July 11 2011
The Latest Salt Study--Just One of Very Many
Scientific American has an important new article calling on governments at all levels to back off anti-salt campaigns in light of the just-released study that shows there is no link between salt intake and an increased risk for heart disease.
"...unless we have clear data, evangelical antisalt campaigns are not just based on shaky science; they are ultimately unfair. "A great number of promises are being made to the public with regard to this enormous benefit and lives saved," Cohen says. But it is "based on wild extrapolations."
The most surprising thing in the article though wasn't this new study, it was just how many studies have come to the same conclusions over the past 20 years. The article cites five similar studies going back as far as 1988. Despite this, governments have continued to pursue vicious anti-salt campaigns--most notably New York Mayor Michael Bloomberg's very personal campaign (though not personally paid for) against salt in which he used millions of taxpayer dollars for a glossy ad campaign.
--In 1988, [A large study] compared sodium intake with blood pressure in subjects from 52 international research centers and found no relationship between sodium intake and the prevalence of hypertension. In fact, the population that ate the most salt, about 14 grams a day, had a lower median blood pressure than the population that ate the least, about 7.2 grams a day.
--In 2003, the Cochrane Collaboration's (an international, independent, not-for-profit health care research organization funded in part by the U.S. Department of Health and Human Services) review of 57 shorter-term trials similarly concluded that "there is little evidence for long-term benefit from reducing salt intake."
--In 2004 the Cochrane Collaboration published a review of 11 salt-reduction trials. Over the long-term, low-salt diets, compared to normal diets, decreased systolic blood pressure (the top number in the blood pressure ratio) in healthy people by 1.1 millimeters of mercury (mmHg) and diastolic blood pressure (the bottom number) by 0.6 mmHg. That is like going from 120/80 to 119/79. The review concluded that "intensive interventions, unsuited to primary care or population prevention programs, provide only minimal reductions in blood pressure during long-term trials."
--A 2006 American Journal of Medicine study compared the reported daily sodium intakes of 78 million Americans to their risk of dying from heart disease over the course of 14 years. It found that the more sodium people ate, the less likely they were to die from heart disease.
--A 2007 study published in the European Journal of Epidemiology followed 1,500 older people for five years and found no association between urinary sodium levels and the risk of coronary vascular disease or death. For every study that suggests that salt is unhealthy, another does not.
The article also addresses why a one-size-fits-all approach won't work to make people healthier:
Part of the problem is that individuals vary in how they respond to salt. "It's tough to nail these associations," admits Lawrence Appel, an epidemiologist at Johns Hopkins University and the chair of the salt committee for the 2010 Dietary Guidelines for Americans. One oft-cited 1987 study published in the Journal of Chronic Diseases reported that the number of people who experience drops in blood pressure after eating high-salt diets almost equals the number who experience blood pressure spikes; many stay exactly the same. That is because "the human kidney is made, by design, to vary the accretion of salt based on the amount you take in," explains Michael Alderman, an epidemiologist at the Albert Einstein College of Medicine and former president of the International Society of Hypertension.
The point here is that humans are different. Humans simply react differently to the things they eat. This makes a one-size-fits-all policy dreamed up by some government bureaucrat doomed to failure.
I'm glad this new study is getting the media attention it deserves. Hopefully someone slipped it into Mayor Bloomberg's in-box. I look forward to his press conference where he vows to pay back the money he wasted on his anti-salt buffoonery.