In this article:
- Recognizing the effect of salt on your blood pressure
- Removing all doubts: Studies on salt and its substitutes
- Concerning salt sensitivity
- Salting to live or living to salt?
There has been a lot of research by laboratories on the effect of salt on the blood pressure and the kidneys in the last 20 years. None of the newly published information causes us to change our minds about the major influence of salt on blood pressure. Although salt is not to blame for high blood pressure, reduction in salt intake can reduce the blood pressure in most cases. In addition, according to an article in the June 2006 American Journal of Nephrology: “There is consistent experimental evidence to link increased salt exposure with kidney tissue damage.”
The Salt Institute, a nonprofit association of salt producers founded in 1914, would have you believe that eating salt doesn’t raise your blood pressure and that there’s no proof that higher blood pressure is harmful to your health. Don’t believe them! With rare exceptions, every expert in the field of high blood pressure recommends reducing salt consumption to lower high blood pressure.
The United States is by far the world’s largest producer of salt. The US makes about 46.5 million metric tons annually compared with the next country, China, which makes 37.1 million metric tons, followed by Germany at 16 million, India at 15 million, Canada at 14.1 million, and Australia at 11.2 million. These six countries account for 140 million of the 209-million metric tons produced each year in the world. Although only 6 percent of that salt is for human consumption, these same countries tend to consume the most per person — a situation that helps explain their equally high prevalence of high blood pressure.
In this article, we explain how your salt intake can elevate your blood pressure, and we show how research has provided overwhelming evidence to this effect. Also, you discover how sensitivity to salt can increase your blood pressure, how you can decrease the amount of salt in your food, what foods are low or high in salt, and what’s in a low-salt diet. You can eat without salting down your plate. We hope that by the end of the article you can put your saltshaker away, never to be seen again — or at least reduce your salt intake so it does you no harm.
Making the Connection between Salt and High Blood Pressure
Salt, which contains 40 percent sodium and 60 percent chloride, is critical to your life. You can’t live without it. Sodium helps maintain your blood’s water content, balances the acids and bases in your blood, and is necessary for the electrical charges in your nerves that move your muscles.
Researchers generally believe that a kidney’s inability to excrete salt is responsible for salt-induced high blood pressure. To compensate for this inability, the body increases blood pressure so the kidney can filter more salt, which then enters the urine. This increased blood pressure helps eliminate more salt, but it also puts a strain on the body’s arteries and sets the downward spiral of blood-pressure damage in motion — a vicious cycle.
Food labels list the amount of sodium, not salt, in the food. The Dietary Guidelines for Americans from the United States Department of Health and Human Services, as well as from the American Heart Association, recommend 2,400 milligrams (mg) (sodium, not salt) (2,400mg sodium = 6000mg salt) daily for adults or 1 teaspoon of salt (2,300 mg sodium to be exact). The average American consumes 5,000 mg of sodium daily — twice the necessary amount. Note: Normal sodium balance can be maintained with 500 mg daily (a little more than 1⁄4 teaspoon of salt), so Americans are eating ten times as much as they really need!
Canada, Australia, the United Kingdom, and Portugal all have about the same recommendation of 2,400 mg of sodium (=6000mg salt). Some countries — Germany (4,000 mg sodium), the Netherlands (3,600 mg sodium), and Belgium (3,500 mg sodium) — are more liberal, and at least one country, Sweden (800 mg sodium), is more restrictive than the United States.
Salt and sodium in your food
Salt is also called sodium chloride (NaCl). Sometimes, food labels only give the figure for sodium. But there is a simple way to work out how much salt you are eating from the sodium figure: Salt = sodium x 2.5
“Where is all this salt coming from?” you may ask. Two sources primarily:
- Many foods are a natural source of salt (like meat and fish).
- Many foods contain salt added during processing (prepared soup and crackers, for example).
For more information on the amount of salt in the foods you eat, see the “Lowering Your Salt Intake” section later in this article.
