Junkfood Science: Salt shaking news

April 21, 2007

Salt shaking news

The media stories in the past day have reached a frightening crescendo, and every corner of the world, all trying to scare us half to death. What makes the headlines so outrageous is not that the results of the study being reported were so foreboding, but that they bear little resemblance to the spin in the news.

The press coverage began yesterday with low-toned stories, such as Reuters which reported:

Salt may affect more than blood pressure: study

Consuming less salt can not only lower blood pressure, but may reduce the risk of heart disease overall, researchers reported on Thursday. They found that people with borderline-high blood pressure who reduced their sodium intake by 25 to 35 percent lowered their risk of total cardiovascular disease by 25 percent. And this lower risk lasted for 10 to 15 years....They were also 20 percent less likely to have died than people assigned to a normal diet...

Salt intake is clearly linked to high blood pressure and the National Heart, Lung and Blood Institute, which paid for the study, recommends that Americans cut down on sodium. More than 65 million U.S. adults — one in three — have unacceptably high blood pressure, above levels of 140/90, the NHLBI said. Another 59 million have prehypertension — defined as blood pressure of 120/80 or above.

The average U.S. and British diets contain far more than the 2,300 mg daily recommended by the NHLBI and expert groups.

By that afternoon, media was claiming that either salt kills or that cutting down on salt adds 12 years to your life!

Ireland-online reported “Salt killing 1,000 per year in North alone, says charity:”

Up to 1,000 people are dying from excessive salt intake in the North every year, a charity said today. Northern Ireland Chest Heart and Stroke (NICHS) is blaming over-indulgence for a quarter of stroke and a fifth of heart deaths. The intervention followed a British Medical Journal study underpinning the link between salt and high blood pressure.

NICHS chief executive Andrew Dougal said: “Food manufacturers must make a commitment to their customers that they will consistently, over a period of time, slash the salt in products."

CanWest News Service told Canadians “Salt at fault in 25 % of heart attacks, strokes:”

A new study suggests salt could be to blame for one-quarter or more of heart attacks, strokes and coronary artery disease. That's the sobering response the salt industry gets today after demanding proof that reducing salt prevents heart attacks and strokes....

The Canadian Stroke Network called the findings “absolutely dramatic.” “A 25-per-cent reduction in cardiovascular disease risk is huge," said Kevin Willis, acting executive director of the Ottawa-based network. “The number of lives saved and cost to the health-care system would be staggering. And all of that by the relatively trivial thing of simply cutting back on the amount of salt in people's diets.”

Dr. Dave Hnida on CBS in Denver, CO, reported “Study Finds Cutting Salt Can Add Years To Life:”

A new study has found the risk of heart disease can be cut by one-third just by cutting salt intake. The study said a lot of salt is hidden in food, especially in processed foods. Finding hidden sources of salt could save lives, even if high blood pressure or heart disease isn't a factor.

The report said cutting salt could add 12 years to your life.

Hiding the salt shaker isn't enough, because most of the salt hidden in surprising places....The daily recommended intake is only 2,000mg....Pick foods that are no-sodium/ low sodium. The term “reduced sodium" may not be good enough since it only cuts salt by 25 percent.

If these stories seem like deja vu, that’s because this same study had been published online back in February 2006, provoking a similar outburst. Remember, the volume of media reports is not a measure of the body of evidence.

Okay, before we all let our blood pressures go up, let’s look at this study to help us put things into perspective and have some evidence upon which to base our choices. Nancy R. Cook, associate professor at Harvard Medical School in Boston, and colleagues lumped together information from two randomized clinical control trials that had been conducted in the late 1980s and early 1990s. This study was a 5-10 year follow-up on those participants. They were contacted by phone calls and mailed questionnaires asking them about their heart disease history, blood pressures, weight and dietary salt intake. Only 77% of the original trial participants were included in this followup.

The first group was from the 18-month Trial of Hypertension Prevention I (TOHP I). Its 744 subjects were 30-54 years old at the start of that study, overweight with BMIs of about 27, and had blood pressures of about 125/84. Half had been put on sodium-reduced diets and lowered the sodium in their diet by about 1,011 mg a day — nearly half! The extreme sodium reduction lowered their blood pressures by a mere 1.71/0.8 mmHg. The control group continued with their usual diets after being given guidelines for “healthy eating.”

The second group was from the 4-year TOHP II with 2,382 adults of the same ages, but these men and women were mostly “obese” with BMIs of about 31 and blood pressures of about 127/86. These participants were divided into sodium-reduced diets (similar to the other study), a control group, a weight loss intervention group, and a weight loss with sodium-reduction group. The sodium reduction groups had reduced their sodium intake by about 758 mg a day and reduced their blood pressure by 1.2/0.7 mmHg.

