Lower Sodium and Salt: A Key to Good Health

Table of Contents

• Introduction
• Salt Basics
• Sources of Salt
• Hazards of Too Much Sodium
  • Salt and the Cardiovascular System
  • Salt and Cancer
  • Salt and Bones
• Taking Action: How to Cut Back on Salt and Sodium

Introduction

We owe a lot to salt. The search for this white crystal and the trade that sprang up around it helped shape some civilizations. Salt was essential to preserve foods, both vegetables and meats, through the winter and during travel. It has given us words like salary and salacious. It has also been a source of conflict, and even bloodshed, as tribes and nations fought for access to salt or guarded their stores. (1)

More recently, even though salt is cheap and abundant, it has sparked fierce battles, only they have been bloodless ones fought in the pages of medical journals and in the halls of government, debated in blogs and on television news. Salt has been the subject of so much scrutiny that some have dubbed 2010 “the year of salt.” (2)

The issue is this: How can we get people to eat less salt?

There’s little question that we all eat far too much salt—and our excessive intake of salt has negative effects on health. Americans consume one-and-a-half or more teaspoons of salt a day. (3) We aren’t alone—studies in dozens of countries have found that adults typically take in the equivalent of more than a teaspoon of salt a day, and more than two teaspoons a day in some Asian countries. (4) That’s far more than is needed to satisfy the body’s need for sodium, the main element we get from salt.

Current U.S. recommendations call for a maximum of one teaspoon of salt (2,300 milligrams of sodium) a day, and two-thirds of a teaspoon (1,500 milligrams of sodium) for people who have high blood pressure or are at high risk of developing it. The latter group includes people who are over the age of 40, are African American, or have somewhat elevated blood pressure (prehypertension)—which encompasses almost 70 percent of adults in the United States! (5) People with diabetes, kidney disease, heart failure and other conditions should cut back, too.

Many experts, including those in the Department of Nutrition at the Harvard School of Public Health, the American Heart Association, and the Center for Science in the Public Interest, believe that cutting back on salt—aiming for a target of 1,500 milligrams of sodium per person per day—would improve health, save lives, and avoid billions of dollars each year in medical costs. (6, 7) Skeptics say that an across-the-board reduction in salt intake would disrupt the food industry but have little impact on public health. Fifteen years ago, there was more room for debate about the benefits of large-scale cutbacks on salt. (Read more about the feud over salt.) During the past decade, however, extensive research on the health effects of excess salt clearly points to evidence of harm. 

The big challenge, then, is how to cut back. Most of our salt comes from prepared foods, like ready-made breads and crackers, canned and frozen foods, ready-to-eat breakfast cereals, cheese, and restaurant foods. (8) Reducing our intake would mean a huge change in how the food industry prepares its products, a challenge for food producers and a change the salt industry isn’t keen to make. After all, salt is a cheap additive that enhances flavor and livens up bland food. (9) It makes meat retain water, adding weight for which we pay top dollar. Salt also makes us thirsty, and is one way the food industry nudges us to buy more soft drinks. (10)

Encouragingly, many food companies have already shown that it is possible to make modest, even significant cutbacks in sodium without sacrificing taste. (11) Others have pledged to do so, on their own or in conjunction with New York City’s nationwide voluntary campaign to cut salt levels in the food supply by 25 percent over the next five years. (12, 13) But it remains to be seen whether all parts of the food industry will as easily—or willingly—embrace sodium cutbacks without new federal leadership. Indeed, a committee appointed by the Institute of Medicine has recommended that the federal Food and Drug Administration (FDA) regulate the amount of salt in commercially prepared food. (14)

In this section of The Nutrition Source, we will review the science on salt and health and highlight the steps that individuals, food companies, health professionals and the government can take to help us all cut back on salt.

Salt Basics

The human body requires only a very small amount of sodium since it is exquisitely effective in conserving whatever is in our body. The transmission of nerve impulses and the contraction of muscle fibers depend on sodium. Along with potassium, it is essential for maintaining a proper fluid balance in and around cells. It takes very little sodium to accomplish these tasks. The Yanomamo people, who inhabit the Amazon forests, take in just 200 milligrams of sodium a day (one-tenth a teaspoon of salt) while the average American gets 3,400 milligrams (about 1½ teaspoons of salt). Before the 1970s, the residents of northern Japan took in a whopping 10,300 milligrams (4½ teaspoons of salt) a day (3); public health efforts have managed to bring that down considerably. (4) Consuming such a low sodium diet protects the Yanomamo from hypertension, which is virtually absent in their society.

