Take This Study With Many Grains Of Salt: More Salt Linked To Fewer Cardiac Deaths

Stop. Step away from the chips and pickles.

True, a European study that just came out in the Journal of the American Medical Association would seem to suggest that eating a lot of salt actually reduces your risk of cardiac death. It would seem to fly in the face of years of warnings that too much salt is bad for us, and the mounting public health efforts in cities like New York and Boston to help people limit their salt.

But Dr. Randall Zusman, director of the section on hypertension and vascular medicine at the Massachusetts General Hospital Heart Center, says the study is absolutely not a “pass” to the pickle jar. Rather, he says, it opens the way to some interesting hypotheses that remain to be explored.

The study followed more than 3,600 subjects for several years, and found the highest number of cardiac deaths in those who consumed the least salt, as tested once in their urine. Those with the highest salt intake had the lowest number of deaths. Higher salt intake also didn’t seem to translate to higher blood pressure over time. The authors conclude that lowering salt intake is helpful for people who already have high blood pressure, but not as a policy for the population at large.

I asked Dr. Zusman to explain.

Q: I’m feeling totally confused. If i’m reading this JAMA study correctly, salt consumption was actually linked to a lower risk of death, which contradicts everything I thought I knew about avoiding salt to avoid hypertension. Please set me straight!

Dr. Randall Zusman of Massachusetts General Hospital

You read it correctly. That’s the conclusion that they would like to suggest as the result of their findings. The problem is that this was not intended to be an assessment of the benefits of the reduction of salt intake as an intervention for global population health.

They took a bunch of people and they looked at their salt intake, and they found, looking in a very narrow fashion, that the more salt you ate, the lower your risk. It’s completely contrary to everything that we believe. But they also found that rather dramatic changes in salt intake — 100 millimoles which is about two grams of salt — changed blood pressure by about two points, which we know from other studies ought to increase risk. Two points on a population basis is significant, though on an individual basis it’s not.

As the authors point out, not only are their results controversial, but they have a lot of faults or shortcomings. They didn’t take these people and then prospectively attempt to control their salt intake and look at the impact of modifying their salt ingestion. They took one urine sample at one point of time and took a hugely broad brush and made conclusions for the world.

Q: So what should we make of their findings? Continue reading

Why To Exercise Today: Fight The Ill Effects Of Salt

Salt is the new nutritional villain that we all love to hate — especially in New York City, which is on an anti-salt campaign. Why salt? Mainly because it is linked to high blood pressure, with its heightened risk of heart disease and stroke.

But what if exercise could help break that link? Not that we could then eat salt with impunity, but at least the salt we do eat might not hurt us so much.

USA Today reports here on a novel study due to be presented this week at an American Heart Association meeting. In part:

Researchers found that the more people exercise, the less their blood pressure will rise in response to a high-salt diet.
“For those with low physical activity, their blood pressure will increase more if they increase their sodium intake,” said study co-author Dr. Jiang He, chair of the department of epidemiology at the Tulane University School of Public Health and Tropical Medicine in New Orleans.
“It’s a little bit of a surprise,” He added. “But this is the first study to look at this particular association between physical activity and salt sensitivity and blood pressure. But after thinking it over it makes sense, because we already know that physical activity will reduce blood pressure.”

How might this work? If you think that sweating is healthy, you may be right:

Lona Sandon, a registered dietitian and assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center at Dallas, said that the findings highlight some of the well-known benefits of regular exercise.
“Even if we don’t understand the mechanism of how it works, we definitely do know that people who exercise regularly have healthier blood vessels,” she noted. “The blood vessels are like a muscle. And if you engage in cardiovascular activity, they are more pliable and respond better to changes in blood volume and blood pressure.”
Why this is so merits exploration, Sandon said. “One explanation might be that people who exercise more lose more salt through their sweat,” she said. “Or it could be that activity sends a different kind of physiological message to the body to excrete sodium. Or it could be that it triggers a mechanism that tells the blood vessels to relax.