Are Low-Salt Diets Necessary (or Healthy) for Most People?

Are Low-Salt Diets Necessary (or Healthy) for Most People?

Some say cutting salt consumption can lower your death risk; others say the salt threat is overblown

By Dr. McCarron in the Wall Street Journal

As Americans have become more aware over the years of nutrition-related health issues, salt has emerged as a major villain in many people’s minds. So much so that the Centers for Disease Control and Prevention describes reducing the U.S. population’s consumption of sodium as “a national priority.” The CDC warns that too much salt can raise people’s blood pressure, putting them at greater risk for heart disease and stroke, among other evils.

But some skeptics believe the threat posed by salt is overblown. Indeed, some say too broad a drive against salt poses its own health risks.

Arguing in favor of a broad reduction in Americans’ salt consumption is Elliott Antman, a cardiologist at Brigham and Women’s Hospital in Boston and president of the American Heart Association. Warning of the possible health consequences of an overzealous antisalt drive is David A. McCarron, an adjunct professor in the University of California-Davis Department of Nutrition and chairman-elect of the American Society for Nutrition’s Medical/Nutrition Council.

YES: Less Salt Reduces the Risk of Heart Disease

Everyone should be taking steps to limit salt in their diet, for one simple reason: to lower their risk of death.

Americans on the whole eat too much sodium. Most professional health authorities and scientific bodies agree on that point. And eating too much sodium can raise your blood pressure, putting you at greater risk of heart disease—the leading cause of death in the U.S.—and stroke, as well as worsening several other conditions.

Reducing salt intake is particularly important for people who already have high blood pressure, as well as those with diabetes or chronic kidney disease, middle-age or older people and African-Americans. All these groups tend to show a greater blood-pressure response than others to lower sodium intake. Together, they represent about half the U.S. population age 2 and older.

But that doesn’t mean the other half of the population shouldn’t be concerned about the amount of salt they eat. The effect of too much sodium on blood pressure also is more pronounced in people who are overweight—who comprise nearly 70% of the U.S. adult population and about a third of American youths. And for everyone, lowering dietary sodium can significantly blunt the rise in blood pressure that tends to occur as we age. This is important because 90% of all Americans are expected to develop high blood pressure in their lifetime.

The good news: Even incremental reductions in sodium consumption can make a big difference. Americans currently consume about 3,500 milligrams of salt a day on average. By one estimate, reducing that average by 400 milligrams a day could avert 15,000 to 32,000 deaths a year and $4 billion to $7 billion in annual health-care expenses. Only patients with very rare disorders, and only on the advice of their doctors, shouldn’t be reducing their sodium intake.

A matter of taste

Some argue that our salt consumption is driven by what our bodies need. But research suggests that taste preferences are the real driving factor. And those preferences are driven by the high salt levels in the global food supply, particularly in packaged and restaurant foods.

Studies show that people who begin eating lower-sodium diets start preferring them, eventually finding that foods they used to enjoy taste too salty. The shift in preference can be moved in the other direction as well; when people are placed on a higher-salt diet, they come to like more salt in their foods.

If sodium is reduced gradually enough, taste differences are often negligible and undetected. This suggests that if the sodium in the U.S. food supply is gradually reduced, American consumers’ preferences for salt in foods would shift downward, and they would still enjoy their food. In the United Kingdom, a salt-reduction program started in 2003, centered on voluntary sodium guidelines, resulted in a 15% reduction over eight years in the population’s sodium intake, as well as reductions in blood pressure, heart attacks and strokes

Making it happen

Another claim made by some is that lowering sodium in the diet can trigger hormonal reactions that increase the risk of heart disease.

First, many of the studies suggesting a link between lower sodium and heart disease have a number of methodological problems. Also, hormonal changes are known to be greater with large, abrupt changes in sodium intake, which may not be relevant to the gradual, sustained reductions advocated by most doctors and public-health officials. There is far greater certainty that high blood pressure is a factor in heart disease than there is about the possible role of these hormonal changes.

We know how to reduce the dangers of high blood pressure. We just need to do it.

NO: A Low-Salt Diet Is Neither Safe Nor Feasible

Current U.S. health policy calls for all Americans to restrict their dietary salt intake. This policy is neither feasible nor safe.

Why not feasible? Because public policy can’t overcome biology. Our appetite for sodium is driven by our body’s needs, not by the foods we eat. A specific range of sodium is needed to maintain adequate blood flow to the body’s critical organs, and our brains know when more or less salt is necessary.

Evidence of the brain’s tight control over our salt appetite comes from multiple government-sponsored surveys demonstrating a remarkably consistent range of sodium intake among people world-wide over many years—despite very different food supplies, with different sodium content, in different societies. In more than 50 surveys over the past five decades, conducted in more than 45 countries and monitoring about 200,000 people, sodium intake ranged from 2,800 to 5,000 milligrams a day and averaged 3,700 milligrams a day—or about what Americans consume on average today.

Why is a policy of restricting dietary sodium not safe? Because recent studies indicate that for many, it can be harmful. When salt consumption is too low, blood flow diminishes. The body’s rescue systems kick in, and the blood levels of the hormones that monitor blood flow to the organs increase, until optimal blood flow is re-established. If sodium intake is inadequate over time, the increased hormone levels impose a price—cardiovascular disease. Numerous reports in the medical literature have documented that people who consume less than 2,800 milligrams of sodium a day are at significantly greater risk of cardiovascular events and death than those who eat salt within the healthy range science has identified.

It’s not for everyone

There may be benefits for some individuals in reducing their salt consumption, but that must be determined individually in consultation with a health professional. For most Americans, it simply isn’t necessary and is potentially harmful.

Researchers from the University of Copenhagen and myself recently analyzed 167 published trials that measured the effect on blood pressure from reduced sodium. We found that in the studies involving only subjects with normal blood pressure, sodium restriction had no significant impact. That means there is no scientific justification for a U.S. sodium policy directed at the entire population, because 65% to 70% of Americans have normal blood pressure and thus wouldn’t benefit from lowering their salt intake.

For those whose blood pressure is sensitive to salt intake, research has shown that their sensitivity can be reduced by eating more fruits, vegetables and dairy products—a safer approach than reducing salt intake to potentially unhealthy levels.

The idea that an entire population can get used to a diet with less salt, overriding the brain’s need-based appetite, has never been proved.

The push by the British government in the past decade succeeded in lowering the sodium content of the food supply, but consumption remained well within the normal range established by the decades of studies I referred to earlier. In other words, the neural network that monitors the body’s need for sodium remained in charge.

Change with the times

The U.S. sodium guidelines of the past 35 years are based in part on the idea that there is little risk, if any, in reducing salt consumption.

But research has identified the biological basis for very real and substantial risks and no blood-pressure benefit for most of us.

This is a predictable shift, as science isn’t static. Our improved understanding of sodium and health should be viewed as a triumph for the public’s support of scientific investigation. Now, health policy must evolve along with the science.

Dr. McCarron is an adjunct professor in the University of California-Davis Department of Nutrition and chairman-elect of the American Society for Nutrition’s Medical/Nutrition Council.