Harvard Men's Health Watch

Salt and your health, Part II: Shaking the habit

Salt is a simple chemical, composed of equal amounts of sodium and chloride. Sodium is the crucial part; it is essential for health, but only tiny amounts are needed. All the experts agree that the average American diet contains much, much more sodium than we need, but until recently, they've been divided about the importance of salt restriction.

The key to the debate is blood pressure. Everyone agrees that high blood pressure is a major cause of strokes, heart attacks, heart failure, and kidney disease. It is also clear that even within the normal range, the lower the blood pressure, the better. But will reducing dietary sodium lower blood pressure and improve health?

It's a scientific question, but the debate has been as political as medical. Since 1998, the evidence has tilted strongly in favor of salt restriction. But progress has been slow, in no small part because of cultural preferences and economic considerations; Americans are accustomed to salty foods, and the salt sellers have a stake in keeping it that way. Much of the research on sodium and health is funded by the National Institutes of Health, but some is sponsored by the Salt Institute, an industry group.

Last month, Harvard Men's Health Watch reviewed three major studies of diet, blood pressure, and health. The multinational INTERSALT study found that a high intake of sodium is linked to high blood pressure, particularly as people age. The DASH trials found that a diet rich in fruits, vegetables, whole grains, and low-fat dairy products can lower blood pressure, and that reducing sodium provides important additional benefits. Most importantly, the two Trials of Hypertension (TOHP) studies and additional evaluations of the DASH diet showed that in addition to lowering blood pressure, sodium restriction reduces the risk of heart attacks, strokes, and cardiovascular deaths.

When it comes to sodium and your health, less is more.

Not by salt alone

Most of us will benefit from sodium restriction. But sodium is only one part of the formula for blood pressure control and cardiovascular health. To round out the picture, you should:

  • Eat a balanced diet, low in saturated fat but high in fruits, vegetables, whole grains, and dietary fiber. The DASH diet is an excellent example.

  • Exercise regularly. Simply walking for 30–40 minutes a day will help lower your blood pressure and improve your overall health.

  • If you choose to drink, keep your alcohol intake low; men should limit themselves to two drinks a day, counting 5 ounces of wine, 12 ounces of beer, or 1 ounces of spirits as one drink.

  • Get as close as you can to your ideal body weight.

  • Reduce the stress in your life.

  • Avoid tobacco in all its forms, including secondhand smoke. It may not lower your blood pressure, but it's the most important thing you can do to prevent cardiovascular disease and preserve health.

  • Get regular checkups; it's the only way to learn if your blood pressure is where it should be. And if you can't meet your goals with good health habits, your doctor can prescribe excellent medications that will help.

How much salt should you eat?

The DASH results show that nearly everyone can benefit from sodium restriction, but they don't tell any individual what to do.

At one extreme, young people with good health and normal blood pressures (below 120/80) have little reason to worry about dietary salt, at least in the short run. At the other pole are patients with heart failure, certain kidney diseases (such as nephrotic syndrome), and certain liver problems (such as cirrhosis). They need medical supervision to reduce dietary sodium to low levels, even if their blood pressures are good.

Most Americans fall in the middle of the spectrum. The average American consumes 3,436 milligrams (mg) of sodium a day, the amount in about 1 teaspoons of table salt. That's five to 10 times more than we need — but it's not necessary to reduce your intake to draconian levels to benefit from salt restriction. In 2005, the U.S. Dietary Guidelines for Americans recommended that adults consume no more than 2,300 mg a day — but that people with high blood pressure, all middle-aged and older adults, and all African Americans restrict sodium intake to no more than 1,500 mg a day. And since so many Americans have hypertension and prehypertension, that means about 70% of all adults should stay under 1,500 mg a day, but less than 5% of adults are meeting that goal.

How about patients with hypertension? According to one study, less than 20% of Americans with hypertension — the very people who need protection the most — adhere to the principles of the DASH diet. Even worse, compliance has actually declined by 7% since 1988 despite all the new evidence about the hazards of sodium. Is it any wonder that over 100,000 Americans die each year because they eat too much salt?

