August 2007

The Great Salt Debate
By Sharon Palmer, RD
Today’s Dietitian
Vol. 9 No. 8 P. 40

Reducing sodium intake seems to fall in line with general health recommendations, especially for those with hypertension. But some say a serious salt shakedown may not be universally warranted.

Salt has always been something worth fighting for. It is one of the most widely and effectively used preservatives of all time, and its use dates back to prehistoric times, with evidence linking it to an era when mastodons walked the earth. In ancient Egypt, it was used to preserve mummies. Throughout history, salt was so highly prized that people waged war over the crystalline stuff. It was even used as currency during many times and places around the world. The word salary originated from salt rations given to early Roman soldiers known as salarium argentums. Salt became such a fixed part of culture and tradition that it spilled into legends, fairy tales, and countless quotes—from Charles Dickens’ ghost story “To Be Taken With a Grain of Salt” to the Swedish folktale “Salt on a Magpie’s Tail.”

Salt Police
Considering the passion that humans have lavished on salt, it almost seems inevitable that in current times, steamy battles over salt should arise. Health experts have cautioned the public for decades to cut back on salt to reduce the risk of high blood pressure and cardiovascular disease (CVD). Public health recommendations for reducing sodium, the element found in salt, within healthy individuals have been pumped out year after year.

Many leading health organizations are unanimous when it comes to telling the general population to cut back on salt. The 2005 Dietary Guidelines call for people to reduce their sodium intake to less than 2,300 milligrams per day—approximately 1 teaspoon of salt—to help lower blood pressure.1 The American Heart Association (AHA) recommends the same limit.2 The National Institutes of Health (NIH) suggests that people should consume less than 2,400 milligrams of sodium per day.3

But the American Medical Association (AMA) took salt bashing to a new level on June 13, 2006, when it recommended a new policy that may help Americans reduce sodium intake and CVD risk, highlighting that by reducing dietary sodium intake, people may be able to prevent future health problems.4

A Low-salt Pillar of Health
The evidence painting salt as the bad guy seems to have piled up. According to a statement by the NIH, various controlled intervention trials and observational studies have provided strong evidence that consuming a moderately reduced intake of sodium contributes to lowering blood pressure. Since available evidence shows that a moderately reduced intake of dietary sodium causes no harm, the NIH recommends a moderate salt intake for all Americans to help prevent and treat hypertension.5

The 2005 Dietary Guidelines note that the higher an individual’s salt intake, the higher his or her blood pressure tends to be, and decreasing salt intake is advisable to reduce the risk of elevated blood pressure. Keeping blood pressure in the normal range reduces an individual’s risk of coronary heart disease, stroke, congestive heart failure, and kidney disease.1 Researchers estimate that approximately one in three people in the United States have hypertension, which is defined as a mean systolic blood pressure of 140 millimeters of mercury or above and a mean diastolic of 90 millimeters of mercury or above or taking antihypertensive drugs. The AMA’s recent policy on sodium restriction considers that excess sodium greatly increases the chance of developing hypertension, heart disease, and stroke, and Americans consume two to three times more sodium than is healthy.4

In a recently published study in the British Medical Journal, the long-term effects of sodium restriction on CVD outcomes of the trials of hypertension prevention were examined. Researchers concluded that sodium reduction, previously shown to lower blood pressure, may also reduce the long-term risk of cardiovascular events.6

The Rise of Salt Sensitivity
Information is also crystallizing on the issue of how individuals respond to salt. Salt sensitivity is a measure of how blood pressure responds to a decrease in salt intake. In addition to hypertension, salt sensitivity increases the risk of developing conditions such as left ventricular hypertrophy, in which the heart’s main pumping chamber is enlarged and does not function properly, and the likelihood of kidney problems. A sensitivity to salt increases the risk of death as much as high blood pressure, according to a study supported by the National Heart, Lung, and Blood Institute.7

“People tend to become more sensitive to sodium as we age, and we now know that nonhypertensive individuals at age 55 have a 90% chance of developing hypertension as they age. It seems prudent to encourage moderation of sodium intake as a lifelong eating pattern,” says Marla Heller, MS, RD, nutrition and food consultant and author of The DASH Diet Action Plan.

Low Sodium or Bust?
Some critics of one-size-fits-all sodium restrictions are stepping forward, expressing concern that low-sodium eating may not be necessary or even good for the general population. Amid the large body of science on sodium restriction and hypertension, some researchers are publishing controversial reports in respected journals, raising questions about the validity of salt restrictions for the masses. Is there indeed enough evidence of disease prevention to support general sodium restriction, especially considering that limiting salt can be considered a quality of life issue?

Heller says, “There is an interesting debate about whether sodium restriction is necessary for everyone. We know that the prevalence of hypertension is almost unknown in cultures with very low sodium intake. However, in these cultures, total calorie intake and BMI [body mass index] tend to be low and activity levels are much higher than in the developed world, which certainly can be confounders as to whether the low sodium intake is the prime influence on blood pressure.”

