Food Bug Zappers

In chapter 10 of Unnaturally Delicious, I wrote about a variety of food safety innovations.  Frank Yiannas, Walmart's vice president for food safety told me a bit about some of the technologies and efforts he's been involved with.  But, first on Walmart itself:

I started by asking about the size of Walmart. More than 120 million Americans (more than a third of the U.S. population) shop at Walmart every week. Does the sheer scale of the operation make the U.S. food system riskier? If Walmart has an outbreak, multitudes would be sickened. Yiannas replied: “One out of every four dollars spent on food are spent at a Walmart. We can make a big difference. Large organizations like Walmart result in a safer food system.” He points out that when Walmart makes a change, it affects the whole system.

He went on to tell me about how they're ensuring rotisserie chickens are properly cooked.  

To address this problem Walmart turned to the power of information technology and Big Data.28 Now all stores are equipped with new handheld sensors that are used to check cooking temperatures of every single batch. The sensors automatically record and send the information to the web in real time. During the month that health inspectors checked Walmart chickens ten times, the company recorded 1.4 million temperature checks. Whereas earlier inspection methods relied on taking a small sample of readings to check for compliance, Yiannas said the new approach is “N = all.” In other words, Walmart employees check every single chicken. Moreover, Walmart no longer has to wait on a report from an inspector or third-party auditor to learn the outcomes. Yiannas can check at any time during the day to see which stores are doing what they should to meet food safety standards. The troves of data can be exploited to find out which stores, which equipment, and which employees are doing better. Perhaps most important, it might just stop you and me from walking out the door with an undercooked chicken.

I also talked to Kevin Myers, the senior vice president of research and development for Hormel, who was involved in implementing a relatively new technology to help ensure safe meat: high pressure processing.  

High-pressure processing (sometimes also called pascalization after the seventeenth-century scientist Blaise Pascal, who studied pressure) allowed Hormel Foods to sanitize both the meat and the package it comes in. The process is particularly well suited for ready-to-eat foods because it takes place after the product is packaged and eliminates potential contamination which could occur after cooking and before packaging.

Myers said the process works by placing the packaged food in a chamber and submitting it to extreme levels of pressure. Have you ever jumped off the diving board at the deep end, only to have your ears hurt as you approached the bottom of the pool? That pain is caused by the pressure exerted on your eardrums by the water above you in the pool. At a depth of about ten feet, your ears are feeling about 4.3 pounds per square inch (psi) of pressure. If you could somehow swim to the deepest point in the ocean (about thirty-six thousand feet down), you’d feel more than 15,600 psi. Well, you wouldn’t actually feel anything because your body would be crushed well before you reached that depth. According to Myers, Hormel’s high-pressure processing system applies 87,000 psi to food products. That is five and a half times more pressure than would be felt at the deepest depth of the ocean.

All that pressure is enough to kill bacteria and other pathogens without adversely affecting the food itself.  Here's a photo of a high pressure pasteurization machine provided by Avure Technologies, which is finding applications of high pressure pasteurization for a wide variety of foods.

There is more in the chapter on Walmart, Hormel, and on innovators working on new, rapid food safety testing devices.  

What Consumers Don't Know about GMOs

Yesterday the Journal of the Federation for American Societies for Experimental Biology (FASEB) published a paper I co-authored with Brandon McFadden from the University of Florida.  We surveyed a representative sample of over 1,000 US consumers and probed the depth of their knowledge about GMOs.  

We asked questions about the number of genes affected by different plant breeding techniques, prevalence of use of GMOs for different crops and foods, true/false questions about genetics and GMOs, knowledge of the length of time biotech crops have been grown, regulatory approval times for GMOs, views on public policies directed toward GMOs.  Before and after asking these questions, we asked respondents to rate their self-assessed knowledge of GMOs and to indicate their belief that GMOS are unsafe or safe to eat.  

