What do farmer's market chickens, motorcycles, and unpasteurized milk have in common?

A friend sent me a link to a new study in the journal in the Journal of Food Safety. The study shows that 90% of the chicken sold at a farmer's tested positive for Salmonella.  By contrast, only 52% of non-organic grocery store chickens and 28% of organic grocery store chickens tested positive for Salmonella.  In addition, the study found that for another illness-causing bacteria, Campylobacter, 28% of farmer's market chickens were positive but only 8% of non-organic grocery store chickens and 20% of organic grocery store chicken.  So regardless of whether you buy conventional or organic chicken at the grocery store, it is likely safer than that bought at the farmers market (at least the farmers analyzed in this study).   For one bacteria (Salmonella), organic is safer, for another (Campylobacter), conventional is safer. 

Why is this result interesting?  Because the findings are likely to be strongly at odds with most people's beliefs.  I suspect (but do not know for sure) that if asked, most people would say they think foods from farmers markets are safer than from grocery stores.  They would also likely assert organic is safer than conventional.  Yet this evidence (and other studies like it) is at odds with people's beliefs.  

I don't have a problem with people eating at farmer's markets.  Go for it!  But, ideally one should act knowledgeably, knowing full well the risks they're undertaking.  And I fear all the hype often causes people to mis-perceive the true benefits and risks of conventional, organic, and local foods.  

A similar problem exists with unpasteurized milk (or raw milk).  Although it is illegal in many states, many people want to buy unpasteurized milk.  Again, I say go for it (as long as they are two consenting adults; kids may be a different story at least if they're not your own).  But, let's not be glib about the safety risks.  Sure, it might be possible that pasteurization kills some healthy bacteria but it is certainly true, and scientific studies clearly show, that pasteurization kills illness-causing bacteria.  

So, why do we have government regulations that ban unpasteurized milk but promote farmer's markets?  Maybe the risks are larger or are more well known in one case (raw milk) than the other (farmers market meat).  One of the proper roles of government, I believe, is to provide objective-science based information.  What people do with that information is up to them.  But, it does bother me a bit when certain foods attain a moral status that causes people to under-estimate risks and over-estimate benefits.  Kahneman talked about this problem in his book Thinking Fast and Slow: something that seems good is therefore perceived unrisky and vice versa.  It also troubled me that many calls for food policies by food activists seem to be based on inaccurate perceptions of risks and benefits.  

What does this have to do with motorcycles?  Regulations in many states don't allow people to ride without helmets (helmet-less riding is banned) .  Clearly, riding a motorcycle without a helmet is risky.  How much riskier is it than eating farmers market chickens or drinking unpastuerized milk?  I don't know.  Strangely, in Oklahoma, we allow motor cycle riding without a helmet.  But, sales of raw milk in grocery stores is banned (my understanding is that it can be bought direct from the farm in OK).  So, people are presumed smart enough to weigh the risks of riding a motorcycle without a hat but not smart enough to buy raw milk from a grocery store?  Seems like a consistent paternalist would outlaw both.  Or a consistent libertarian would make both fully legal.  Either way, shouldn't we all want the best information to make choices?  

What is Natural Food Anyway?

At little over a month ago, I discussed some of the ongoing legal challenges that are swirling around "natural" claims on foods.  One of the big challenges is that the word "natural" is nebulous and is vaguely defined by regulators.   

I thought I'd try to shed a little light on the subject by making use of the survey project I just started and asking consumers what they think the word means.  In June, I added two questions to the survey.  The first question listed 10 statements and individuals had to place them in a box that said "I believe foods containing this ingredient are natural" or one that said "I DO NOT believe foods containing this ingredient are natural."  The order of items was randomized across respondents (sample size is 1,004, demographically weighted to match the US population, sampling error is about +/- 3%).  

The results indicate that most people think added cane sugar, salt, at beet sugar are "natural" but HFCS, sodium chloride, and biotechnology are not.  Interestingly, salt and Sodium Chloride are the same thing!  Yet, using the technical/scientific name reduces the % perceiving salt as natural from 65.6% to 32%!

Processed foods are seen as least natural.  "Processed food" is also a vague term.  Is cheese a processed food?   

The second question I asked was the following, "Which of the following best fits your definition of 'natural food'?"  I gave four options, and here is the % of respondents choosing each option.

The majority of respondents thought that the best definition (at least among the four I included) was, "fresh foods with no added ingredients and no processing."  

I suspect many of the foods sitting on a grocery store shelf that use the word "natural" do not meet this definition consumers found most descriptive.  

Assorted Links

A new estimate of the volume of food waste

Was the unapproved release of GMO wheat a result of sabotage?   

