May 12, 2000 -- Do you crave pickles, splash on the soy sauce with reckless abandon, sinfully savor each grain of salt on your pretzels? If you are like most Americans, you are probably taking in more salt than current guidelines recommend -- whether you know it, or want it.
What you might not know is, that question has created a veritable storm in a saltshaker, if you will, within the medical community.
The role of salt in high blood pressure and heart disease is not as clear as it once seemed, and many experts disagree about the importance of salt intake and current recommendations for salt consumption. It is clear that some groups of patients need to carefully watch salt consumption, but whether the entire population benefits from restriction is uncertain. In addition, newer research has brought to light other factors in blood pressure control which may be even more important than salt. Some researchers argue that salt restriction has been overemphasized. But others feel that current recommendations are helpful, and should be continued.
The latest battlefield for the great salt debate is the American Journal of Clinical Nutrition, where two experts in the field argue for and against keeping the current American Heart Association (AHA) recommendation of no more than six grams of salt a day for an adult. Studies show Americans currently average about nine grams of salt a day.
Norman Kaplan, MD, is in favor of keeping the current recommendations with an eye towards lowering them in the future. Kaplan, a professor of internal medicine at the University of Texas Southwestern Medical Center in Dallas, writes that high blood pressure is a problem for about one in five Americans (including more than half of the elderly) and the problem is probably growing.
Kaplan says there is enough evidence from human and animal studies to show that excess salt intake is "intimately" involved with high blood pressure, even though a direct cause-and-effect cannot be proven. And that even modest reductions in salt intake can lead to modest reductions in blood pressure, leading to health benefits for individuals. These small individual benefits translate into big benefits for society as a whole. Kaplan also argues that a decrease in salt intake may also provide other benefits, including less bone thinning, fewer kidney stones and less thickening of the heart muscle.
"The evidence supporting the need for a reduction in dietary sodium intake is convincing and supports the appropriateness of the current U.S. dietary guidelines. As noted, this guideline may not be set low enough to prevent the development of hypertension ... If this goal can be reached, perhaps even greater reductions will be feasible in the future," writes Kaplan.
David McCarron, MD, a professor of medicine at the Oregon Health Sciences University, writes that the current recommendations are based on faulty old studies that vilified salt, not on modern studies and a more sophisticated understanding of the human body. These old studies don't consider genes that can make some people more "salt-sensitive" than others. Nor do they take into account the interaction of other important minerals, such as potassium, that also affect blood pressure. He also makes reference to some newer trials that found reducing salt intake doesn't lead to a lower risk of heart disease deaths, and that it may even increase it.
McCarron argues that by combining the results of these old studies and analyzing them on a large scale, it becomes apparent that people who have normal blood pressure reap very little benefit from reducing salt intake. Additionally, he says, new studies have shown blood pressure is better regulated by adopting the so-called DASH (Dietary Approaches to Stop Hypertension) diet, which includes more fruits, vegetables, and dairy products -- not just by reducing salt. The DASH studies have also suggested that increased potassium, rather than decreased salt, is much more helpful in blood pressure control.
"I would never argue that some people, those who have heart, liver, kidney disease, should watch their sodium intake," says McCarron. But, he says, "we are burning precious resources in terms of public policy" by trying to get the general population to reduce sodium intake.
"By definition, public health policy is intended to promote the health of the public," writes McCarron. Since reducing salt doesn't appear to benefit most of the population in a significant way, since it may not reduce heart disease, and since there are other ways of reducing high blood pressure, the answer to the question 'Should we shake up the dietary guideline for sodium?' is "Unequivocally, yes."
"The issue about salt has become unnecessarily polarized, and I am not sure why," Theodore Kotchen, MD, tells WebMD. "I think the more balanced overview is that salt is one component of a diet that affects blood pressure -- but it is an important component." Kotchen, a professor and chairman of the department of medicine at the Medical College of Wisconsin in Milwaukee, is also a member of the Nutrition Committee of the AHA, which makes up the recommendations.
"Kaplan's position reflects the thinking of a relatively large number of professional organizations including the AHA, the National Heart, Lung, and Blood Institute [part of the National Institutes of Health], and others," says Kotchen. "I think it is a balanced and accurate assessment of the salt issue.
"I think McCarron does make some important points, and I think it's true that we don't have the definitive evidence that perhaps some people would like before making population-based recommendations, but I do think his conclusions are somewhat distorted," he says.
But McCarron stands firm. "We have made too much of the issue of low sodium diets helping reduce blood pressure, and in that process we have not been talking to people about the issues that really matter," McCarron tells WebMD. Those issues are weight, too much alcohol, and getting a balanced diet. "We're not promoting the DASH diet, which has shown an effect that is probably 10 times as powerful as reducing salt." The DASH diet includes eating a lot of fruits and vegetables and low-fat dairy products.
"The problem is we started setting policy before we did the science," says McCarron. "What happens is that you get policy and education, and basically the bias is built-in. And then you get the data, and then what do you do?"
"Sometimes science get brushed aside in the interest of politics," he says, noting that it is hard to turn the tide of public policy.
Despite their differences, both men can agree on one thing: the need for Americans to adopt a healthier diet.
"I think the positive message, in terms of both blood pressure and overall [heart] health, is people should pay attention to their overall diet," says Kotchen, adding that it is "probably a mistake" to focus exclusively on salt. He says we should avoid obesity, avoid eating too much salt, and make sure we eat plenty of fruits and vegetables.
McCarron agrees. "The data say the most important thing to do is get a balanced diet," he says. "And we are doing a terrible job of that in this country -- the evidence is staring at us, walking down the street."
Sometimes it's not so easy to cut back on salt. "Most of the salt in the diet is hidden salt," says Kotchen. "It's not added from a salt shaker, but it's in products. Baked products and processed foods are generally very high in salt." He recommends that we look for sodium levels on food labels.
As for whether those guidelines will be changed when the Nutrition Committee meets next month, Kotchen says, "I suspect there will be no drastic change in the sodium recommendation."
- The American Heart Association recommends a healthy adult consume no more than six grams of salt each day. Research shows most Americans get about nine grams of salt a day.
- Experts may disagree on the exact relationship between salt intake and one's blood pressure and how to counsel patients about it, but many feel that the importance of salt has been overemphasized.
- Experts agree that there are other important contributors to consider, such as getting a balanced, low-fat diet that includes a lot of fruits and vegetables.