By Jeff Novick, M.S., R.D.

Evidence has shown that excess sodium/salt intake raises blood pressure (hypertension), which is an established risk factor for heart disease, stroke, and kidney disease. In addition, excess sodium/salt intake has been associated with stomach cancer, osteoporosis, edema, gastro-esophageal reflux disease, headache, angina, left ventricular hypertrophy, arteriosclerosis, and autoimmune problems.

A 2009 review, The Preventable Causes of Death in the United States: Comparative Risk Assessment of Dietary, Lifestyle, and Metabolic Risk Factors, estimated that each year 102,000 premature preventable deaths are caused by excess salt intake.¹  The weight of this evidence has led health organizations to recommend a sharp reduction of sodium/salt intake.

Reducing sodium/salt intake leads to increased health and decreased medical bills. It also leads to lower profits for powerful food interests, which may explain a number of poorly researched media reports articles that have recently appeared. What is happening is that a comment from a May 2013 Institute of Medicine (IOM) report² is being misinterpreted to give the impression that 1) reducing sodium/salt intake might carry some risk and 2) that major health organizations no longer agree on sodium/salt intake recommendations. This has led to headlines like these:

“No Benefit Seen in Sharp Limits on Salt in Diet”
“Doubts About Restricting Salt”
“Report Questions Reducing Salt Intake Too Dramatically”

Is there any truth to the headlines and reports now floating around? Has the IOM changed its sodium/salt recommendations? Is there disagreement about sodium/salt intake between major health organizations? The answer to all three questions is “No!” Let’s take a look at the facts so that you can see through the confusion.

When it comes to sodium/salt intake, there is agreement that keeping consumption less than 1500 mg/day with a Tolerable Upper Limit of 2300 mg/day would benefit the 90 percent of people who currently exceed these levels. According to a study published in the American Journal of Clinical Nutrition, “Overall, 99.4 percent of US adults consumed more sodium daily than recommended by the American Heart Association (<1500 mg), and 90.7 percent consumed more than the IOM Tolerable Upper Intake Level (2300 mg).”³  The comment in the IOM report that is being so widely misinterpreted refers only to individuals with serious health conditions whose aggressive medical treatment adversely affects sodium metabolism, not to the general population. You can read the comment for yourself.

“The committee found that the evidence from multiple randomized controlled trials (RCTs) that were conducted by a single investigative team indicated that low sodium intake (e.g., to 1840 mg/day) may lead to greater risk of adverse events in congestive heart failure (CHF) patients with reduced ejection fraction and who are receiving certain aggressive therapeutic regimens.”

In addition to making it clear that they were only referring to a small group of very sick patients, the committee made a point of saying that the risks to these patients may, in fact, have come from the disease itself rather than the lower sodium intake.

“Specifically, in some studies, low sodium intakes apparently appeared to show an association with risk of disease, when, in fact, the relationship may have been that the disease itself led to low or incomplete measures of sodium among those with pre-existing disease.”

How have prominent health organizations reacted to newspaper coverage of this issue?

American Heart Association
Media Alert: May 14, 2013⁴
Much of the research suggesting that decreasing sodium intake has no effect on or leads to increased heart disease and death has been conducted among sick patients, rather than the general population. “The research that the IOM partially based their conclusions on showed inconsistencies in the relationship between sodium intake and health outcomes. Yet these studies were not designed to assess the impact of various levels of sodium intake on cardiovascular health,” said Elliott Antman, M.D., a spokesperson for the American Heart Association, a cardiologist at the Brigham and Women’s Hospital, and a professor of medicine at Harvard Medical School in Boston.

Although the scientific community continues to debate the use of biomarkers in general and surrogate indicators of health outcomes, recent evidence attributes 35 percent of heart attack and stroke events, 49 percent of heart failure episodes, and 24 percent of premature deaths to high blood pressure.

A recent review of current research conducted by the American Heart Association concluded that people who don’t currently have high blood pressure will benefit from consuming less than 1500 mg of sodium daily, because less dietary sodium will significantly reduce the rise in blood pressure that occurs as we age. Ninety percent of all Americans are expected to develop high blood pressure in their lifetime. Independent of its effects on blood pressure, excess sodium intake adversely affects the heart, kidneys, and blood vessels.

The Lancet
Salt: friend or foe?⁵
A high intake of sodium causes raised blood pressure-an established risk factor for heart disease, stroke, and kidney disease . . . The [IOM] report needs cautious interpretation –  it does not suggest that people use salt freely. The Institute agrees that a link between high salt consumption and increased risk of cardiovascular disease persists, and that average intake needs to be reduced.

Journal of the American Medical Association
Sodium Reduction in Populations: Insights from the Institute of Medicine Committee⁶ 
After release of the IOM report, several news outlets highlighted disagreement among health agencies about targets for dietary sodium intake and reported that experts disagreed about the importance of blood pressure. Focusing the debate on specific targets misses the larger conclusion with which all are in agreement and may hinder implementation of important public health policy. Rather than focusing on disagreements about specific targets that currently affect less than 10 percent of the US population (i.e., sodium intake of <2300 mg/day vs <1500 mg/day), the IOM, AHA, WHO, and DGA are congruent in suggesting that excess sodium intake should be reduced, and this is likely to have significant public health effects. Accomplishing such a reduction will require efforts to decrease sodium in the food environment and provide individual consumers more choice in their dietary consumption of sodium.

