Champagne corks will be popping at the Salt Institute, and fast food executives and food processors will be joining the party. A new study published in the May 4, 2011 issue of the Journal of the American Medical Association concluded that subjects who consumed the least amount of salt were the most likely to die of cardiovascular disease - exactly the opposite of the results that would be expected. The study followed mostly Caucasian Europeans, none with a history of cardiovascular disease, for an average of 7.9 years. You can view the abstract here, but full text is available by subscription only.
As reported in the "New York Times," the Centers for Disease Control and Prevention (CDC) immediately criticized the study, stating that there weren't enough subjects and they were too young. Except that there were 3,681 subjects, and their average age was 40.
This is not the first study with results that challenge conventional wisdom about what we should or shouldn't eat, and it surely won't be the last. The difficulty with human subjects in the best of nutritional studies is there is absolutely no way to control every aspect of diet over a long period of time. People forget what they eat, even when keeping journals, and sometimes they don't report the truth. Quality of foods consumed varies as well. And just one nutrient segmented for investigation means all others are ignored.
In this case, the nutrient is sodium, the consumption of which authors Katarzyna Stolarz-Skrzypek, M.D.PhD, et al. measured by urinary excretion (they consider that to be the best way to assess salt intake. A questionnaire at baseline, and follow up, collected medical history that included smoking and drinking habits, weight as measured by body mass index (BMI), medication use, education and blood glucose and cholesterol levels. Diabetes was self-reported.
I read the study. Exercise and diet were not a part of baseline or follow up questions, but it would be terrific to know if those who consumed the most salt were also more active, or if they ate less sugar, less fat and more fruits and vegetables. But this study had one objective only -- to determine if sodium intake in and of itself can predict cardiovascular disease and death in healthy subjects because, as stated in the abstract, "observational studies and short-term intervention trials suggest that population-wide moderation of salt intake might reduce cardiovascular events."
In other words, we are told that we should eat less salt to prevent heart disease. This has resulted in aisles filled with low-sodium and no-sodium foods, and now, a lot of questions. Is the loss of flavor worth it? Is something else in high-sodium foods, which are always processed, causing heart disease? Can the people who took their salt shakers off the table put them back? When we cook at home, can we stop worrying and salt to taste?
This study is intriguing enough on its own, but the fast food and food processing industries will make sure the message reverberates for a long time. And this will just add to the confusion about what to eat -- we may see "The High Sodium Diet" any day now.
Current Guidelines for Sodium
Sodium and salt are not the same thing. Table salt is sodium chloride - 40 percent sodium and 60 percent chloride. Processed foods are loaded with it to add what some food technologists call "craveability."
The CDC currently tells us to limit intake to 2.3 grams of sodium per day, which equals about one teaspoon of table salt. If one is 51 years of age or older, African American, has high blood pressure, diabetes or chronic kidney disease, that amount is lowered to 1.5 grams. The "Dietary Guidelines for Americans" published similar recommendations in January. The American Heart Association states 1.5 grams a day -- which is about 2/3 of a teaspoon -- is ideal for everyone.
The CDC and AHA have numerous studies to support the theory that lowering sodium intake will prevent heart disease. For example, one published in JAMA less than a year ago concluded: "Excessive dietary sodium consumption increases blood pressure, which increases risk for stroke, coronary heart disease, heart failure, and renal disease." ( Gunn et al, "Sodium Intake Among Adults, United States, 2005-2006." August 18,2010, JAMA. Vol. 304 Iss.7; pg. 738).
The fact is, there are studies that support a low-salt diet as being heart friendly, and others that don't. It is not definitively known if salt should be avoided as much as possible, if it is fine in moderation, or if it can be consumed freely. We do know that as a species we have been using salt for millennia and we need it for optimal health.
Processed foods account for 75 oercent of the salt in our diets, and when our diet shifted away from real foods to food that is fast, convenient and processed, our salt intake greatly increased. If we eat real food -- fruits, vegetables, whole grains, seafood, poultry and lean meats -- we can probably say "pass the salt" whenever we want, and be just fine.