A new skirmish has begun in the battle over how much salt we should eat, which is only going to strengthen the ongoing war on science. Science is losing.
The National Academies of Science Engineering and Medicine (NASEM), at the behest of Congress, is convening a new panel to revamp the dietary recommendations for sodium.
The more we scientists and policy makers continue to act the way we have been, the more likely you will be harmed.
Scientific credibility is at an all-time low. Convincing the general public that medical research is not a conspiracy to sell snake oil to line the pockets of Big Pharma is a failing effort. But science is partly to blame.
When we continuously change guidelines, and then fight about them, we deliver the message that we don’t know what we are talking about. But, in a lot of important ways, hidden in all the noise, we do know a thing or two.
Failure to successfully implement the policies that we know will help, will cost lives and drain money out of the medical system. But success requires credibility and consistency.
On the issue of sodium, we have been giving the public the wrong message, or at least one that is ill informed. Most of the recommendations made for sodium intake, and for dietary intake in general, have been made based on epidemiology (population research based on observation).
This type of research describes correlations, not cause and effect. To be able to reliably determine if X intervention results in Y outcome, a group must be randomly assigned to a treatment and a comparator.
Earlier research on sodium had led us to conclude that higher sodium intakes were harmful. But the science has progressed, and our understanding of how sodium is handled has become far more sophisticated. Further, new epidemiology, larger than any prior and spanning more than 100,000 subjects over decades, strongly suggests that low sodium diets shorten, rather than extend, life expectancy.
While highly excessive intake (in the range of 5-15 grams per day) of sodium is associated with increases in mortality in certain groups, restriction below about 3 grams per day is associated with a striking and consistent increase in mortality in all groups.
The current recommendation from the American Heart Association (AHA) is for 2 grams (2000 milligrams) per day if you’re healthy, 1.5 grams if you have heart failure. But even that recommendation may be harmful.
Every time we make recommendations, we give people expectations. Our failure to responsibly manage these expectations has the world believing that eating and exercising properly, and thinking the right thoughts, will result in perfect health until we suddenly drop dead at 95 years old. This is, of course, utter nonsense, but the unintended consequence is a population that blames themselves, and science, whenever they become ill.
Finally, recommendations are invalid if they are impossible to implement. My research group has analyzed the existing research on sodium restriction for heart failure, and found that none of the randomized trials resulted in sodium intake anywhere near as low as the AHA guidelines.
So, even in the most rigorous of research settings, achieving the guidelines is impossible. Mind you, the studies did not apply many of the currently available behavioral techniques. But this was the state of the art as the AHA decided to stick with their recommendations.
The World Heart Federation, the European Society of Hypertension, and the European Public Health Association have concluded that current research supports a goal of less than 5 grams of sodium per day, not below 2 grams.
The Institute of Medicine found, in their review, that there was insufficient evidence to support sodium restriction to the levels currently recommended (2300 milligrams per day).
For all these reasons, and many more, the empaneling of a group of experts to opine on healthful sodium intake has huge consequences. This is a laudable effort. However, both Congress and the American Society for Nutrition (ASN) have called for more balance on the committee.
It is important that the panel contain adequate representation of the range of viewpoints on this issue, and that the group be guided by the continually evolving science, not by any other factors, for the resulting guidelines to be credible.
Letters from both the House Committee on Appropriations and ASN have been sent to NASEM requesting a rebalancing of the panel. Both should be applauded for their willingness to protect the interests of the populace by protecting the integrity of science.
David Seres M.D. is the director of medical nutrition, associate clinical ethicist, and an associate professor of medicine at Columbia University Irving Medical Center, and chair elect of the Medical Nutrition Council at The American Society for Nutrition.