It's now clear: I lack the patience to await the full four parts of a powerful new series of posts on Junk Food Science before sharing it with Salt Sensibilty readers. They're too good to wait. They examine the subject: “Paradoxes – Compel us to think.” So far, two posts: Part One and Part Two . Sandy Szwarc introduces the quest to “separate science from ideology” (phrase from JAMA ) as follows:

We may know, intellectually, that correlations can never show causation, but when a correlation seems to confirm a reason we believe, it’s very easy to find ourselves falling for the fallacy, anyway, and to not even consider other explanations. We may call our belief “common sense” or what “everyone knows,” without realizing that we’ve come to believe it simply because it’s all we ever hear. It may never even occur to us to question an axiom — especially if we never hear about the evidence which contradicts or disproves it.

Her primary focus remains obesity as we may remember since I've often blogged on her relevant posts. Nevertheless, many of the observations pertain equally to the salt and health controversy. She notes that “The obesity paradox wouldn’t be a paradox at all, for example, if the public had been hearing objective reports of medical research all along.” How true for salt. I've just been participating in an online discussion at Toronto's Globe and Mail that well illustrates the pervasive retreat to unexamined acceptance of asserted medical “truths.”

Understanding the limitations of the scientific method employed is crucial. She observes:

(E)pidemiology has become a vehicle to find associations between every aspect of our everyday lives or our physical features and risks for some feared disease. And it’s being misused to convince us that our diets and lifestyles or appearances are the cause of ill-health. Blame, guilt and fear are the bread and butter of health marketing. That’s why carefully controlled epidemiological studies that find no link — those null studies that rarely get reported — are especially valuable. If there’s not even a strong link between two variables, then a variable can’t possibly have a causal role. Null studies tell credible scientists, and should tell us, to move on and stop worrying about that.

Among the reasons all this matters, she offers as an example the question of exercise. “Everyone” knows exercise is good for us. I feel better when I'm in shape and when I exercise. Of course. Common sense. But there are always unintended consequences. In this case, she provides data from the Centers for Disease Control and Prevention (CDC) that, next to the common cold, sports and exercise injuries are the leading cause of doctor's visits. That doesn't mean: don't exercise. It means, weigh the evidence ( and, probably, engage moderately). Federal data confirm that 488 million work days are impaired by sports injuries and that baby boomer sports injuries cost $18.7 billion in 1998.

Bottom line, she concludes in Part One:

Scientists understand the importance of testing hypotheses about causes and effects — and balancing overall benefits over risks — using carefully designed randomized, controlled clinical trials and measuring hard clinical outcomes. Yet, every randomized, controlled clinical trial of “healthy lifestyles,” as popularly defined, has failed to significantly reduce premature deaths from all causes or to prevent chronic diseases of old age.

Part Two continues to bust obesity-related myths, in this case: that obese individuals have worse health outcomes. “Everyone” believes that, too. Common sense. She offers the Helsinki Businessmen Study as a confounding input. The conclusion:

The only statistically significant inverse correlations to the men’s BMIs were with diabetes and hypertension — but they didn’t affect the men’s mortality rates, perhaps because, as we’ve seen, heavier people with both conditions have lower health complications compared to slender people with those conditions. Other popular myths weren’t supported in this study, which also won’t surprise regular readers who’ve followed the research. The men who gained weight as they aged and those who lost weight to achieve a normal weight had identical rates of developing diabetes, and the same cholesterol levels and blood pressures , as they aged.

Once again, the conclusions track closely with how the salt and health debate was sidetracked into the blind alley of a solitary focus on blood pressure. See the parallel:

Time and again in randomized clinical trials of pharmaceuticals and other medical interventions, we’ve seen the importance of examining confirmed clinical endpoints — with all-cause mortality the most important — rather than surrogate endpoints. Not understanding risk factors and believing that these surrogate health indices are measures of health and future disease has been the greatest way the public been led to believe that weight loss is beneficial, even when it’s not supported in well controlled studies looking at actual clinical outcomes and mortality.

The only difference here is that there have not been repeated RCTs on salt reduction – only a dozen or so observational studies, though they have suggested our uncritical acceptance of the salt hypothesis has been erroneous. It matters not only because we waste time, effort and expense pursuing the wrong remedy, but because the fallacious intervention can actually create health risks. Take the obesity case again:

German epidemiologists, examining 13,362 middle-aged adult men and women in the European Prospective Investigation into Cancer and Nutrition-Potsdam Study, for example, found that fat people who had normal blood pressures prior to weight loss had a nearly 7-fold increased risk of developing essential hypertension during the following two years after weight loss, and those whose weight yo-yoed had a 4.29-fold increase in hypertension.

And, referencing Dr. Thorkild Sorensen at the Institute of Preventive Medicine in Copenhagen from an article in the International Journal of Obesity:

It’s been argued, he summarized, that weight loss does not equal improvement in health and longevity, that staying fat is safer than weight fluctuations, and dieting has negative psychological effects. “In summary, we still do not have conclusive evidence that weight loss has overall beneficial effects.”

She wraps up Part Two with a warning:

The possible healthfulness of natural weight gain with aging, however, is a paradoxical idea in popular media. People may never think to question their beliefs about the deadliness of fat and benefits of weight loss when they never hear anything different.

The importance of research finding seeming paradoxes is that it make us think, question and not be afraid to learn where the evidence might really take us.

Echoes of the salt and health debate. We need to change our paradigm and become evidence-based.