These researchers found that 5-10 years later, those who’d undergone intense education and efforts to reduce their sodium intake had maintained their fear of sodium. Nearly half said they usually or always used low-sodium foods and read labels, and more than a quarter kept track of their daily sodium intake. There were 124 self-reported cases of heart disease and 25 heart disease-related deaths (0.8% of participants). Of those deaths, 10 were in the intervention groups and 15 in the control groups — a difference of only 5 people. So all of these dramatic conclusions are being based on 5 people.

The researchers did a computer statistical analysis to come up with odds ratios for the association between mortality and sodium reduction (factoring for the clinic, age, race, sex and weight loss intervention) and found a 19% lower odds ratio for mortality associated with sodium reduction.

The most glaring problem you’ve probably already noticed is that not only is this an untenable odds ratio — a number so low it could just as easily be a minute error in their computer model or an unreproduceable fluke— but that it’s an association, which does not mean causation. Yet, virtually every media report is eagerly jumping to conclude that lowering salt will add years to your life and save lives or that eating salt kills.

Another notable flaw in the logic here is that countless other contributing factors could be (and likely were) much more significant than sodium in explaining those correlations, yet the researchers failed to include them in their computer model. For example, it appears they didn’t account for socioeconomic status, stress, alcohol consumption, exercise or smoking! So to conclude it was the sodium is a huge stretch of the evidence.

Since this study was splitting hairs, another detail from TOHP II that won’t make the news is that 2 more people died who had been put on the weight loss intervention than had been in the control or the sodium reduction groups. Although their causes of death are unknown, this study doesn’t support claims that weight loss is all together health promoting.

The bottom line is that this study didn’t provide any credible evidence or answer any questions. There were numerous flaws and glaring missing information. It doesn’t offer evidence that population-wide recommendations for the general public to reduce sodium are beneficial or that the current levels of sodium we eat are harming us.

There’s been some talk that the people in these studies were at risk because of their “normal-high” blood pressures. But we know that blood pressures are naturally slightly higher with larger people and that attempts to medicalize these readings as being “pre-hypertension” are extremely controversial. Systolic blood pressures naturally rise with age, too, (some genetically predisposed to sooner) as the elasticity in our arteries drops and they become stiffer. In fact, 90% of us will have hypertension if we live long enough. And the increases with age are seen among all racial/ethnic groups.

In 2003, the threshold for high blood pressure was lowered again by the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure. This committee is under the National Heart, Lung and Blood Institute (NHLBI). High blood pressure had been defined as greater or equal to 160/100, then went to 140/90, with now a new even lower category in the normal range created, called “pre-hypertension.” The NHLBI’s blood pressure clinical guidelines have been met with considerable controversy in the medical community for lacking credible evidence, for the significant conflicts of interest with the pharmaceutical industry among the committee members, and that it now means that about 60% of all American adults have blood pressures potentially “too high.” [Yet, as we’ve seen, diet doesn’t appreciably lower blood pressures, which might help explain the pages of prescription medications in the guidelines.]

The NHLBI funded and participated in this study, as well as the two TOHP studies.

The NHLBI has also been heavily recommending Americans reduce the sodium in their diet to increasingly lower amounts. Its consumer website goes on to say: “If lifestyle changes alone are not effective in keeping your pressure controlled, it may be necessary to add blood pressure medications.” And oftentimes, “two or more drugs work better than one.”

Yet, few consumers realize that even drastic salt-reduced diets might give them a mere one point reduction in their systolic blood pressure. How many would think the hassle, expense and bland food is worth it, if they did? The belief, however, results in those with “bad” numbers being looked down on as being to blame for not eating right.

But what might be more surprising for many people to learn is that there is no evidence to support beliefs that the reduction in blood pressure from sodium-reduced diets is even clinically meaningful.

The latest Cochrane review of clinical trial evidence on advice to lower salt in foods and its long-term effects on deaths, heart disease and blood pressure. It concluded:

Intensive support and encouragement to reduce salt intake did lead to reduction in salt eaten. It also lowered blood pressure but only by a small amount (about 1 mmHg for systolic blood pressure, less for diastolic) after more than a year. This reduction was not enough to expect an important health benefit. It was also very hard to keep to a low salt diet.

You may be thinking: “But surely, there is evidence behind the government’s guidelines!” Surprisingly, this study’s authors admitted there wasn’t, saying in their introduction:

[D]ata on the effect of dietary sodium intake on subsequent morbidity and mortality are limited and inconclusive.

This had also been noted by researchers at Albert Einstein College of Medicine in Bronx, NY, in a study published last March in the American Journal of Medicine. It revealed that the “U.S.Dietary Guidelines recommend a daily sodium intake <2,300 mg, but evidence linking sodium intake to mortality outcomes is scant and inconsistent.”

Most of us probably think government guidelines had been based on something....like a body of sound evidence. Yet, the only long-term clinical trials on the efficacy of sodium reduction for everyone that these researchers could pull out in their closing discussions was that study of infants, reviewed here.

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, although 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.”

