If you doubt salt is necessary for life, simply recall what blood tastes like. It’s salty. Salt is essential for survival. No human system functions without it. The sodium in it controls the body’s moisture content and thus the amount of blood within it. It regulates what goes in and out of every body cell.
Salt also has a primary influence on how you perceive flavor. The tongue senses saltiness along with the other three basic tastes: sour, sweet and bitter.
For centuries salt has been the world’s most common food preservative, an integral part of food processing and cooking. In Old Testament times it was worshiped. Later it was the subject of wars. The word “salary” derives from the money allotted to Roman soldiers to purchase rations of salt.
Of the 3.7 percent of dissolved matter in the world’s oceans, 77 percent is salt, a chemical blend of metallic sodium and chlorine gas.
Another side to salt
But in an ironic side effect of civilization, our taste for salt, perhaps a leftover evolutionary survival skill, may be promoting disease and early death. Salt is in almost everything we eat.
The culprit is sodium. Government nutrition guidelines, the National Heart, Lung and Blood Institute and the National High Blood Pressure Education Program all warn that excessive sodium can cause high blood pressure and contribute to diseases such as osteoporosis, stomach cancer and enlargement of the heart.
Nevertheless, some researchers assert that the fear of salt is overblown and that its danger applies only to a small segment of society.
Physiologists know that the body requires about 500 milligrams a day to maintain its precise concentration of sodium. Most people consume 10 times that much. One cup of chicken noodle soup, for instance, supplies about two times the daily requirement.
When the supply of sodium in the blood drops due to profuse sweating, excessive diarrhea or extreme heat, blood pressure falls and blood volume decreases until the kidneys, which filter the blood, stop excreting water and salt. (Before this mechanism was well understood, athletes and others often took salt tablets if they were sweating a lot. But researchers discovered that was unnecessary: The American diet provides more than enough salt.)
When we take in too much
The mechanism also works the opposite way: When the body has too much sodium, blood pressure increases to force out the excess through urine or sweating.
Most people can tolerate a lot of excess sodium without ill effects, researchers say, but it requires them to maintain a higher than normal blood pressure.
What’s wrong with high blood pressure, or hypertension, as a doctor would call it?
It puts additional strain on the arteries and makes them more susceptible to blood clots and rupture, or stroke. The risk increases with age, because blood vessels become less flexible, contributing to consistently higher blood pressures.
High blood pressure also causes the heart to work harder until it wears down and fails to pump efficiently, making hypertension a major contributor to heart attacks.
And although the kidneys can handle a wide range of sodium intakes, continuously high blood pressure can cause them to fail.
It is well established that restricting sodium lowers blood pressure for some people, particularly older people and those who already suffer hypertension. Still open to debate is whether a low-salt diet can prevent hypertension from developing in the first place.
Weaning from salt
Even for people who clearly would benefit from a lower-salt diet, sticking to one is difficult, says dietitian Richard Mattes, a professor of nutrition at Purdue University, West Lafayette, Ind.
“Marked and sustained reductions have been problematic even among those who are highly motivated,” Mattes says.
It’s not that humans can’t reduce their craving for salt, he says. Research shows that after limiting their exposure to salt for as short a time as 8 to 12 weeks, people can wean themselves away from a taste for it. They even find salted food unappetizing.
But we don’t live in a low-salt world. Most people believe they can cut down on salt by throwing away the salt shaker. The truth is, most salt comes from less controllable sources. Any attempts to do without it are immediately thwarted by even the most innocuous foods, such as a piece of cheese or a peanut butter sandwich.
Americans get up to 80 percent of their salt from processed foods and restaurant meals, surveys show.
Some sources are obvious, such as soups, pickles and crackers. Many are not, such as bread, cereal, lunch meats, milk, cheese and canned foods. (See chart on this page.) Companies add salt to processed food for the same reason it’s on the dinner table: Salt is an inexpensive way to boost flavor.
And America loves it. Despite health professionals’ efforts during the 1970s to reduce national consumption, the amount of salt each American consumes each day hasn’t changed in the last 10 years, says Richard L. Hanneman, president of the Salt Institute.
Institute statistics show that food grade salt sales have fluctuated from about 9 pounds per person in 1978 to 7.2 pounds in 1983 (a low), back to 9 pounds in 1990 and up to 10.4 pounds per person in 1995.
Americans get 9 to 10 grams of salt a day (5,000 milligrams of sodium). That’s about 2 teaspoons, or almost twice the limit recommended by the dietary guidelines.
HOW MUCH SALT IS IN IT?
Here’s how the sodium can sneak up on you. (Nutrition guidelines recommend no more than 2,400 milligrams of sodium per day.)
All numbers are for one serving. %%
Fast food: milligrams
Denny’s grilled cheese 2,690
Hardee’s Big Country Breakfast w/sausage 2,240
Long John Silver’s shrimp scampi 2,050
Arby’s biscuit with ham 1,169
Burger King chicken sandwich 1,440
Burger King ham, egg and cheese Croisan’wich 1,373
Pizza Hut Supreme Personal Pan pizza 1,313
Popeye’s Cajun rice 1,260
Taco Bell Burrito Supreme 1,181
Arby’s cashew chicken salad 1,140
KFC Colonel’s chicken sandwich 1,060
Domino’s veggie pizza (2 slices) 1,035
Wendy’s large baked potato 1,000
McDonald’s Quarter Pounder w/cheese 890
IHOP Belgian waffle 882
Taco Bell taco salad 910
McDonald’s Egg McMuffin 710
Wendy’s french fries (large) 280
From the grocery shelves (per serving): milligrams
Campbell’s black bean soup (1/2 cup) 1,030
Oscar Mayer baked ham (3 slices) 790
V8 juice (6 ounces) 770
Bravo sausage pizza (1 slice) 760
Prego spaghetti sauce (1/2 cup) 700
Weight Watcher’s Paella Rice and Vegetable entree 680
Tyson Fat Free chicken (2 slices) 460
Oscar Mayer hot dog (1) 450
Velveeta cheese (1 ounce) 420
Kellogg’s Raisin Bran (1 cup) 390
Green Giant frozen corn with butter sauce (3/4 cup) 320
Kraft Swiss single (1 slice) 320
General Mills Cheerios (1 cup) 290
Pepperidge Farm sandwich bread (2 slices) 260
Butternut white bread (2 slices) 250
Starkist canned tuna (2 ounces) 250
Walden Farms fat-free blue cheese dressing (2 tablespoons) 240
Butternut hot dog bun (1) 220
Quaker Oats Cap’n Crunch cereal ( 3/4 cup) 210
Stella Mozzarella (1 ounce) 200
Ruffles potato chips (1 ounce) 190
Nabisco Oat Thins (1 ounce) 190
Skippy peanut butter (2 tablespoons) 150
Ritz Crackers (5) 135
Hellman’s mayonnaise (1 tablespoon) 80
%% Sources: ”The Fast-Food Nutrition Counter”and product labels
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Steven Pratt’s e-mail address is SMPrattNEXT WEEK: Is our typical daily dose of salt unhealthful? Two prominent medical journals can’t agree.