As far as I can see, the only group of people not on blood pressure drugs who can be harmed by reducing sodium intake to less than 1500 mg/day are those with untreated Addison’s Disease. In these people, the lack of aldosterone production in their adrenal glands makes them excrete lots of sodium. People with normal adrenal glands and reasonably healthy kidneys simply reduce salt excretion when salt intake is reduced, so there is no health risk at all. Indeed, the sodium reduction benefits them by reducing blood pressure, cardiovascular disease, and all of the other problems caused by excess sodium.

It should be clear by now that the media has been misinterpreting the “news” about sodium/salt intake. The facts are that the small “at-risk population” discussed in the IOM report consist of people with failing hearts who are on massive doses of diuretics and other blood pressure medications. In these very ill people, drastically lowering their salt intake without changing their medications can indeed cause problems. But the vast majority of people need to dramatically reduce their sodium/salt intake.

References:

1. The Preventable Causes of Death in the United States: Comparative Risk Assessment of Dietary, Lifestyle, and Metabolic Risk Factors. PLoS Med. 2009 April; 6(4): e1000058.
2. Institute of Medicine Consensus Report: Sodium Intake in Populations: Assessment of Evidence, May 14, 2013. http://www.iom.edu/Reports/2013/Sodium-Intake-in-Populations-assessment-of-Evidence.aspx.
3. Sodium and potassium intakes among US adults: NHANES 2003-2008. Am J Clin Nutr. 2012 Sep;96(3):647-57. doi: 10.3945/ajcn.112.034413. Epub 2012 Aug 1.
4. New IOM report an incomplete review of sodium’s impact, American Heart Association Media Alert, May 14, 2013. http://newsroom.heart.org/news/new-iom-report-an-incomplete-review-of-sodiums-impact-says-american-heart-association
5. Lancet Volume 381, Issue 9880, 25-31 May 2013, Pages 1790.
6. Sodium Reduction in Populations: Insights from the Institute of Medicine Committee. JAMA. 2013;1-2. doi:10.1001/jama.2013.7687. Strom BL, Anderson CM, Ix JH.

Five Important Facts About Sodium/Salt Intake

With food industry groups trying so hard to confuse the issue of sodium/salt intake, it is important to understand just how much sodium/salt the average American consumes and the serious ramifications that has on health. Let’s put it into perspective by looking at five key points.

What are healthful salt/sodium consumption levels? 

The American Heart Association, Institute of Medicine, and the National Academy of Science recommend keeping consumption less than 1500 mg/day with a Tolerable Upper Limit of 2300 mg/day.

How much sodium/salt do people consume daily?

Surveys based on people’s descriptions of what and how much they eat report that, on average, Americans take in around 3500 mg of sodium each day, which is more than one and a half times the recommended upper limit of 2300 mg/day. But because people tend to underestimate how much they eat and how much salt they use, it is more likely that they take in over 6000 mg/day, which is more than two and a half times the upper limit. Just check out typical restaurant meals and packaged foods, and you will see how easy it is to take in that much. Regardless of whether we use the 3500 mg/day or a higher amount, over 99.4 percent of American adults consume more than the recommended 1500 mg/day, and 90.7 percent consume more than the Tolerable Upper Limit of 2300 mg/day. 

What are the health risks associated with excess sodium/salt consumption? 

Excess sodium/salt raises blood pressure (hypertension), which is an established risk factor for heart disease, stroke, and kidney disease. In addition, excess sodium/salt consumption has been associated with stomach cancer, osteoporosis, edema, gastro-esophageal reflux disease, migraines, angina, left ventricular hypertrophy, arteriosclerosis, and autoimmune problems. It is estimated that 102,000 premature preventable deaths are caused by excess salt consumption each year. 

How many people could benefit from a reduction in sodium/salt intake? 

About 31 percent of American adults have hypertension (high blood pressure), and another 30 percent of American adults have prehypertension (blood pressure measurements that are higher than normal, but not yet in the high blood pressure range, raising the risk of developing high blood pressure). So, 61 percent of Americans could most likely benefit, and that doesn’t count all the people who have not yet developed hypertension or prehypertension. According to the American Heart Association, 90 percent of all Americans are expected to develop high blood pressure during their lifetime. 

If salt causes hypertension, why does salt reduction fail to reduce hypertension in some people? 

Many people with hypertension think (or have been told) they are not “salt responders” because they tried eating a “low-salt diet,” and it did not lower their blood pressure. The most likely reason these people didn’t get the result they wanted is that the diet they tried wasn’t actually a low-salt diet. Most people, including many physicians, do not know how to design a diet low enough in sodium/salt because they don’t realize where all the salt is coming from. Fortunately, once non-responders learn how to design a diet that is actually low in salt, most of them do respond and eventually get off their medications.

References:

1. Sodium and potassium intakes among US adults: NHANES 2003-2008. Am J Clin Nutr. 2012 Sep;96(3):647-57. doi:10.3945/ajcn.112.034413. Epub 2012 Aug 1.
2. The Preventable Causes of Death in the United States: Comparative Risk Assessment of Dietary, Lifestyle, and Metabolic Risk Factors. PLoS Med. 2009 April; 6(4): e1000058.
3. New IOM report an incomplete review of sodium’s impact, American Heart Association Media Alert, May 14, 2013. http://newsroom.heart.org/news/new-iom-report-an-incomplete-review-of-sodiums-impact-says-american-heart-association.