Proving the Salt-Blood Pressure Connection
An experiment that involved the overabundant consumption of salt would be hard to do on human beings because their salt intake is so high to begin with. Also, a person would need to take an unpalatable amount of additional salt to significantly raise his body’s salt level. However, studies of people with high blood pressure who undergo periods of salt reduction are easily performed.
Although reducing salt intake hasn’t been proven to always lower blood pressure, studies have shown that eating less salt, in most cases, leads to lower blood pressure and fewer instances of heart attack and brain attack. For example, the blood pressure measurements of individuals with a great craving for salt were extremely high when they ate an abundance of salt. When the same individuals reduced their salt intake, blood pressures dropped significantly.
Examining early experiments
In the early twentieth-century, the first experiments on the salt-blood pressure connection showed that blood pressure fell as salt was reduced. You can find these studies in the Archives of General Medicine (February 1904).
A low-salt diet lowered blood pressure in half of the patients who had high blood pressure. In the rest of the patients, changes may have been irreversible (in other words, the blood pressure no longer responded to salt deprivation alone), or some patients may not have been salt sensitive (I discuss salt sensitivity later in this article).
In the American Journal of Medicine (March 1948), a study established without a doubt that salt restriction lowers blood pressure. Shortly afterwards, however, the first diuretics (blood pressure drugs that increase salt and water excretion; see article 13) came on the market. As a result, salt restriction as a means of lowering blood pressure fell out of favor. However, as side effects from these drugs became a problem, salt restriction became more popular again.
In 1988, the Intersalt Study, a huge study of over 10,000 people from many nations, showed that salt intake is directly related to the rise of both systolic and diastolic blood pressures with age (see article 2 for more about these types of blood pressure). The researchers concluded that reducing salt intake by 1 teaspoon daily from age 25 to 55 can reduce the blood pressure by 9 mm Hg. Many people with prehypertension can lower their blood pressure to normal just by restricting salt. Note: People who lived where the salt intake was lowest had no increase in blood pressure with age.
Taking some study results with a grain of salt
At first glance, the evidence for the connection between excess salt and high blood pressure appears overwhelming. However, a few studies seem to show that salt isn’t dangerous to your health. In one particular study reported in Hypertension (June 1995), Alderman wrote that heart attacks increased among the men who had the lowest salt intake. Note: This study had a number of problems associated with it. The most serious problem was that the patients had their salt intake tested only one time in four years; their intake was considered high or low based on that single test. The average of multiple tests would have been more accurate.
Considering chloride’s effects on blood pressure
Current professional opinion maintains that sodium alone doesn’t raise blood pressure. Instead, the combination of sodium and chloride raises blood pressure. Studies at the University of California in San Francisco by Dr. R. Curtis Morris and his associates have shown that some people are sensitive to both sodium and chloride, but others are sensitive to chloride even when it’s not combined with sodium.
In rats that are genetically prone to high blood pressure, potassium chloride (a common replacement for sodium chloride — salt) can raise blood pressure just as much as sodium chloride does. Whether this finding is applicable to human beings is uncertain at the present time. However, over 20 years years ago, Morris and his associates showed that sodium bicarbonate (baking soda) does not raise blood pressure in salt-sensitive people. As a result, they recommend that potassium bicarbonate or potassium citrate (not potassium chloride) replace sodium chloride.
A study of people with high blood pressure in Germany (October 1990 Hypertension) offers evidence that chloride plays a part in high blood pressure. A group of patients with high blood pressure was given either potassium chloride or potassium citrate in place of sodium chloride. Those who received potassium citrate lowered their blood pressure significantly, but those who received potassium chloride did not. Note: The potassium in fruits and vegetables is not potassium chloride. This difference may help to explain the positive effects of fruits and vegetables on high blood pressure (see article 9 for more information).
