets, examined the incidence of heart attacks and strokes, cardiovascular mortality and all-cause mortality. Unfortunately, all the studies are observational (this is a case-cohort analysis); a controlled trial is required to address the question. The paper was published in the October issue of the European Journal of Epidemiology .
The research team headed by Diederick E. Grobbee examined a large, high-quality and much-admired database that contains data unavailable to some of the earlier studies. The authors reported:
Urinary sodium was not significantly associated with incident myocardial infarction, incident stroke, or overall mortality. For CVD mortality, however, a borderline significant inverse association was observed (RR = 0.77 (0.60-1.01) per 1-SD, model 3) but the relationship was attenuated after excluding subjects with a history of CVD or hypertension (RR = 0.83 (0.47-1.44) per 1-SD, model 3). In subjects initially free of CVD, the risk of all-cause mortality was also examined across quartiles of 24-h urinary sodium (median values: 45, 87, 125 and 190 mmol, respectively). RR in consecutive quartiles, using the lower quartile as the reference, were 0.80 (0.43-1.49), 0.66 (0.34-1.27) and 0.98 (0.54-1.78), respectively (model 3). In a subgroup analysis of CVD free subjects with a body mass index ≥25 kg/m2, the association of urinary sodium with CVD mortality or all-cause mortality was neither statistically significant (RR = 0.91 (0.44-1.89) and RR = 1.19 (0.86-1.66) per 1-SD, respectively; model 3).
... the biggest threat to science has been quietly occurring under the radar, even though it may be changing the very foundation of American innovation. The threat is money-specifically, the decline of government support for science and the growing dominance of private spending over American research.
In 1965, the federal government financed more than 60 percent of all R&D in the United States. By 2006, the balance had flipped, with 65 percent of R&D in this country being funded by private interests.
That's the complaint in a story by Jennifer Washburn in this month's Discover magazine on "Science's Worst Enemy: Corporate Funding ."
I haven't checked her figures, but I doubt that the government ever funded two-thirds of US R&D; a more reasonable figure is the 40% today. But worse than the math is the author's implicit assumption that socializing the country's research and development investments is a good thing -- that private investments reflect a for-profit bias while government investments are "pure" and "untainted." Washburn fears that "if the balance tips too far, the 'public interest' side of the science system-known for its commitment to independence and objectivity-will atrophy."
Some would question the "commitment to independence and objectivity" of federal researchers and those enjoying their largesse. Rather than rehearse the numerous and egregious examples, I'd suggest a simple reflection on the wisdom of our Founding Fathers in setting up a government recognizing that every person and institution has self-interests. The question is how they pursue them and how we can sort through competing interests to get the truth upon which to base our decisions and public policies.
In the salt area, we badly need explicit "evidence-based" policy based not on passion and emotion, but on replicable, quality science. We need to look at evidence to answer the question: would reducing population salt intakes improve health? It turns out that virtually all the studies in this area are government-funded. While often characterized by government-convened "expert" groups, the actual research does not find a health outcomes benefit to salt reduction .
Without doubt, corporate-funded research employed to support public policy deserves to be held to the highest standard and its analysis held to the standards of the Data Quality Act. So, too, does government-funded research. There should be no comfort taken -- nor relief granted -- to conclusions of government-funded scientists because they work for "the public." Sorry, Jennifer.
Reading Gina Kolata's New York Times book review of Gary Taubes' new book, Good Calories, Bad Calories, I'm struck that the book is really two-in-one. The first "book" is the heavily-researched and compellingly-argued critique of the scientific foundation of current dietary guidance. As Kolata summarizes his argument: "nutrition and public policy research and policy have been driven by poor science and a sort of pigheaded insistence on failed hypotheses." Sounds like the sodium and health debate to me. Kolata says "much of what Taubes relates will be eye-opening to those who have not closely followed the science, or lack of science, in this area." The second "book" is Taubes argument favoring low-carb diets.
I fear too many may neglect the impeccable research buttressing "book one" if they don't accept Taubes' answer to the narrower question of the role of carbohydrate, fat and protein as causes of heart disease. That would be a great loss. "Book one" is a great stand-alone read and a devastating critique of the "consensus" method - as opposed to an "evidence-based" method - of formulating dietary recommendations.
