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.

Wednesday, April 24, 2013

How to tell if a patient is eating well

Today I was invited to give a talk to medical students at UCSF.  The talk was about how to talk to patients about nutrition and behavior change.  I started with this question:

"How do you know if your patient is eating well?"

The first responses I received from the audience were:

"Test cholesterol."

"Test blood sugar."

"Weigh them."

"Waist circumference."

Finally, a brilliant student said, "Talk to them."

I had to reframe the question to: "How would you assess a patient's eating by only talking to them?"  We then had a good talk on objective methods to assess eating behaviors.

I was floored that most of the first answers to the question were, "order more tests."  The medical community has already taught these early medical students that a test is the answer to every question in medicine.  Is it any surprise that we order too many tests with minimal value?

On the positive side, we spent the rest of the hour talking about nutrition and behavior.  I was surprised how well the students knew about current concepts in nutrition.  I hope the next generation of physicians become engaged with their patients about nutrition.  I have faith they will, as long as the current system does not steer them in the wrong way.

Friday, January 25, 2013

Is Local Food the Answer?

In this fascinating post, the authors of Freakonomics talk about a study showing that eating local food may actually increase environmental and monetary costs.  Why?  Economists know that specialization reduces cost.  It actually make take less energy to grow something far away and transport it by boat to California, rather than just grow it here.

So local food may not be the answer to global warming.  But, was that the problem it was supposed to solve?

Growing and purchasing food locally has other advantages.  It makes food-born illness easier to track, as we know where the food is grown.  In an even larger sense, it promotes social cohesion and social interaction.

Many of the problems in our food system arise because we do not know where food comes from.  We do not know who grew it or how they grew it.  For instance, let's take eggs.  For those that eat animal products, would you eat an egg if you knew the hens lived in a crowded, dark shelter with feces covering the ground?  Or would you prefer to eat an egg that came from a farmer that you could ask how the animal lived, what it was fed, and how fresh the egg was?  Buying directly from a farmer does not require a food label; it just relies on talking.

We have created a society that is not in touch with real food.  We don't know what food is.  We think a Big Mac is food.  Buying locally restores our connection to where our food comes from.  We have to weigh those benefits with the possible negative consequences of local food.

We don't need to eat all our food locally.  We just need to be more conscious of where our food comes from.  Eating locally is only part of the answer to the problems with our food system.  It surely solves some problems, but not all.