|Posted by Carole Allen on October 30, 2013 at 7:20 PM|
The drive to bring about “sweeping,” sharp reductions in salt consumption is based more on zealotry than science, and should be halted until there’s better evidence, one of Canada’s foremost heart researchers charges in a provocative new commentary.
Reducing ingestion of sodium has been a major focus of public-health advocates in recent years, and generated widespread, sometimes-alarming media coverage.
But there is only modest evidence that cutting back on salt radically will reduce high blood pressure, and little or none that it would actually prevent heart attacks and other cardiovascular problems, argues Dr. Salim Yusuf in a journal article.
He does not question that some people whose salt levels are higher than the average should eat less of it or risk health problems, but criticizes calls by Health Canada and others for deep, population-wide cuts.
“The zeal to recommend extreme reductions in sodium that are difficult to achieve in the entire population … is a case of ideology replacing good science,” said Dr. Yusuf, the Heart-and-Stroke-Foundation Chair in Cardiovascular Science at Hamilton’s McMaster University.
Is it wise to divert resources to poorly proven strategies
“Is it wise to divert resources to poorly proven strategies when so much more can be achieved by interventions where the evidence is far stronger?”
Efforts to curb cardiovascular disease — Canada’s number-two killer — would be better focused on trying to further reduce smoking rates, fighting obesity and using cheap and safe drugs to control high blood pressure, he wrote in the American Journal of Hypertension.
One of the country’s leading experts on hypertension and sodium, however, voiced dismay at the commentary, saying that Dr. Yusuf has wrongly analyzed the evidence, playing up research that supports his thesis while ignoring other science.
He is a “very influential cardiologist” but the studies he cites for arguing that reducing salt will not necessary improve heart health — or could even worsen it — are rife with “fatal flaws,” said Dr. Norm Campbell of the University of Calgary.
With one exception, major medical groups, including the World Health Organization, that have reviewed the evidence recently strongly conclude that salt consumption needs to be cut, Dr. Campbell said.
“[Dr. Yusuf] is way off his area of expertise,” charged the physician. “His strength has been in conducting randomized controlled trials of drugs, and I think he’s wandered into an area where he doesn’t have a strong understanding of what the evidence is.”
Reducing salt to the extent recommended by various authorities requires largely eschewing processed food and making meals from fresh fruit, vegetables, meat and fish — which would bring a host of other health benefits, too, he added.
To suggest that such a low-sodium diet might not be beneficial is “almost completely absurd,” said Dr. Campbell.
Dr. Yusuf countered in an interview that Dr. Campbell is among a relatively small number of well-meaning experts who have promoted dramatic public-health measures based on scant evidence. “Norman has been one of those — in polite terms — evangelists about sodium — in impolite terms, Talibans about sodium.”
Randomized controlled trials of drugs
The WHO has estimated that hypertension is the single largest cause of death in the world, and it has long been accepted that eating too much salt raises blood pressure. How much is too much is more contentious.
Health Canada recommends Canadian adults cut their current, average sodium consumption from about 3,400 milligrams a day — 1-1/2 teaspoons of table salt — to 1,500 mgs.
The issue came to the fore recently when the Institute of Medicine (IOM), a respected U.S. scientific advisory body, issued a report in May suggesting there is insufficient evidence currently to advise major cuts in salt ingestion — though it said people should not eat “high” volumes.
Dr. Yusuf, who became an officer of the Order of Canada earlier this year, and two McMaster colleagues argue that no study has shown that reducing sodium consumption below 3,000 mg a day reduces cardiovascular disease events, though some show that cardiovascular problems are more likely when consumption tops 5,000 mg.
We’re eating way too much crap
Dr. Campbell said he did his own review recently of studies cited in the IOM’s report, which he described as “not one of their stellar efforts.”
All 10 studies the Institute cited that suggested sharp cuts in salt would produce no benefit or actually do harm had fatal flaws, he said. Among those were studies suffering from “reverse causation” — they looked at patients who were already very sick and, because of their illness, ate relatively little food, reducing their sodium intake. It was likely the existing illness, not lower salt, that caused cardiovascular events, Dr. Campbell said.
The whole debate over sodium’s specific impact on health may be a non sequitur, suggested Dr. Yoni Freedhoff, a weight-loss physician and University of Ottawa professor. High salt content in a way is just a marker for generally poor diets heavy in processed food, he said.
“When we worry about exactly how many grams of sodium a person is consuming, we forget to worry about the fact we’re eating way too much crap — and that’s the issue.”