Taubes concludes: "From the inception of the diet-heart hypothesis in the early 1950s, those who argued that dietary fat caused heart disease accumulated the evidential equivalent of a mythology to support their belief. These myths are still passed on faithfully to the present day." Kolata adds: "The story is similar for salt and blood pressure, and for dietary fiber and cancer," concluding "Taubes convincingly shows that much of what is believed about nutrition and health is based on the flimsiest science."
There's much more in Taubes' 450-page book. Make sure you read at least "book one."
Gary Taubes' new book prompted a second article in The New York Times in which NYT science writer John Tierney explains how the science underlying our dietary guidelines departed so sharply from quality science. He attributes it to the process of soliciting "expert opinion" and declares the process an "informational cascade" where an initial error is compounded and implanted as policy as successive "experts" sign-on.
"Cascades are especially common in medicine as doctors take their cues from others, leading them to overdiagnose some faddish ailments (called bandwagon diseases) and overprescribe certain treatments (like the tonsillectomies once popular for children)." Tierney recounts several of Taubes' examples, in particular that eating fat has produced an epidemic of heart disease. The original hypothesis was embraced by politicians (Sen. George McGovern (D-SD) and President Jimmy Carter's USDA activist Carol Tucker Foreman leading to the Dietary Guidelines for Americans and, eventually, today, to the Food Guide Pyramid. Unconvinced scientists were intimidated by politicians and the media; Tierney quotes economist Timur Kuran's description as "a reputational cascade, in which it becomes a career risk for dissidents to question the popular wisdom." Taubes' book includes the anecdote of an exchange of a prominent nutrition scientist responded to Sen. McGovern when McGovern asked him why he refused to accept the conclusions of "92% of the world's leading doctors." The scientist called for policy based on science, not "by anything that smacks of a Gallup poll."
Anti-salt zealots display a religious fervor for their cause, trampling scientists who remind them that actual evidence of a health benefit exists only in the end product of elaborate mathematical models extrapolating only blood pressure effects (and even those are often shrouded in withheld statistics preventing replication). There's an arrogance to their advocacy. And a familiarity.
Investigative science reporter Gary Taubes published the lead story in the New York Times Magazine on September 16, asking "Do We Really Know What Makes Us Healthy?" It's the tragic story of well-intended, plausible advocacy of hormone replacement therapy (HRT) for post-menopausal women. The bright promise, the powerful claims and the glittering possibilities all came crashing down a few years ago when it was found that for many if not most of the target audience, the "cure" was killing far more than it was helping.
Taubes called for more "self-doubt" and recommital to the discipline of scientific investigation, foregoing the passion of the righteous objective for the surer cycle of scientific advance -- proposing hypotheses, testing them to discard most of them and then repeating the cycle to refine those who pass muster.
As he pointed out:
While it is easy to find authority figures in medicine and public health who will argue that today's version of H.R.T. wisdom is assuredly the correct one, it's equally easy to find authorities who will say that surely we don't know. The one thing on which they will all agree is that the kind of experimental trial necessary to determine the truth would be excessively expensive and time-consuming and so will almost assuredly never happen. Meanwhile, the question of how many women may have died prematurely or suffered strokes or breast cancer because they were taking a pill that their physicians had prescribed to protect them against heart disease lingers unanswered. A reasonable estimate would be tens of thousands.
In conclusion, Taubes cautions:
All of this suggests that the best advice is to keep in mind the law of unintended consequences. The reason clinicians test drugs with randomized trials is to establish whether the hoped-for benefits are real and, if so, whether there are unforeseen side effects that may outweigh the benefits. If the implication of an epidemiologist's study is that some drug or diet will bring us improved prosperity and health, then wonder about the unforeseen consequences. In these cases, it's never a bad idea to remain skeptical until somebody spends the time and the money to do a randomized trial and, contrary to much of the history of the endeavor to date, fails to refute it.