Michael Alderman, MD, of Albert Einstein College of Medicine in New York, who was recently appointed editor-in-chief of the American Journal of Hypertension, says, “There’s no question that sodium intake is related to blood pressure. But the reduced salt intake of a whole population doesn’t translate into better health for everybody. A change in sodium intake has other consequences, such as an increased resistance to insulin, and it activates the hormone system renin-angiotensin with symptoms of increased heart attack and stroke risk.”

Alderman authored an article published in the Journal of the American College of Nutrition in June 2006 regarding the evidence relating dietary sodium to CVD. Alderman reported that the available data provided no support for any universal recommendation of a particular level of dietary sodium.8

In another article published in the same journal, researchers from the University of Alabama at Birmingham noted that careful observations revealed only a weak relationship between sodium intake/excretion and blood pressure in the general population. The authors noted that the effects of dietary sodium reduction on blood pressure were minimal; there was no relationship between the magnitude of reduction in sodium intake/excretion and blood pressure effect; and there was no evidence of an effect of sodium reduction on death or cardiovascular events. Some individuals demonstrate large blood pressure changes in response to acute salt depletion or repletion and are termed salt sensitive.9

In a meta-analysis published in The Journal of the American Medical Association in May 1998, studies of sodium intake and hypertension revealed that the effects of sodium reduction on blood pressure in normotensive patients did not support general recommendations for a sodium-restricted diet in this population, but sodium reduction may be beneficial as an adjunctive treatment for patients with hypertension.10

In the Second National Health and Nutrition Examination Survey follow-up study published in the The American Journal of Medicine in March 2006, researchers from Albert Einstein College of Medicine noted that evidence relating sodium intake to mortality was scant and inconsistent and concluded that the inverse association of sodium to CVD mortality discovered raised questions regarding the likelihood of a survival advantage with a lower-sodium diet.11

“There is no data showing that people who eat less than 2,300 milligrams of sodium live longer or have less heart attacks. Before we tell all Americans to cut sodium intake, we need evidence that a decreased salt diet will improve or extend life,” says Alderman.

A DASHing Diet
Meanwhile, the Dietary Approaches to Stop Hypertension diet—better known as the DASH diet—has gained momentum in blood pressure management and prevention. In the study called DASH, an excellent blood-pressure-lowering effect was demonstrated for the prevention and basic treatment of elevated blood pressure. The focus of the DASH diet is on a combination eating plan emphasizing what people should eat rather than what they shouldn’t eat. Rich in fruits, vegetables, complex carbohydrates, and low-fat dairy products, the DASH diet is lower in fat, saturated fat, cholesterol, and sodium and higher in potassium, calcium, and magnesium than the typical American diet. In the DASH program, there are two levels of daily sodium consumption: 2,300 milligrams per day and 1,500 milligrams per day, of which the latter may lower blood pressure further.12

“I tend to encourage people to choose more food without labels, emphasizing fresh fruits, vegetables, and lean cuts of meat, fish, or poultry. It is a more positive, less ‘medicalized’ approach to eating. And it achieves the outcome of having a diet with less added sodium and, at the same time, pumps up the intake of potassium-rich foods, which may help counterbalance dietary sodium. That seems to be one of the ways that the DASH diet works to help lower blood pressure,” says Heller.

Ubiquitous Sodium
Even though the human body requires salt—as sodium is the main component of the body’s extracellular fluids, helps carry nutrients into the cells, and regulates body functions such as blood pressure and fluid volume—people need only approximately 0.5 grams of salt (200 milligrams of sodium) per day. But Americans are on sodium overload. According to the AHA, the average American consumes 6 to 18 grams of salt (equivalent to 2,400 to 7,200 milligrams of sodium) per day.2

As the country’s diet became more processed and less reliant on whole foods, its sodium level increased. The natural salt content of food accounts for only approximately 10% of total intake, while added salt use at the table or in cooking provides another 5% to 10% of total intake. A whopping 75% of our sodium intake comes from salt added by manufacturers. There’s a hefty dose of sodium that people get from consuming restaurant fare and fast foods, too. It’s not unusual to find more than 1,000 milligrams of sodium in a single serving of highly processed foods or restaurant dishes.1

“A lot of people use convenience foods and high-sodium canned products as a quick fix. Younger people don’t know how to cook. People consume high quantities of sodium in convenience foods, processed foods, and foods in restaurants,” says Dee Sandquist, MS, RD, CD, an American Dietetic Association spokesperson and director of nutrition, diabetes, weight management, and wound healing at Southwest Washington Medical Center in Vancouver, Wash.