Think farmer's market chickens is safer than grocery store chicken?  Think again.   

Apparently Stossel got a little push back for his segment on GMOs  

Stossel teaches the kids

Last night, I talked about biotech and GMOs on the John Stossel show.  I haven't yet been able to find a link to the entire show, but it is summarized here.   They edited down the segment I was in but overall, I was pleased with how it turned out.  

 I was particularly pleased when my older sister sent me the following picture of her kids (my niece and nephew) watching the show.  I suppose the lesson here is that if you want your kids (and nieces and nephews) to pay attention to you - get on TV.  Hey, they might have actually learned something!   

Economists, Fat Taxes, and the 3500kcal rule

Economists are often sought out to help determine the effects of fat and soda taxes.  We are generally well-equipped to estimate how much less of a particular type of food will be eaten when prices increase as a results of a tax.  However, we are much less well-equipped to go the next step and figure out how changes in the consumption of a food results in a change in weight - the key statistic of interest.  That last step requires some knowledge of nutrition, biology, and metabolism.  

Unfortunately, it turns out that one of the critical "thumb rules" that we economists have used from those literatures, that a change in 3500 kcal will equate to a change in 1 pound of body weight, is likely highly misleading and overstates the effects of the tax (not to mention that it says nothing of when the weight change will happen or how long it will take to happen).  

I've previously blogged about some of the issues with this thumb rule but I'm not sure how widely the problem is understood or recognized among economists.  For example, here are some quotes from some recent, otherwise well-done papers.     

Okrent and Alston in the American Journal of Agricultural Economics in 2012 (free version here) said:

One frequently used relationship in textbooks (e.g., Whitney, Cataldo, and Rolfes 1994) and academic articles that address the potential impacts of fiscal policies on weight (e.g., Chouinard et al. 2007; Smith, Lin and Lee 2010) is that a pound of fat tissue has about 3,500 calories. We used this multiplier to convert changes in annual calorie consumption into changes in body weight.

Dharmasena and Capps in the Health Economics in 2011 said:

Finally, using the conversion ratio of 3500 cal per pound of body weight, we calculate the induced change in the per capita body weight in pounds as a result of aforementioned change in the per capita caloric intake.

Kulcher et al in Applied Economic Perspectives and Policy (formerly the Review of Agricultural Economics) in 2005 said: 

Assuming that no food would be substituted, at 3,500 calories per pound of body weight (American Dietetic Association), the [estimated] reduction translates into less than a fourth of a pound.

To be fair, I didn't appreciate the problem till only recently.  My own paper with Schroeter and Tyner in the Journal of Health Economics in 2008 stated the following (although we used a different calculation to derive weight changes):

On average, in order to gain (lose) one pound, a person needs to consume (burn) 3500 calories in addition to the typical caloric intake (expenditure). Overall, a surplus (deficit) of 500 kcal a day brings about a gain (loss) of body fat at the rate of one pound per week and a surplus (deficit) of 1000 kcal a gain (loss) of two pounds per week (Whitney et al., 2002).

In this context, I was pleased to see this recent article in the International Journal of Obesity, which we economists can use to derive better weight effects.  Here is the abstract

Despite theoretical evidence that the model commonly referred to as the 3500-kcal rule grossly overestimates actual weight loss, widespread application of the 3500-kcal formula continues to appear in textbooks, on respected government- and health-related websites, and scientific research publications. Here we demonstrate the risk of applying the 3500-kcal rule even as a convenient estimate by comparing predicted against actual weight loss in seven weight loss experiments conducted in confinement under total supervision or objectively measured energy intake. We offer three newly developed, downloadable applications housed in Microsoft Excel and Java, which simulates a rigorously validated, dynamic model of weight change. The first two tools available at http://www.pbrc.edu/sswcp, provide a convenient alternative method for providing patients with projected weight loss/gain estimates in response to changes in dietary intake. The second tool, which can be downloaded from the URL http://www.pbrc.edu/mswcp, projects estimated weight loss simultaneously for multiple subjects. This tool was developed to inform weight change experimental design and analysis. While complex dynamic models may not be directly tractable, the newly developed tools offer the opportunity to deliver dynamic model predictions as a convenient and significantly more accurate alternative to the 3500-kcal rule.

Finally, I will end by noting that there are many papers that use economic models to project how a tax/subsidy will change the consumption of certain nutrients, and similar thumb rules are used to translate to changes in heart attacks, diabetes, etc.  Although I don't know for sure, I suspect many of the exact same sorts of problems exist with these thumb rule extrapolations as exists with the 3500kcal=1lb rule, not to mention the larger difficulty of ascribing causation in those models.