The body has an intricate system of checks and balances to maintain a steady amount of sodium in the fluid that bathes cells and in the bloodstream, regardless of intake. When sodium levels fall, or the mineral is in short supply, the kidneys and sweat glands hold onto water. This keeps sodium from leaving the body. The opposite happens when you take in more sodium than you need—the kidneys flush out the excess by making more urine, or making it saltier.

In most people, the kidneys have trouble keeping up with the excess sodium in the bloodstream. As it begins to accumulate, the body responds by holding onto water to dilute the sodium. This increases both the amount of fluid surrounding cells and the volume of blood in the bloodstream. That means more work for the heart and more pressure on blood vessels. Over time, the extra work and pressure can stiffen blood vessels, leading to high blood pressure, heart attack, or stroke. It can also lead to heart failure. There is also some evidence that too much salt can damage the heart, aorta, and kidneys without increasing blood pressure, and that it may be bad for bones, too.

Although many factors contribute to poor health—genes, smoking, excess weight, little physical activity, stress, excess alcohol, and others—high blood pressure is a leading cause of cardiovascular disease. It accounts for two-thirds of all strokes and half of heart disease. (10) In China, high blood pressure is the leading cause of preventable death, responsible for more than one million deaths a year. (15)

Sources of Salt

When humans roamed the Earth hunting and gathering, potassium was abundant, sodium scarce. The so-called Paleolithic diet provided upwards of 10,000 mg of potassium a day and under 700 milligrams of sodium. (16) The historical scarcity of sodium is reflected in the human body’s tenacious ability to hold onto it.

But today, many common processed foods contain a lot of sodium. According to data from the National Health and Nutrition Examination Surveys, the top 10 individual food sources of sodium in the American diet, based on the combination of sodium content and frequency of consumption, are as follows: (18)

Today, if you eat nothing but unprocessed foods—plenty of fruits, vegetables, whole grains, and nuts, with a smattering of wild fish and naturally raised beef, chicken, eggs, and milk—that you prepare yourself with a light hand on the salt shaker, you are taking in far more potassium than sodium (not to mention plenty of vitamins, minerals, fiber, phytonutrients, healthy fats, and other elements of a healthful diet). More potassium than sodium is a good thing. But few Americans eat this way. Instead, our reliance on fast and prepared foods tips the balance in the other direction.

High salt use is by no means limited to fast food and chain restaurants. Even many chefs of fine dining restaurants use excessive amounts of salt in the meals they prepare for us. Their intent is to dazzle us with flavors of their foods, and one of the easiest, most reliable ways to do this is by ramping up the addition of salt. Since we already eat a lot of salt and are conditioned to high-salt taste experiences, chefs often find that they must raise the salt levels in their food to stand out.

Most of us get far more sodium than we need while averaging just 2,500 mg of potassium, about half of what is recommended for adults. (3) Equally worrisome, our hunger for salt appears to be growing. In the United States, there has been a 55 percent increase in the average sodium intake since the 1970s. (17)

Most Americans and Europeans get the majority of their daily sodium, on the order of 75 percent, from prepared foods. (4) And it’s a safe bet that most have no idea how much salt these foods deliver. It is truly hidden salt, since many sodium-rich foods don’t taste salty.

For example, even something as innocuous and seemingly unsalty as a bowl of Kellogg’s Raisin Bran has 354 milligrams of sodium, or 24 percent of a day’s healthy allotment. In the U.S. Department of Agriculture’s National Nutrient Database for Standard Reference, the first 500 items in its list of sodium in food are all prepared foods. (19). Portion sizes on food labels are often smaller than what people might typically eat—so if you eat 15 pita chips instead of 10 (the serving size on the label), you will be consuming about 400 milligrams of sodium, or 27 percent of your daily sodium budget.

Restaurant foods can be even worse, in part due to their larger portion sizes and the fact that one menu item may combine several high-sodium foods. Indeed, it’s possible to consume far more than a day’s worth of sodium in a single meal. An All-Natural Pepperoni P’Zone pizza with a bread stick and a Sierra Mist deliver 3,610 milligrams; Chili’s Buffalo Chicken Fajitas and a Dr. Pepper, 6,916 milligrams; and Red Lobster’s “Admiral’s Feast,” 7,106 milligrams, (20) more than four times the healthy daily target.

It’s a different—yet still highly salty—story in China and Japan, where the salt shaker and salty condiments like soy sauce are the leading sources of sodium. (4) (Read more about sodium sources in China and Japan.)