Fostering a Low-sodium Habit
In today’s climate of “in-your-face” nutrition issues being translated to food products—from zero trans fats to eliminating pesticides in produce—low-sodium verbiage seems to get pushed out of claims on food labels. After all, food manufacturers have to keep in tune with the latest public outcry. And with so many things to worry about when perusing a food label, perhaps health-conscious consumers are starting to place sodium content at the bottom of a growing list. “I don’t think a lot of consumers think about sodium when ordering or buying food. The people who think about it are those [who] have gone to the doctor and their blood pressure is high,” says Sandquist.

According to ACNielsen’s LabelTrends report, products with antioxidants, fiber, no preservatives, and organic claims on their labels grew by 10% or more for the 52 weeks ending December 3, 2005 (vs. the previous year). The reduced-fat category, the No. 1 health claim, brought in $35 billion in annual sales, with the low-fat category claiming an additional $15.5 billion in annual sales. Low-sodium products brought in a smaller share of the market with $11 billion in annual sales.

Within the AMA’s recent recommendations to reduce sodium, there is an urge for the FDA to revoke the generally recognized as safe status of salt and develop regulatory measures to limit sodium in processed and restaurant foods, calling for a reduction of 50% in the amount of sodium in processed foods and restaurant meals over the next decade, public education to reduce sodium intake, and an improvement in food labeling to better assist consumers in understanding sodium in foods.4

But numerous food processors have already successfully created reduced-sodium retail food products—from canned soups to snack foods—that are tasty and acceptable to consumers. And in the culinary world, low-sodium cookbooks abound. Finding low-sodium dishes in fast-food and other restaurants is still a challenge, even though low-sodium cuisine may easily be accomplished by adapting culinary modifications within operations. As more restaurant chains publish sodium information for menu offerings and offer custom ordering options that may limit the meal’s sodium intake, perhaps finding moderate sodium choices in the dining scene may no longer seem like an impossible feat.

“For the average consumer, sodium is difficult to grasp. It is important for dietitians to help translate the message of reducing sodium to a reality. What does it mean? Develop one or two key points for consumers,” suggests Sandquist. “As a profession, it is really difficult to focus on the overall quality of the diet. It is easy for consumers to pick up the latest edition of the paper and read about a nutrition study. We need to help people put it into perspective for the overall diet.”

“I think dietitians are doing a good job of continuing to focus on moderation of sodium intake as a desirable patient outcome. Moderation may mean different things in various population groups, depending on the percentage of the diet that comes from processed and fast foods and patients having the skills and time availability to prepare meals with less processed foods. Sometimes, a very simple goal is to include some fresh or frozen vegetables at lunch and dinner,” says Heller. When it comes to promoting optimal health for the general population, few should find that advice controversial.

— Sharon Palmer, RD, is a contributing editor at Today’s Dietitian and a freelance food and nutrition writer in southern California.

References

1. Health and Human Services, U.S. Department of Agriculture. “Dietary Guidelines for Americans 2005 — Chapter 8 Sodium and Potassium.” Updated February 5, 2007. Available here.

2. American Heart Association. “Cutting Down on Salt.” Available here.

3. National Heart, Lung, and Blood Institute. “Your Guide to Lowering High Blood Pressure — Reduce Salt and Sodium in Your Diet.” Available here.

4. American Medical Association. “AMA calls for measures to reduce sodium intake in U.S. diet.” June 13, 2006. Available at here.

5. National Institutes of Health Update. “Statement on Sodium Intake and High Blood Pressure.” August 17, 1998. Available at here.

6. Cook NR, Cutler JA, Obarzanek E, et al. Long term effects of dietary sodium reduction on cardiovascular disease outcomes: Observational follow-up of the trials of hypertension prevention (TOHP). BMJ. 2007;334(7599):885.

7. National Institutes of Health News Release. “Study Shows New Link Between Salt Sensitivity and Risk of Death.” February 15, 2001. Available here.

8. Alderman MH. Evidence relating dietary sodium to cardiovascular disease. J Am Coll Nutr. 2006;25(3 Suppl):256S-261S.

9. Franco V, Oparil S. Salt sensitivity, a determinant of blood pressure, cardiovascular disease and survival. J Am Coll Nutr. 2006;25(3 Suppl):247S-255S.

10. Graudal NA, Galloe AM, Garred P. Effects of sodium restriction on blood pressure, renin, aldosterone, catecholamines, cholesterols, and triglyceride: A meta-analysis. JAMA. 1998;279(17):1383-1391.

11. Cohen HW, Hailpern SM, Fang J, et al. Sodium intake and mortality in the NHANES II follow-up study. Am J Med. 2006;119(3):275.e7-14.

12. Health and Human Services, National Institutes of Health, National Heart, Lung, and Blood Institute. “Your Guide to Lowering Your Blood Pressure With DASH.” Revised April 2006. Available here.