The DASH diet

The Dietary Approaches to Stop Hypertension (DASH) trial showed that a good diet can reduce blood pressure significantly. The diet provides twice as many servings of fruits, vegetables, and low-fat dairy products as the average American diet — but just half the average amount of fats and oils, one-third the beef and pork, and one-quarter the number of snacks and sweets. All in all, it provides about twice the volume of healthful food but just a fraction of calorie-dense junk food. The key elements of the DASH diet are:

6–8 servings of grain products a day; whole grains are best. Count one slice of bread, 1 ounce of dry cereal, and cup of cooked pasta or rice (preferably brown rice) as one serving.

4–5 servings of vegetables a day. Count cup of cooked or raw vegetables or 1 cup of raw leafy vegetables as one serving.

4–5 servings of fruit a day. Count 1 medium apple, pear, orange, or banana, cup of frozen or canned fruits, or 4 ounces of juice as one serving.

2–4 servings of low-fat dairy products a day. Count 1 cup of non- or low-fat milk or yogurt as one serving.

4–5 servings of nuts, seeds, or legumes a week. Count ? cup of nuts, 2 tablespoons of seeds, or cup of cooked beans as one serving.

No more than 2 servings of meat, poultry, or fish a day. Count 3–4 ounces, a chunk about the size of a deck of cards, as one serving.

Limited amounts of sweets and fats.

Where's the sodium?

In the salt shaker, of course. But sodium is also abundant in other additives such as baking soda, baking powder, and MSG. Remember, too, that sea salt, brine, garlic salt, onion salt, and seasoned salt all have as much sodium as ordinary table salt. "Low-sodium" salt is not much better; it's simply sodium chloride that's been diluted to make the sodium less concentrated.

These additives have lots of sodium, but they are only the tip of the salt mine. The average American gets only 6% of his daily sodium intake from table salt. Another 5% is added during cooking. Just 12% occurs naturally in foods. The remaining 77% is the sodium added to processed foods and restaurant meals.

Nearly all fresh and natural foods are low in sodium, but salt is added to many prepared and processed foods. The leading culprits include snack foods (pickles, pretzels, chips, crackers and dips, salted popcorn and nuts, and the like); sandwich meats (ham, salami, franks); smoked and cured meat; canned juices; canned and dry soups; pizza and other fast foods; many condiments, relishes, and sauces; packaged mixes for baked goods; gravies and sauces; and frozen dinners. To help you find the salt hidden in your diet, Table 1 lists the sodium content of select processed and restaurant foods. And in today's world, unfortunately, even "all natural" foods may have hidden added sodium. A typical American eats about 90 pounds of chicken a year. Without treatment, chicken has only 45 mg to 60 mg of sodium per 4-ounce portion. But one-third of the chicken on the market has been "enhanced" or "plumped" by pumping in salt water, which increases the sodium content to 200 mg to 400 mg per portion. That's not chicken feed, so if you don't want to pay chicken prices for salt water, check the fine print on the nutrition label before you check out.

If salt plays such a small role in the natural human diet, why is it so prominent in the typical American diet? Salt is an acquired taste. Over the years, we've become conditioned to the taste of salt; the food industry gives us what we want and encourages our preference to keep their profits from tumbling. It's a vicious cycle, but it can be broken. One step would be for the FDA to adopt the American Medical Association's recommendation that high-sodium foods carry a warning label. For decades, salt has been designated as an ingredient "that is generally recognized as safe," so the food industry can add as much as it wants to processed foods. Call it a toxic additive and that would change.

Table 1: Approximate sodium content of select foods

Food

Serving size

Sodium content (milligrams)

Grain products

Pasta

cup

less than 5

Rice

cup

less than 5

Cooked cereal

cup

less than 5

Instant oatmeal, cream of wheat

1 packet

100–300

Bread

1 slice

110–240

Cake and pastry

1 slice

100–400

Muffins and biscuits

1

170–590

Pancakes (from mix)

1

200–250

Ready-to-eat cereals

1 oz

75–210

Vegetables

Fresh (cooked without salt)

cup

most less than 50

Frozen (without sauce)

cup

most less than 70

Frozen (with sauce)

cup

140–460

Canned

cup

140–500

Canned (with sauce)

cup

150–900

Beans

Dried beans, peas, lentils (cooked without salt)

