Impacts of Dietary Recommendations

Following the government's dietary recommendations may lead to . . . climate change?

New research suggests the following:

“if Americans adopted the recommendations in USDA’s “Dietary Guidelines for Americans, 2010,” while keeping caloric intake constant, diet-related greenhouse gas emissions would increase 12 percent.”

Rather than trying to anticipate the unintended consequences of such recommendations, the study authors want to add another layer on top of the nutritional recommendations

“The take-home message is that health and environmental agendas are not aligned in the current dietary recommendations,” Heller said.

The paper’s findings are especially relevant now because the USDA Dietary Guidelines Advisory Committee is for the first time considering food sustainability within the context of dietary recommendations, he said.”

As I've pointed out before, trying to integrate nutritional and environmental objectives into recommendations involves value judgement that go beyond scientific evidence. Moreover, focusing just on C02 emissions or nutritional composition (as if that's easy to characterize) ignores many other factors.  On a per-acre basis, which crops are the biggest users of pesticides or water? You might be surprised to find out that it is not corn, soybeans, or wheat but rather many fruits and veggies like lemons, strawberries, etc. 

Rather than trying to add layer upon layer to the dietary recommendations, why not respect people's choices?  The price of food reflects the resources used and the demands on those resources.  If the problem is that prices don't fully reflect water use or C02 emissions, then the idea is to think about assigning property rights in a way that that information-aggregating markets help allocate those resources.  But, I suppose it's less fun to let markets allocate resources.  That would take away our power to tell others what to eat.  

Reducing Food Insecurity

Last week, I mentioned the new USDA report on food insecurity.  I also mentioned a WSJ editorial by James Bovard arguing that food stamps don't reduce food insecurity because the number of people enrolled in food stamps has risen dramatically while food insecurity remains essentially unchanged.

I noted that we don't know the counterfactual (i.e., how much food insecurity would have changed had enrollment in food stamps not increased).  And, I also noted that there is some good academic research on the relationship on food insecurity and food stamp participation.

One of the big problems with trying to tease out the link between these two is that they are jointly determined.  That is, I may enroll in food stamps precisely because I'm food insecure. This sort of selection effect will make it look like being on food stamps is associated with food insecurity, but clearly this is just correlation, not causation.

Here is a careful paper published in the Journal of the American Statistical Association that tries to get at the issue:

“Under the weakest restrictions, there is substantial ambiguity; we cannot rule out the possibility that SNAP increases or decreases poor health. Under stronger but plausible assumptions used to address the selection and classification error problems, we find that commonly cited relationships between SNAP and poor health outcomes provide a misleading picture about the true impacts of the program. Our tightest bounds identify favorable impacts of SNAP on child health.”

One of the measures of "child health" is food insecurity, and this research seems to suggest null to positive effects of food stamp participation and child food insecurity.  

A lot of the discussion on the web related to the USDA report seems to be wrapped up in ideological baggage associated with beliefs about the desirability of cutting or expanding the food stamp program (or, for example, utilizing work requirements).  Those who would like to reduce the size and scope of the food stamp program often try to argue that food stamps do not reduce food insecurity and may actually increase it.  My view is that the best analysis doesn't support such an argument.  There may be other good reasons for reducing the size of the food stamp program, but the food security argument isn't one of them.  

Another argument I made in my previous post was that technological development that leads to lower food prices seems a comparatively good strategy for reducing food insecurity.  

As such, I was intrigued to see this white paper by Graig Gundersen at the University of Illinois on food insecurity.  One of the five drivers he discusses to reduce food insecurity is to focus on the importance of low food prices.  

He also writes, when discussing, what food groups can do (or perhaps what they shouldn't do):

“Third, they can view proposals encouraging organic foods and local foods with skepticism. While proposals to encourage, say, local food procurement by supermarkets can have ancillary benefits, these benefits do not generally extend to low-income households because they cannot afford these items. Instead, the benefits are more likely to extend to upper-income households that can afford these items. Moreover, by devoting scarce resources to encouraging the entrance of these into the food supply chain, this diverts resources away from factors that would help low-income households. ”

Assorted Links

Simply eating more fruits and veggies does not necessarily reduce weight

How to solve the California water shortage problem?  These authors say the answer is simple: raise the price

10 reasons fair trade coffee doesn't work (I normally don't like these sorts of lists, but this one is actually pretty good)

Popeye was wrong. Or was he right?

Fascinating information from Ole Bjørn Rekdal in a paper on academic urban legends:

“The following quote, including the reference, is taken from an article published by K. Sune Larsson in the Journal of Internal Medicine:

The myth from the 1930s that spinach is a rich source of iron was due to misleading information in the original publication: a malpositioned decimal point gave a 10-fold overestimate of iron content [Hamblin, 1981]. (Larsson, 1995: 448–449)1

The quote caught my attention for two reasons. First, it falsified an idea that I had carried with me since I was a child, that spinach is an excellent source of iron. The most striking
thing, however, was that a single decimal point, misplaced 80 years ago, had affected not just myself and my now deceased parents, but also a large number of others in what we place on our table.”

and

“Truth be told, there is iron in spinach, but not significantly more than in other green vegetables, and few people can consume spinach in large quantities. A larger problem
with the idea of spinach as a good source of iron, however, is that it also contains substances that strongly inhibit the intestinal absorption of iron (see e.g. Garrison, 2009:
400). Simply put, spinach should not at all be the first food choice of those suffering from iron deficiency.

Larsson’s article made me aware of the remarkable fact that a large number of people in the Western world have been misled for a staggeringly long time. Since so many people
still believe that spinach is a good source of iron, I have good reason to convey this newfound knowledge to others. The story of this decimal point error is, in addition, a brilliant illustration of how a small stroke may fell a great oak, and a reminder of the importance of accuracy and quality control in the production and distribution of scientific knowledge.”

Rekdal goes on to show the assertion that that spinach-is-high-in-iron belief is a more complicated story that may involve more than a decimal issue, and he reveals the challenge in tracking down the original source of that claim. 

He exposes an even bigger irony, as revealed through another quote:

“The story that the iron content of spinach was a myth based on a misplaced decimal point is itself a myth. Spinach has a lot of iron, just like other green vegetables, but it is unavailable for absorption.

I should know, I was the one who was responsible for propagating the myth in a BMJ article.”

and

“Now some fascinating research by Mike Sutton has found out the whole truth behind the decimal point and the iron in spinach myth and I am pleased to be able to say that I was right about spinach being useless as a source of iron, but utterly wrong about why the myth has taken hold. … The moral of this story is that a good story is not necessarily a true story. (Hamblin, 2010)”

Calorie Labeling at Harvard

“There have been some suggestions that we need to post calories at schools and certainly in college dorms … it’s not really a good solution, and Harvard recently removed this information for fear of contributing to eating disorders, because students were going in and selecting their foods based on the calories and not necessarily the nutritional value.”

That's from Anding, Roberta A. Professor, Baylor College of Medicine and Texas Children’s Hospital. “Lecture 20: Obesity—Public Health Enemy Number One.” Nutrition Made Clear from the Teaching Company (HT Bailey Norwood; one transcript is here)