Saturday, February 28, 2015

Nutrition Confusionism

The new draft Dietary Guidelines were just released. I won't post the link here, because few people will read the dense document. The major take home points were: eat more whole fruits and vegetables, less sugar, less meat, less saturated fat, less salt, and don't worry about cholesterol too much.

I was just at the Partnership for a Healthier America conference, where lots of nutrition experts mingled with lots of food company executives. There was a lot of confusion and snickering amongst the group. Some decried the Committee for stating that how much cholesterol you eat is not that important. Others asked why saturated fat and salt were still emphasized, even though the best evidence does not support reducing these food ingredients to improve health.

The non-scientists asked the scientists why nutrition is so confusing. They made it sound like the science was constantly changing, but the guidelines committees ignored the science. I listened to this segment of NPR's Science Friday, where the host asks why the nutritionists, "have known that eggs are ok to eat, but the rest of us didn't."

Who is at fault here? I'm not sure. But I recently skimmed through my nutrition courses from when I was an undergraduate at Cornell. I went through my notes where I indicated that we were taught that is very difficult to find an association between salt and hypertension within a population. I also had copious notes stating that the connection between calcium intake and bone health was weak. (Thanks to Charles McCormick for this great class!)

I then went to my intro course table of contents and found our lecture titles: "Diet and serum cholesterol: environment or biology?", implicating that cholesterol in the diet doesn't matter that much. Another was, "Ambiguous connections: salt and hypertension". Thank you Dr. Levitsky for teaching us how to think about the facts without the hype.

The "new" news that we do not have great evidence dietary cholesterol, salt, and other nutrients are critical for health, is really not that new. I was learning it back in 1997.

So now people are telling us nutrition is confusing and that we said salt, cholesterol, and fat are bad and then good. I'm not sure where the confusion comes from. Is it from nutrition researchers who devote their careers to studying the role of one nutrient and its effect on health? Is it from journalists who love to sensationalize the latest food craze based on one study? Or is it from food companies who make so many claims about food and health, that we end up just buying whatever sounds good at the time?

I'm not going to blame one group. We are all part of the problem. But, one thing has been consistent throughout the years. This fact is summed up in this line in the new dietary guidelines report:
"Vegetables and fruit are the only characteristics of the diet that were consistently identified in every conclusion statement across the health outcomes."
So just follow the simple advice to eat more (whole) fruits and vegetables. (Sorry smoothies and vegetable juices don't count.) Avoid the processed junk. That advice is probably a few generations old. 

Monday, November 10, 2014

Thoughts on the Berkeley Soda Tax

This is a repost from the National Physician's Alliance Blog:

Many political pundits are trying to decipher the lessons from the 2014 midterm elections. I will not try and do that here. But, some of the most interesting results have come from ballot measures. While many people voted for conservative officials, these same voters voted to legalize marijuana, prevent a personhood amendment, and raise the minimum wage.
One of the most interesting measures that passed was the soda tax in Berkeley. San Francisco voters also voted in favor of the tax, but did not reach the 2/3rds majority needed to pass. (The 2/3rds threshold has to do with California law on new taxes.) Others have tried institute a soda tax. The two most notable examples were New York City and Richmond, CA. Both resulted in the American Beverage Association (ABA), an industry trade group, spending millions of dollars to defeat the measures. The ABA spent a few more million in the recent ballot initiative in Berkeley. By law, companies have a fiduciary responsibility to maintain profits for their shareholders. Thus, my conclusion is that they had to spend this money. They feared profits would decline if these measures passed.
The evidence is fairly clear on the likely effects of a soda tax. Various economists have done simulations to show that a tax will likely decrease consumption and purchasing. The health economists have also simulated how many people will be prevented from getting diabetes and heart attacks. Of course, all simulations are based on assumptions. Since we do not have an actual soda tax yet, it is hard to predict exactly what will happen.
But, early indications from data in Mexico, after their soda tax was instituted recently, is that sales are decreasing. If other assumptions hold up (e.g. that people will not go eat candy instead), Mexico’s policy could have an impact on public health. The effects will be more difficult to measure in Berkeley. Berkeley is a small city with many surrounding urban areas without a soda tax. It also has a population that is often changing, due to the University population. However, it still offers us an interesting experiment to see the possible effects of a soda tax. Particularly interesting will be the effect on Berkeley youth.
A signifiant consequence of Berkeley passing a soda tax is a possible ripple effect. Other cities interested in experimenting with public health policy could think about passing a soda tax. California has often been an experimentation ground for innovative policies. The policies preventing smoking in public places started here, leading the way for cities worldwide to institute these bans.
While libertarians may protest against these policies, people still have the freedom to choose whatever they like to purchase. Taxes already exist on other foods in California, such as restaurant food and frozen meals. The soda tax just adds sugary beverages to the mix, albeit at a slightly higher rate.
Finally, many believe that the actual tax is not the real intervention here. The tax on sugary beverages just gets us all talking about the harms of drinking 10 (or many more) teaspoons of sugar at a time. The media is talking about it. Social media is talking about it. If the tax in Berkeley signals to people that drinking sugar is not the “cool” thing to do, than maybe a few more parents will think twice about buying their kids a sugary drink.