Reviewing recent studies
A Finnish study in the September 2006 Progress in Cardiovascular Disease showed that a one-third decrease in salt intake over 30 years led to a drop in systolic pressure of more than 10 mm of mercury in both systolic and diastolic pressure throughout the population. In addition, the population showed a 75 percent decrease in deaths due to heart attacks and strokes (brain attacks). After reviewing this study, We threw out our saltshakers!
This is a truly remarkable accomplishment. The Finns believe they have been able to greatly reduce blood pressure and its complications — heart attacks and strokes — by the following methods:
- Hundreds of articles in leading newspapers since 1978 have emphasized the toxicity of salt.
- Extensive reports to the public have recommended sodium-reduced, potassium- and magnesium-enriched, healthier salt alternatives.
- Food manufacturers, the major source of salt in Finnish diets, have to add High Salt Content to the label if a product’s percentage of salt is higher than the allowable amount. Rather than put this label on their foods, they have lowered the salt content. (They’re also allowed to label their food Low Salt Content if the product meets certain levels.)
- Restaurants are allowed to label their food Pansalt if it has reduced sodium and increased potassium and magnesium salts. Owners find this to be a good marketing technique.
Salt through human history
Human beings who lived away from the seashores several thousand years ago didn’t eat much salt because most salt comes from the sea. They existed on no more than 200 to 400 milligrams (less than 1⁄2 teaspoon) of salt each day because the human body generally conserves it. When an athlete sweats, he puts out sweat with less and less salt as exercise continues. Meanwhile, the kidneys return all the filtered salt back to the body.
When people discovered that salt preserved and extended the life of some foods (about 3,000 BC), salt became much more valuable. At the same time, the salty taste of food became the norm and unsalted food was considered bland. At that time salt became such a sought-after commodity that governments began to put a tax on salt transactions to gain revenue. The salt tax was a major reason for the French Revolution.
Around 1850, salt became cheap as methods of producing it improved. Salt consumption rose enormously. By the nineteenth century, people consumed as much as 20 grams (or 4 teaspoons) of salt daily. Luckily, with refrigeration, adding salt as a preservative to food began to decline.
Determining Whether You’re Salt Sensitive
Salt was first shown to raise blood pressure in rats in experiments published in the February 1957 Journal of the American Dietetic Association. At the end of nine months, the rats that had consumed the most salt had the highest blood pressure. However, not all rats in this study showed this increase in blood pressure; some were sensitive to salt and some weren’t. This study showed that the sensitivity was hereditary, that is, passed down through the genes.
Salt sensitivity in humans is similar:
- When children of parents with high blood pressure eat salt in large quantities, they can’t get rid of it through their urine as rapidly as children of parents who don’t have high blood pressure.
- When children of parents with high blood pressure eat salt, their blood pressure is higher if both parents have high blood pressure than if only one parent has high blood pressure.
- When children of parents without high blood pressure eat salt in large quantities, their blood pressure isn’t elevated at all.
These findings are published in the Journal of Hypertension (April 1986).
About half the United States population (and, where studied, half the populations in other industrialized countries) is salt sensitive. This high percentage has caused plenty of confusion in experiments meant to show the effects of salt on human beings. Among the people who tend to be more salt sensitive are:
- Elderly individuals (over age 65)
- Overweight individuals
- African Americans
- People with kidney disease
Reduce your salt intake whether you’re salt sensitive or not because:
- If you are sensitive, the reduction helps to reduce your blood pressure.
- If you’re not sensitive, the reduced salt intake can reduce the extra water that your body naturally retains due to salt.
Linking salt sensitivity and metabolic syndrome
Salt sensitivity seems to be the cause of high blood pressure in metabolic syndrome, a condition that includes high blood pressure, decreased sensitivity to the body’s insulin, usually increased abdominal fat (due to being over-weight), high levels of the fat triglyceride and LDL (bad) cholesterol, and low levels of the good (HDL) cholesterol. This condition is present in more than 50 million Americans. With their salt restricted, many people with metabolic syndrome experience a significant fall in their blood pressure to normal levels.
