"The word is out to shake the salt habit," notes Brookline, Mass., sports nutritionist Nancy Clark. "I regularly counsel nutrition-conscious athletes who restrict their sodium intake by choosing only salt-free foods." When these active people complain of muscle cramps and excessive fatigue, they're shocked to learn that these symptoms might be related to sodium depletion.
"But isn't salt bad?" is their typical reply.
"It's a paradox," acknowledges Beverly Hills sports nutritionist Evelyn Tribole. "On the one hand, most Americans ingest at least three times the recommended upper limit of sodium." This is why public health officials have advised Americans to cut back on salt. "But on the other hand," she says, "if you're careful about your diet and you're working out a lot and sweating profusely, restricting sodium may get you into trouble."
In the extreme, too little sodium can send people into a salt-depleted state called hyponatremia, characterized by dizziness, confusion, muscle weakness and loss of coordination. Once considered rare, hyponatremia is increasing, says Tribole, who says 13% of the finishers in the 1987 Ironman Triathlon in Kona, Hawaii, developed the ailment. Those at greatest risk are participants in events lasting longer than four hours, she says, or in events in which the action is intermittent but lengthy, such as tennis matches. Athletes in lengthy events who drink only water can develop the problem, since the water can dilute the levels of sodium in their blood.
Although sodium is an essential mineral, it became villainized because "scientists once thought that sodium caused or increased the risk of high blood pressure," notes Kris Clark, director of sports nutrition at Pennsylvania State University. "But we now know that only a small segment of the population experiences salt-related changes in blood pressure. In fact, sodium is just one mineral out of several [including calcium and magnesium] that may or may not affect hypertension."
Most active, fit people don't need to restrict their salt intake, says Clark, who advises athletes to be sure to replace the sodium they lose in sweat. But that doesn't mean putting saltshakers back on the table.
"The best way to replace your sodium is by eating nutritious foods that contain it," she says. Examples of healthy foods high in sodium include cheeses, nuts and some cereals. Downing a sports drink after working out can be an easy way to replace lost sodium. And even a bag of salted pretzels or popcorn can be a good choice on a hot, active day, says Clark.
Sodium isn't the only mineral lost in sweat that needs to be replaced, says Seattle nutritionist Susan M. Kleiner.
"Sodium is lost in the greatest amount," she says, "but potassium, chloride and magnesium are all lost in sweat too," she says. Fruit and vegetables contain minerals and are excellent post-workout snacks, says Kleiner, who advised the Cleveland Browns to have a "huge table of fresh fruits" available at their training camp when players were working out twice a day in intense heat. Potassium-rich juices such as orange, pineapple and apricot are also great post-workout drinks.
A healthful sodium intake ranges from 500 to 2,400 milligrams, or no more than 1 1/4 teaspoons of table salt daily, Kleiner says. This is much less than the American average of two to three teaspoons per day. Yet it is more than the trace amounts consumed by nutrition-conscious athletes who unnecessarily restrict their sodium intake.
However, if your physician has found that you have sodium-sensitive hypertension, ask for sodium guidelines individualized to your condition and activity level. Even if you don't have sodium-sensitive hypertension, you may need to limit your salt intake if you are in a high-risk group. This includes people who have a parent with the condition, are over 50, have kidney disease or are African American.
But most active people don't need to restrict sodium and should replace lost salt by eating nutritious foods containing it.
"If after a bout of sweaty exercise you hanker for some pretzels or salty food," says nutritionist Clark, "eat them!"
* Fitness runs Monday in Health.