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. And many opponents point to the Japanese, for example — they have one of the highest salt intakes in the world, as well as the highest life expectancy.

We are talking about primary preventative measures here, not specific medical conditions that entail sodium reduction as part of their treatment. But just because certain health problems are treated by reducing sodium does not mean that reducing sodium can prevent health problems or is good for everyone. Why, that would be like saying that everyone should be on chemo to prevent cancer, since it is a treatment for cancers. Or, that if everyone ate less sugar it could prevent diabetes, since controlling blood sugars is a widespread treatment for diabetes.

If lowering sodium in our diet was entirely benign, then guidelines telling all of us to eat less sodium wouldn’t be such a concern, but there is evidence of possible harm. The European Society of Cardiology Guidelines for the Management of Arterial Hypertension reported in a 2003 issue of the Journal of Hypertension that recent research has shown 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, in turn, leads to an increase of the cardiovascular risk-factors, they concluded.

And the benefits of sodium, besides just making food taste better (can't have that!), are typically overlooked. We’ve already looked at how salt improves the flavor of many foods that are “good for us,” helping to prevent nutritional deficiencies especially among vulnerable populations such as children and elderly. 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.”

So why do so many people have a bee in their bonnet about the sodium in our diet? An Op-Ed in the Guardian, entitled “The Salt Sellers,” provides a sad insight:

...The immediate problem for anyone who wants to act on these [study] results is that if you base your diet on processed food, you aren't really in charge of your salt intake. Ninety per cent of the salt we eat comes in familiar processed foods... Refined white salt occupies number one position in the food industry's armoury of additives. Without it, everything from cornflakes to crackers would taste of zilch. Salt disguises the dullness of commodity ingredients like white flour and intensively-reared chicken. It replaces the natural intrinsic flavours in fresh foods that are destroyed by industrial food-processing methods. It corrupts our palates and sets up an expectation that every mouthful of savoury food must deliver a mouth-mugging dose of sodium.

I avoid processed convenience food and base my diet around whole, raw, unprocessed ingredients, which I cook myself. I buy good-quality sea salt which has a slightly lower level of sodium and some useful trace elements like iodine, iron, zinc and potassium... On the odd occasion that I have to settle for ready-made soup or a train station prawn sandwich, within the hour, my body has gone into revolt. I am left choking with thirst.

What’s really at work here is a negative agenda (and successful one among some it appears) to scare us so we won’t eat certain foods some don’t believe we should be eating and, instead, eat what they think is right. The root of fears being generated over sodium, added sugars, trans fats, and “chemicals” in processed foods; and claims that we’re eating horribly more bad ingredients today; really comes down to marketing interests. Even the beliefs surrounding the virtues and dangers of different salts, which we looked at here, are not based on science.

Of course, when we’re scared, we don’t always think very clearly. If we’re eating so much more of these supposed “bad” things and they are that harmful, why are we healthier, living longer and enjoying lower rates of heart disease and cancers? The sticky wicket in claims that today’s modern food industry has dramatically increased the fats, sugars or salts in our diet, as we’ve seen with fats and sugars, don’t hold up to the evidence. Like many scary claims, they usually don’t give the full story. Take the popular claim that our sodium intake has increased dramatically since the 1980s because we’re all eating out more and eating processed foods. The best biological measure of sodium intake is considered 24-hour urine tests and in clinical studies those have consistently shown that our intakes per capita haven’t changed in generation after generation. Yes, salt intakes have increased 41% in the U.S. in the past 15 years — but we’ve also added 50 million people to our population during those years. Popular figures of an increase are also based on food salt supplies and don’t account for exports, salt used in processing and waste, or salt’s myriad of other uses from baths, gargles, cleaning, to even 65 other fun uses around the house. :)

The belief that homecooked meals used to have significantly less salt than what’s in the foods we buy today is another romantic notion of the “good old days.” Salt shakers once held a permanent place on most dining tables in our country — ever since the development of free-flowing salt crystals in the mid-nineteenth century — and countless generations used to salt their home-cooked meals generously, not to mention use inordinate amounts of salts in home food preserving and processing. One result of recent salt fears, is that salt shakers are becoming a thing of the past and popular, saught-after collectors’ items. Did you know there’s even a national Salt & Pepper Novelty Shakers Club with chapters all over the country and a national convention? There’s even a Salt and Pepper Shakers WebRing! Imagine that.

With everything, I guess, even salt and pepper shaker collecting can go overboard. One Australian lady has about 5,000 pairs filling her house and “admits that she is finding it difficult to dust them all.” :)

But I digress...

It’s easy to get swept up in fear and to hope or believe that every health problem can be prevented, and that we’ll guarantee ourselves a long, healthy life, if only we eat right and make sure all our numbers line up. Having sound facts can only help us make the best choices for ourselves and hopefully enjoy life and whatever we choose to eat with a little less worry.

© 2007 Sandy Szwarc

Bookmark and Share