Lowering Your Salt Intake
Surprisingly, you’re responsible for only 15 percent of the salt in your diet, and food naturally has about 10 percent of your salt. This means the food industry is responsible for 75 percent of the salt you consume. For example, the following additives contain plenty of it:
- Color Developer: Promotes the development of color in meats and sauerkraut
- Fermentation Controller: Slows the process of fermentation in cheeses, sauerkraut, and baked goods
- Binder: Keeps meat together as it cooks
- Texture Aid: Allows dough to expand and not tear
For these and other reasons, salt is a part of food processing — it’s not all for taste.
The only way to successfully reduce the salt in your diet is by switching from processed foods to fresh foods or by selecting low-salt processed foods.
Buying low-salt foods
The Food and Drug Administration has definite guidelines for food companies regarding a product’s salt-content description. Keep these terms in mind and make a point of buying low-salt foods on your next trip to the grocery store:
- Low sodium means less than 140 mg sodium in a portion.
- Very low sodium means less than 35 mg sodium in a portion.
- Sodium free means less than 5 mg sodium in a portion.
- Reduced sodium food contains 25 percent less sodium than the original food item.
- Light in sodium food has 50 percent less sodium than the original food item.
- Unsalted, No salt added, or Without added salt means absolutely no salt has been added to a food that’s normally processed with salt.
Take time to read the Nutrition Facts label on food items. Avoid items that contain more than 180 milligrams of sodium.
Avoiding high-salt foods
Table 1 shows the processed foods that are particularly high in salt. Avoid eating these foods as much as possible. Fortunately, after many years of urging and recommendations from health organizations, manufacturers have begun to lower the salt in foods, so you may find several of these items in a low-salt form. Check the food label.
|Bacon||Cooking sauces||Salad dressings|
|Bouillon cubes||Cottage cheese||Salsa|
|Canned tuna||Gravy||Sea salt|
|Canned vegetables||Ham||Soy sauce|
|Cheese||Hot dogs||Spaghetti sauce|
|Cold cuts||Olives||Tomato or vegetable juice|
Table 1 Prepared High-Salt Foods
Going on a low-salt diet
Besides avoiding high-salt foods, you can make a few other changes to lower your salt intake:
- Cook with herbs, spices, fruit juices, and vinegars, instead of salt, to add flavor.
- Eat fresh vegetables.
- Keep the saltshaker in the kitchen cupboard instead of at the table, where it’s so easy to use.
- Use less salt than the recipe calls for.
- Select low-salt canned foods or rinse your food with water.
- Select low-salt frozen dinners.
- Use high-salt condiments like ketchup and mustard sparingly.
- Snack on fresh fruits instead of salted crackers or chips.
When eating out, ask that your food be prepared with only a little salt. Request your salad dressing on the side so you can control the amount. Be careful of salt substitutes because some contain sodium. You may end up eating so much of the substitute to get that salty taste that your total sodium intake is just as high as using salt. Check the label! Some salt substitutes contain potassium and should not be used by people with impaired kidney function.
Combining a low-salt diet with DASH
Article 9 explains the DASH nutritional program in detail. Combine DASH with a low-salt diet to get the maximum blood-pressure-lower-ing effect. Some recommendations for the var-ious food groups in DASH are as follows:
- Grains: Check the salt content of all prepared grain foods, and keep the sodium less than 180 mg in each serving. Avoid any salted grain foods such as salted popcorn.
- Fruits: Avoid dried fruits with salt.
- Vegetables: Eat fresh vegetables and read the label on prepared vegetables.
- Meats: Eat fresh meats, fish, and poultry; avoid salt-cured products.
- Dairy products: Read the label and avoid products with more than 180 mg of sodium per serving.
- Fats: Avoid high-salt salad dressings and salted butter.
- Nuts and seeds: Avoid salted varieties.
- Sweets: Check the box and stay away from prepared mixes that contain more than 180 mg of sodium per serving.