Salt & Human Health

As we move into holiday mode, substituting our normal focus on salt for visions of sugarplums, some "highly encouraging" news from this week's journal Hypertension. Drs. Kwok Leung Ong and colleagues in Hong Kong, studying the massive US federal NHANES database, report that 75.7% of Americans with hypertension know that fact (up from 68.7% four years earlier) and 36.8% have it controlled (compared with 29.2% in the earlier study).

Good news indeed. And it's siginficantly grounded in the biggest federal database. As the authors note: "The NHANES database has been valuable for the study of the trends in the health status of a population because of its large sample size, complex sampling design, good quality control, and comprehensive content."

The authors found four reasons for the improvement: 1) obesity isn't increasing (missed that in the MSM, I'll bet!), 2) "better publicity and education," 3) better use of treatment guidelines for medications (as opposed to development on new meds themselves) and 4) "an increase in the use of antihypertensive medications."

No mention of salt, by the way. An ealier NHANES analysis found that those on lower salt diets don't benefit anyway. They had 37% higher cardiovascular mortality than those on normal salt. That's some pretty good news too! Merry Christmas.

Posted by Dick Hanneman at 05:08 PM | Permalink

No doubt the UK's anti-salt publicity machine was feeling pleased with their success in generating headlines for a recent piece that suggested that infants need to cut their salt in half. That is, until junkfoodscience called their bluff.

We don't know if blogger-nurse Sandy Szwarc knew anything about the multi-million pound British anti-salt ad campaign featuring "Sid, the Slug," a cartoon reminder of one of the 14,000 beneficial uses of salt -- to kill slugs. Szwarc suggests the public "pour salt on it" -- the study in question. As she laments:

Such extraordinary claims require extraordinary evidence. Does this study hold up?

This study is said to be the “first ever meta-analysis of salt reduction studies in children.” And it epitomizes every caveat of these types of studies. MacGregor and He “developed a strategy” of their own design to look for words in several databases and through reference lists at the end of articles to find studies of salt reduction in children. They only used studies published in English and of the 33 they found, decided to use 10 on children for this report. The studies all had different designs, with only one being a double-blind trail and only 9 were randomized; the studies varied in length from 2 weeks to 3 years; compliance with salt reductions appeared poor in two of the studies; we have no information on the racial/ethnic mix of the children and if it is representative of the general population; and only 3 measured 24-hour urinary sodium levels — which the researchers admitted is “the only accurate way to assess dietary salt intake.” Simplifying what they did next, they pooled the data on blood pressures and net changes in salt intake, and used statistics to estimate the changes as needed to fill in missing data. Then, they applied two computer models to plot the results and more statistical analyses to reach their findings.

What they reported was that cutting salt intake by 42% reduced systolic blood pressures in the children by 1.17 mmHg. Most parents and children would consider such a salt reduction — nearly in half — to be extreme; while most doctors would debate the clinical significance of a mere 1 point reduction in blood pressure. Taking blood pressures in young children is an imprecise task at best and the children in these different studies were also at varying stages of development, with corresponding variable changes in blood pressures over the study durations, according to their growth and size.

The researchers stated that the “physiological need for salt intake in children has not been studied,” but concluded anyway that “current salt intake in children is unnecessarily high and is very likely to predispose children to develop hypertension later.”

They went on to declare that these results “provide strong support for a reduction in salt intake for children. [And] if continued, may well lessen the subsequent rise in BP with age and prevent the development of hypertension. This would result in major reductions in cardiovascular disease.”

Their press release promised possible “massive population health gains.”

·But this study did not examine a single child.

·It conducted no clinical research to learn how much salt is needed or might be harmful for children.

·It offered no clinical evidence to know if a lower blood pressure reading of 1 point means anything for children’s health or is maintained as a child grows.

·It offered no proof that a blood pressure reading during childhood has any bearing on adult blood pressures or heart disease.

·And worse, it didn’t follow a single child to see if there were any health effects from the salt restrictions they are recommending.

In other words, this study offered no clinically meaningful evidence, only speculations. ...

Shouldn’t we have something tenable to go on before experimenting on an entire generation of children? I suspect most parents would think so.

She notes approvingly the award-winning expose of games-playing by the anti-salt crowd as documented in Science magazine and recent research showing that low-salt diets may be creating additional risk.

Posted by Dick Hanneman at 10:31 PM | Permalink

Beginning in 2007, the American Journal of Hypertension will have a new Editor-in-Chief, replacing its founder, Dr. John Laragh, a Time magazine cover story subject for his breakthrough work on blood pressure and heart disease. Laragh will be succeeded by Dr. Michael Alderman who has just completed his stint as president of the International Society of Hypertension.

