SODIUM-WATCHERS, take heart. If it seems that cutting back on salt only makes you crave it more, just be patient. A new study shows that though the desire for salt can get worse before it gets better, it definitely can get better, and in only a matter of months.
As concern about the relationship of sodium to high blood pressure has grown, taste experts (officially known as "taste physiologists") have been experimenting with the practical side of the issue. People eat salt because it tastes good to them, says Dr. Gary Beauchamp of the Monell Chemical Senses Center in Philadelphia. He's been trying to figure out how to lower the sodium content of the diet with the least insult to the tastebuds.
Beauchamp has measured the preference for salt before, during and after subjects follow salt-restricted diets. In his first study, subjects actually preferred higher levels of salt after eating a salt-restricted diet for three weeks. Beauchamp hoped, of course, that the subjects would get used to less salty food and would end up preferring it.
But in a follow-up study, Beauchamp extended the salt-restricted diet from three weeks to five months. This time, the news was heartening. After five months on the lower-salt diet, the subjects rejected foods that had originally tasted good to them as "too salty."
From his perspective as a taste expert, Beauchamp concluded that it will probably be possible to reduce sodium in people's diets if we can "get them over the hump," the apparently temporary period of increased liking for salty foods.
Beauchamp presented his findings at a conference, "Nutrition and Blood Pressure Control," that was jointly sponsored this month by the National Kidney Foundation, the U.S. Department of Health and Human Services and the International Life Sciences Institute, a food industry group.
The conference was the scene of lively debate on the merits of lowering the sodium content of the American diet. But to anyone familiar with the decade-old issue, few new facts emerged about the role of sodium in high blood pressure, a condition that affects at least 60 million Americans.
No one denied that sodium can raise blood pressure, but as in the past, some argued that sodium-restricted diets should be reserved for those with proven sensitivity to the substance. "The data do support a relationship of sodium to high blood pressure , but it does not hold in every individual," said Dr. John H. Laragh.
Laragh, who heads the cardiology division at New York Hospital-Cornell Medical Center, expressed his belief that sodium-restricted diets are appropriate only for a minority of the population. He argued that some people might actually be harmed by diets lower in sodium.
But advocates of diets lower in sodium said it is virtually inconceivable that a moderate reduction in sodium intake could hurt anyone. Americans currently consume 10 to 20 times as much sodium as needed. "No one has shown any benefit . . . from excessive sodium in the diet," countered Dr. James Hunt, chancellor of the University of Tennessee Center for the Health Sciences.
Like other speakers at the three-day meeting, Hunt argued that drug treatment should not be considered the only approach to control of blood pressure. Nor is it necessarily the best approach to treatment, he insisted. A coauthor of the popular book "Living With High Blood Pressure," Hunt said that sodium restriction, coupled with drug treatment, often gives better control of blood pressure than drug treatment alone. In some patients, said some of the speakers, dietary changes alone can bring high blood pressure down to normal levels.
Some who support lowering the sodium content of the American diet point out that fully half the population risks developing high blood pressure. By age 65, roughly half of all Americans have the condition. For this reason, some experts believe it advisable for the general population to eat less sodium, but they acknowledge that not everyone will benefit.
Several speakers at the conference addressed the possiblity that cutting back on sodium might adversely affect health by reducing intake of important nutrients.
Two nutritionists from General Mills presented results of a survey showing the food groups that contribute the most sodium to the American diet. Grain foods headed the list. According to their survey, grain foods provide 21 percent of the "non-discretionary" sodium in the American diet. ("Non-discretionary" refers to sodium already in food at the point of purchase -- in other words, to sodium not added to food by the consumer.)
Next in line to grain foods were flesh foods -- meat, poultry and fish -- which supply 15 percent of the non-discretionary sodium. Milk and dairy products placed third, at 12 percent.
The authors of the study argued that eliminating foods in these groups from the diet in order to reduce sodium intake could cause deficiencies of important nutrients such as vitamins B-6, iron and calcium.
But the study provided critical commentary from other participants who replied that grains and many flesh foods are not naturally high in sodium. If the food manufacturers didn't add it during processing, there wouldn't be a problem, retorted Dr. Louis Tobian, who heads the Hypertension Section of the University of Minnesota Hospital. As for dairy products, only some, such as processed cheese and some natural cheeses, are high in sodium. Unless patients are on an extremely low-sodium diet, they can consume lowfat milk, yogurt and ice milk to provide the nutrients found in dairy products.
The amount of sodium added during processing has been a longstanding sore point between medical researchers and food companies. Nutritionist Bonnie Liebman pointed out that contrary to common belief, the amount of sodium added does not necessarily correspond to optimal taste. If it did, she said, different brands of the same product would have similar levels of sodium.
In fact, sodium content of the same food can vary dramatically among competing brands. Thomas' English Muffins contain 215 mg of sodium in a 2-ounce serving, while Pepperidge Farm English Muffins contain 633 mg. Differences such as these are common, says Liebman, who has been urging the FDA to require sodium labeling of foods so that consumers can compare brands.
Although sodium dominated the conference agenda, researchers also presented evidence that other substances in food may affect the blood pressure. There is now reasonably good evidence that potassium and polyunsaturated fats have beneficial effects on blood pressure. Researchers are also pursuing leads that indicate a possible role for calcium, magnesium and fiber in the control of blood pressure.