Hazards of Too Much Sodium

Thousands of studies have explored the effects of sodium on health. They have covered the range of medical research from broad comparisons of sodium intake and health across countries (ecological studies) to look-back studies comparing people with heart disease or stomach cancer to those without (case-control studies), long-term follow-up studies (prospective observational studies), experiments in which one group of people consumed less sodium than another group (randomized controlled trials), and laboratory studies of the impact of sodium on cells and tissues. All this effort has yielded a broad consensus about connections between sodium and health.

Salt and the Cardiovascular System

The lion’s share of research on sodium and health has focused on high blood pressure, stroke, heart disease, and heart failure. The majority of these studies show that blood pressure rises with increasing amounts of sodium in the diet, and that sodium reduction lowers cardiovascular disease and death rates over the long term.

One way to make sense out of so much information is with a technique called meta-analysis. It takes the data from all the available studies and provides a statistical summary of the results.

Several meta-analyses have been done on studies of salt intake and blood pressure. The largest and most recent of these was conducted by a team from the University of Naples Medical School in Italy and the University of Warwick in England. (21) They pooled the results of 13 cohort studies that included 177,025 men and women who were followed for 3.5 years to 19 years. Over the course of the follow-up, more than 11,000 of the participants experienced a heart attack or stroke, developed another form of cardiovascular disease, or died of cardiovascular disease. Higher salt intake was associated with a 23 percent increase in stroke and a 14 percent increase in heart disease.

Describing the most important studies would take pages. Instead, you can read a summary of three key studies, all different types, that highlight the various findings on sodium and cardiovascular disease: Intersalt, DASH (Dietary Approaches to Stop Hypertension), and TOHP (Trials of Hypertension Prevention).

Salt and Cancer

Several dozen studies have explored connections between salt, sodium, or salty foods and cancer. The data from these studies show that, in general, higher intakes of salt, sodium, or salty foods is linked to an increase in stomach cancer. The World Cancer Research Fund and American Institute for Cancer Research concluded that salt, as well as salted and salty foods, are a “probable cause of stomach cancer.” (22)

Salt and Bones

The more salt you take in, the more calcium your body flushes out in the urine. If calcium is in short supply, it can be leached out of the bones. So a diet high in sodium could have an additional unwanted effect—the bone-thinning disease known as osteoporosis. (10) A study in post-menopausal women showed that the loss of hip bone density over two years was related to the 24-hour urinary sodium excretion at the start of the study, and that the connection with bone loss was as strong as that for calcium intake. (23) Other studies have shown that reducing salt intake causes a positive calcium balance, suggesting that reducing salt intake could slow the loss of calcium from bone that occurs with aging.

Taking Action: How to Cut Back on Salt and Sodium

It’s clear that an abundance of salt in our food is a silent killer, responsible for thousands of deaths each year. The real question is, what can be done to help people reduce their intake? The answer is simple. Turning it into practice will take a concerted action between four groups: individuals, health professionals, food companies and food service operators, and governments.

Despite substantial government efforts, the biggest gains will come from food companies and food service operators reducing the amount of salt used in prepared foods—and that’s certainly why FDA regulation of salt in commercially prepared food was the centerpiece recommendation of the Institute of Medicine’s report. (14) Many in the food industry have already taken the lead in reducing sodium, and we commend them on their efforts. But sodium reduction won’t happen on a broad scale without strong pressure and leadership from the other three groups, and some political will.

In the meantime, you can do something about your, and your family’s, salt intake, simply by cutting back on processed foods and choosing more fresh foods. Creative chefs and food service operators can also make changes in the kitchen to cut back on salt without cutting back on flavor.

• For delicious ideas on how to reduce salt, read Tasting Success with Cutting Salt: Twenty-Five Science-Based Strategies & Culinary Insights, from the HSPH Dept. of Nutrition and The Culinary Institute of America.
• Check out these lower-sodium recipes from The Culinary Institute of America.

Health professionals can get out the message that salt isn’t an innocuous flavor enhancer. They can also advocate for rules, recommendations, community pressure, and laws that reduce the salt content of prepared foods and that make it easier for consumers to tell how much salt is in a particular food. The American Medical Association and American Public Health Association, for example, have been lobbying Congress for several years, promoting a reduction in salt in prepared foods.

