Wednesday, May 15, 2013

Salt: How bad is it?

Back in the 1990s, I took two courses that studied the effects of salt on health. Both courses questioned whether reducing salt intake would improve health. In my introductory nutrition course at Cornell, Dr. David Levitsky started to break down the evidence on salt. He showed that reducing salt only reduced blood pressure in some individuals (i.e. those that were salt sensitive). 

I took another course where we really dove into the evidence around salt. Dr. Charles McCormick showed us evidence that there was tremendous variation in salt's relationship with blood pressure. In addition, weight was an important determinant of blood pressure, that overshadowed the effects of salt. Finally the ratio of sodium to potassium was a stronger predictor of high blood pressure, than sodium alone. (Potassium is found in fruits and vegetables.)

A good review of the recent evidence doubting the connection between salt and cardiovascular mortality is here, by friend Dr. Sean Lucan. He states, "Attempting to Reduce Sodium Intake Might Do Harm and Distract From a Greater Enemy."

There have been many skeptics in the salt and high blood pressure connection. Now we finally have an ally: the prestigious Institute of Medicine. They issued a report today saying:

“These new studies support previous findings that reducing sodium from very high intake levels to moderate levels improves health,” said committee chair Brian Strom, George S. Pepper Professor of Public Health and Preventive Medicine at the University of Pennsylvania Perelman School of Medicine. “But they also suggest that lowering sodium intake too much may actually increase a person’s risk of some health problems.”

While salt may not be a primary cause of death, it is a marker of processed food. In our recent study, we found that adolescents ate a tremendous amount of sodium at Subway and McDonald's. It may not be that the salt itself is the harmful part of this diet. It simply may be that foods with high salt are are heavily processed food-like substances. Reducing the amount of salt in these heavily processed "foods", such as processed meat and snack foods, is unlikely to have a very positive effect on health. The real gains will happens if we can get people to eat less of these foods and more potassium containing foods: vegetables.

So enjoy your salt when you add a little to your food. But stay away from foods with a lot of salt on the label. They are likely foods that are shortening your life.


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