Salt and Sodium

 

 Salt and Sodium

Eating less salt is good for everyone's health. Choose more fresh foods and fewer processed foods.

Americans consume one-and-a-half or more teaspoons of salt a day. That's far more than is needed to satisfy the body's need for sodium, the main element we get from salt. And that’s a big problem: A high-sodium diet can raise your risk of high blood pressure, heart disease, and stroke.

 







1. Get fresh. Most processed foods are high in sodium. Choose fresh foods and season them with herbs, spices, and citrus—not salt.
2. Scan the label. Look for canned, boxed, frozen, and prepared foods with less than 300 milligrams of sodium per serving.
3. Downsize your portions. A good rule of thumb is that the more calories a meal has, the more sodium it has. So skip the supersize. Share a dish and you can cut your salt by half.
4. Seek low-salt options when dining out. Check restaurant websites for sodium info. Ask the server for dishes that use salt sparingly. Use a light hand on salty condiments.
5. Call for action. Food makers and restaurants listen to consumers. If more people ask them to slash the salt, they will. Call, e-mail, text, or just ask to speak to the chef.

The government says we should limit sodium to 2,300 milligrams, and that people at high risk of health problems from salt should make 1,500 milligrams their limit. Who’s at high risk? Nearly 70 percent of U.S. adults! The high-risk group includes people who are over age 40, people who have high blood pressure or slightly elevated blood pressure, people who have diabetes, and African Americans.
If we get used to eating high-salt diets in childhood, it can be harder to cut back later on. That’s why it’s a smart choice for everyone to make 1,500 milligrams their daily sodium budget.

Salt Basics

The word "salt" is actually a technical term. To a chemist, a salt is what you get when you react an acid with a base. To the rest of us, salt is sodium chloride, the white crystals we sprinkle on food to give it extra taste. One teaspoon of table salt weighs about 6,000 milligrams (6 grams). Of that, about 2,300 milligrams (2.3 grams) is sodium.

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 ; public health efforts have managed to bring that down considerably.  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.  In China, high blood pressure is the leading cause of preventable death, responsible for more than one million deaths a year.

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.  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." 

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. 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.  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.

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. 

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.  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.

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