You can't discern the cankers and the warts at 30,000 feet, but taking in the big picture often helps us understand the motivations that play out as the tangled inconsistencies of daily news stories about health. There are some whose mission in life is to point in alarm at instances where individuals or society comes up short -- where problems mar perfection. These professional and persistent pessimists, in the health arena, would have us focus attention and resources on such interventions as dietary changes ostensibly to effect improved health outcomes, but based only on plausible, but unproven scientific evidence.
A blog today on JunkFoodScience hits the nail on the head:
There's been so much good news recently about the state of our health and that of children. This has clearly distressed alarmists. To keep their gloomy myths alive, they've tried to: A). bury the news and B). convince us that good is really bad.
With people not buying any of that, they've added plan C: scream louder. As Dr Ian Campbell, medical director of Weight Concern, told the BBC news this week: "We are not making enough progress!"
Facts have such a troublesome habit of getting in the way of agendas. Let's look at three major new health reports that all brought good news.
Author Sandy Szwarc points out that the 2006 National Health Interview Survey released recently found 88% of Americans self-report good or excellent health, new figures released this past week from the Centers for Disease Control and Prevention showing strong historic trends of lengthening life expectancies and falling rates of heart disease, and a UNCEF announcement this week that more children are surviving today than ever before in history.
We think the glass is at least half full, and filling steadily.
During our daily review of all legislation related to salt, it was a pleasant surprise to come across the final filing and adoption of the West Virginia division of health nursing home licensure rule that became effective July 1, 2007. The purpose of this legislation was to implement state and federal law governing the licensing, operation, and standard of care in nursing homes located in the State of West Virginia. The goal is to help each nursing home resident attain or maintain the highest practicable physical, mental and psychosocial well-being.
Among the requirements explicitly stated are:
8.15.d. - A nursing home shall provide each resident with: Food prepared with salt, unless contraindicated by a physician's order; and, the salt should be iodized.
Finally, legislation based on the genuine requirements of a person rather than a politically correct interpretation of populist nutrition. Time and time again we have read of the negative effects of low salt diets prescribed to nursing home residents leading to chronic dehydration and hyponatriumia (salt deficiency). Often, these low salt diets lead to other major complications including bone fragility and increased cardiovascular risk. The insistence that the salt be iodized is an additional indication that whoever wrote up this rule did their homework. Bravo!It is refreshing to see that there are still legislators out there willing to take on the responsibility of doing things right.
Perhaps you read the article published this week in the online Journal of Human Hypertension (paid subscription required) by Dr. Graham MacGregor claiming dietary salt was responsible for high blood pressure in children. MacGregor and colleagues claim their results support "a reduction in salt intake for children and adolescents."
Not so fast. Though the media carried the author's conclusions from the study, an accompanying editorial (free) by Dr. Michael H. Alderman, immediate past president of the International Society of Hypertension, in the same edition points out that the entire relationship is due to the fact that those who ate more salt ate more food. Adjusting for caloric intake wiped out the significance of the relationship. Nor was there any difference between the high-salt and low-salt groups in terms of preference for adding salt at the table. Alderman pointed out that those consuming more salt and calories may also have had more adequate intakes of other vital, growth-related nutrients, but that the study did not include these data. Thus, Alderman concludes that the data "support the Cochrane Collaboration conclusion that there was not sufficient evidence for a general dietary recommendation to reduce sodium intake."
Alderman cautioned against following MacGregor's prescription of having children reduce dietary salt.
...randomized clinical trials in adults have shown that lowering sodium intake increases sympathetic nerve activity, reduces insulin sensitivity, increases the activity of the renin-angiotensin system and increases aldosterone secretion.
Do these or other changes occur in children? This is critical because, of course, the health impact of any intervention is the sum total of all its consequences. While I remain an agnostic on that score, I continue to believe firmly that solid knowledge based on evidence of benefit and risk must precede any clinical or public health intervention -- particularly when it comes to dependent children. Good observational studies such as this one generate hypotheses. They need to be tested in clinical trials. Absent such evidence, and absent some pressing public health challenge, therapeutic restraint may be the best and safest way to avoid doing harm.
Alderman may be "agnostic" with regard to his pursuit of an evidentiary basis for an intervention. It's too bad too many proponents of salt reduction seem to advance their arguments with strong faith and religious zeal -- and without scientific basis. We've heard no better argument against the establishment of a state religion.