In his parting editorial, Dr. Laragh says:

It is a pleasure for me to announce that Dr. Michael Alderman will replace me as Editor-in-Chief of the American Journal of Hypertension effective January 1, 2007. Dr. Alderman is a world-renowned epidemiologist who is unique among his peers because he has been especially interested in asking pathophysiologic questions in performing his population trials. This penchant led him to demonstrate, in a classic eight-year trial of 1717 hypertensive worksite employees, that the height of the entry ambulatory plasma renin level was directly related to the subsequent occurrence of a myocardial infarction (MI). At the same time, he found that no MI’s occurred in the 251 patients who had low entry plasma renin levels. This led Alderman to do a confirming follow up study showing that dietary salt-depleted hypertensives with consequent higher renin values and lower urinary sodium values had proportionally higher heart attack rates than did those who ate more salt, and therefore had progressively lower renin values.

Dr. Alderman’s research rightly questions the popular wisdom of unselectively advising salt avoidance for all hypertensives, and for all normotensive people, - a popular public health strategy which will surely chronically raise all of their plasma renin values and may have other unintended adverse consequences. Furthermore, this research has clearly reaffirmed the existence of only two mechanistically different types of long-term hypertension, each one of which is caused and sustained by either a body sodium (plasma and ECF fluid-volume) excess or instead by a plasma renin-angiotensin excess. This construction is supported by evidence that the hypertensive states caused by a body salt excess or a plasma renin excess are each quite selectively correctable respectively by giving a natriuretic drug or instead an antirenin antihypertensive drug.

The American Journal of Hypertension is in good hands.

Posted by Dick Hanneman at 01:04 PM | Permalink

The anti-salt crowd has been trying to expand its messaging globally, but a story in this week's "Health Minutes" by Dr. Norman Swan on Australia's most popular station ABC NewsRadio sets the record straight. Cutting through the charges implicating salt in blood pressure changes, Dr. Swan puts the question exactly right:

Salt gets a shake in a large study, reinforcing previous research which questions the value of a low salt diet - and suggests it might even be harmful.

I know. One day they’re telling you one thing and the next the opposite. The trouble is that with salt, doctors and dietitians have assumed because a low salt intake may help blood pressure, that it saves lives.

A 13 year follow up of 7000 people has found that in most groups, the lower the salt intake, the higher the risk of dying from a heart attack or stroke - independent of other lifestyle factors. The study wasn’t a trial; it observed people’s health rather than tested a proposition, so had potential problems. But the authors say that applies to almost all the studies which supposedly justify reducing salt and that none, they claim, show that a low salt diet saves lives.

The reason for the possible risk is that a low salt diet may increase artery damaging hormones.

So while it’s not carte blanche for salt, it’s probably okay to enjoy the taste of food again.

Hear that good news from Dr. Swan himself.

Posted by Dick Hanneman at 10:55 AM | Permalink

The American Council for Science and Health (ACSH) has struck another blow for science and sanity. ACSH president Elizabeth Whelan's column yesterday, "Are Foods 'Addictive'?" laments the tactic of critics of "Big Food" who try to make customers the victim of a conspiracy -- unable to protect their interests (in this case, their health) and, unstated but implied, requiring protection through more government intervention. Not so fast, Whelan says.

The word "addiction" is used very loosely today -- as when people claim they are "addicted" to exercise, chocolate, or the Internet. But addiction is a medical term referring to compulsive, habitual use of a substance that has physiological effects but is not necessary for survival. Addictive substances produce tolerance (meaning that it takes an increasing amount of the substance to produce the desired effect) and physical dependence -- and unpleasant symptoms of withdrawal if use is discontinued. The nicotine in cigarettes fits all these criteria. Food does not.

There have been claims that eating high-fat or high-sugar foods overactivates drug-like substances in the brain called endogenous opioid peptides, leading to food cravings, overeating, and obesity. Food, it is argued, causes an increase in neurotransmitter levels just as addicting drugs do. Some animal experiments may support this idea, but other animal data and human observations do not. If overeating were induced through an opioid-like mechanism, one might expect that opioid-antagonists would be useful in treating overeating, but they are not.

If this sounds familiar to salt-interested readers, it should. More than 20 years ago the Center for Science in the Public Interest (CSPI) conflated salt with cocaine -- "another white powder we snort" -- and labeled salt addictive. This past summer, critics accused "Big Salt" of heading a "conspiracy" as we tried to mobilize resources for a definitive controlled trial of the question of whether the amount of salt in a person's diet is related to their health outcomes, particularly to cardiovascular mortality. We have only observational studies addressing this question to date and they tend to suggest just the opposite of our current policy. Existing studies show no health benefits for reducing dietary sodium and several have identified heightened risk.

Fortunately, over these past 20 years, we've seen serious scientists express revulsion and reject this fear-mongering. The Cochrane Collaboration grew from a core of concerned research scientists at Oxford University to become first the inventor and then a worldwide force for "evidence-based" medicine (now everybody claims their product is "evidence-based" even when they stray from the Cochrane Collaboration's evidentiary rules). Now groups like ACSH and blogs like JunkScience and Junkfoodscience have taken up the watchdog role protecting the public against those who would pervert science to advance their policy objectives.

Posted by Dick Hanneman at 07:04 AM | Permalink