Friday, February 28, 2014

Childhood Obesity, Headlines, and Jelly Beans

Remember that game where you guess how many jelly beans are in a jar? Well, if I guess once, I'll probably be wrong. But if I'm allowed to guess 500 times, I might get it right once. But that doesn't mean I'm a good guesser of jelly beans numbers.

The same concept applies to research studies. The more times you test a question, the more likely you are to get a postive result. That doesn't mean that the answer to the question is "yes". It just means you guessed so many times that your were bound to get a correct answer.

The New York Times Missed this point in their article when they wrote the headline:

"Obesity Rate for Young Children Plummets 43% in a Decade"

Sounds like a huge drop. I wish it was. But the researchers tested many age groups to see if there was a decline over 10 years. They checked the age ranges 2-5, 6-11, 12-19, 20-39, 40-59, and >60. When you "guess" if there is a decrease in obesity in all of these age groups, you are likely to find one "yes".

The researchers admit this and even caution interpreting their results this way:

"When multiple statistical tests are undertaken, by chance some tests will be statistically significant (eg, 5% of the time using α of .05). " 

And they conclude:

"Overall, there have been no significant changes in obesity prevalence in youth or adults between 2003-2004 and 2011-2012. "

Yet some how the New York Times missed this, and focused their headline on a minor result. While we might have made small gains against childhood obesity, we haven't really begun to change the trajectory of the epidemic.


Friday, January 24, 2014

Can Subway be Healthy?

Today, Subway announced a new agreement with the Partnership for a Healthier America (PHA). PHA is a non-profit group that was started by First Lady Obama to reduce obesity in America.

When I saw Mrs. Obama speak last year at the PHA conference, she was really starting to emphasize that marketing is a big cause of overeating. You can provide all the "health choices" you want, but if you price the unhealthy ones lower, and have ads all over the television for them, they are going to sell more.

The new PHA agreement with Subway takes a step in the right direction. As part of the agreement, Subway will form a policy on advertising to children. (Hopefully PHA will have to approve this policy.) In addition, they will spend $41 million to advertise fruits and veggies to children. This type of advertising is badly needed to compete with the billions of dollars that advertise junk foods to kids.

So the real question is: will this get kids to eat healthier at Subway? In our study of what teenagers buy at Subway and McDonald's, we found they were eating a lot of processed food, few veggies, and a lot of calories.

My view is that the change in marketing is a positive step. But, there is still a problem with much of the food at Subway. We found that teens ate 2,149 mg of sodium in a Subway meal. That's more than 3 times what the National School Lunch Program recommends. Now, in truth, salt amounts are not very important for young kids. But the amount of salt tells us that the food at Subway is highly processed. For instance, the meat and bread have a lot of salt because they are highly processed. And we know that processed food leads to many of the problems of obesity. Notably, in the agreement they were only able to agree to 935mg of sodium in kids meals. That is more than our panel of experts and RAND recommended (700mg).

How else could we know if kids are eating healthier at Subway? I would want to know if they are eating more vegetables. I do not see any specifics in this agreement about Subway reporting how many servings of veggies they are selling to kids. PHA often does require these types of reports, but I do not see it in the press release. The best way to study this is doing what I did: collect receipts from kids and calculate what they are eating. But, it would be much easier if Subway would give vegetable sales out, so that researchers (like me) could analyze it.

What happens if they do get kids to eat more veggies, and somehow less meat and refined grains? What happens when the kids get to the cash register? For those of you who frequent Subway, you know there is a giant display of cookies. The sales clerk almost always asks, "Would you like a cookie and a drink with your sub?" Having cookies at the cash register is a risk factor for disease. So the easiest thing Subway could have done to improve health is to move the cookies to a place kids are less likely to ask for them, and parents are less likely to buy them.

I congratulate Subway and PHA for the agreement, but would like to see some objective and public research/analysis. Without this analysis, the public will not know if this is another Subway marketing scheme or an improvement in what kids are eating.

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.