The overall finding is 1) consumers, as a group, are unknowledgeable about GMOs, genetics, and plant breeding and, perhaps more interestingly, 2) simply asking these objective knowledge questions served to lower subjective, self-assessed knowledge of GMOs (i.e., people realize they didn't know as much as they thought they did) and increase the belief that it is safe to eat GM food.  

The implications are two fold: 1) using consumer opinions about GMOs to guide public policy is problematic given the low levels of knowledge, and 2) using something like the Socratic Method may as effective at changing safety beliefs than simply providing information.    

Enriched colonies

A couple months ago, I discussed the book chapter I wrote on a different type of hen housing system: the enriched colony . Today, the Wall Street Journal ran a piece I wrote about this hen housing system and the costs of alternative housing systems.   

A few snippets:

A 2014 California voter initiative and subsequent state legislation ultimately led to a ban on sales of battery-cage eggs in the Golden State. Because eggs have few close substitutes, demand tends to be relatively insensitive to changes in price. When demand is inelastic, a small-percentage change in the quantity supplied causes an even greater increase in price.

Comparing the prices of eggs sold in California before and after the law with the prices of eggs sold in other states reveals that the legislation increased egg prices for Californians by at least 22%—or about 75 cents for a dozen. A related analysis using Agriculture Department wholesale price data indicates the California law increased prices between 33% and 70%. Poor Americans, who spend a larger share of their incomes on food, are disproportionately affected.


Rather than getting rid of the cages entirely, one answer is to use a relatively new type of housing: the enriched-colony cage system. Unlike the barren environment in the battery cages, the much larger, enriched-colonies have nesting areas for egg laying and a matted area that allows the hens to exercise their natural urge to scratch. Also available are perches that allow the hens to get up off the wire floor.

An enriched colony is not a Ritz-Carlton, and some animal advocates think the systems do not go far enough. However, they represent an innovative compromise that attempts to balance cost and the hens’ well-being.

Food Demand Survey (FooDS) - May 2016

The May 2016 edition of the Food Demand Survey (FooDS) is now out.  

Some noteworthy results from the regular tracking portion of the survey:

  • For the second month in a row WTP fell for all food products except hamburger, which increased 5.4% this month compared to last.  
  • Compared to one year ago, WTP is lower for all food products.
  • Consumers expect lower chicken and pork prices this month compared to last (and about the same prices for beef), and say they plan to buy more chicken, beef, and pork than they did last month.  
  • GMOs were less visible in the news this month; pink slime and LFTB were more visible.  
  • Concern for GMOs fell this month.

For the ad-hoc questions, we delved into consumers' beliefs about the use of added growth hormones in livestock and poultry production.  

First, participants were asked: “What percentage of the following types of farm animals in the United States are given added hormones to promote growth and muscle development?”.  The average answers were 60% for beef, 54% for pork, and 55% for broiler chickens.  These answers are quite wrong.

Virtually all feedlot cattle in the US are given added growth hormones but NONE of the hogs or broiler chickens are given added hormones.  Fewer than 2% of respondents knew this last fact. That is, 98% of respondents incorrectly think hormones are used in pork and chicken production.  

What impacts might these false beliefs have?  As it turns out, the impacts are non-trivial.  For example, consumers' responses to our initial choice questions that are used to derive WTP for each of the meat cuts depend on consumers perceptions about the prevalence of hormone use.  The larger the fraction of animals a consumer believes receives hormones, the less they're willing to pay for meat from that type of animal.  Here's a quick analysis I ran asking the question: how would consumers' WTP change if they went from having the current average level of false beliefs to knowing the truth?  

WTP for ground beef and steak would fall (because more cattle are given hormones than most people think) and WTP for pork and chicken would increase (because none of these animals are given added hormones despite the fact people think they are).  What this suggests is that demand for pork and chicken is depressed by false beliefs.

We can also see the impact of these sorts of false beliefs in a different way.  Participants were asked a second ad-hoc question on the survey: “If you walked into your local grocery store and saw a package of meat with the label ‘no added hormones’, what is the highest premium you would be willing to pay for the following meats with this label over meats without this label?

