With holiday cooking on most of our minds this week, it's worth celebrating some good news about one of the most beleaguered food ingredients: table salt. For years, consumers and food producers have been bombarded with demands to reduce sodium consumption by nanny state regulators hoping to improve public health, even though the evidence linking high sodium diets and serious health concerns has always been ambiguous at best. But this year alone, several major scientific studies have cast that link in even further doubt.
The folks over at the Salt Institute -- the trade association representing salt producers and commercial users -- are touting these results as "The Biggest Health & Nutrition Story of 2011." "In 2011, half a dozen medical studies quantified the health benefits of salt or revealed the significant risks of low-sodium diets, making it a year of vindication for this essential nutrient and the people who love it. ... The latest data should raise fresh questions about the federal government’s effort to put all Americans on a low-salt diet that could do far more harm than good."
This wasn't surprising to us. For years, we at CEI have been pointing out that the belief that sodium consumption in the United States has reached extreme and unhealthy levels is mistaken. And, as more and more high-quality research has been conducted on this subject during the past 40 years, the link between high-sodium diets and negative health effects has become more tenuous, not more certain.
The Institute of Medicine (IOM) has recommended a Tolerable Upper Intake Level of just 2,300 mg of sodium per day and an Adequate Intake of just 1,500 mg per day. And regulators are concerned that average sodium intake per person in the U.S. is approximately 3,300 mg per day. Yet decades of scaremongering have had little effect on consumer behavior, as sodium consumption has remained essentially flat since the 1950s. As my colleague Dan Compton wrote nearly two years ago, U.S. sodium consumption isn't particularly high by global standards. And efforts to reduce the salt content in foods is typically frustrated by consumers who adjust their dietary intake by seeking out foods with more salt -- even when they're not aware that the salt content of the foods they've been eating has been reduced.
Last month, CEI submitted comments on a joint Food and Drug Administration-U.S. Department of Agriculture query about the effectiveness of various approaches to reducing sodium consumption. We argued that:
Public health analysts who continue to advocate for mandatory sodium reductions have selectively highlighted only those research results that suggest a clear and direct link between sodium consumption and higher blood pressure. They have ignored or attempted to explain away contrary findings. In some cases, analysts even appear to have cherry-picked individual observations from within studies that reveal both positive and negative associations between salt consumption and blood pressure in order to bolster arguments that the link is definitive.
In some ways, this type of behavior is unsurprising. It is well-established that researchers often exhibit what is sometimes known as “White Hat Bias,” the propensity to give preferential treatment to studies or data that confirm a widely held “politically correct” view on scientific issues. A study of White Hat Bias published last year in the International Journal of Obesity found that, when referring to the results of previously published research, authors frequently cite data incorrectly and cite only findings that confirm the commonly accepted or politically correct view. An accompanying editorial explained further that “negative results may be ignored and secondarily positive analyses are cited as the conclusions of the study.”
Of course, some people do unequivocally benefit from reducing their sodium intake: many individuals with high blood pressure, for example, as well as African Americans (who tend to have higher blood pressure). But reducing salt consumption does not lower every individual’s blood pressure, even those with hypertension. A Cochrane Collaboration review published this year, examined 167 studies in the peer reviewed literature and found that reducing salt consumption lowered average systolic blood pressure in healthy individuals by just 1 millimeter of mercury (mmHg), and reduced systolic blood pressure among hypertensives by 3.5 mmHg. That's not a heck of a lot.
More importantly, lowering blood pressure by reducing salt intake does not clearly improve overall health (see here and here, for example). Lowering blood pressure substantially does appear to be associated with a reduction in heart disease, particularly among hypertensives. However, the blood pressure-reducing effect of eating less salt is so small that it does not appear to be associated with morbidity or mortality benefits. Another of the major studies published this year, in the Journal of the American Medical Association, found that, while higher sodium consumption was associated with slightly higher blood pressure, this “association did not translate into a higher risk of hypertension or [cardio-vascular disease] complications.” More surprising, however, the authors found that lower sodium consumption was associated with higher cardiovascular disease (CVD) mortality. The third of study subjects who consumed the least salt had three times the mortality as the third who consumed the most salt.
None of this suggests that those with average sodium consumption should switch to a high-salt diet. And again, some consumers should indeed try to cut back. But the overwhelming weight of scientific evidence does suggest that we have a lot less to worry about than the public health nannies would like us to believe.