Salt or high sodium intake in diet has drawn attention of researchers for a while now. The U.S. Food and Drug Administration held a day-long hearing today, discussing strategies to help Americans cut the salt from their diets as a latest attempt to curb sodium in the American diet.
A diet high in salt raises blood pressure, which increases the risk of heart attacks, strokes and a host of other cardiovascular problems. If the food industry, restaurants and citizens cut their daily salt intake, the FDA says, the national burden of cardiovascular disease would be eased.
The FDA's goal is to get the food industry to gradually reduce the amount of salt in processed and restaurant foods, which account for 75 percent of Americans' salt intake, according to the U.S. Centers for Disease Control and Prevention.
However many experts believe that the risk of heart disease due to too much salt may be overrated. “Other than in those patients with underlying heart or kidney failure, there is little conclusive evidence that moderate salt intake actually increases heart disease risk,” said Dr. Stuart Seides, associate director of cardiology at the Washington Hospital Center.
At the forefront of the fight to save salt is the Salt Institute, an industry group representing salt manufacturers. “There are biological processes, physiological processes that respond when the body gets too little salt,” Mortin Satin vice president of research at the Salt Institute said. “The data is not there to warrant salt reduction, and the government is willing to put the entire country into what is effectively a clinical trial.”
Satin and other pro-salt supporters point to a handful of studies suggesting that low-sodium diets are ineffective and may even do harm.
The new analysis, led by Niels A. Graudal, M.D., a researcher at Copenhagen University Hospital, in Denmark, is an update of a similar study (known as a Cochrane Review) published by the same authors in 2003. Graudal and his colleagues report no financial ties to the salt or food industries. Their study published Wednesday in the American Journal of Hypertension analyzed 167 studies of salt intake and found that a low-salt diet seemed to have a minimal effect on reducing blood pressure, and increased certain factors associated with heart disease, such as cholesterol, triglycerides and hormones associated with heart attacks.
The study found that eating less than 2,800 milligrams of sodium a day helped lower blood pressure. But the reductions were small - an average of 1% for people who had normal blood pressure to begin with and 3.5% for people with high blood pressure. People on lower-sodium diets had an average 2.5% increase in cholesterol and a 7% increase in bad blood fats called triglycerides compared to people who were eating more than 3,450 milligrams of sodium - an amount that's close to what the CDC says the average American eats every day.
Lower-sodium diets also boosted levels of the hormones renin and aldosterone, which can raise blood pressure. Researchers say that may be one reason that slashing salt from the diet has only modest effects on blood pressure.
“We know that a decrease in blood pressure would probably improve or decrease the risk of cardiovascular death but, on the other hand, an increase in [cholesterol] would increase the risk of cardiovascular death,” Graudal says. “It's likely that these two antagonistic effects will out-balance each other, so there will be no net effect of sodium reduction on people with normal blood pressure.”
Overall, experts say there is overwhelming evidence that a reduction in sodium improves heart health. Dr. Norman Kaplan, a professor of internal medicine at the University of Texas Southwestern Medical Center, called it a life-and-death issue. “More than 99 percent of the medical/scientific world simply are not wrong,” Kaplan said. “Moderate salt reduction is an absolute necessity and can be attained by deletion of some of the salt added to virtually all processed food.”
“Salt intake is most dangerous for the person with left ventricular weakening, or congestive heart failure, who really need to be on a low sodium diet,” said Dr. Chip Lavie, medical director of cardiac prevention at the Ochsner Clinic Foundation and Hospital in New Orleans. “However, for thin people with good heart function who have low levels of blood pressure, it probably is not so important to keep salt low.”
For those groups at special risk or for others who simply want to keep their salt low, Dr. Clyde Yancy, chief of cardiology at Northwestern Memorial Hospital in Chicago, said it's exceedingly difficult, given the amount of salt that hides in unlikely foods like bread, cookies, and ketchup. “Nearly 60 percent of our sodium consumption is embedded in our foodstuff and is consumed passively,” Yancy said. “Ideally, we would consistently have lower sodium options for most if not all food items with clear labeling. How can a message of the provision of choice in a free market society not be palatable?”
Certain food companies have proved willing to compromise on the salt content of their foods, balancing consumer demand for taste with medical and federal concerns about salt. McDonald's, Kraft, and Campbell's are among the companies that have instituted voluntary sodium reductions in some of their products.
Dr. Jay Cohn, director of the Rasmussen Center for Cardiovascular Disease Prevention at the University of Minnesota, said even eliminating the very high salt content of certain foods like soups or tomato juice would make a difference. “Modest restriction will not harm anyone and probably will have some small benefit on the whole population,” Cohn said. “It is nothing like smoking, which helps nobody and has a profound adverse effect on individuals and on the population.”
Last week, in a news release, Michael F. Jacobson, executive director of the Center for Science in the Public Interest, called the high amounts of salt in processed foods “the single deadliest ingredient in the food supply, contributing to the premature deaths of tens of thousands of Americans each year.”
New U.S. dietary guidelines now recommend that people aged 2 and older limit daily sodium intake to less than 2,300 milligrams (mg). People aged 51 and older, blacks and anyone with high blood pressure, diabetes or chronic kidney disease should consider going down to 1,500 mg per day, many experts say. And the American Heart Association believes the 1,500-milligram-a-day recommendation should apply to all Americans. The average American probably consumes 3,400 milligrams of sodium a day which, by these standards, is way too much.
The advice to cut salt should be taken seriously by people who are “salt-sensitive” – those whose bodies hang on to the salt they consume, which drives up their blood pressure and creates chronic problems. About 20 percent of the population is salt-sensitive, particularly people who are overweight, African-American, or who have high blood pressure. The CDC recommends that these groups keep their daily salt consumption under 1,500 milligrams.
Study shows link between air pollution, stress, and heart health risk