On average, respondents said they were willing to pay premiums between $1 and $2 for each of the meat cuts for ‘no added hormones.”  

The highest was for steak ($2.14/lb) and the lowest was for deli ham ($1.32). Of
course, paying a premium for chicken or pork labeled ‘no added hormone’ is superfluous because all pork and chicken production avoids the use of added growth hormones.

False beliefs tend to inflate WTP for ‘no hormone added’ labels. People’s beliefs about hormone use are correlated with their willingness to pay a premium for ‘no added hormone.’ For example, a person who thinks no hormones are used in pork is predicted to pay a premium of $1.44 for pork chops with a ‘no added hormone’ label, whereas a person who thinks 100% of pigs are given hormones is predicted to pay a premium of $1.81. For chicken breast, the same figures are $1.42 and $1.92.

All this perhaps explains why many pork and poultry producers add the claim "no added hormones" to the label.  These labels, however, while truthful, might also be misleading. Because, as our survey shows, people think there are high levels of hormone use in pork and poultry production.  

Does Diet Coke Cause Fat Babies?

O.k., I just couldn't let this one slide.  I've seen the results of this study in JAMA Pediatrics discussed in a variety of news outlets with the claim that researchers have found a link between mothers drinking artificially sweetened beverages and the subsequent weight of their infants.

I'm going to be harsh here, but this sort of study represents everything wrong with a big chunk of the nutritional and epidemiology studies that are published and how they're covered by the media.  

First, what did the authors do?  They looked at the weight of babies one year after birth and looked at how those baby weights correlated with whether (and how much) Coke and Diet Coke the mom drank, as indicated in a survey, during pregnancy.  

The headline result is that moms who drank artificially sweetened beverages every day in pregnancy had slightly larger babies, on average, a year later than the babies from moms who didn't drink any artificially sweetened beverages at all.  Before I get to the fundamental problem with this result, it is useful to look at a few more results contained in the same study which might give us pause.

  • Mom's drinking sugar sweetened beverages (in any amount) had no effect on infants' later body weights.  So drinking a lot of sugar didn't affect babys' outcomes at all but drinking artificial sweeteners did?
  • The researchers only found an effect for moms who drank artificially sweetened beverages every day.  Compared to moms who never drink them, those who drink diet sodas less than once a week actually had lighter babies! (though the result isn't statistically significant).  Also, moms drinking artificially sweetened beverages 2-6 times per week had roughly the same weight babies as moms who never drank artificially sweetened beverages.  In short, there is no evidence of a dose-response relationship that one would expect to find if there was a causal relationship at play.  

And, that's the big issue here: causality.  The researchers have found a single statistically significant correlation in one of six comparisons they made (three levels of drinking compared to none for sugar sweetened beverages and for artificially sweetened beverages).  But, as the researchers themselves admit, this is NOT a casual link (somehow that didn't prevent the NYT editors from using the word "link" in the title of their story).  

Causality is what we want to know.  An expecting mother wants to know: if I stop drinking Diet Coke every day will that lower the weight of my baby?  That's a very different question than what the researchers actually answered: are the types of moms who drink Diet Coke every day different from moms who never drink Diet Coke in a whole host of ways, including how much their infants weigh?  

Why might this finding be only a correlation and not causation? There are a bunch of possible reasons.  For example, moms who expect their future children might have weight problems may choose to drink diet instead of regular.  If so, the the moms drinking diet have selected themselves into a group that is already likely to have heavy children.  Another possible explanation: moms who never drink Diet Cokes may be more health conscious overall.  This is an attitude that is likely to carry over to how they feed and raise their children which will affect their weight in ways that has nothing to do with artificially sweetened beverages.

Fortunately economics (at least applied microeconomics) has undergone a bit of credibility revolution.  If you attend a research seminar in virtually any economist department these days, you're almost certain to hear questions like, "what is your identification strategy?" or "how did you deal with endogeneity or selection?"  In short, the question is: how do we know the effects you're reporting are causal effects and not just correlations.  

Its high time for a credibility revolution in nutrition and epidemiology.