The Sodium Reduction Payoff: Saving Lives and Money

A study by the RAND Corporation estimated what would happen if we were able to reduce the average sodium intake to 2,300 milligrams—the current recommended daily intake—in the United States. According to the model, that shift would prevent 11 million cases of high blood pressure and save $18 billion in direct medical costs each year. (24)

A more recent study in The New England Journal of Medicine modeled what would happen if Americans cut back their average daily sodium consumption by 1,200 milligrams—an amount that would still leave many people above the recommended intake, but would be a significant decrease from current levels. (25) Such a cutback would prevent up to 120,000 new cases of heart disease each year, researchers estimate, and would save up to 92,000 lives and $24 billion in health costs. That’s a huge public health payoff—similar to what the U.S. would see if Americans cut their tobacco use in half. Even smaller cutbacks would save tens of thousands of lives and would be cost effective. Reductions in less developed countries, where excess salt is an even greater problem, could have an even greater impact. A modest cutback in sodium seems to be a tiny price to pay—since most of us would never even notice it— for such a benefit.

References

1. Kurlansky M. Salt:a world history. New York: Walker and Co., 2002.

2.Jacobson, M. 2010: The year of salt. Nutrition Action Health Letter. January/February 2010.

3. Dietary reference intakes for water, potassium, sodium, chloride, and sulfate. National Academy Press.

4. Brown IJ, Tzoulaki I, Candeias V, Elliott P. Salt intakes around the world: implications for public health. Int J Epidemiol. 2009; 38:791-813.

5. Application of lower sodium intake recommendations to adults—United States, 1999-2006. MMWR Morb Mortal Wkly Rep. 2009; 58:281-3.

6. American Heart Association. Statement to IOM Committee on Strategies to Reduce Sodium Intake. March 3, 2009.

7. Center for Science in the Public Interest. Salt: the forgotten killer. Washington, D.C., 2009.

8. Subar AF, Krebs-Smith SM, Cook A, Kahle LL. Dietary sources of nutrients among US adults, 1989 to 1991. J Am Diet Assoc. 1998; 98:537-47.

9. Grocery Manufacturers Association. Sodium and salt: a guide for consumers, policymakers, and the media. Washington, D.C., 2008.

10. He FJ, MacGregor GA. A comprehensive review on salt and health and current experience of worldwide salt reduction programmes. J Hum Hypertens. 2009; 23:363-84.

11. Campbell Soup Company. Press release: Campbell further reduces sodium in V8^® 100% Vegetable Juices. January 28, 2010.

12. New York City Dept. of Health and Mental Hygiene. Health department announces proposed targets for voluntary salt reduction in packaged and restaurant foods. January 11, 2010.

13.  Unilever. Press release: Unilever makes a commitment to reduce salt across its portfolio. April 21, 2009.

14. Institute of Medicine. Strategies to Reduce Sodium Intake in the United States. April 20, 2010.

15. He J, Gu D, Chen J, et al. Premature deaths attributable to blood pressure in China: a prospective cohort study. Lancet. 2009; 374:1765-72.

16. Eaton SB, Konner M. Paleolithic nutrition. A consideration of its nature and current implications. N Engl J Med. 1985; 312:283-9.

17. Briefel RR, Johnson CL. Secular trends in dietary intake in the United States. Annu Rev Nutr. 2004; 24:401-31.

18. Cotton PA, Subar AF, Friday JE, Cook A. Dietary sources of nutrients among US adults, 1994 to 1996. J Am Diet Assoc. 2004; 104:921-30.

19. Sodium content of selected foods (sorted by nutrient content). USDA National Nutrient Database for Standard Reference, Release 22. Last updated December 14, 2009.

20. Center for Science in the Public Interest. Heart attack entrées and side orders of stroke. 2009.

21. Strazzullo P, D’Elia L, Kandala NB, Cappuccio FP. Salt intake, stroke, and cardiovascular disease: meta-analysis of prospective studies. BMJ. 2009; 339:b4567.

22. World Cancer Research Fund, American Institute for Cancer Research. Food, futrition, physical activity, and the prevention of cancer: a global perspective. London, 2007.

23. Devine A, Criddle RA, Dick IM, Kerr DA, Prince RL. A longitudinal study of the effect of sodium and calcium intakes on regional bone density in postmenopausal women. Am J Clin Nutr. 1995; 62:740-5.

24. Palar K, Sturm R. Potential societal savings from reduced sodium consumption in the U.S. adult population. Am J Health Promot 2009; 24:49-57.

25. Bibbins-Domingo K, Chertow GM, Coxson PG, et al. Projected effect of dietary salt reductions on future cardiovascular disease. N Engl J Med. 2010; 362:590-9.

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