1 cup

less than 5

Baked beans, canned

cup

380–550

Nuts

Peanuts, cashews, almonds, walnuts, pistachios (fresh or roasted, unsalted)

1 cup

less than 20

Salted nuts

1 cup

600–1,200

Fruits

Fresh, frozen, or canned

cup

less than 10

Meat

Fresh meat

3 oz

less than 90

Ham

1 oz (about 1 slice)

240–380

Bacon

2 slices

240–350

Breakfast sausage

3

310–610

Corned beef

3 oz

850

Hamburger (fast food)

3 oz

500

Cheeseburger

1

740–810

Hot dog

1

420–680

Bologna

1 slice

220

Salami

1 slice

200–300

Poultry

Fresh poultry

3 oz

less than 90

Turkey roll

3 oz

500

Frozen turkey or chicken dinner

1 dinner

1,000–2,000

Chicken nuggets

4–5 pieces

380–470

Grilled chicken sandwich

1

920–1270

Buffalo wings with dressing

1 order

2,460

Fish

Fresh fish

3 oz

less than 90

Tuna, canned

3 oz

300

Salmon, canned

3 oz

300–470

Sardines, canned

3 oz

430

Shrimp, canned

3 oz

660

Herring, smoked

3 oz

350

Dairy products

Egg

1

60

Egg substitute, frozen

cup

120

Milk

1 cup

120–160

Yogurt

1 cup

120–160

Unsalted butter or margarine

1 tsp

2

Salted butter or margarine

1 tsp

115

Natural cheeses

oz

110–450

Cottage cheese

cup

240–450

Processed cheese

2 oz

700–900

Cheese spread

2 oz

700–900

Juices and soups

Fruit juice; fresh, frozen, or canned

1 cup

less than 10

Tomato juice, canned

1 cup

650

Vegetable juice, canned

1 cup

650

Canned, condensed, and dehydrated soups

1 cup

600–1,200

Condiments and dressings

Oil and vinegar

1 tbsp

less than 5

Prepared salad dressing

1 tbsp

80–250

Ketchup

1 tbsp

150

Meat tenderizer

1 tbsp

1,750

Condiments and dressings

Mustard

1 tbsp

170

Barbecue sauce

1 tbsp

130

Soy sauce

1 tbsp

920–1260

Teriyaki sauce

1 tbsp

690

Worcestershire sauce

1 tbsp

69

Tomato sauce

1 cup

1,500

Tomato paste

1 cup

200

Snack and convenience foods

Pizza

1 slice

500–1,000

TV dinner

10 oz

1,000–2,000

Candy

1 oz

less than 25

Peanut butter

1 tbsp

75

Pickle

2 oz

700

Olives, canned

5

192

Pretzels

1 oz

450

Potato chips

1 oz

250

Ritz-type crackers

1 oz (about 10 crackers)

270–370

Crackers, cheese flavor

1 oz

300

Popcorn, air popped

1 oz

1

Popcorn, buttered and salted

1 oz

550

Beverages

Coffee, tea

1 cup

2

Carbonated beverages

8 oz

less than 40

Wine

4 oz

12

Beer

12 oz

25

Principal source: U.S. Department of Agriculture

Shaking the habit

Since salt is so common in the American diet, low-sodium eating may seem impossible. Indeed, low-salt foods will prob ably seem bland and unappetizing — at first. But salt is an acquired taste, and you can acquire a taste for less. In fact, most people actually come to like low-sodium eating; it's no surprise, since they can taste food instead of salt.

Here are some tips to help you attain your personal goals.

  • Start changing early, so you can change gradually. People who wait until they have high blood pressure or heart disease often find it hard to cut down on salt abruptly.

  • Encourage the rest of your household to join your program. You can enjoy experimenting with low-salt recipes together, and success will be easier if there are no chips stashed in the pantry.

  • Begin by omitting salt from your table, then from your cooking. Boil rice, pasta, and hot cereal without adding salt to the water. Rinse canned foods such as tuna to remove some of the sodium.

