Are GMOs Safe to Eat?

The New York Times ran a story yesterday, highlighting the findings of a paper coming out in the journal Food and Chemical Toxicology.  The study reports that rats fed genetically modified corn developed more tumors and died more quickly than rats not fed genetically modified corn.  

The study will no doubt ignite a firestorm on par with the Monarch butterfly scandal a decade ago (in that episode, Cornell researchers originally reported butterflies being killed by crops containing the Bt gene but later studies published in the Proceedings of the National Academies of Science concluded the effects were negligible).  

In many ways, I applaud the efforts of the French scientists conducting the research.  This is how science is done.  Publish a result.  Be upfront and honest with the methods.  Others will see if they can replicate.  ​

That said, an reasonable person must interpret these new results in light of the existing knowledge on the science of eating GM foods.  The new study did to appear in a vacuum, and there are a large​ number of similar studies finding no such effects from eating GM food.  Given this large baseline of previous research, we can't expect the present study have much influence on our prior beliefs.  This is especially true in light of the fact that the statistical analysis used by at least some of these  authors has been questioned before by none other than the European Food Safety Authority.  And that the supposed causal mechanism between the effects the authors report and the genes involved in conveying resistance to herbicide seems, to me, highly speculative at best. 

I am not on expert on rat feeding trials.  But, the first thing that stood out to me about this study was the very small sample size.  For each gender, there are only 10 rats per treatment group.  It would be difficult, if not impossible, to publish an experimental paper in an ​economics journal with such a small sample size.  Why?  Because with such a small sample you can never really be sure whether the outcomes observed are simply due to chance.  

Using a standard sample size calculation, we can find that with a sample of 10 individuals, the margin of error on a dichotomous variable (like whether a tumor is present or not) is over 30%.  That means, assuming that that the researchers found 50% of rats had a tumor, that if we repeated the study over and over and over, that 95% of the time we'd find expect to find tumor rates between 20% and 70%.  In other words, we cannot have much confidence that the effect the authors observe is "really there" or simply due to chance.  

Obesity Hype

The Robert Wood Johnson Foundation and Trust for America's Health just released a report entitled F as in Fat: How Obesity Threatens America's Future 2012.   The associated press release reports:

For the first time, the annual report includes an analysis that forecasts 2030 adult obesity rates in each state and the likely resulting rise in obesity-related disease rates and health care costs. 

and​

If obesity rates continue on their current trajectories, by 2030, 13 states could have adult obesity rates above 60 percent, 39 states could have rates above 50 percent, and all 50 states could have rates above 44 percent.

​Obesity is out of control!  Or is it?  If we look at the actual data, we can see that no such explosion in obesity rates are occurring.  One group of researchers writing in 2010 in the Journal of the American Medical Association reported that that the prevalence of obesity :    

may have entered another period of relative stability.

Another re-appraisal in 2012 by the same authors using new data in the Journal of the American Medical Association reported

Over the 12-year period from 1999 through 2010, obesity showed no significant increase among women overall

and only slight increases for men​.

Here is the key graph from the JAMA paper​:

As you can see, trends in BMI since 1990-2000 are basically flat.

​So, how is it that the Robert Wood Johnson Foundation and Trust for America's Health can claim run-away trends?  I don't know, but it makes me suspicious of anything else they claim in their report not to mention their policy prescriptions.  

Indeed, it might have done the authors of the report some good  to read  or at least acknowledge what was written in the 2012 JAMA paper (footnotes omitted):

In part because we know relatively little about the precise causes of the trends previously observed, it is hard to predict the future trends in obesity. Several analyses have modeled increasing obesity prevalence as a function of calendar time and then projected future obesity prevalence from these models. These obesity predictions in effect assume that the causal factors for obesity will continue to rise with time or will have an increasing effect over time, and therefore calendar time itself is a reasonable predictor of future obesity prevalence. However, the results reported here and the apparent slowing of trends suggest these may not be valid assumptions and these predictions may be inaccurate.

​

A Symbol of Government Over-Reach

The Huffington Post just published an editorial​ by yours truly about the ban on large sodas in New York City.  Here are the concluding paragraphs:

I doubt Bloomberg really expects his large-sized-soda ban to have much impact. Rather, it serves as a symbol. But a symbol of what? Perhaps, it symbolizes his passion about the health of New Yorkers. Yet, it is also a symbol of government over-reach; of a government that knows no bounds in reaching into the minutia of our daily lives for the sole purpose of creating a symbol.

Bloomberg is right to presume people know best whom to marry and whether to indulge in a little cannabis. All I'm asking is that he give the same leeway at the soda fountain.

In the article, I point out the hypocrisy of Bloomberg's liberal stance on everything from gay marriage to abortion to pot smoking.  These things he wants to legalize;  selling large sodas, however, is a criminal offence.  This cartoon by Mike Luckovich​ says it all:

Food Police Alert

In an opinion piece in the Journal of the American Medical Association, Thomas Farley praises New York City policies and calls for ramped up regulation to fight obesity:​

New York City supported a 1-cent-per-ounce excise tax on sugary drinks to lessen the industry's financial incentive to market large portion sizes and to encourage consumers to choose smaller portions and switch to low-calorie beverages. The city also supported a change in policy on the Supplemental Nutrition Assistance Program that would have prohibited the use of program benefits to purchase sugary drinks, arguing that government should not subsidize the purchase of a product known to be particularly unhealthful. In addition, the city's health department proposed a cap on the portion size of sugary drinks served at restaurants.

​He doesn't justify the regulations by showing that they worked or by demonstrating that the benefits are greater than the costs.  Rather, his key argument is that the government already regulates many areas of your life:

. . .  tens of thousands of restaurant inspections are conducted each year, enforcing rules such as those mandating the temperature at which food can be stored, all to prevent foodborne infectious diseases. The federal government mandates safety features, such as seat belts, in automobiles. Governments at all levels prohibit the use of lead in paint.

​The reason you should acquiesce to new government rules is apparently that you've already acquiesced to other government rules.   

In the end, the argument amounts to little more than paternalism.  People aren't presumed to know what is best for them so let the "experts" decide.  It is telling that in the piece, Farley writes:​

The sale of huge portions is driven by the food industry, not by consumer demand.

 ​I don't recall the food industry ever forcing me to  supersize my Big Mac.

Do Consumers Really Want GMO Labeling?

Mark Bittman on his NYT blog claims:​

IT’S not an exaggeration to say that almost everyone wants to see the labeling of genetically engineered materials contained in their food products.

and​

Nationally, on the broader issue of labeling, in answer to the question of whether the Food and Drug Administration should require that “foods which have been genetically engineered or containing genetically engineered ingredients be labeled to indicate that,” a whopping 91 percent of voters say yes and 5 percent say no.  

I agree that's what people will tell you in surveys.​  But, as Bryan Caplan has recently put it:

When lies sound better than truth, people tend to lie.

I don't think most people purposefully lie on surveys.  Rather, they often don't think about the consequences of the things they're saying.  In these cases, the "socially acceptable" answer is the easy one to give.  I've literally written dozens of journal articles showing that people will say one thing in a survey and do something entirely different when shopping.

When we look at what people actually buy in the grocery store, the data reveals that they don't buy a lot of organic or non-GMO products.  Why?  Because they're a lot more expensive.  ​

So, the question isn't whether surveyed people tell you that they are in favor of labeling GMOs.  They real question is what they are willing to pay to get it when they have to put their money where their mouth is.

Addendum: Tyler Cowen's response to Bittman's post is right on the money.​