  • Learn to use other seasonings, such as pepper, lemon or lime juice, vinegar, or herbs. Unless you have kidney disease; you take a medication that may retain potassium, such as spironolactone, triamterene, an ACE inhibitor, or a high-dose nonsteroidal anti-inflammatory drug; or you have certain other medical problems, salt substitutes that contain potassium chloride are fine.

  • Avoid frozen dinners, fast foods, convenience foods, salty snacks, and other junk food. Beware of sauces and condiments, including mustard, ketchup, horseradish, and teriyaki and soy sauces.

  • Read food labels carefully, and ask about the salt in restaurant offerings. Avoid prepared soups and tomato sauces, which are typically loaded with sodium.

  • Shop for products that are "sodium free" (less than 5 mg a serving), "very low sodium" (no more than 35 mg a serving), or "low sodium" (no more than 140 mg a serving).

  • Choose fresh and homemade foods over processed foods whenever possible. Favor fruits, vegetables, and whole grains.

Table 2: Potassium content of select foods

Food

Serving size

Potassium (milligrams)

Fruits

Apricots (raw)

1 medium

91

Bananas

1 medium

422

Cantaloupe

melon

368

Dates

5

233

Oranges

1 large

333

Peaches

1 medium

285

Raisins

cup

307

Vegetables

Asparagus

4 spears

134

Beans, kidney

1 cup

717

Beets

1 cup

518

Broccoli

1 cup

457

Carrots, raw

1 medium

195

Mushrooms

1 cup

233

Potatoes

1 medium

942

Spinach

1 cup

839

Squash, winter

1 cup

494

Tomatoes

1 medium

292

Dairy products

Milk

1 cup

349

Yogurt

8 oz

531

Fish, poultry, meat

Cod

3 oz

439

Tuna

3 oz

201

Chicken

3 oz

211

Hamburger

3 oz

297

Grain products

All-Bran cereal

cup

306

Source: USDA Nutrient Database

Perspectives

Salt is a simple chemical with an important role in human history, a complex role in human biology, and a controversial impact on human health. Although salt is no longer rare and precious, it retains enough economic clout to irritate the wounds of scientists who study the relationships between sodium, blood pressure, and health. Although some questions persist, the weight of research adds to the evidence suggesting that sodium restriction can help lower blood pressure. People who are overweight, hypertensive, or elderly need help the most — and they are just the folks who stand to gain the most from low-sodium diets. Since about 127 million Americans have hypertension or prehypertension, two-thirds of all adults are overweight or obese, and everyone will grow old, it's easy to make a case for shaking the sodium habit throughout the land.

Potassium: Good news for blood pressure

In many ways, sodium and potassium occupy opposite roles in the human body. High concentrations of sodium are present in the fluid component of blood (plasma) and in the fluids that surround the body's cells; low concentrates of potassium are found in the these same fluids. Inside cells, the situation is reversed, with potassium present in high concentration, sodium in small amounts. A large intake of potassium in the diet promotes the excretion of a large amount of sodium in the urine.

Sodium and potassium occupy opposite positions in the American diet. Lots of sodium is present in processed foods, but little is found in natural foods. Potassium, on the other hand, is abundant in many natural foods. We eat far too much sodium, but not enough potassium.

Sodium and potassium also have opposite effects on blood pressure. High dietary sodium raises blood pressure; high dietary potassium tends to lower blood pressure. In fact, potassium is an important component of the DASH diet, and a low sodium–to–potassium ratio was linked to a reduced risk of cardiovascular disease in the TOHP studies.

Setting your goals for potassium

How much potassium should be in your diet? The body can conserve potassium much as it can sodium, so we can get along with small amounts of the mineral. Still, the Dietary Guidelines for Americans recommend 4,700 mg of potassium a day, about twice what the average American gets. Remember, though, that patients with kidney disease and certain other problems need medical supervision of their dietary potassium, as do patients taking potassium-retaining diuretics (such as spironolactone and triamterene) and some other medications (such as ACE inhibitors and high-dose NSAIDs).

Foods are the best source of potassium; have a look at Table 2, and add lots of potassium to your diet — naturally.